Cruise AF and VE tables

[Telco]

2000 Chevy Silverado 5.3L auto

After playing with my computer settings, I've been able to limit how rich the truck gets, it now goes no richer than 12-1. But, after a long cruise with the scanner going, I've found that it also goes no leaner than 14.68-1. Is there a setting that will allow me to go leaner in cruise?

Also, in the VE table. What is the effect of a cell getting a larger or smaller number? I've searched all over and not been able to find anything that clearly says "if this number goes up X happens, lower and Y happens." Any help would be appreciated. The work I've done so far has worked wonders for responsiveness and WOT power, but I've not been able to increase mileage by a single drop per gallon. And, I promised my dad I'd get him from 19 hwy to 23 hwy when I return his truck. I'd like to do it with programming but am fully prepared to start slapping in hard parts if necessary :rockon: .

I will admit that I've not had time to read the whole tuning manual (I did print it out :D ) so if anyone says that my specific questions can be answered by reading the manuals I'll buckle down on them this weekend.

Thanks for any assistance.

[joecar]

Increasing VE table means the PCM calculates a greater cylinder airmass, which causes the PCM to calculate a greater fuelmass to meet the same specific commanded AFR... so if your engine's actual physical VE has stayed the same, then increasing the VE table causes the actual measured AFR to go richer.

If you run OL:
If you get the VE table dialed in (commaned AFR equals actual AFR), then you can run leaner by making the commanded fuel open loop table (B3605 or B3647) leaner in the cruise regions... (but do a safe amount of richness in the load/wot regions).

[Mr. P.]

:iamwithstupid: I am repeating Ben here from the EFI101 class this summer... he shared that he has a 5.3L EC Silverado and has been playing with lean cruise ideas in his tune; his observation/suggestion was to first use a dyno and tune the vehicle's AFR & timing for max power/efficiency, then after your normal tune was complete revisit the half-dozen or so cells in the VE table that the vehicle operates in during a typical cruise situation and reduce their values (lean it out) until you see a measured 5% drop in HP on the dyno. He said that with his truck it turned out to be about 15.4:1 and if my memory is correct I think he said he gained an honest 2-3 mpg without adversely affecting driveability. But only modify the cells that are low-load, the motor will not tolerate being run that lean if there is any load present (you'll build up a lot of combustion chamber heat).

Mr. P.

[Lextech]

Joecar---I am not understanding something. If we want to run slightly leaner in low load cruise cells--How does B3605-Commanded Fuel Open Loop help us? I am not disagreeing, I just don't understand. My dad has a 99 5.3 Silverado and I have lowered the O2 switch points in the 0,8,16 boxes. He doesn't care about performance at all, only low load cruise fuel mileage.

[joecar]

Joecar---I am not understanding something. If we want to run slightly leaner in low load cruise cells--How does B3605-Commanded Fuel Open Loop help us? I am not disagreeing, I just don't understand. My dad has a 99 5.3 Silverado and I have lowered the O2 switch points in the 0,8,16 boxes. He doesn't care about performance at all, only low load cruise fuel mileage. You're right, I asssumed OL... :doh:...I don't know what happened, I'm in OL by habit...

my bad, I'll retract/edit the 2nd part of my post (see my edit)... :redface:... I need more Monster/Jolt... :idea:

[Telco]

Outstanding. I'll leave the factory VE alone then, aside from the few cells for cruise. Unfortunately I can't get that much dyno time and don't have a wideband, so I won't tweak far. I've seen the results of a lean engine, and that's something that has been scaring me about doing this. Luckily low mile 5.3s can be had in my area complete for 900 bucks, from salvage. And I'm talking computer, harness, everything needed to put one into a non-computerized rig :muahaha: :cheers: :D :D .

[ScarabEpic22]

Good info, Ill do some logging this week on my TrailBlazer 4.2L and see if i can reduce the VE in cruise areas for more mileage.

[Telco]

Have a question on the fuel/air mix now. There is a field where you set the fuel air mix stoich number, and on my truck it was set to 14.68. I adjusted it to 15.5 at the same time as adjusting the VE tables on the assumption that since my data log didn't go over 14.68 in lean that this might be stopping it. But, after doing this and setting the truck up with a lower VE number in the cruise cells, I'm seeing a little worse mileage.

What affect is there to the computer if the stoich number for the fuel used is adjusted? My assumption was that it would allow it to run leaner, but now I'm thinking that it's assuming that an O2 voltage of .450 is 15.5 instead of 14.68, and is still trying for a 14.68 mix due to other tables in the computer. Does this sound logical, or am I interpreting the results wrong?

[Telco]

Anyone? Anyone? Bueeeeeeeeeler? Heh heh...

Well, if nobody knows I guess I'll find out as I'm going to change ONLY this parameter and see what happens. Last mileage check was 15.5, but I'm not sure if it's due to the program or the extremely cold weather we've been having. I'm not one to let the engine idle, but since it's been so cold I've been very easy on the engine until the temp needle deflects, and the danged thing doesn't get warmed up until I'm almost to work so I'm afraid that the last 2 weeks it's been in warmup mode more than it's been in closed loop operation.

[5.7ute]

Changing B3601 to 15.5 tells the PCM that the AFR is 15.5 to 1 at an EQ of 1.0. This will stuff up all your fuelling calculations & make the engine run richer not leaner.

[Telco]

After much consideration I came to the same conclusion. Luckily for me, looks like that particular save didn't take. When I went in to modify it, found that the FA mix was still 14.68. Going to leave that one alone. Starting to think that the Mileage was down due to mileage WAS down due to the extreme cold. Danged thing takes forever to warm up compared to my own electric fan having truck. It's really getting to be time to install electric fans on it, just gotta convince Pop that it needs to be done. Thanks.

[Telco]

OK, next challenge. Found that the max retard was set to 8 degrees, and I was hitting it. Adjusted the max retard to 12 degrees and backed my high octane table back 3 degrees. I've lost power across the board, but am now getting a max retard of 8.7 degrees. Before this latest adjust I was able to spin tires through first and into second, and flooring it at 70MPH pushed you back in the seat, and it's not quite doing that now.

Looking at the data logs, I see that the same timing tables are being used under different load situations, meaning that the timing will be in a particular cell both when there is no retard, and when retardation is close to max. This tells me that there is some other field that affects this. Can anyone point me in the right direction on which other table I need to be looking at? Ideally I'd like to see timing retarded around 6-8 degrees while running 87 octane, the idea being that I could run one set of timing maps, with the computer retarding timing to compensate for 87 vs 93 octane. So, I need to find whatever other table is adjusting the final timing in relation to, say, throttle position, so I can figure out what adjustments need to be made to get the maximum possible timing regardless of octane rating, with some insurance to boot.

Comments or suggestions? Thanks.

[joecar]

Telco,

You may have to log the spark pids: the pids whose names begin with "EST_".

These should show you where the timing is coming from or going to.

[Telco]

Excellent, thanks. I'll work on that, be a while before I get to it and get back on here though.

[joecar]

We'll be here. :cheers:

[Telco]

K, I pulled the info with the EST logs, and don't see what I need to adjust. And, it pulled even more timing on the latest run. Bounced off 12 degrees of retard this time, but think it just barely went past 12 degrees. I can email a copy of my current tune and log if anyone cares to assist with this. Thanks.

[joecar]

Post tune file and log files.

[Telco]

How do I go about posting the files? I can email, but have never posted anything other than a picture.

[joecar]

Press the Go Advanced button at the bottom of the pane titled Quick Reply;
then scroll down to the pane titled Additional Options;
press the Manage Attachments button;
press one of the Browse buttons, find the tun file you want to post, press OK;
repeat using the other Browse button for the log file, press OK;
press the Upload button, wait for the upload to complete;
in the Manage Attachments window, click Close This Window;
finish typing your reply text, submit the reply.

[Telco]

Superior! This is the first board I've ever been on that allows a direct attachment upload. Here's the file, and thanks for any advice.

[joecar]

I'll take a look when I get home tonite.

[Telco]

Excellent, thanks. Main goal here is max fuel efficiency between 1600 and 2400 during cruise conditions, max power under other conditions. And I gotta finish this up quick, Pop's kinda hinting around that I've had his truck too long. And I agree, I've had that thing waaaaay too long. Slow as it is, I miss my S15 ext cab, and it's almost roadworthy again.

[joecar]

I'm not going to be home until pretty late tonite, so I be in "dead-mode"... :eek: ...but we'll see how I go... :notacrook:

[joecar]

I got a chance to look at your log very briefly just now, it shows lots of knock retard (very bad for your motor)...
I think you're running too lean, and you have virtually no PE;
your tune shows you're too lean, and you have too much spark advance;
you should be able to hear it pinging.

Too run lean cruise, it will be easier to run in open loop and set up B3605 to be lean at low-mid MAP; but at high MAP you want to be rich (so that you can accelerate without pinging); you will also need to enable PE at a lower throttle (say 65% below 3600 RPM and 35% above that), and richen PE also; your hi-octane spark table has too much advance at higher airmass... I think at your highest airmass you will want no more than 25-28 degrees... you want to ramp up to that as RPM increases.

My $0.02.

I welcome comments/opinions from anyone else... :jump:

Cheers,
Joe
:cheers:

[Telco]

You'd think if it was running too lean it would be getting better mileage, it's gotten a bit worse. Power was actually very good until the last tune when I pulled some timing. The thing about the knock retard, it pulls more or less timing for the same cells, and I don't understand what is making the decision that this time on WOT on a flat road no wind at 4500RPM it'll pull 6 degrees, but that time on WOT on a flat road with no wind at 4500RPM it'll pull 12 degrees. Something in there is different, and the only thing I'm aware of is outside temps were about 20 degrees different. I know you only have the one log, but I had two to look at.

Think it might be time to revert to the original tune and strike out again then. I'll recheck this post while working on it, but will definitely get the original fuel/spark tune back in first thing. I've actually not heard it knocking, but since the knock sensor will pick up on it before I will and I know it's been hearing it... Thanks though, I'll appreciate any info on this that comes my way. Running open loop's not really going to be an option here as it's not my truck.

[Telco]

Got to thinking about it, and the PE might be the whole problem here. A lean charge will burn faster than a rich charge and requires less timing. So, I fattened the PE up quite a bit (actually put it back to stock) and loaded it last night. I'll have to get a new log on it now to see where I stand. I think the timing portion is correct, at least on the cruise area, so if the logs look clean on knock retard I might go ahead and add the timing back in. I've not seen any issues with the knock sensor pulling timing in any low power situations.

Naturally I'm still accepting any and all advice, but what I've gotten so far has been a huge help. I'll see about posting up a new log and program load in the next day or three.

[cmitchell17]

Got to thinking about it, and the PE might be the whole problem here. A lean charge will burn faster than a rich charge and requires less timing. So, I fattened the PE up quite a bit (actually put it back to stock) and loaded it last night. I'll have to get a new log on it now to see where I stand. I think the timing portion is correct, at least on the cruise area, so if the logs look clean on knock retard I might go ahead and add the timing back in. I've not seen any issues with the knock sensor pulling timing in any low power situations.

Naturally I'm still accepting any and all advice, but what I've gotten so far has been a huge help. I'll see about posting up a new log and program load in the next day or three.


I thought that did too, but then a read something that said a richer charge burns faster than a lean charge.
So why do you need more timing when there is a richer charge.

For the lean cruise why don't you just adjust the O2 switchpoints?
That way you fueling is normal except for light loads it goes leaner. I think ive noticed some mpgs from this.

I do that and then make my truck enter pe early like 60% throttle. Ive also been experimenting to make pe enable in second gear. Like when your accelerating and it shifts to second and you dont want to go to first becuase it will go to very high rpms. So im trying to make it enter pe to see if it won't lug so much.

[cmitchell17]

Try my tune.

If you have a 2000 5.3, this is also the updated operating system, so you should be able to do a full refalsh with my tune and have the updated os.

[Telco]

I'll take a look tonight. New info, I put in 93 octane on this tank and did a log, looks like I'm still seeing the same amount of KR. One thing I did notice this time, I seem to be seeing the KR more on decel than accel. Going to have to get this wrapped up soon, Pop's wanting his truck back.

[cmitchell17]

Are your burst knock settings stock?

I heard that burst knock dosent show up in the regular gm kr pid.

[Telco]

The only change I made to any knock tables was to increase allowed knock to 12 degrees when I found that I was hitting 8 degrees and 8 degrees was the max amount of knock it could pull. With 12 degrees of knock retard allowed, it's never pulled more than 11.7 degrees. So, I'm on the ragged edge there.

What I need to do here is find what's causing the truck to pull so much timing on reducing throttle conditions, not necessarily WOT to full close but where the TPS reading reduces. One point, I had 11 degrees of retard on a 5 percent reduction of throttle. I've also noted high retard at very slow speeds, such as giving a little bump in gas in a line of traffic approaching a left turn to a new road. If I can nail this one thing down, I can put the 3 degrees of high octane timing back in and get the power back that I'm missing.

On the O2 setpoint, here's what I'm running now:

CL Mode Bank-1 Bank-2
0 365.001374 365.001374
8 379.989353 379.989353
16 379.989353 379.989353
24 379.989353 379.989353
32 389.992642 389.992642
40 389.992642 389.992642
48 389.992642 389.992642
56 389.992642 389.992642
64 389.992642 389.992642

I'll look your table over now. Just so you know, I was seeing 19MPG mixed driving on the one tune, just got to get the KR dealt with. If I can, I think I might be able to more selectively adjust timing and tweak up to a full 20MPG with city driving, AND be able to spin the tires through first and into second like it was before. I figure I'm about 80 percent there, and if I can get 20 out of a full size 5.3L I'll feel very confident about getting 25+ out of a 4.8 in my own S10. Or, if I go the way my dad wants me, 30+ out of a 3.8L V6. :D

[cmitchell17]

I never had any luck advancing timing in the low airmass cruise cells.

Although I did not really do any testing, I just never felt in increase in torque.

If you think about it at the low load cells gm spent millions of dollars making a spark table to provide the best economy and emissions. (Emssions always wants MBT timing right? gm would not take out timing for emissions would they?)

But at high load they decreased timing to allow for 87 octane regular gas.
(which makes you think you could get MBT timing for all loads with 87, but then you figure you better run 87+ after you hear knock)

So what I did was use a blend of the high octane table and the optimal timing table. I blended about 80high octane/20 optimal timing in the airmass cells above 1800-2000rpms (Under 1800rpms I kept the timing stock becuase the TC likes to lock making you push the throttle more and then you have more airmass and it likes to knock)

Then I added the rest of the timing through the fuel mixture spark correction table so it would only come in at PE.

[BlackGMC]

IMO your running WAYYYYYYYYYYYYYYYYYY to much timing..... You need to go back to a stock timing table and increase in small amounts, then adjust your VE table, the log, then repeat.... Also your PE table is WAYYYYYYYYY to lean, your commanding 16+ AFR while in PE.... Also your Commanded Fuel while in OL table is also really lean in the wrong areas 85kpa+.... IMO if you continue to drive the vehicle your going to shopping for a new motor very sooon....

[dc_justin]

Absolutely agree with Corey (BlackGMC). Timing is WAY too high here and PE is not utilized properly. I understand the desire to lean the commanded afr out a bit, but this must be done only at light-moderate load. Leaning in PE mode will yield a significant power loss, and with the timing you're running, will also quickly lead to severe engine damage...

[BlackGMC]

Absolutely agree with Corey (BlackGMC). Timing is WAY too high here and PE is not utilized properly. I understand the desire to lean the commanded afr out a bit, but this must be done only at light-moderate load. Leaning in PE mode will yield a significant power loss, and with the timing you're running, will also quickly lead to severe engine damage...

What's up Justin? How was your trip to Texas? Sorry I did not get to meet up with you, while you were tuning Erics truck... Maybe next time..

[dc_justin]

What's up Justin? How was your trip to Texas? Sorry I did not get to meet up with you, while you were tuning Erics truck... Maybe next time..

Trip went well. Really wasn't much more that Eric's truck needed. Very stout setup given the mods and gearing. There will definitely be a next time. :cool:

[BlackGMC]

Trip went well. Really wasn't much more that Eric's truck needed. Very stout setup given the mods and gearing. There will definitely be a next time. :cool:

Yep he definately needs gears... Next time your in town you gotta let me buy lunch or dinner, something for all the help you have given me..

[Telco]

Yes, PE's already been adjusted, that's now an old file. Under PE I'm now anywhere from 12 to 13 to 1. Not really sure what the deal is on the timing because it's really not all that far off from what the factory tune had.

Yesterday I discovered that I can move the scan through one frame at a time (still learning the particulars of the program) and discovered that I'm seeing 99 percent of my knock retard on actual decel. Anytime the MAF detects a decrease in air, this is when I see the KR engage. Ran out of time to look yesterday, going to pick back up on it tonight and see if I can tweak it some more.

[BlackGMC]

Not really sure what the deal is on the timing because it's really not all that far off from what the factory tune had.


Can you post up your new tune and logs? There are 3 main tables that control the ending timing... HI octane, Lo octane, and Fuel mixture spark correction...

[Telco]

I'll try to get it on tonight.

[Telco]

Sorry this took so long. Here's my latest attempt. There seems to be some multiplier that I'm just not finding that is adjusting the final timing. With this setting it really, really runs good.

One thing I noticed when doing a frame by frame is I'm seeing a lot of KR at the same time the main VE table jumps to around 2.0 and higher. Not sure if it would be a good idea to lower this or not.

Getting to the point that I'm going to go try and find a dyno shop with a wideband, was hoping to be able to do this as is but I'm running out of time.

[joecar]

Timing is way too far advanced, this is one reason why you see knock when the throttle is opened up; the other reason is that the actual AFR may be lean at WOT as indicated by the NBO2 voltages (WOT average HO2S11=864mv and HO2S21=897mV); without a wideband we can only guesstimate what the actual AFR is.

[Telco]

Which timing field is too advanced? Is there a field that will tell me what actual, final timing is on the Scan field? If there were, this would help me tons on this.

I've tweaked the timing some more, and gotten the max retard down some again, it is back below 12 degrees which is the max amount of timing the computer is allowed to pull, so I know that I'm at least not doing any damage here. Ideally I'd like to get it down so it will pull timing during normal driving, but no more than 4 degrees at any time.

Nice thing about the current load, normally I am at the half tank mark by 200 miles, I'm past that and still between half and 3 quarters.

Edit - I've tried pulling timing in several different areas, and it seems that when I do I get retard in more areas, lower RPMs, and the truck isn't running as well. What field should I be pulling timing from? I agree that it looks like there is too much timing, as it should be running around 40 degrees max, but it will run as high as 60 degrees and seem to run fine. Other times it doesn't like 30 degrees. I don't know what the deal is here, but I do know that the problem is that I'm either not looking at the right fields, or I'm not comprehending what I am looking at. Can anyone break down what exactly I should be looking at here? On the dyno thing, I may have located one that I can use, will be calling them Tuesday when I get back to work to see what I need to do to arrange a several hour block for tuning purposes, but even then I'll need a better understanding of what fields need manipulating, what fields need watching, and how they interact. If there is a more comprehensive guide to this than the setup manuals I've found I'd welcome a link too. I really want to get this nailed down for my dad, he's really done me a huge favor by loaning me his truck for as long as he has so I could get my own back on the road.

[Telco]

OK, huge rampup in what I've learned, now to see if I comprehend what I've learned. I've backed timing way off, to be safe, and I think I've figured out how to read the data points to fine tune. Still have to figure out exactly what all affects timing though.

There still has to be something adjusting the algorithms that hasn't been found that would cause the same high octane, low octane and main VE table to show the same fields, yet put different amounts of timing retard into the system. What was also odd was in the three tune changes I made that backed timing off in both the high octane and optimal timing fields it would cause timing to retard even more. It was odd. I included those runs in here as well, if anyone's interested.

[BlackGMC]

Your timing is still way to high, Honestly you need to take out about 10-20* in all cells.... Your High Octane table is really really high and your adding to it with Fuel mixture spark correction table... Honestly you need to go back to a stock High octane table and add in very very small increments before you pop the motor.... At WOT you getting 10+ degrees of knock!!!

[Telco]

Yes, I've done this. Stock high octane table from an LS1 is in place. I am currently NOT running any of the files currently in place.

I'd still not mind knowing what is causing the KR to increase across the RPM band though. On the last three files I posted, I decreased timing and KR decreased on the peaks, but increased overall in the lower RPM bands.

It's snowing here today so it'll be a day or three before I can pull a new log. Current tune, to put everyone's mind at ease is also loaded.

[joecar]

If it's running lean at the lower RPM's then it may knock;
if it is running lean, then the question is "why?".

Or you may have some other problem:
- MAF sensor is dirty/oily;
- fuel filter may need replacing;
- carbon deposits in combustion chambers;
- oil being ingested (thru PCV, or thru worn valve guides/seals);
- worn/damaged spark plugs and wires;
- overheating;

Evaulate the condition of your vehicle and see if you can rule out these things.

[BlackGMC]

I am not sure why you are using a LS1 timing table, that timing table was designed for a completely engine different displacement and heads, but if you are then you need to zero out the B5908-Fuel Mixture Spark Correction, becuase it adds to the High octane table, and if you add that table and the LS1 timing table together you will have too much overall timing........

How did you get the values in your VE table? Did you perform AutoVE?

[Telco]

The only table I moved from the LS1 engine was the high octane table.

What is this AutoVE of which you speak? The VE table is stock, aside from the tables I ID's as being the cruise tables for highway cruising.

I have another question here, I saw an option for using the scan data to adjust the tune, how well does this work?

Thanks for the patience with me on this, I wasn't trying to be dense on the timing on purpose, just seemed like it was running well off it. Thanks.

[BlackGMC]

AutoVE tunes/adjusts the Main VE table which directly affects your fueling...

http://68.178.219.18/tutorials/PDF/AutoVE%20Tuning%20Tutorial.pdf

[joecar]

Telco,

No worries... we encourage you to ask questions, we want you to understand it.

Even if it seem to be running good with excess timing, it may be causing damage (elevated chamber temps and knocking)... and you're not making anymore power necessarily... it may be a symptom of the airflow not being right if it doesn't run good with reasonable timing... you should also check for airleaks... or you could just be running too lean.

The AutoVE procedure uses a wideband to dial in the VE table which allows the PCM to compute the correct airmass (which then allows it to add the right fuelmass to meet the AFR specified by your tune and/or closed loop mode).

For most people, the AutoVE procedure seems to work fairly well; there also are various ways of doing the same thing in a different manner or sequence, but the AutoVE procedure shows you how some of the various tables work together and is a good starting point.

[Telco]

Neat. Did a little reading into it. I don't see a wideband on the horizon any time soon though.

One thing I did note, on the current tune/log on this post. This is something I've noted in the previous tunes with the drastic timing put in. The only time I show any knock retard is when the VE table is in the MAP PSI field of 15.2, over 4000RPM. Seems any time the VE is over 2.0 I start seeing retard. Also noted in the dashboard that I've got saved that I get KR when the measured MAF reading is quite a bit higher than the calculated airflow rate. I'm assuming the AutoVE procedure is supposed to get the VE table to read the same as the MAF, is this correct? If so, then I may know where I need to go with this.

On the mechanical side, got a set of plugs I'm going to get installed this week. Everything else looks fine.

[BlackGMC]

You should try to reduce the number of PIDs your logging so you can get more frames per sec... Your logging 42 channels, I believe you don't want to log anymore than 24 to get maxium resolution...

[joecar]

...I'm assuming the AutoVE procedure is supposed to get the VE table to read the same as the MAF, is this correct? If so, then I may know where I need to go with this.The idea is this:
- disable both CL and MAF and then tune VE table using AutoVE (VE table is now a "known");
- enable MAF and tune MAF using a similar "AutoMAF" procedure (MAF is now a "known");

Also, before doing any of this, the IFR (injector flow rate) table must match the injectors, or it needs to be recalculated.

That gives at least 3 ways to arrive at tuning:
- tweaking IFR,
- tweaking VE,
- tweaking MAF.

[BlackGMC]

Also, before doing any of this, the IFR (injector flow rate) table must match the injectors, or it needs to be recalculated..

Is this necessary if the injectors are stock?

[Telco]

Sorry it took so long to get back, last time I tried the board was down.

I'd like to know if there might be a fourth possibility for testing. The thing is, I still don't see what all affects timing since the fields are staying the same yet knock retard is coming in. What I'm thinking is that when the knock retard engages, it should knock it back to ideal timing.

SPARKADV Ignition Timing Advance for #1 Cylinder 28.5 Degrees -5.0 36.7 52.0 SAE.SPARKADV Spark
KR Retard Due to Knock 4.2 Degrees 0.0 0.1 5.2 GM.KR Spark

It would seem to me that I should be able to use these two fields would allow me to tune to the correct timing point, since putting too much timing in will take it too far, but knock retard would pull it back. KR should pull it back to the max timing for the condition, which you could then reset the tune to set as the max tune. Thoughts?

[cmitchell17]

I am pretty sure that my knock sensor no longer works.

At wot in second the knock is the loudest thing but it shows nothing on the scanner. I don't even remember the last time I saw KR on the scanner besides when I had the stock tune back on when burst knock was enabeld.

[cmitchell17]

But when your knock sensor comes on it will push your timing down more towards the low octane timing table which should be lower timing.

[joecar]

Also, before doing any of this, the IFR (injector flow rate) table must match the injectors, or it needs to be recalculated.
Is this necessary if the injectors are stock? It might be good to see how close your table is... if it's out significantly, then you would have to decide if you wanted to paste the calculated values into the table, or to just leave it alone.

[joecar]

Yes, when knock is detected, timing slides down toward low octane table (uses a weighted average of the 2 tables)...

the pid GM.ASPARK shows how much of each table is used (100% = ho table, 0% = lo table).

[joecar]

With 28.5 degrees you may still get knock... I am wondering if you're running lean.

[Telco]

Was the lean comment posted towards me? I guess it's possible, but I've richened the WOT tables quite a bit. Guess I could add a little more.

On the timing, the description on KR is that it will pull X amount of timing per crank revolution when KR is detected until KR is eliminated, then add X amount (smaller number) per crank revolution until it reaches the max timing possible under the high octane table, if I interpret what I read correctly. Looking at the data, there is a final timing reading (cyl 1 timing) along with the KR reading. So, the KR should be a usable tool to set the max allowable timing for the engine. It would just be a matter of knowing what the variables are that affect final timing, like in a flowchart or something, along with the weighting. With that you could tweak timing so it ran the ragged edge all the way up the RPM band, with the knock retard available for special circumstances like towing a trailer up a hill or something.

Oh well, I'm down to adding a degree of timing here, taking a run, then drawing it back where I get the KR now, so I can get something to give to Pop in the next 2 weeks. My own truck is almost done enough to start driving, might even be able to get it finished today.

[BlackGMC]

Are you adjusting your VE or MAF tables inbetween the timing adds?

[Telco]

I was, but here on out I'm adjusting one table at a time then taking it for a run to see what happens. I've not been playing with the MAF table, mainly just the VE and spark. Thinking of adjusting the PE table to be a little richer on the next tune though. Might make it a straight 13 to 1, then see what the KR does.

[cmitchell17]

I don't know if I already asked you this, but what are you burst knock settings like.

Zero all of them and then see if you still get knock.

[Telco]

I'll have to try that later. Question now is, why would the low octane table have higher numbers than the high octane table? I'm showing this in the left side of the screen when comparing the two tables. I've found that the O2 voltage was showing too lean in the WOT acceleration and have adjusted, but am now seeing this disparity. Should not the low octane table ALWAYS have a lower number than the high octane table for the same cell? No idea how this happened, but I've adjusted the low octane tables to lower than the high octane tables.

[cmitchell17]

You sure its the stock timing?

[Telco]

I gave it some thought as I was driving down to my dad's house yesterday, and it was not. The stock timing map was identical for the low and high octane tables. The problem is that I never actually compared the stock low octane table (never adjusted it) with the new high octane table to make sure there were no issues. I've also got my own truck back on the road now, so I've now got less than 2 weeks to get this squared away before the truck goes back. I hate it when I make stupid mistakes like this, but I feel a lot more confident with the software now than I did.

Now that I realized my mistake here, I'm thinking of restarting the process again by putting the stock tables back in, then just adding 10 degrees across the board on the high octane table, then tweak from there.

Question - Will a wideband O2 sensor work to tune if it is hanging in the tailpipe or does it have to be up front and installed in a bung in front of the cat?

[dc_justin]

I gave it some thought as I was driving down to my dad's house yesterday, and it was not. The stock timing map was identical for the low and high octane tables. The problem is that I never actually compared the stock low octane table (never adjusted it) with the new high octane table to make sure there were no issues. I've also got my own truck back on the road now, so I've now got less than 2 weeks to get this squared away before the truck goes back. I hate it when I make stupid mistakes like this, but I feel a lot more confident with the software now than I did.

Now that I realized my mistake here, I'm thinking of restarting the process again by putting the stock tables back in, then just adding 10 degrees across the board on the high octane table, then tweak from there.

Question - Will a wideband O2 sensor work to tune if it is hanging in the tailpipe or does it have to be up front and installed in a bung in front of the cat?

10 degrees is a LOT of timing. You won't *need* more than 3 or 4 in most places. Take small steps towards your goal and your engine will be much happier with you for it.

[Telco]

OK, examined the base factory tune that I pulled when I first got the truck in my hot little hands, and IT was showing an inversion in the table. Unreal. I know for a fact that I'm the only one outside GM that's ever messed with this computer.

dc_justin, thanks, that's what I plan to do. I'm just setting up the initial table and decided to go with an 8 degree difference between the two, not 10 like I had planned. I'm also smoothing the low octane table out some, there are fields where the difference is as much as 15 degrees. I'm feeling a lot more confident in this table over the last bunch.

[ScarabEpic22]

I would smooth the low octane table and add maybe 3-5 deg to the high. As justin said, 10 deg is a lot, 8 is still too much. Start with baby steps and you will be much happier.

[Telco]

The latest tune is working great. The low octane table was smoothed, and the high octane was set 8 degrees over the low in the appropriate areas. Latest scan showed a max of 3 degrees KR and only under WOT. Now I can begin the baby steps and get it perfect. :muahaha: Thanks for the help with this so far folks, I'll be posting the final tune on the board for anyone interested.

[cmitchell17]

I couldnt notice anything from adding any timing on my 5.3, but I don't have a dyno or anything else to tell a diffrence.

One thing I did was use a newer timing table used in I think the 02+ used a smoother timing table. The 01s had a diffrent timing table.
You can't really tell which year had the most timing or the least it just changed all around usally only about 1 or 2 degrees in the normal airflows but in the .60-70 airmass and above the older tables usally had more timing and on the 04+ has less timing in the high airmass. I would guess to aid traction control.

I would guess that the best timing table to use would be the 04+ as they have not changed that one for the lm7s. Im pretty sure the motors are almost exactly the same for 04-07 same heads compression.

However on top of the stock timing I added about 20% timing from the optimal timing table so its raised about 1-2 degrees in most areas as I run higher octane gas and a higher octane always requires more timing as it burns slower.

[Telco]

Crap, don't have it after all. I adusted the fuel mix under PE to a richer level to try and knock out the last bit of KR in case it was too lean, and wound up getting more knock. Looks like I'm getting up to 8 degrees now.

What affect does optimal timing have on the works? I see that in some fields the optimal timing map has more timing than the same high octane timing map. I've readusted the F/A mix back where it was and plan to remove a bit of timing, but this will just put the optimal timing map further out. I've considered copying the high octane map to the optimal timing map to see what would happen, but as I don't understand it I'd like more info first. Thanks.

[cmitchell17]

I wish I knew exactly where the table came from. But from what I think its a table that the computer uses the figure how far the commanded timing is away from the values in the optimal table.

Im guessing if the commanded timing is far away from the optimal timing the delievered engine torque is going to be lower and if the commanded is close to the optimal timing the delivered torque is going to be higher.

So if this is true this means gm found the timing that would make the best torque and this optimal timing is it. But what conditions was this tested in? Cold ait hot air high octane low octane. My guess would be that is would be tested in the worst conditions becuase of the factory conservitive tuning.

Although in some places very light airmass, optimal is lower than the high octane.

But this is all just a guess?:nixweiss:

[Telco]

I dunno. At some points the optimal timing is over 50 degrees, which seems high. Going to knock timing back a bit in the high octane table to see what I get on KR after work today. Might try just copying selected high octane tables to the optimal timing to see what effect it has too.

[cmitchell17]

From what I heard at very light loads 50 degrees is what it needs, but it seems to drop sharply as load increases.

[Telco]

I give up. I pulled timing and pulled timing, tweaked what I could, and still get the knock. Last night I put the factory tune back in, with its timing tables going as high as 51 degrees, and got less than 2 degrees KR which can be attributed to the spark plugs still needing to be changed. My dad didn't want to run the AC Delco plugs I was going to put back in, so I took them back. Decided that I'm just going to make the transmission and exhaust system adjustments he wanted, advance timing 4 degrees across the board in the high octane table, and call it quits. Every adjustment I made otherwise either made it worse or made no change, except for one tune, but none of the adjustments worked as well as the factory tune does now. Feels like it has the most power it's had since I've had the truck. :frown: Evidently I suck at tuning. Oh well, can't be tops at everything I guess...

[BlackGMC]

Naw you don't suck, you just need to tune with a wideband...

[Telco]

Heh heh... I know, just isn't in the cards right now. Thanks.

[cmitchell17]

I think I already asked you this but did you disable burst knock?

Burst knock will make that random 6-8 degrees of knock retard, I don't know why.

[Telco]

Yes you have and no I haven't. I never remember it when I've got the program up. What exactly is burst knock?

Still wish I knew what all affected timing, and by what percentages, like the formula used for adjusting it. The only thing I can think of why it didn't work out is if the computer is using the O2 sensor for a spot check under WOT, and was seeing it "rich" since under all the previous tunes I had the O2 switchpoints kinda low. When I adjusted the VE table hoping to make it think it had less to fill none of the fields I had adjusted were being used at the time of knock. It no longer matters now though, as this weekend the truck goes back to Pop. My own truck is back on the road as of yesterday, and while I really miss the power of Pop's truck it's all I miss. I really enjoy driving my S15 ext cab, more than anything I've had since my 79 GMC halfton shortwide. Now that Interior 0.5 is complete, I'm going to take a breather, then start investigating a more powerful, efficient engine for my truck.

Edit - Looked the burst knock tables over, and I see the reason for them. Rather than disable it, I set all values to .0016, higher than the highest value there. If airflow goes over this much, I think it would be a good idea for timing to pull back. GM wouldn't have gone through the trouble and expense to make this particular field if there wasn't a reason for it.

[Telco]

I wonder if I might not have found why I was able to pull timing yet not see KR reduce. I had the B4105 O2 switch points set way down, but just noticed in table B4206 that I had Use O2 with Open Loop Commanded Fuel Table set to Enable as well. If this is the case, and I had the O2s to switch lean, then it would think that the new switch point was 14.7 and would adjust the mix according to what it thought the commanded ratio was, rather than just commanding X amount of fuel for Y amount of air. Academic now though, as I am taking the truck back to my dad today and likely won't drive it again. I've set the table to disable and will pull a log on my way down to his house to see what effect it has on a WOT run.

Anyway, thanks for the help everyone, I really appreciate it. Hopefully I'll have a 411 controlled vehicle of my own before long, because the 2.8L in my S15 just isn't cutting it.

[Telco]

I'm not a happy camper now. If only I'd discovered this a week or two ago! I took the truck back to my dad's house on Saturday, driving 70-75MPH for 130 miles I burned 5.5 gallons with a few WOT runs due to traffic being stupid. This is 23.6MPG on a 2000 reg cab narrow bed Chevy with a 5.3/auto! Danged thing might see 25+MPG going 60-65 with no WOT runs. I also found the field that was forcing the truck to only downshift to 3rd gear on a WOT at 70MPH, it will now downshift to 2nd at 75MPH and is going 85+MPH in just a couple of seconds instead of 15 seconds to go up 10MPH. And, with the current tune under several WOT runs knock retard stayed less than 2 degrees. Told Pop to write down what he doesn't like and I'll try to tweak next time I visit.

I'll post the current tune up next time I'm on the internet with his laptop, which I still have at home. May be a few days. Thanks again for the help everyone. :D

Edit - Here's the latest tune. Anyone feel free to use it. I'd look at the low speed shifting, might be too low. My dad's a big fan of a transmission that shifts imperceptibly, and I've got it down a little too low.

[cmitchell17]

Yeah with my 2000 ex cab I used to avarage about 18-19 in the city and on trips going 55-65 I could get up to about 22-23 avarage.

I don't like my trans to shift hard either except at WOT it gets anyoying

But having efi live is annoying becuase you are constantly changing stuff and your never satisfied.