Need help with understanding MAF adjustments. [Archive]

dfe1

January 24th, 2006, 05:02 PM

Everyone who tunes an engine develops a specific approach that seems to work best for that particular individual. Consequently, there are about as many "right" ways to tune as their are wrong. One of the "problems" I see with FlashScan is that it offers so much capability and is so easy to use, people start making changes just because they can. I think changing MAF calibration generally falls in this category. I have to assume that the engineers at Generous Motors spent quite a bit of time on the original calibration. That being the case, one has to assume that MAF readings are an accurate measurement of the amount of air flowing through the sensor. Unless the MAF is changed or modified, what's the point of altering the calibration-- unless you're trying to fudge the data flowing to the PCM? (Note the FlashScan instructions note that MAF calibration should only be altered if the MAF has been modified.)

On the other hand, it is frequently necessary to do a bit of fudging in order to get LTFTs in range. However, in my experience, you can get the AFRs you want by working only with VE or with VE and IFR. In the end, it really doesn't matter how you achieve the desired results, as long as you achieve them. I just think that using MAF calibration as a tuning device, as opposed to as a correction, is not the best way to go.

If you're running out of MAF range, the easiest approach is treat the system as speed/density once the MAF range has been exceeded and use the PE table (B3618) to add the amount of fuel necessary to obtain the desired AFR.

joecar

January 25th, 2006, 06:10 AM

If you got IFR table and VE table both correct, then while still in Auto VE Tune mode, compare MAF airflow with GM.DYNAIR (PCM calculated airflow based on VE and not MAF); if they're different, then the MAF table is out.

redhardsupra

January 25th, 2006, 06:18 AM

joecar: dead on!
dfe1: your IFR/MAF tweaks make baby jesus cry ;)
no fudging is required if you know all the parameters. there are many ways to skin a cat, but some of the methods end up with a much bigger, cleaner skin

Dirk Diggler

January 25th, 2006, 07:28 AM

or you can build a new maf table based on BENS using an external and hopefully accurate WB that measure the ratio betweer AIR and FUEL. I wouldnt give GM to much credit as these car are set to run way rich from the factory WOT 11.75:1 with castrated values for timing (01-02) if you ever verified that on a stock car you will soon see how far they are out.

dfe1

January 25th, 2006, 08:37 AM

dfe1: your IFR/MAF tweaks make baby jesus cry ;)
no fudging is required if you know all the parameters. there are many ways to skin a cat, but some of the methods end up with a much bigger, cleaner skin I disagree. In my experience, there always seems to be some fudging required unless you want to spend a lifetime tuning an engine. If yo think IFR/VE tweaks make baby Jesus cry, you should see what MAF tweaks do to him. :Eyecrazy:

Dirk Diggler

January 25th, 2006, 09:08 AM

LOL he said IFR/MAF tweaks make baby jesus cry and I think he is referring to those being used as the only two tables to tune car.

My tuning procedure goes as follows

1 Unplug maf
2 fit wb to the car
3 tune the ve tables using bens * 3-4
4 plug the maf back in and watch the WB read in excess of 10% lean
5. Use a map (freq vs Ben) and apply the ben back to the maf table * 3-4
6 verify actuall = commanded pt and wot
7 put car back in closed loop
8 watch the shit eating grin on customers face when you give them back a car that doesnt smell, buck, accelrates smooth and many more.....

jfpilla

January 25th, 2006, 09:32 AM

Joe,Red,Dirk,
I'm with you. IFRs and VE's are the absolutes. Dirk, you mention looking at stock settings. There's a lot to be learned from them. For eaxample,IFRs for same size injectors are always the same. Unless IFRs are correct PE values will be further off.
dfe1,
Fudging may or may not be needed regardless of the methods but it is for sure necessary if you do a "work around" tune and then the issues that remain, that people put up with, are sure to arise under changing conditions. At my age a lifetime is not too long but I have put in the time to get it right. I think we do it ourselves because the PROs don't have the time to get other than an adequate tune. Unless your willing to pay big $.
The only tables I have used for cruise tuning are: VE,MAF,DES.AIRFLOW,TIMING,IFR and STARTUP FRICTION.
Joe
PS If you drag race have you noticed you may not always have cell 22 lock at 0? Heat soak can cause your trims positive if thet are set too close to 0. Mine are set at -6 at 0*C IAT. This generally is enough since I don't race in the hot summer.

Dirk Diggler

January 25th, 2006, 10:06 AM

With all the access and different tables EFILive has given us some need to abandoned the LS1Edit way of thinking eg (IFR and MAF with PE values that wont or dont represent a real AFR or all idle issue deal with in the RAF table when we have a few more to choose from for different conditions ie startup)

dfe1

January 25th, 2006, 10:42 AM

dfe1,
Fudging may or may not be needed regardless of the methods but it is for sure necessary if you do a "work around" tune and then the issues that remain, that people put up with, are sure to arise under changing conditions. At my age a lifetime is not too long but I have put in the time to get it right. I guess it all boils down to what you're trying to achieve. I've always taken the approach that it's best to achieve the desired results with the fewest changes. With respect to fuel flow, if the engine makes maximum power at 12.9:1 it does't care how that's achieved. The problem I see with making changes to the MAF table is that it's a relatively esoteric table for anyone other than a veteran tuner. If something goes wrong with a vehicle and someone else has to troubleshoot it, there's a good chance that changes to MAF table will be missed. That's obviously not an issue if you're tuning your own vehicle, but is a problem for a customer who goes down the road. The other potential issue is that if you change too many things, you wind up chasing your tail when a problem arises. My whole reason for responding to this thread isn't to tell people how to tune, but to hopefully save some guys from a head-bashing marathon in the event of a problem either during or after tuning.

Dirk Diggler

January 25th, 2006, 01:08 PM

Ususally if a customer comes to me with a borked tune i start from scratch anyways. 6 and 1/2 dozen of the other

VetPet

January 25th, 2006, 02:30 PM

As a novice to the tuning world, I've been doing a lot of reading and researching this winter as I'll have to wait until spring for the chance to tune. The question of tuning the MAF has been rolling around in my head and this post has certainly brought up some interesting thoughts.

All of the information I've read so far does suggest that the MAF table does not need to be adjusted. The assumption here being that the MAF is properly calibrated from the factory within an acceptable tolerance. The MAF is a measuring tool and will provide the correct input based on what it sees. Changing your intake will provide cooler air than from under the hood but you won't change the volume entering the engine, only the mass (weight) of the air. That's why it's called a Mass Airflow Sensor and why the measurement is in grams/sec. The same type of conclusion can be drawn with reference to the IFR table. Unless you're changing your injectors to other than stock, why mess with it?

Before I put my car away last fall, I was able to get some scan data before and after installing my cold air intake. When I compared my LTFT's, the jump in values from before the installation was doubled or more. What this told me was that my engine was being fed a much higher quantity of oxygen than before which in turn required more fuel. Since the MAF is the primary air sensor, it must be reading correctly, otherwise the LTFT's wouldn't have changed so much.

There's one other thing that I've read which might surprise a lot of people. Most opinion is that the MAF does not handle throttle transitions well and that the VE table is there to help in these situations. Apparently, the MAF doesn't need the help of the VE table at all and is quite capable on it's own. The VE table is there as a backup in case of a MAF failure and open loop operation during cold start. At WOT open loop operation, the MAF signal is used and thus the need to adjust the PE table using a WB02 to compare actual AFR vs Commanded AFR.

I've still got a lot to learn but it is these types of discussions that make you think and get a better grasp of the concepts and strategies of EFI systems. My thanks to all of you.

:cheers:

Dirk Diggler

January 25th, 2006, 03:05 PM

I am done everyone has their way of tuning and we will disagree to the end of time. I have spent countless hours tuning my own car and other peoples cars, are my ways right I guess we will never know. VetPet can you point me to any references which state the maf doesnt need to be touched.

If the injectors are calibrated right, pe set to 1.13 ve table dialed in in SD mode and you hook the maf up and you either see your trims go positive or the WB go lean what do you do?

Mater of fact I can post logs where the ve table was dialed in in SDmode and as soon as i went back to MAF operatoin the WB read 7-10 leaner makes sense to me that the maf needs to be dialed in at this point

jfpilla

January 25th, 2006, 03:15 PM

VetPet,
Your too modest. :notacrook:

Dirk,
I don't think he's saying not to use it but just the opposite. I think he's referring to an old belief expressed in many posts.

"If the injectors are calibrated right, pe set to 1.13 ve table dialed in in SD mode and you hook the maf up and you either see your trims go positive or the WB go lean what do you do?":exactly:

Great way to put this question. I feel your Pain.
Joe

Redline Motorsports

January 25th, 2006, 04:59 PM

To all;

Thank you very much for expression all your views. I always get concerned when asking some of these questions but they always yield some great debate and ideas.

It has become quite apparent that the individuals who responded to this post are looked at as "advanced" members of this forum. I have spent more hours with a pad of paper taking detailed notes from all of these threads and it is much appreciated.

I guess if you are going to keep the MAF in the tuning equation, it needs to be at least checked after a VE tune is completed to make sure that it hasn't affected the VE tune.

Before I got into the tuning I always had other shops tune the cars we built. There approach, now that I understand the tuning better, was one of smoke and lights.

Lets keep the thread going!

Thanks

Howard

caver

January 25th, 2006, 06:24 PM

My understanding is that when the maf is connected the pcm uses that input exclusively with the VE table used to make sure the values are sane?

Every car I have done has had commanded afr miles from actual therefore I believe it is neccessary to adjust the maf tables.
I autotune the MAF as a matter of course.

joecar

January 26th, 2006, 05:46 AM

Thank you very much for expression all your views. I always get concerned when asking some of these questions but they always yield some great debate and ideas. This thread is a good read, and we're all able to discuss and respect other people's opinions... :two thumbs up:

..."advanced" members... Yes, there's smart and knowledgeable people here, and I've been learning alot from them; thanks to all!

...if you are going to keep the MAF in the tuning equation, it needs to be at least checked after a VE tune...
that's what is comes down to: checking and not making assumptions.:exactly:

Lets keep the thread going! :cheers:

joecar

January 26th, 2006, 05:50 AM

So, is there a summary of when (what conditions) the airflow is from the MAF and when it's from the VE table...?

Edit: Oh, I just saw this thread: showthread.php?t=1815 (http://forum.efilive.com/showthread.php?t=1815)

VetPet

January 26th, 2006, 07:58 AM

[quote=Dirk Diggler]I am done everyone has their way of tuning and we will disagree to the end of time. I have spent countless hours tuning my own car and other peoples cars, are my ways right I guess we will never know. VetPet can you point me to any references which state the maf doesnt need to be touched.

Dirk, I'm referencing a book by Charles O. Probst, Corvette Fuel Injection. I'm sure you've probably heard of it. If you haven't had a chance to read it I would certainly recommend it. I think the GM engineers working on the Corvette projects are a pretty bright group of people and wouldn't throw on parts without some thought. The EFI program doesn't recommend changing the MAF table unless you change to a larger MAF as well.

I'm not saying that adjusting the MAF table is totally incorrect. I'd just like to know what's really causing the mixture to go lean once you put the MAF back on. Is it really the MAF calibration or is the MAF signal being modified by some other sensor input that's causing the problem. It just doesn't seem right to try and recalibrate a measurement device unless you know for sure that it isn't right to begin with.

There's one either item that I found interesting in reading the above book. I was under the impression that if your LTFT's are positive that they affect fueling under WOT. If I"ve read correctly, once you're in WOT open loop operation, the LTFT's are out of the picture and have no effect. Your WOT AFR would be dictated by the commanded AFR based on your PE table values and MAF sensor input. I'll have to look to find the page reference for this.

:cheers:

redhardsupra

January 26th, 2006, 08:22 AM

Dirk Diggler

January 26th, 2006, 08:34 AM

Dirk, I'm referencing a book by Charles O. Probst, Corvette Fuel Injection. I'm sure you've probably heard of it. If you haven't had a chance to read it I would certainly recommend it. I think the GM engineers working on the Corvette projects are a pretty bright group of people and wouldn't throw on parts without some thought. The EFI program doesn't recommend changing the MAF table unless you change to a larger MAF as well.

[quote]
I'm not saying that adjusting the MAF table is totally incorrect. I'd just like to know what's really causing the mixture to go lean once you put the MAF back on. Is it really the MAF calibration or is the MAF signal being modified by some other sensor input that's causing the problem. It just doesn't seem right to try and recalibrate a measurement device unless you know for sure that it isn't right to begin with.

My take on it is the hardcoded air values vs frequency get thrown outta wack if you look at your stock klid you will notice the lids neck is a little oval shaped. Aftermarket lids are completely round. I am assuming the oval shape helps direct the air more to the center of the resistors in the maf. When you swap to an aftermarket lid and you now get more air that travels to the edges of the maf these frequencies vs are no longer valid IMHO. Also I feel what causes it to go lean is the pcm is still using these hardcoded values to figure out fueling for the same hz and now they are mismatched esp when you cam the car and are getting a lot of reversion (reading air twice amongst other things). I can prolly bet my right arm that my WB is an accurate external device (after all that is what we are paying for) so what better way to calibrate a HARDCODED sensor with a device that is able to measure exactly what we need to dial the maf back in. Question with all the electroincs in our vehicles do you think a one stop shop harcoded value will take into account all of the tolerances of the electrical components in the vehicle. Any grounding feedback, radio noise from the ignition sytem and everything else that can contribute to dirtying that signal. I am pretty sure when the calibrated it they calibrated it in a controlled environment where this wasnt an issue. Also I feel to avoid waranty work the best way not to cook a motor under ANY condition is to run it a little richer. Ie come up with a calibration and then add 10% for good luck. Has anyone logged a bone stock car where commanded = actual via the ve or them maf?

If you TRIMS are derived from your o2 sensors closing the loop, fueling is based on the primary air metering device (MAF) and your trims are + who is to blame and how do you fix it?

PS GM spent millions of dollars in development for the LS1 to stick a damn 10 bolt behind it. You think I am gonna trust them with calibrating a sensor for me.

PPS If these MAF sensors are as acurate as we believe there would be no reason to buy EFILive, WB's and all the other fancy smancy tools we have. It wouldve all been taken care of at the calibration plant one time and one time only unless you spent 650 to change your rear end gears :muahaha:

There's one either item that I found interesting in reading the above book. I was under the impression that if your LTFT's are positive that they affect fueling under WOT. If I"ve read correctly, once you're in WOT open loop operation, the LTFT's are out of the picture and have no effect. Your WOT AFR would be dictated by the commanded AFR based on your PE table values and MAF sensor input. I'll have to look to find the page reference for this.

:cheers:
I am not a LTFT tuner I havent been for some time. I dont like narrow bands and how headers affect them and the likes. I will stick with my FJO unit. I dont know what all the pcm does to come up with LTFT values but I do know that after dialing in my ve table with my WB and then calibrating the maf with my WB the LTFT's are perfect. I have shortened my tuning experience since i have elimintated the need to wait for the car to relearn the trim values and can vurn more gs tuning instead of driving 40 pointless miles to get them to settle in again.

My tuning method was developed by hours of logging cause and effect open loop and closed I didnt follow any of the stickies but helped pioneeer some of them you just dont see my name in them but I have proof read most of them. You can do searches on Tech under my HumpinSS handle and read all the way back in 04 when i first started messing around with this SD/MAF stuff and my findings and methods. Marcin (RedhardSupra) will tell you as him, I, Black02SS, txhorns, TAQuickness and a few others hashed most of this stuff out. People like wait4me and NoGo also spoke of some of this stuff even before that but it never caught on and they were chastized for their beliefs. I was doing ve tuning with edit (before hpt, right BINK ;)) using excel and access to derive all the information you are getting today via maps/histograms. Could you imagine trying to average and change a ve table with 65k lines of data in excel filtering out FTC 21 and then when i got smarter with excel using formulas to derive the AFR error/BEN then trying to apply it. LOL talk about a long freaking time. The inconsistencies in the maf is what got me to unplug it because i once believed it was a perfectly calibrated sensor it bothered me that my trims would go -10 when unpluged and then I would plug it back up and everything would go +10 so i set out to find why. Now that I/we have figured most of it out I am just to lazy to put one back on the car and stick with full time OL SD

joecar

January 26th, 2006, 09:06 AM

More info: http://www.ls1tech.com/forums/showthread.php?t=363392

VetPet

January 26th, 2006, 10:06 AM

VetPet, do an experiment: get all your stuff working flawless in SD, and then reenable your MAF with stock calibration. then come back and tell me how well this pinnacle of GM engineering working for you ;)

if you want more verification, calculate it with my method from DynAir (histogram or my old spreadsheet), or the old HumpinSS' method by AFR% that was stolen, 'scuse me, popularized, by SoundEngineer.
I bet you you're gonna come with two pretty similar results, and they're not gonna be too close to the stock config.

remember that airflow is one of the hardest things to measure, very finicky and a permanently moving target, and this is the best we've come up with to deal with it, and it doesn't look bad. it doesn't reflect on the performance of the car, it just says what's the frequency of electric blips it takes to keep the heated element in the MAF at steady temp. it's very arbitrary, so i feel zero guilt about mucking with it, as long as i do it in well educated, repeatable, and verifiable manner.

try it, it doesn't hurt, and you can always go back if you don't like it.

I plan to do just that in the springtime. I'm fully prepared for tuning now having the equipment and a lot more knowledge, thanks in no small way to this site and in particular people like yourself, humpinSS, dirkdiggler, joecar, topless texan, jpfilla and more. It is because of your efforts and great programs from EFILIve that tuning has become a lot easier. I'm certainly looking forward to tuning and will continue to look for help from you guys. I hope that I can make a useful contribution soon.

:thankyou2: :cheers:

TAQuickness

January 26th, 2006, 10:32 AM

More info: http://www.ls1tech.com/forums/showthread.php?t=363392

Beat me to it Joe... FYI that thread starts off very well with MAF fuctionality and how engine mods effect performance of the MAF and ends with splitting hairs.

To summarize that thread, any modification to the engine that effects airflow will have consequense on the MAF. Some mods have greater consequence than others.:cucumber: :banana: :cucumber:

dfe1

January 26th, 2006, 11:27 AM

Let's bat this around--

Assuming that the stock MAF table is correct-- correct meaning that if we put a MAF on a flow bench and its output was the same as the bench's-- there's no need to alter the table. If the mass says the engine is using 300 grams/second of air, then that's what it's using. Now, if we look at commanded versus actual AFR and find that it's off by quite a bit, why do we want to correct it by changing the MAF calibration? In so doing, we're fudging the MAF readings so the PCM will alter fuel flow appropriately. Isn't altering the VE or IFR tables a more realistic way to correct AFRs? If commanded versus actual AFR is off, that's more a function of VE and IFR values than anything else.

If the MAF output is not correct, how do we know, and how do we know how far off it is, unless we test it? The engineers at GM are pretty sharp, and they have to calibrate engines that meet some pretty demanding emissions and fuel economy standards. They're also under the gun to do things cheaply. My guess is that if they could meet these requirements without using a fairly expensive sensor, they would. In turn, that indicates that they consider the self-adjusting aspects of a MAF to be essential, which further indicates it must be accurate. If changes are made that significantly alter the way air flow into the sensor, then some tuning of the MAF table may be warranted.

The IFR table presents a similar situation. If the stock numbers are correct, then altering them is another way of fudging. This isn't meant to imply that fudging is bad-- somethimes there's no other choice-- but it should be called what it is so you can maintain proper perspective on the tuning process.

On the other hand, I've seen many cases in the past, where the injector constant (L98 and LT1 engines) and actual injector size didn't match. The injector constant in the factory calibration had been fudged. I haven't had a chance to flow test my injectors yet to see if actual matches IFR values, so I can't comment beyond that yet.

I've also noticed that when operating in MAF mode, changing VE values definitely alters LTFTs. That means the VE table is part of normal MAF mode. (If you multiply the VE table by 50-60%, the engine will barely start, if at all.) I've also found that simply switching to speed density- no other changes-- really whacks the LTFT values. That tells me that the PCM alters fuel flow when it detects that the MAF has failed. Don't forget that speed density is only enabled if the PCM thinks the MAF has failed. We don't know what other calibration changes the PCM makes when running in "sensor failure mode".

Using LTFTs to tune when in closed loop isn't a bad way to go. The narrow band sensors are surprisingly accurate as long as AFR is stochiometric. They are a complete waste of time at other AFRs. I once dyno'd a car with a wide band, changed AFRs by a full ration (as indicated by the wide band) and the car's narrow band sensors indicated a change of only 25 millivolts. Obviously, the best approach is to use a wide band for all tuning, but if you don't have one, you can get really close with a narrow band sensor (except as noted).

Comments?

TAQuickness

January 26th, 2006, 12:03 PM

Let's bat this around--

Assuming that the stock MAF table is correct-- correct meaning that if we put a MAF on a flow bench and its output was the same as the bench's-- there's no need to alter the table. If the mass says the engine is using 300 grams/second of air, then that's what it's using. Now, we look at commanded versus actual AFR and find that it's off by quite a bit. Why do we want to correct AFR by changing the MAF calibration? In so doing, we're fudging the MAF readings so the PCM will alter fuel flow appropriately. Isn't altering the VE or IFR tables a more realistic way to correct AFRs? If commanded versus actual AFR is off, that's more a function of VE and IFR values than anything else.

Very good point you bring up. Flow on a bench is not the same as flow on an engine. Flow on the bench is uni-directional, on the motor, it's bi-directional. There is quite a bit of detail on this topic in the link Joe posted.

The IFR table presents a similar situation. If the stock numbers are correct, then altering them is another way of fudging. This isn't meant to imply that fudging is bad-- somethimes there's no other choice-- but it should be called what it is so you can maintain proper perspective on the tuning process.

I agree, it's just fugding at this point.

On the other hand, I've seen many cases in the past, where the injector constant (L98 and LT1 engines) and actual injector size didn't match. The injector constant in the factory calibration had been fudged. I haven't had a chance to flow test my injectors yet to see if actual matches IFR values, so I can't comment beyond that yet.

I'm sure GM had their reasons, and it doesn't necessarily make it right.

I've also noticed that when operating in MAF mode, changing VE values definitely alters LTFTs. That means the VE table is part of normal MAF mode. (If you multiply the VE table by 50-60%, the engine will barely start, if at all.) I've also found that simply switching to speed density- no other changes-- really whacks the LTFT values. That tells me that the PCM alters fuel flow when it detects that the MAF has failed. Don't forget that speed density is only enabled if the PCM thinks the MAF has failed. We don't know what other calibration changes the PCM makes when running in "sensor failure mode".

One of the other changes is the PCM reverts to the low octane spark table. Adjusting your spark has a major effect on your actual AFR.

Comments?

No matter your prefered tuning method, you have to start from somewhere. In the case of LSx engines, I find the IFR table is the easiest starting point. If the injectors are stock, leave it alone. If you upgraded injectors, scale the table accordingly. By starting with the IFR table, you know have a single point to reference the rest of your tune to.

Next would be to get the idle in-line. Since the IFR table is now a constant, you can adjust the idle settings preparing you for the rest of your tune.

Next, get your VE table in-line. You now have your IFR and Idle as a constant, your VE should fall into place with relative ease. You must have a VE table in line to base the rest of your tuning on.

Then, if so desired, dial in the MAF. With the IFR, Idle and VE now constants, you can base the MAF table on them.

Does this mean the tune is correct, not necessarily, BUT, your tune will be correct to itself.

No matter what your tuning method, so long as you are consistant, and achive consistant results, then it's good enough for government work.

:notacrook:

Dirk Diggler

January 26th, 2006, 12:07 PM

Let's bat this around--

Assuming that the stock MAF table is correct-- correct meaning that if we put a MAF on a flow bench and its output was the same as the bench's-- there's no need to alter the table. If the mass says the engine is using 300 grams/second of air, then that's what it's using. Now, we look at commanded versus actual AFR and find that it's off by quite a bit. Why do we want to correct AFR by changing the MAF calibration? In so doing, we're fudging the MAF readings so the PCM will alter fuel flow appropriately. Isn't altering the VE or IFR tables a more realistic way to correct AFRs? If commanded versus actual AFR is off, that's more a function of VE and IFR values than anything else.

First of the bench will only measure a straight airflow not the ever changing conditions of the engine and you surely cant account for an revisions even with the stock cam. Why would you alter the ifr the ifr table is a representation of fueling hardware ie the injectors. Lets not forget our widebands are reading AIR and Fuel it is outputing to us the ratio between the two. So yes it totatally plausible to adjust the maf to get you AIR:FUEL ratio in line. The ve table is only used for sanity checking and to my understanding only used really at idle and unstable maps. Ive tried altering the ve table in maf mode at WOT and PT driving conditons and it takes large ve movements to see changes in LTRIMS or AFR something on the order of 4:1.

The IFR table presents a similar situation. If the stock numbers are correct, then altering them is another way of fudging. This isn't meant to imply that fudging is bad-- somethimes there's no other choice-- but it should be called what it is so you can maintain proper perspective on the tuning process.

I trust that at 58 psi an 0 vaccum that my injector flow X lbs/hour. Ive changed injectors and kept it along the same line as the stock GM flow rates but with representation for my injectors so I can assume these are correct. On all the cars i have tuned the ifr table was changed ONLY if the customer had changed his injectors. If they havent I havent ever ran into a situation where i had to fudge that table. I set it and forget it. I tune the car modeling the engine for its air requirements inthe Ve and MAF tables.

I've also noticed that when operating in MAF mode, changing VE values definitely alters LTFTs. That means the VE table is part of normal MAF mode. (If you multiply the VE table by 50-60%, the engine will barely start, if at all.)

At idle the map sensor works faster than the maf and the reason it wont start is because the ve table is being used for idle conditions. Pretty much belwo 4k the pcm is using both tables to figure out fueling so yes you are correct by saying the car wont start. You have actually flooded the engine by telling the PCM the engine is 50% more efficient at 00 rpm than it really is

I've also found that simply switching to speed density- no other changes-- really whacks the LTFT values. That tells me that the PCM alters fuel flow when it detects that the MAF has failed. Don't forget that speed density is only enabled if the PCM thinks the MAF has failed. We don't know what other calibration changes the PCM makes when running in "sensor failure mode".

Comments?

I wouldnt necesarily say the pcm alters fuel. It uses the ve table which may or may not be dialed in for fueling (defualt ve units are in air just like the maf table). With those hardcoded values the calibration engineer coded into those table the PCM thinks the enigne is pumping x amout of air for the given rpm and kpa and decides on fueling. Can this be wrong hell yes that is why we have these tools and are on a neverending quest to dial them in.

Will anyone answer my question

If the car is dialed in in SD mode via ve, the IFR table presumably correct and you plug the maf in and the car goes lean who is to blame?

TAQuickness

January 26th, 2006, 12:50 PM

I'll take a stab at it...

If the car is dialed in in SD mode via ve, the IFR table presumably correct and you plug the maf in and the car goes lean who is to blame?

You are. You shouldn't have plugged the MAF back in.:doh: :anitoof: :jump:

redhardsupra

January 26th, 2006, 12:56 PM

TAquickness, contrary to the popular opinion, MAF is not the source of all evil ;)
i seriously have problems being able to tell the difference between both modes, if i disable the SES light for SD operation. The only time where i can tell the difference is at the track (the one with turns) 'cause SD is a bit quicker to react to minute changes in throttle, which you can only feel while pushing it through a corner and trying to precisely feed it gas.
so in the vain of 'guns don't kill people--people kill people':
MAFs don't fuck up your tunes--people who don't tune MAFs fuck up their own tunes ;)

bink

January 26th, 2006, 01:12 PM

I too was a MAF follower.....yes I admit it. :D (I do believe it's a great sensor when recalibrated as needed)

I was very wrong .......HumpinSS/Dirk was very right.:D

There are a couple of ways to intuitively see the inherent inaccuracies of the MAF:

1.) The existance and utilization of the VE table.

2.) LTFTs and STFTs.

The MAF is an inexpensive, reliable sensor which enables GM to meet federal standards.

The really NEAT part of all this, for me, is how far tuning has come from the old days of spreadsheets and voodoo.
Thank you.... EVERYONE!!!!:master:

:cheers:
joel

Dirk Diggler

January 26th, 2006, 01:19 PM

Voodoo is right spreadsheets are the devil LOL

bink

January 26th, 2006, 01:20 PM

jfpilla

January 27th, 2006, 09:23 AM

bink

January 30th, 2006, 12:55 PM

Joel.
You are joking? Aren't you?
Joe

No, not joking.
I'm not sure what your questioning joe?
Maybe I'm not clearly stating my thoughts/opinion.

I used to think GM had mega dollars and therefore mega instruments to check/verify the MAF. That is to say the MAF, as GM scaled it, was at it's optimum - period.
As I followed threads by HumpinSS, TAQuickness, RedHardSupra, txhorns281, and the rest, I realised they were getting good results with Speed Density tuning. In fact HumpinSS told me many times that I should at least try it - try it you'll like it.

One day jfpilla (That's you!) puts up a post about the importance of accurate injector flow rates and the importance of known, quantitative values. Do you remember this?? Well, something went "Boing" in my brain - damn I hadn't thought about that!! Constants!
So over the course of a few weeks/months I look at countless factory tunes. I looked closely at the ASA tunes (Thanks Dave Farmer and Jess/wait4me) also - since I use the GTP/ASA injectors. Seems like the Injectors are constant and everthing else is tweaked or varible. Airmass Calcs , VE, LTFTs, STFTs, Idle Airflow Trims.........MAF.
We know, or can know accurate injector flow rates, fuel rail pressure and accurate AFR.
As I see it -> we develope the VE table in SD and then IF we want.... go back on the MAF. Scale the MAF so AFR is equal to Commanded and were good to go.
I think this is probably similar to GMs methods (I don't think they use EFILive though.... I bet they wish they could have!!). What I'm amazed by is the way GM was able to crutch the MAF at lower RPM...the aimass calcs/dynamic airflow.
I'm begining to ramble...I'll shut up!:D

I hope this makes sense.
:cheers:
joel

jfpilla

January 30th, 2006, 03:12 PM

I too was a MAF follower.....yes I admit it. :D (I do believe it's a great sensor when recalibrated as needed)

I was very wrong .......HumpinSS/Dirk was very right.

There are a couple of ways to intuitively see the inherent inaccuracies of the MAF:

1.) The existance and utilization of the VE table.

2.) LTFTs and STFTs.

The MAF is an inexpensive, reliable sensor which enables GM to meet federal standards.

The really NEAT part of all this, for me, is how far tuning has come from the old days of spreadsheets and voodoo.
Thank you.... EVERYONE!!!!:master:

:cheers:
joel

Joel,
Seems as if I upset you. Sorry if I did.
I was surprised that you see the existance of the VE table and Trims as proof of the MAF's inaccuracies.
The MAF is only a meter. It's part of a "system". It doesn't nor can it stand alone. It is meant to take up for the shortcomings of a MAP system.
Auto manufacturers would love to eliminate the cost of the air sensor, but have not quite succeeded. It's very complicated to make it work for all driving conditions and R&D is costly. The MAP system does not handle VE changes very well. Hence the MAF was developed, not the opposite. The MAF system is highly accurate for maintaining A/F ratios and GM's system is well respected. If I had a track only car I would get rid of the restriction. For a daily driver though, the meter is better in my opinion.
That's all I was referencing.
Regarding your answer. I agree with it. I like to do the MAF final tweak by getting my LTrims negative by way of the MAF and comparing the results with the Dynair Map.
Regards
Joe:beer:

bink

January 30th, 2006, 04:59 PM

Joel,
Seems as if I upset you. Sorry if I did.
I was surprised that you see the existance of the VE table and Trims as proof of the MAF's inaccuracies.
Joe:beer:
No way am I upset :D.
(We never know intent or mood in these things - bummer :( ).
I look at the retention of an active VE table as a crutch for the MAF - if the MAF was accurate at lower RPM we wouldn't need the VE table and it's overlaid Fuel Trims. It's semantics I guess.

My overall point was the MAF is not perfect and it may need to be rescaled. At one point in time I did believe it was crazy to rescale the MAF - as it was designed/calibrated to function with the airmass calculations. Of course I no longer hold this to be true:nixweiss:

Once my car is back together I'm going to try Closed Loop with the MAF, again. That was my original goal.....2+ (or has it been 3+) years ago!!!

Cheers,
joel

johnsZ06

January 31st, 2006, 02:58 AM

The Misunderstood Airflow Fixture (MAF) is part of a large conspiracy perpetrated by the big three to make tuners pull out their hair and spend countless hours of arguing and debating on the Internet, it's purpose, function and usefulness. So far, I'd say it's working! :mrgreen:

redhardsupra

January 31st, 2006, 04:36 AM

to all the MAF haters: other than the 512g/sec limit and having actual physical presence in the path of air, what are you major issues with it? for a long time it was calibration, but we solved that. i know that's not great in low rpm yet, but i'm working on it. what else?

johnsZ06

January 31st, 2006, 08:32 AM

TAQuickness

January 31st, 2006, 08:49 AM

Can we get it in a color other than black? http://www.z06vette.com/fcalmes/rofl.gif

ROTFLMFAO!

RHS - The MAF is not necessarily a bad thing. Dry shot users need/love it. Other than keeping papers from flying off my desk and deep internet forum discussions of how it works, I have no need for it on my time machine.

joecar

January 31st, 2006, 12:50 PM

So is there a way to run MAF-less with the stock OS and use both spark tables...?

TAQuickness

January 31st, 2006, 12:56 PM

So is there a way to run MAF-less with the stock OS and use both spark tables...?

Copy high to low. Otherwise, I beleive the PCM reverts to the low table under a failed MAF condition.

redhardsupra

January 31st, 2006, 01:04 PM

ROTFLMFAO!

RHS - The MAF is not necessarily a bad thing. Dry shot users need/love it. Other than keeping papers from flying off my desk and deep internet forum discussions of how it works, I have no need for it on my time machine.
i'm just asking because the way MAF gets talked about by it's opponents makes it look so evil like it's something between Jack the Ripper and public transportation...

TAQuickness

January 31st, 2006, 01:32 PM

i'm just asking because the way MAF gets talked about by it's opponents makes it look so evil like it's something between Jack the Ripper and public transportation...

I'd say it's more along the lines of public transportation. It's got it's purpose, but it's not for everyone.

joecar

January 31st, 2006, 01:42 PM

So is there a way to run MAF-less with the stock OS and use both spark tables...?
Copy high to low. Otherwise, I beleive the PCM reverts to the low table under a failed MAF condition.
Oh, that's what I do now; I meant without throwing DTC's.

dfe1

January 31st, 2006, 03:42 PM

I think some of the contributors to this thread need to back up and get a more realistic perspective on the subject. From 1986 to 1989, GM used MAF-based systems on Camaros/Firebirds and Corvettes. Then they got into a pissing contest with Bosch (the MAF supplier at the time) and from 1990 through 1993, L98 and LT1 engines employed speed density systems. Beginning in 1994, GM reverted to mass air systems. Although each of these systems have advantages and disadvantages, there are an awful lot of MAF-equipped cars that run extremely well, so I don't think it's correct to categorically classify a MAF sensor as "evil". It compensates for a variety of environmental conditions and also makes up for all types of tuning errors. And, all things being equal, anyone would have a difficult time determining whether an engine was mass air or speed density controlled if the evaluation had to be done from the driver's seat with no data logging equipment at hand.

Now, when you start dealing with heavily modified engines, especially those with a lot of camshaft, a MAF sensor is really out of its element. For these applications, a speed density system is clearly more advantageous because the pulsing and reversion that's typical of a long duration camshaft can give a MAF sensor fits. But without programs like FlashScan that tremendously simplify tuning, running speed density wouldn't be a viable option for most people. Building spark and fuel maps with the rudimentary systems that were the only choice just a few years ago was tremendously time consuming.

The simple fact is mass air is superior for some applications and speed density is superior for others. In the end, the BEST system is the one that the individual tuner or car owner is most comfortable with.

VetPet

February 1st, 2006, 03:27 PM

Redline Motorsports

February 1st, 2006, 03:42 PM

Yes, it's all about choices and making the best one for your particular conditions or applications. There's no one right way or wrong way....just whatever way works best for the individual. Having said that, making the right choice means having a full understanding of the pros and cons of each method in order to truly take advantage of the best means to achieve the desired results.

That's what a forum is intended to do and this forum and all who contribute to it make it the great place that it is.

:thankyou2: Now it's time for a beer! :beer:

You ain't kiddin! I got more out this post then I ever expected! It put it all on the table. It seems to me that there is more then one way to skin a cat with respect to tuning and what works for some may not work for others. It is truly amazing how many things play into adjusting fuel and timing.

:thankyou2:

jfpilla

February 1st, 2006, 04:05 PM

Oh my God! Relativist tuners.:Eyecrazy:

TAQuickness

February 2nd, 2006, 03:19 AM

It seems to me that there is more then one way to skin a cat with respect to tuning...
Bout 101 IIRC, but that doesn't mean the other 100 are correct :muahaha:

It is truly amazing how many things play into adjusting fuel and timing.

And when it comes right down to it, it's either 1 or 0 :Eyecrazy:

trudynosports

February 3rd, 2006, 03:41 AM

I get the AFR's where I want them in SD mode by tuning the VE. I then tweak the MAF by percentage so that the AFR's match no matter what mode the car is operating in. Most of the time I don't have to change the curve, just add or subtract a percentage of the whole curve.

I also tune Ford EEC's and In the Ford system they rely on the MAF for fuel and load calculations for timing adjustments. For that reason the only correct way to tune a Ford is by MAF adjustments. I use the same prinicples on both Ford and Chevrolet to make sure that the vehicle is thouroughly tuned.

EFILive is great and I use all available tables that I need to make the adjustments that are needed.

Thumper

March 8th, 2008, 06:03 PM

Very interesting thread guys. I must say that from a noob's point of view, its very enlightening. Definitley worth a read.

cmitchell17

March 9th, 2008, 06:08 AM

Yeah it is interesting. So if I took thoes little tubes that direct airflow into the airbox I probably just messed with the Maf. I have a truck so nobody probably knows what im talking about, but its a tube gm put in the inside bottom of the airbox.

Bruce Melton

March 9th, 2008, 08:29 AM

The latest Hitachi sensor is a marvel compared to the old bare wire clunkers in the foiled, screened housings. The new sensor is shielded from reversion and lots smarter. I talked to the GM PCM guys @PRI and they caution on proper placement in the air stream, but are betting the ranch (and the LS9- check out the MAF table for the 08 LS3) on MAF technolgy to to produce predictable emissions (AFRs).
If you watch your fuel trims trying to second guess a maffless tune, it is indicative of the problem. Have watched my carefull prepared SD tune go to hell in the course of a summer evening at the track. Temps drop 25*, humidity changes, and the tune drifts further from reality. Not to say a "right on" SD tune is not great but, if we all lived in Honolulu it would be a different story, and crowded.

redhardsupra

March 9th, 2008, 08:49 AM

hey Bruce, how can MAF be shielded from reversion? isn't the whole idea behind MAF that air goes through/around the hot element, which requires you to have both ends open? could you elaborate a bit?

Bruce Melton

March 9th, 2008, 10:34 AM

hey Bruce, how can MAF be shielded from reversion? isn't the whole idea behind MAF that air goes through/around the hot element, which requires you to have both ends open? could you elaborate a bit?

A few pics> LINK (http://powrmax.com/MAF%20unpub.html)

hquick

April 8th, 2008, 05:58 PM

I was in the process of tuning my MAF after switching back to a stock op system and the whole feeling of the tune felt terrible. I was throwing various codes, it was getting high KR and in general was running terrible.
There's so much info on here....it's sometimes hard to work out which way to follow.
I asked a buddy of mine who works for GM how they go about setting up the their base tunes and dialling it all in.
This is a reply I just got from him.

Checking the MAF frequency and changing the curve to suit should work. I have actually done this once before to improve emissions in an early experimental HSV engine (new air intake completely changed the airflow characteristics). Normally it would be done on a proper test bench with the entire air intake setup - but that isn't going to be easy to do in your case.
A real quick and dirty way to do it is to see how much your fuelling is compensating (for example, -12%), and just pull out 8% or so from the predicted airflow in your MAF curve . If the fuelling heads the right way, then chances are you are on the right track. From there you can fine tune each frequency point as required.
The MAF curve is obtained by testing the entire intake system with the MAF in it, not just the MAF itself. That alone indicates that the intake plays a part in the MAFs response to airflow changes. Otherwise we would just get a curve from the MAF manufacturer and use that.
I'd imagine that the difference is due to changes in airflow/reversion etc around the MAF depending on the geometry of the intake.
As an example: We had a car a while ago that all of a sudden would hardly idle. After some investigation, it was found that a thermocouple had been placed in the intake, about 4 inches in front of the MAF. That was enough to make the airflow so turbulent in the MAF that it was getting airflow swings as high as 50% at steady state.

joecar

April 8th, 2008, 06:21 PM

Basically the MAF behaves like a waveguide with constant+alternating (DC+AC) pulses (waves) going in both directions (interfering with each other to create high/low pressure nodes) and being very dependent on the physical geometry... if you change something in the tract or the motor, then the MAF calibration is wrong...

hquick

April 8th, 2008, 06:24 PM

Thanks Joe..yeah...alot of people say "don't touch the MAF it's a calibrated instrument".
Well for me..this kinda proves it's the (one of) right way to go.

dfe1

April 9th, 2008, 02:38 AM

One of the "challenges" of MAF tuning is having the proper "tools" to get it right. As an example, some "high flow" air cleaner systems introduce vortexes in the intake tract that don't exist with a stock air cleaner. So, at any given throttle setting, how do you tell whether a MAF is reading laminar air flow, or a vortex induced by the air cleaner? The same situation may exist when an aggressive camshaft is installed. Reversion and other abnormal (compared to a stock system) intake flow characteristics may leave the mass air meter reading a vortex rather than laminar flow at various points. And these vortexes may change considerably depending on degree of throttle opening and engine load. So the question is, how do you determine what the MAF sensor is actually reading, and whether it's reading consistently at a particular flow rate? I'm not suggesting that it's impossible to make those determinations, only that most people won't spend the time, or don't have the tools to do it. As a result, many MAF tuners have become known as big wheels because they run in circles.

jetblast

April 12th, 2008, 06:07 PM

i believe the pcms protocol for fueling is a weighted average of all the fueling tables, if and all the supporting systems are working properly, although some tables play a larger or smaller role in computing the final fuel for a given eng. but. above 4krpm the maf has a major role in fueling and more so than the ve table. also if you install a bigger cam, the shape of the maps will change, but no other table will change its shape more than the ve, especially the peak torque section of the map, the maf should also encrease but the basic curve should remain the same unless the track is modified, for example: removing the maf screen. suppose the maf fails at wot, the pcm must be set up so that there is enough fueling and less timing as a safety measure. if you zero out the ve table the eng. will not run. if you compare 2 stock tunes from two types of cars, each one having different intake track routing and different cams and injectors. you will see that the shape of the ve tables will be different and reflect that specific cam and the maf table will also be different but not in the same way, the change is more subtle. in the end having the correct balance is what its all about or somewhat close to it. just my humble opinion, i have only tuned and owned one muscle car since 04. so i'm probably wrong. still learning.

dfe1

April 13th, 2008, 04:53 AM

i have only tuned and owned one muscle car since 04. so i'm probably wrong. still learning.
Quite the contrary, you're undoubtedly right. As has been stated previously, MAF readings are influenced by a variety of factors, and I think the real challenge is in finding a legitimate way to correct MAF readings after camshaft and intake tract changes are made. I think a lot of people cause themselves unnecessary problems because they change MAF tables, when the real problem is the data in the VE or IFR tables. In essence, they're correcting one error that was actually caused by another. At the end of the day, all that really matters is that the commanded and actual AFRs are close enough to be considered the same. So the question becomes, is it better to crutch the VE or IFR tables to compensate for errors in the MAF table or vice versa?

redhardsupra

April 13th, 2008, 07:04 AM

if you wanna find out what's really going on with MAF, SD and tuning using a wideband, read this:
http://redhardsupra.blogspot.com/2008/04/three-airmass-models.html

Bruce Melton

April 13th, 2008, 09:31 AM

TAQ and Marcin and all,

I think what we need to end up with here is an agreed upon MAF "dial in" procedure. There are a few short versions around and some refer to portions of the AutoVE tutorial but for me and others, I think, it is hard to know reference step by step procedure how and where to enter and how to exit the current AutoVE tut. which itself has changed, (thankfully).

B3605 setup in AutoVE should end up @ ~13:1 in what will end up in PE range I assume, and the sum of all the influences in RHS's math models should tune to the 14.7 and ~13 combination that can be tweaked.

After the AutoVE without MAF> MAF dial in> MAF re- enabling> then PE tweaking we seek a happy balanced tune where all the GM guru and tuner work yields smooth safe results. I hope that is what we all want what EFILive is all about.

Some of us are big MAF fans (for various reasons) and mother GM seems committed to them. I for one, feel better if I send a tuned car loose, into the climate extremes we suffer, knowing a MAF (preferably, a big new non restrictive MAF:)) is watching over the tune.

jetblast

April 13th, 2008, 10:59 AM

if you wanna find out what's really going on with MAF, SD and tuning using a wideband, read this:
http://redhardsupra.blogspot.com/2008/04/three-airmass-models.html

that article seems to imply that dynamics of the operating range of a gasoline engine are infinite and so to arrive at an operating model as good as the gm, ford, chrysler guys when modding, would require using their testing facilities, and so therefore using their model as a reference point is worth some coin, coupled with fuel consumption {mpg} info. a reasonable tune for a modded eng. is then possible. so if you have two identical modded engs. with two different tunes one having a bit more bias towards the maf than the ve, if both have good starting, driveability, wot characteristics, and good satisfactory fuel consumption under various temps and altitudes than i would be satisfied, except for wot which if you go the the track being flexible can gain you a .1 or more on any given day. i'm just a beginer and my perception of how things work maybe wrong.

redhardsupra

April 13th, 2008, 12:33 PM

this writeup says few things:
1. we finally know the exact models for airmass in both SD and MAF
2. know how to know how to convert one to the other
3. the only 'starting point' as far as airmass goes is fuel consumption. unfortunately this is the 'noisiest' airmass model we got, so it's gonna take some interesting math to get the junk out.

and to answer Bruce here...
From where I'm sitting, there's not much to agree on here. if you read my derivations, you know the steps that would go into the MAF calibrations:
1. go pure MAF mode
2. estimate airmass from fuel consumption
3. clean the data
4. convert airmass to airflow
5. fit 3rd order poly to the airflow estimations
6. use the fit to generate the calibration for points needed (since start/end/intervals change on different cars)

or, if you already have a perfect VE table, then just convert one airmass model to the other.

joecar

April 13th, 2008, 03:49 PM

A "simple" matter of starting from the "least" number of "unknowns"...

:crash::chair::bash::bangin: :wallbash:

...are there any other "banging" icons...

hquick

April 13th, 2008, 07:36 PM

Lol! that's me in all of those Joe.
Unknowns????...What are 'KNOWNS"?
:Eyecrazy: :throw: :bawl:

jetblast

April 14th, 2008, 02:07 AM

i dont mean to undermine some of the great thinkers here. i have no doubt that my tune is not perfect, but i'm satisfied that i have great fuel economy, i can idle for long periods of time and not foul my plugs, cold and hot starts are normal, winter or summer, and wot, the most fun of all, is giving me great results. now if i could just break 10s!

jfpilla

April 14th, 2008, 02:58 AM

Lol! that's me in all of those Joe.
Unknowns????...What are 'KNOWNS"?
:Eyecrazy: :throw: :bawl:
I think it's as simple as your post #58.
Jetblast,:cheers:

Just one point that I think needs to be plastered somewhere.

You should not and cannot tune VE's with the MAF enabled.
Sorry for yelling!

joecar

April 14th, 2008, 04:25 AM

...

Just one point that I think needs to be plastered somewhere.

You should not and cannot tune VE's with the MAF enabled.
Yell louder.

hymey

April 20th, 2008, 03:11 PM

I think many people do not understand the maf system in these computers. The maf is an accurate way of measuring airflow to an engine but there is nowhere in the software that allows you to tune afrs accurately at every load point.

We only see rpms as the input and hz as the output. The is no tables like we see in a Turbo Nissan where we have a proper fuel map.

That is why the maf table only takes effect after 4000rpm. The throttle butterfly will be all the way open anything above this.

Anything below 4000rpm the maf tables are useless. I can drive on the freeway at 20% throttle and 3000rpms and have low maf readings. Or I could have 80% at 3000rpms and have high maf readings.

I still dont know why GM didnt implement the MAF as the main source of fuel calibration and implenting proper fuel tables.

After all with WOT 4000rpm+ loads the pcm is still using the MAP vs rpm table for fueling calculations.

As discussed already. The only thing we can do is correct calculated frlow rate to actual flow rate.

I know the whole MAF tuning thing is bigger in the states. But speed density is more popular in Aus. I can obtain more accurate WOT fueling with sd as with MAF tuning afrs oscillate at high rpms even after the VE and MAF are both dialled in.

redhardsupra

April 20th, 2008, 03:41 PM

MAFhz is not an output, it's about as much of an independent variable as we got.

as per SD vs MAF tuning, read this: http://redhardsupra.blogspot.com/2008/04/three-airmass-models.html

dfe1

April 21st, 2008, 05:57 AM

Frankly, I think all this conversation is great mental exercise, and although it does lead to a better understanding of system functions, most of it is irrelevant. All we really care about is actual air/fuel ratio being as close to commanded as possible. If you're commanding 14.68:1 and a wide band indicates 14.68:1, what else really matters? If tuner A achieves stoichiometric bliss be altering VE and tuner B achieves it by tuning the MAF table, it really doesn't make much difference-- personal preferences aside.

As for "should not, cannot" tune VEs with the MAF enabled I have to disagree. I've found that the VE tables for MAF and SD are significantly different. Try optimizing a VE table in SD mode and switch back to MAF or vice versa and see what happens. If you tune in SD and switch to MAF, you have to make adjustments either to the VE table or the MAF table. As an experiment, I tuned a stock 5.3 in a truck by only altering the VE table until I got the long term fuel trims between 0 and -4%. So if the fuel trims are where I want them, and the wide band is telling me that what I want is what I've got, how does it get any better?

The MAF systems used from 1986 through 1989 were true MAF systems- there was no MAP sensor installed and no VE table. The 1990-93 speed systems were true speed density systems with no MAF included. The LS systems are actually hybrids that use MAF, MAP and a combination of both, depending on the operating environment.

From a theoretical viewpoint, this is certainly not the most elegant solution, but it's relatively straightforward and it works. I'm not saying this is the "be all, end all" of the subject, but I just don't see the payback in spending all kinds of time working with variables that don't seem to do much besides add complexity to a relatively simple situation. If someone has a good explanation with practical application, please post it.

joecar

April 21st, 2008, 08:44 AM

From a practical viwpoint, if MAF is enabled, how do you determine at any instant if airmass is coming from MAF or VE (you want to know which table to apply the correction to)...?

jfpilla

April 21st, 2008, 09:04 AM

Quote:
Originally Posted by dfe1 http://forum.efilive.com/images/buttons/viewpost.gif (http://forum.efilive.com/showthread.php?p=68389#post68389)
Frankly, I think all this conversation is great mental exercise, and although it does lead to a better understanding of system functions, most of it is irrelevant. All we really care about is actual air/fuel ratio being as close to commanded as possible. If you're commanding 14.68:1 and a wide band indicates 14.68:1, what else really matters?
xxxxxThis must be in SD, so it's fine.

If tuner A achieves stoichiometric bliss be altering VE and tuner B achieves it by tuning the MAF table,
xxxxxThe MAF does not command Stoich.

it really doesn't make much difference-- personal preferences aside.

As for "should not, cannot" tune VEs with the MAF enabled I have to disagree. I've found that the VE tables for MAF and SD are significantly different. Try optimizing a VE table in SD mode and switch back to MAF or vice versa and see what happens. If you tune in SD and switch to MAF, you have to make adjustments either to the VE table or the MAF table. As an experiment, I tuned a stock 5.3 in a truck by only altering the VE table until I got the long term fuel trims between 0 and -4%.
xxxxxNext time you do this disable the MAF and see how badly the car
runs.
-VE's have 3 functions, as far as I know, in an MAF system.
open loop startup.
-Rapid throttle transitions
-MAF failure.
xxxxxxWith your method the MAF better not fail.

So if the fuel trims are where I want them, and the wide band is telling me that what I want is what I've got, how does it get any better?

The MAF systems used from 1986 through 1989 were true MAF systems- there was no MAP sensor installed and no VE table. The 1990-93 speed systems were true speed density systems with no MAF included. The LS systems are actually hybrids that use MAF, MAP and a combination of both, depending on the operating environment.

From a theoretical viewpoint, this is certainly not the most elegant solution, but it's relatively straightforward and it works. I'm not saying this is the "be all, end all" of the subject, but I just don't see the payback in spending all kinds of time working with variables that don't seem to do much besides add complexity to a relatively simple situation. If someone has a good explanation with practical application, please post it.

xxxxxThis is the relativist approach usually argued for by tuners that won't spend the time to do it right. We have tuners that do it right on this forum. I would rather tune it the "best way" possible and avoid the learning out problem .[/quote]

joecar

April 21st, 2008, 10:12 AM

Basically, how do you "correct" some thing based on feedback from output derived from other sources mutually orthogonal to this thing...? :nixweiss:

jetblast

April 21st, 2008, 04:13 PM

i've read that volumetric efficiency continues to encrease up to 20k miles and then begins to fall off, the fellows that tune in op loop first,do you take this variable into account?

hymey

April 21st, 2008, 11:04 PM

The proper way to alter the afr for maf calculation is to dial in the VE table first and then scale the maf air flow output to suit.

I would like to see someone do this with an e38 though. With the MAF connected the afr oscillate at high rpm. You can fix this 2 ways. Fudge the maf table even more to correct the difference in fuel mixtures or go to the VE table and correct it there.

I have tuned using solely the VE table with the MAF still connected and also disconnecting the MAF and tuning the VE table first.

I said previously. The delphi computers use solely a rpm vs MAP table to control injector duty cycle. The MAF is only a patch over the top. At full throttle the MAF gives an output reading which then corresponds back to the VE table to obtain the correct figure required. SO why have it there at all.

I understand the VE table is only accurate in the weather conditions it was tuned in and that a correctly scaled MAF will correct any slight changes in air pressure and temperature due to the simple fact that air flow is a much better way of calculating and tuning for optimum conditions than Manifold air pressure.

I believe some earlier models used a MAF vs rpm table for fuel mixtures. No MAP sensor existed. Why didnt GM keep using this type of MAP. The Japanese use it religously on all there performance cars and with the 6.0L having 90mm MAF sensors it would be nice to see a table like this in the later model computers.

Some engineers I studied with a while back always believed the manifold air flow was the best data to collect for accurate fueling.

But all I see is people perservering with scaling MAF tables by a few percent here and there.

Does anyone see my point?

hymey

April 21st, 2008, 11:21 PM

MAFhz is not an output, it's about as much of an independent variable as we got.

as per SD vs MAF tuning, read this: http://redhardsupra.blogspot.com/2008/04/three-airmass-models.html

I stand corrected. Hertz isnt and ouput but data from the MAF sensor. With the air/flow being the output function in grams per sec.

Very interesting write up.

dfe1

April 22nd, 2008, 01:55 PM

Does anyone see my point?
I definitely see your point. I believe GM abandoned the MAF-only system because of issues with response time during rapid throttle transitions. The older MAF-only systems (1986-89) had excellent drivability characteristics, but I'm sure the LS-style MAF/MAP systems offer improved fuel efficiency and lower emissions.

hymey

June 2nd, 2008, 01:16 AM

I tuned a VE Maloo HSV today with LS2 and e38, M6. Apart from spending 6 hours diagnosing why the motor ran of 4 cylinders.(A broken wire from the heavy handed exhaust fitter) I finally got it running on 8 and started to tune it mafless, we ran into some other minor tuning issues which were quickly sorted but once the sd tune was complete. The MAF was plugged back in. To my surprise the car now idled at 16.3:1 compared to the mafless tune of 14.7:1. Topend mixtures were spot on at 12.9:1 but I had to scale the bottom end of the MAF to get fuel mixtures spot on. And just to prove that this is the correct way of MAF tuning I tried to alter the VVE table(with the proper one saved) to alter afrs at idle and light loads, but It didnt help. Scaling the MAF sore immediate results. So when your MAF is out like this adjusting the VE tables won't help. It required significant adjustment. So I am all in favor for the mafless tune first then maf calibration last!:hihi: Not fudging figures to get required results:bad:

joecar

June 2nd, 2008, 03:04 AM

Joel, good job...:cheers:

jfpilla

June 2nd, 2008, 04:08 AM

Joel, good job...:cheers:

:rockon:I'm with Joe. My favorite method.

swingtan

June 2nd, 2008, 10:16 AM

So I am all in favor for the mafless tune first then maf calibration last!:hihi: Not fudging figures to get required results:bad:

I'm with Joel here as well. Over the past couple of weeks Joel and I have been talking about the 90mm MAF and how it works with the E38 ECM. I know there are a lot of guys out there that swear by the "SD Rules" philosophy, but things are changing with the E38 ( at least for the moment ). Here's a few points that I've come up with on this....

The 90mm MAF is large enough to not be a significant restriction is most applications. Sure if you are chasing every last kW / HP for a full race car, it may be an issue, but for most street cars it's not too bad.
The E38 ECM is much faster than the LS1 PCM. It seems to suffer much less from the old "MAF Delay" issues seen in the earlier cars. From what I've read and heard, the biggest advantage of SD is the responsiveness that comes with it. Both Joel and I have tested E38's and found that there is not much between a correctly set up SD tune and a correctly set up MAF tune.
The new Transient Fueling tables for the E38 seem to rely heavily on MAF data. Turn off the MAF in the tune and you turn off Transient fueling as well.
In std. form, the 90MM MAF is calibrated to just over 500g/S of air. Again, this should be OK for most street applications. If you need to measure more than 512g/S of air, then it may not work for you.

There is one big issue that the MAF suffers from. With a SD tune, you can place the IAT sensor in an optimal place to get accurate air temps while reducing the effects of heat soak. The 90mm MAF has the IAT sensor built into it and it can suffer from heat soak. You can cut the IAT sensor wires and splice in a remote mount unit, or you can modify the stock unit to reduce the effects of heat soak. I had a play on the weekend and came up with a mod that may help. Rather than clutter this thread, I'll post up some pics in a new thread.

Simon.

dfe1

June 2nd, 2008, 03:23 PM

For what it's worth, I think the only significant advantage of SD over Mass Air is more consistent fuel control at idle on engines with long duration camshafts. Tuning LS1/E40/E38/E67 systems can be a bit confusing because the processor may be using speed/density calculations, MAF readings or some combination thereof to determine fuel flow. That being the case, the tuning sequence noted in previous posts is the only one that really makes sense. Since injector flow rate is a known constant, it's best to start by making sure IFR reflects actual injector flow. With that done, the next logical step is to disable the MAF and optimize the VE table. Following that, the MAF table can be optimized. When that's done, switching between Mass Air and speed/density should have a minimal effect on fuel trims-- until atmospheric conditions change.

Chuck CoW

December 25th, 2008, 09:09 AM

I know you guys thought this thread was long gone...

Sorry to open this back up, but..........I've got an interesting question that I've always thought about and could never resolve a solid answer for myself.

Let's take a stock corvette and note the fuel trims after a drive.

After adding a CAI and Headers, the fuel trims rise by about 8% or so clearly reflecting that we've added airflow and the compensation trend is for the pcm to need to add about 8% fuel to bring it back in line.

This seems to hold true for LS1 and E40 pcms using a conventional VE table and a MAF.

Back when the E38 first appeared in Vettes, I noticed that I'd add the same CAI and Headers and would take her for a drive and the fuel trims would be the opposite....The LTFTs I was tracking would go negative indicating that the pcm had subtracted fuel as if it was too rich...

But Why? In the LS1 example we've ADDED AIRFLOW and fuel trims went up indicating the need for more fuel.....

Why is it that in the E38/E67 controllers ADDING airflow caused the trims to dive negative? Doesn't adding airflow dictate adding more fuel?

While I've got plenty of these vehicles under my belt now and I've got it working to my liking....I often wonder if I've missed something simple here....

At times I've assumed that the new generation of MAFs gets overstimulated by an increase in airflow and/or over reacts at low airflow....or maybe that a vortex of air is responsible for the overstimulation?

Maybe it's just because the math and the lack of a conventional VE table has changed?

In principal, they should be the same....and it threw me for a loop for the first bunch I tuned.....But, then it just became the same old "just make em' happy" procedure....

Anyone ever thought about/notice this besides me?

I welcome your thoughts.
Chuck CoW

johnsZ06

December 25th, 2008, 01:44 PM

Anyone ever thought about/notice this besides me?

I welcome your thoughts.
Chuck CoW

I've experienced the same thing with my 07 Z06. It had a CAI and headers plus a ported TB. Monitoring the trims showed -10% on average. I was like, WTF? It was completely opposite on my 02 just as one would hypothesize.

What does it mean? Hell if I know but, like you, would like to hear from the pros!

Redline Motorsports

December 25th, 2008, 04:03 PM

Chuck CoW

December 25th, 2008, 05:45 PM

Chuck,

One thing to consider is that when making changes like a CAI to a "factory" calibrated air system, its not just the increase of air that effects the MAF's but also the change in airflow through the MAF has changed. Maybe more so with the new style MAF....

I think the other issue is the coefficients that are used for fuel computation in the E38/E67 process. More factors are used in the final calculation that we forget have an impact.

I agree with the "make it work" method sometimes!

HT

No doubt...I've considered that....But, I realize we've altered not just the MASS or VOLUME but, the flow characteristics....

Eventhough, it still should be as simple as we've added MORE air and with that the trims should reflect it by turning positive...

Another thought is that while we've obviously added more air (especially at WOT) but, maybe we've significantly added more WOT air, but with the larger more efficient flow potential, we've actually lost velocity in the idle areas resulting in slower air or that the meter just isn't efficient at the lowest air flow rates resulting in the negative trims???

Make sense to anyone?
Chuck CoW

Aint Skeered

January 11th, 2009, 02:44 AM

I have been doing a maf only tune on my race car. I am bypassing the ve table to where anything over 400 rpm's is maf derived.
I went to the track and it was way lean with just maf tune in stock form. Injectors were scaled using marcin's spread sheet. I have 30 lb/hr redtop injectos .
When i first made a pass at the track ,(no dyno yet) my car was lean. WOT read around 14.2/1 which I only made a partial run to watch the log.
Instead of dicking with the table , I hooked up my old mass air flow translater and set it at 14% rich for wot and 10% pt. Went back and logged it, 10.2/1 air fuel at wot.

I pulled it back to 8% rich and the air fuel ratio went to 12.2- 13.2/1 in that range through out the rpm range.

the problem is that my maf was reading almost 11,000 htz and my timing went down from a commanded 26deg to a whopping 2.5-6 degrees at wot . It showed 1.2 deg of knock when I first started into the throttle but then the knock went away. as soon as I went to wot is when the timing went way down to the single digits.

Last night I took the Maft off and scaled the injectors -3% to see what it would do with the timing and launched the car in my driveway( neighbors love me) . ON the log, my timing bounced between 24 down to 16.5 and back up to 24 with 0 knock.

Air fuel went to 14.1 again , I was thinking that I need to drop the injectors down a little more to see if that helps.

I am a little on the lean side through out the tune idle all the way up the rpm range , I command 14.63 at idle and it see's 16.5/1 up and down a little from there. I command 12.0/1 at wot (starting on the safe side) and am seeing 14/1.

I tried to do a auto ve tune first and no matter what I tried the car was so lean that it would not idle. I added the 15% to the ve table and it just wont stay running and when I touch the throttle , it bogs down and dies.

THis is why I started fooling with the maf tuneing. Less tables to fool with and changes with the weather.

I would not fool with injector flow rate on my Trans am that I drive, my race car is Idleing great and doesn not stall or surge when I come from high rpm back to idle with the maf only tune in it.

Am I completely wrong in thinking of playing with the inj. flow rate to get it in the air fuel that I want?

joecar

January 11th, 2009, 09:10 AM

Aint Skeered,

Do what works for you...

there may be something going on that is not immediately apparent (maybe we need to look at your tune/logs again to figure it out).

Also do keep in mind that a racecar is different than a daily driver...

the racecar spends 95% of its time at idle or WOT, whereas the daily driver spends 95% of its time at idle or part throttle...

however, having all the tables correct has the following benefits (for both racecar and DD'r):
- part throttle driveability/repsonse of the the daily driver is better/improved (tip in, tip out, cruise, coast, ...),
- WOT AFR's are easier to set (what you edit in B3618/B3605/B3647 is the actual output AFR you see),

The tables all work together... so there are many combinations of values that will produce desired results in most cases...

...but if that is not working, then do what works... tweaking the IFR is not necessarily wrong, it is another method.

Cheers
Joe
:)

dfe1

January 11th, 2009, 03:40 PM

Aint Skeered-- and anyone else who's listening--

As joecar has noted, "Do what works for you". There are all kinds of theories about tuning-- some are right, some are wrong and some are both, depending on the situation. The philosophical problem I have with altering IFR is that it's the one variable that you can tie to an actual known value. On the other hand, I haven't found conversion factors to be all that accurate, and I'm pretty sure that some of the factory IFRs have a fudge factor built in. As an example, I have a set of LS2 injectors installed in a 5.3-liter truck engine. With the stock injectors, fuel trims were in the 0 to -4% range. Afer installing the new injectors and changing the IFR table, fuel trims were positive 10%. Fuel rail pressure is the same as test pressure, nothing else was changed, so the only thing that made sense was to change IFR.

Something else to consider-- on the old mass air systems, altering IFR was the only viable option because these systems didn't have a VE table and working through the mass air calibration tables was a painfully slow process. I've done a lot of chips for these cars using changes in IFR to dial in air/fuel ratios and gotten the results I was after.

In spite of all the theories and explanations, if wide band readings and commanded AFR are the same, it doesn't get any better than that. Someone can tell you that everything you're doing is wrong, but if the results are right, that's all that matters. Just be sure to keep accurate notes so that a month from now, you'll know what you did and why.

Aint Skeered

January 11th, 2009, 04:18 PM

Thanks Guy's. I am dropping my ifr a total of 6% and I added 20% to my voltage correction table . I am going to try that Wensday night at the track to see if it puts me close. I also set my pe to command 1.22 eq to start. I am going to keep modding my Ifr untill I get air fuel to match commanded and then start reducing the fuel in pe.

I do have a little stumble on tip in , I guess that is going into pe mode. Any suggestions on getting that out? I only have the log of a short launch in my drive way with the tune that is in it now, Also can you see why on my log the timing at wot goes to 24 then down to 16.5 and back to 24?

Oh yeah, on the few cars that I do tuning on I save every tune with a discription. The files add up but untill I get one I am happy with , I save them before I change them.

The log is of the tune with -3% on fuel injectors.
The -6% is what I am going to load and try out.

Just so you know what I have for an engine and trans. It is a 347 with 11.63 /1 compression, cam is 239/243 at .050 with .612 lift int. .610 lift exh 112lsa 110 icl.
I have a truck intake with a 75 mm t/b that seems be not in need of porting. It is different then car t/b's and has a 3/16 th hole in the throttle body. It Idles really well as far as not surging but does seem to have a cleaner sound to it when it is closer to 14.7
When it is close to 18 /1 it still idles but it is not a clean lope.
Trans is a th350 with a 8" converter.

My timing is copied from my Trans AM which is a 6 spd. Will the th350 want a different timing table to hit the converter harder?

joecar

January 11th, 2009, 06:49 PM

in spite of all the theories and explanations, if wide band readings and commanded afr are the same, it doesn't get any better than that. Someone can tell you that everything you're doing is wrong, but if the results are right, that's all that matters. Just be sure to keep accurate notes so that a month from now, you'll know what you did and why.+1.

Aint Skeered

January 12th, 2009, 01:45 AM

Thanks Joe. I am sticking with this method for this car for a while to see how it responds at the track. I may try to fool with the ve tables if I ever get on a dyno but its to hard with out being able to drive the car on the street.

I have a friend with a 408 ls1 that he had tuned by a pro and that is what gave me the idea for maf tune. His car runs and drives perfect and its all maf. The tuner is use to doing fords and this is mostly how he has to do them from what he told me so he stuck with that method.
His car drives really good with no surging also.

SSpdDmon

January 12th, 2009, 08:27 AM

I offer you another option (might get some flack for this - but oh well).

1-Disable VE by dropping MAF threshold from 4,000rpm to 200rpm.
2-Using WBO2, alter IFR table (down for more fuel - up for less) based on stock MAF curve (extend top end if necessary) and %AFR error. Rinse/repeat 2~3 times if necessary.
3-Unplug MAF and tune VE with newly developed IFR table.
4-Plug in MAF, restore 4,000rpm threshold and enjoy.

Now, timing won't shift grams/cylinder calculations from altered MAF tables. A4 trans pressure calcs too. Basically, anything that refers to MAF input for load calculation. :)

mr.prick

January 12th, 2009, 08:57 AM

Or you can set your injectors, "Disable VE by dropping MAF threshold {B0120} from 4,000rpm to 200rpm" and use BEN against {B5001}.

this is easy with RTACS without RTACS i suggest increasing {B5001}
by X amount first so you don`t run overly lean.

after injectors are set and Auto VE, this is your best bet. IMO
"Auto MAF" :hihi:

joecar

January 12th, 2009, 08:57 AM

Flack is not necessary... it will be interesting to see how close the IFR table gets. ;)

Aint Skeered

January 12th, 2009, 10:04 AM

mr.prick

January 12th, 2009, 10:17 AM

I have never tried messing with Rtacs, could you go a little further into what to do?

RTACS works with the RoadRunner LS1 Realtime Emulation PCM. (http://www.moates.net/product_info.php?cPath=53_56&products_id=105)
http://www.moates.net/images/box.jpg

Aint Skeered

January 12th, 2009, 01:39 PM

I dont have the road runner. thanks anyways.

SSpdDmon

January 12th, 2009, 07:53 PM

I am going to look at this again tonight and try them out. Not sure which way yet but if you can go more into detail on both methods as I dont understand what rinse and repeat meens or what you meen by setting AFR %error and extending the Maf curve.

Mr Prick, I have never tried messing with Rtacs, could you go a little further into what to do?

Thanks guy's., I am leaving work to go home. I will check back in a couple of hours . Thanks, Chad.

Rinse/repeat simply means, after you go out and log your data, upload the new tune with changes and log again. Make changes and upload that new tune. By the 3rd time around, it should be pretty close.

As for further detail....all your doing is logging the parameters of the table your changing along with the data you need to make the changes. So, in this case, you'd log MANVAC, WBO2 AFR, and Commanded AFR along with the normal stuff. AFR% Error for IFR table = Commanded AFR / WBO2 AFR. That way, if you see 15:1 when you're commanding 12:1, the result would be 12/15=0.8....which is saying reduce that cell by 20% to keep the injectors open 20% longer. If it was the other way around (seeing 12 when commanding 15), it'd be 15/12=1.25.....which is saying increase that cell by 25% so the injectors only stay open 75% of the time they were. Make sense?

Since there's only a handful of cells in the IFR table vs. the MANY cells in the MAF table, it shouldn't take too long. One trick is to use your filters so that you're focusing on the data in the middle of the cells. In other words, for the 35kPa cell, I'd filter out any data above 36kPa and any data below 34kPa. Filter out any transitional throttle (TP% is changing more than 3% over 500ms) along with any lower airflow scenarios (i.e. RPMs less than 1800 or so). You'll see the new IFR shape start to take place...

mr.prick

January 12th, 2009, 08:30 PM

As for further detail....all your doing is logging the parameters of the table your changing along with the data you need to make the changes. So, in this case, you'd log MANVAC, WBO2 AFR, and Commanded AFR along with the normal stuff. AFR% Error for IFR table = Commanded AFR / WBO2 AFR. That way, if you see 15:1 when you're commanding 12:1, the result would be 12/15=0.8....which is saying reduce that cell by 20% to keep the injectors open 20% longer. If it was the other way around (seeing 12 when commanding 15), it'd be 15/12=1.25.....which is saying increase that cell by 25% so the injectors only stay open 75% of the time they were. Make sense?

this is good advice for {B4001},
a calc.pid comes in handy here commanded/actual ("reverse BEN factor").
to overcome a rich condition with {B4001} you must increase the values and,
vice versa for lean.
also you can change {B3701} with BEN, which may be easier for you.

IMO
it is easier to alter {B0101} to a set {B4001} than the reverse.

joecar

January 13th, 2009, 04:39 AM

Good points... B4001 is in "reverse"... increase B4001 to go leaner.

Aint Skeered

January 13th, 2009, 04:41 AM

Rinse/repeat simply means, after you go out and log your data, upload the new tune with changes and log again. Make changes and upload that new tune. By the 3rd time around, it should be pretty close.

As for further detail....all your doing is logging the parameters of the table your changing along with the data you need to make the changes. So, in this case, you'd log MANVAC, WBO2 AFR, and Commanded AFR along with the normal stuff. AFR% Error for IFR table = Commanded AFR / WBO2 AFR. That way, if you see 15:1 when you're commanding 12:1, the result would be 12/15=0.8....which is saying reduce that cell by 20% to keep the injectors open 20% longer. If it was the other way around (seeing 12 when commanding 15), it'd be 15/12=1.25.....which is saying increase that cell by 25% so the injectors only stay open 75% of the time they were. Make sense?

Since there's only a handful of cells in the IFR table vs. the MANY cells in the MAF table, it shouldn't take too long. One trick is to use your filters so that you're focusing on the data in the middle of the cells. In other words, for the 35kPa cell, I'd filter out any data above 36kPa and any data below 34kPa. Filter out any transitional throttle (TP% is changing more than 3% over 500ms) along with any lower airflow scenarios (i.e. RPMs less than 1800 or so). You'll see the new IFR shape start to take place...

so at 100kpa it is at 13.67 when commanding 12.0 , that is 12%out so I would subtract 12% from what I already have subtracted .

That is just a question, I am going to take a look at the logs and see if i have what I need.

Thanks.

Aint Skeered

January 13th, 2009, 04:41 AM

Good points... B4001 is in "reverse"... increase B4001 to go leaner.

That is how I have been doing it, Learned that after getting efi live and that is how Futral had my trans am tuned from IFR tables.

SSpdDmon

January 13th, 2009, 02:56 PM

so at 100kpa it is at 13.67 when commanding 12.0 , that is 12%out so I would subtract 12% from what I already have subtracted .

That is just a question, I am going to take a look at the logs and see if i have what I need.

Thanks.
Again - keep in mind 100kPa on the MAP sensor is probably 0 or 1kPa in MANVAC. MAKE SURE YOU'RE USING MANVAC AS A REFERENCE WHEN ADJUSTING IFR!!! :) So, assuming you're commanding 12.0:1 at WOT and you're seeing 13.67:1, you would adjust the 0kPa cell of IFR down by 12.2%.

MAVNAC 0kPa = WOT
MANVAC 75kPa = idle

Aint Skeered

January 13th, 2009, 05:17 PM

I am not using the long term fuel trim pids in my black box as my nova that I am tuning does not have narrow bands. Could I take them out of my options ini and replace them with manvac?

Another question, can you log wideband through serial cable in pass through mode yet?

5.7ute

January 13th, 2009, 05:34 PM

Aint Skeered

January 13th, 2009, 05:56 PM

ok I think I got it right in my options. I replaced the eops with cylair , Longterm 1 wiht dynair and also longterm 2 with manvac.

How do I go about manually validateing serial pids ? Just select pids and plug into car to validate?

joecar

January 13th, 2009, 06:00 PM

Connect to car,
select pids,
save pid selection to file (for future reference),
File->Connect,
Info->Validate PIDs.

Aint Skeered

January 13th, 2009, 06:46 PM

I will do that tomorrow Joe, Thanks. You guy's have been lots of help, I have learned a lot the last few days.

I will post results of how the nova runs tomorrow night if i can get the tune done in a few passes. Hope to be close enough to run the bracket race tomorrow night.

Aint Skeered

January 15th, 2009, 03:54 AM

Races were cancelled after I made the 90 mile trip. The freeze busted the tracks water mains. I will try again later.

joecar

January 15th, 2009, 07:20 AM

:bawl:

Aint Skeered

January 18th, 2009, 04:48 AM

Went to the track yesterday. car was pulling timing again but I figured that out. Tq management in the transmission even though I dont have a 4l60 in it, (th350) was pulling timing. I also dont have a vss so the car did not know it was moving . I turned everything that I could find off that could pull timing and that fixxed it. with tq mng. I ran 12.06 @ 110 mph.

After fixxing the timing issue It went 11.24 @ 119.5mph with a 1.62 60 ft. Not spinning, the car is leaving like it has a 2 step. Intake air temp was at 115+ leaving the line and it was weak off the line. once I go wot it leaves soft and Then breaths a good gulp of air in and its like nitrous hits it. air fuel on that pass was around 12.0/1
next pass was a 11.12 @ 119.8 with a 1.59 60 ft leaned it out to 12.3/1
After that pass I pulled it back to about 12.6 but have not read the data logg on these yet. It reacted to nice with a 11.05 @ 120.2 and a 1.54 60 ft. (still have that 2step going on) and I was so wanting that 10 anything that I went back around without changeing anything. Car had a long break to cool off since a friend of mine smashed his oil pan ,the track crew spent an hour cleaning up.

After the cool down(not sure yet on iat yet) my car left with a 1.57 60 ft(still hesitateing) and ran 10.96 @ 120.69 mph.

I am moving my Iat sensor and my filter all the way out by the grill to get the hot header air away from going into the engine. That should fix that 2 step feeling and ram some air in at the same time.