Temporarily tune around WOT fuel preesure drop?

[samh_08]

I have been going lean under heavy load lately (up to 14.5:1 WOT). I hooked up a fuel pressure gauge and noticed my fuel pressure drops off to 52 psi WOT. I was wondering if I could fudge my tune a bit for now to compensate for this pressure loss? I assume this amount of pressure loss would create this drastic of lean condition...?

My injector values are as follows:
Injector Rated Fuel Pressure: 43.5 psi Your Fuel Rail Pressure: 58 psi Injector Rated Flow Rate 36 lb/hr

[mr.prick]

Don't tune around this.
Does battery voltage drop too?

[eficalibrator]

Agreed. Fix the mechanical problem (dropping rail pressure) first, then worry about finishing the tuning.

[mr.prick]

Also make sure your FP is actually dropping.
I had 2 VDO mechanical FP gauges that were inaccurate.
False lean under load could be a burnt out WBO2 sensor.

If it's from a voltage drop the injector offsets should compensate for that.
Does it miss or have any side effects other than the WBO2 reading lean?

[samh_08]

Agreed that the mechanical problem should be fixed first. Either way the mechanical problem will get fixed, but I would like to see if tuning around it for a couple days would work for now.

mr prick: The battery voltage stays rock solid at 13.9 all the way through the RPM range, maybe fluttering between 13.8 and 13.9 at times with .52vdc total fuel pump circuit drop. The walbro pump I have was supposed to be good to 650bhp and Im only about 420rwhp. Anything in my tune look suspicious and could have a hand in going lean?

[samh_08]

Posted at the same time :hihi:.

As far as the FP dropping is concerned, its pretty clear that it as actually dropping constantly under heavy throttle to about 52 psi every time. The gauge says 58 psi at all other times so I assume the gauge is accurate.

I have a month old LC1 with a serial connection so I would hope that wouldn't be burnt out already. Besides that, the WBO2 seems to be in check with my narrowbands at 14.7.

If I didn't have a wideband, I wouldn't guess that Im running lean because it goes like a raped ape and doesn't miss a beat. If it is truly lean at 14.5:1 at WOT, should it be missing and running like garbage?

[mr.prick]

I had the fuel line in the tank come loose from my Wahlbro.
Maybe you have a dirty Fuel filter.
Make sure FP is dropping so you don't have to do anything unnecessary. :hihi:
I've had to replace the sensor for my LC-1 yearly for my DD. :rippedhand:

[joecar]

0.52V drop between the battery positive terminal and the fuel pump...?

Can you reduce the drop (apply dielectric grease to the connections, try swapping the fuel pump relay)...?

If you have access to an oscilloscope, capture waveform of pump draw current (using amp clamp)... this will allow you to see if the pump motor is spinning at the correct rpms... I know, this might be hard to do while spinning the engine at higher rpm... I know, it might be hard to access a scope.

Like mr.prick said, check filter and screen.

[samh_08]

.52 total circuit drop, positive and ground combined which is good considering the wires on the stock sending unit. This is a swap into a 86 monte carlo so my options with fitment and aftermarket parts are limited or all custom.

I had the pump out of the tank and checked all connections and all was good. The screen was dark so I replaced that (it was a brand new clean tank:nixweiss:) so I guess I could replace the fuel filter as well even though its 2 months old..

Anything suspicious in my tune?

[redhardsupra]

you dont wanna do it, but if you must, here's how to do hack it correctly ;)

http://redhardsupra.blogspot.com/2006/12/ifr-spreadsheet-for-logged-fuel.html

[98 tigershark]

Is this a new problem? If you dont know or if it has been like that what size are you fuel lines. ON the turboedBuick forum the fuel lines are very restrictive on the models.
allot of bends, old style fittings and on. So check out the lines and maybe visit a site specific forum like the turboedbuick as I believe the lines are very similar.
You can tune around this bit it is a band aid.
98 tigershark

[samh_08]

you dont wanna do it, but if you must, here's how to do hack it correctly ;)

http://redhardsupra.blogspot.com/2006/12/ifr-spreadsheet-for-logged-fuel.html
Nice spreadsheet :cheers:. So I would only modify the 80kPa number for my actual WOT fuel pressure? I have a solid 58 psi 80kPa and below..


This seems to be a new problem with injectors and time. When I just completed the swap I was more worried about getting the odds and ends cleared up and making it drivable, but when I punched it for a bit with the stock injectors, it was good for a bit then started a go a little lean. That is why I bought bigger injectors.

The only spot in my fuel system that might be causing restriction is the lines going through my fuel tank sending unit. They seem necked down a bit, but no smaller than the output on the walbro pump..

[98 tigershark]

Yes, Red hard supra is very good.
I do think it does neck down to around 1/4 inche. Racetronicx was dealing with that back in 02 or 3 with a dual pump system.
You might want to check out turbobuick forum as that is the year and body style for GM.
Good Luck,
98 tigershark

Nice spreadsheet :cheers:. So I would only modify the 80kPa number for my actual WOT fuel pressure? I have a solid 58 psi 80kPa and below..


This seems to be a new problem with injectors and time. When I just completed the swap I was more worried about getting the odds and ends cleared up and making it drivable, but when I punched it for a bit with the stock injectors, it was good for a bit then started a go a little lean. That is why I bought bigger injectors.

The only spot in my fuel system that might be causing restriction is the lines going through my fuel tank sending unit. They seem necked down a bit, but no smaller than the output on the walbro pump..

[samh_08]

Thanks tigershark. I just went out and tried numbers a came up with using redhardsupras spreadsheet. Same exact results as before. I went from 45.5 lb/hr flow to a 43.5 lb/hr in the 11.6 MANVAC cell with no change in WOT AFR. Am I changing the wrong side of things? This is where a noob gets lots...I would have expected to see a change with a change to do with a main fueling table.

Does this mean something else is whacky with my tune or what? I have a returnless fuel system, meaning I should have sloped IFR table right?

[5.7ute]

Did your fuel pressure drop any more?

[samh_08]

Steady at 52 at WOT..Same as before :doh2:

[5.7ute]

Log manvac & ensure you are lowering the correct cells.

[98 tigershark]

Are you running the stock fuel pump it would seem. The 58 PSI on 36LB/hr injectors with a 43 PSI rated Fuel pump at how many gallon per hour is your pump?? It looks like classic fuel starvation. Check the fuel pump size and what or how many HP is your motor. That would give us an Idea if you have enough pump. A single old style fuel line is also very restrictive. Fuel starvation= loss of pressure= to small of a pump, restriction or a small fuel line. Do you know the pump specs.
98 tifershark

[samh_08]

Here is the exact pump I have installed.
http://www.fullthrottlespeed.com/customkititems.asp+kc+834GMHP+eq+


I am running a returnless fuel system with a Corvette fuel filter/regulator that gives me 58 psi all the time (supposed to.)

My new injectors are flow matched resized LS2 injectors from Fuel Injection Connection. They are resized to 36lb/hr and rated at 43.5psi. That makes them 42lb/hr at 58psi.

[98 tigershark]

I know exactly what the regulator is as I had to use that same one on my vette as the new motor used a different reg than the 97-98 in rail one. But the real question is what are your fuel pump specs??
I had or have fuel starvation too because my pump cannot keep up with my motor. The regulator has nothing to do with the amount of fuel the pump puts out!
I hope I said that right. SO even if you had a walbro corvette pump in my case it is to small for my motor and the same thing happened to me (fuel starvation). So if you have the stock 86 pump I would bet it is too small or you have built a really narely motor 500+hp but the stock 86 pump as I said sounds too small for an LS1 I bet.
If it is the stock one I would be happy too look up the specs for you.
Regards,
98 tigershark


Here is the exact pump I have installed.
http://www.fullthrottlespeed.com/customkititems.asp+kc+834GMHP+eq+


I am running a returnless fuel system with a Corvette fuel filter/regulator that gives me 58 psi all the time (supposed to.)

My new injectors are flow matched resized LS2 injectors from Fuel Injection Connection. They are resized to 36lb/hr and rated at 43.5psi. That makes them 42lb/hr at 58psi.

[samh_08]

........did you click on the link? Its a walbro pump that supports upwards of 600hp. I wouldn't even question why my fuel pressure is dropping under load if I had a stock pump. :hihi:

[98 tigershark]

Sorry I am looking at it now. Looks like a good one. What is the voltage rating?
1 volt can drop you down 20% I cant tell by the pump info. Did you get the plug and play fuel pump Hot Wire Kit for maximum pump performance. That is how it is good for 600-hp. It takes the voltage right off of the alternator around 13.7 Volts there. Other wise I think you said you had 12 volts. That is about 36% drop in pumping ability (384HP at the crank) very possibly. Do you think you have more than that voltage or HP?
Thanks for the Link and sorry I missed it.
98 tigershark

98 tigershark

[98 tigershark]

Hello sam_08,

I just checked racetrinix and it looks like it is a high performance but a stock one without the harness Plug and play it shows the exact same pump you bought model # and everything. They (racetronixs) did a test and it supported 278 rwhp and maybe a little more without he plug and play same exact model and also a newer one. I think you need the plug and play harness bud. I do not think that all by itself supports 600 hp. I wish that wold do it for me.
Even the one for the C5 corvette needs the plug and play harness to get the numbers they post.
Let me know how it goes as I have a real fuel supply issue too. I would call racetronix for sure. They are really good guys, I think.
Again let me know, you dont have the Plug and play right.
Take care,
98 tigershark

[samh_08]

Thanks tigershark. The pump definitely supports more than 278rwhp but lets put that aside.

I have tried adjusting my IFR table to reflect the cells where I drop to 52 psi. I have not had a change in WOT AFR. This leads me to believe there is something else in my tune that might be causing this. Can I please have some input on my tune to eliminate that also..?

[98 tigershark]

Hello sam_08,

I would be happy to look at the tune with the adjustments you made.
I did not look at what redhardsupra sent, but I am sure I understand what he was doing. Too let you know, I called 3 top fuel guys this week, as I said I am having supply issues. It is my experience that these things are 90% a physical issue and not tuning. I was told by three of the best fuel supply guys that if your regulator is too far away like by the rear tank without a return this is normal to drop in pressure (from 58 to 52 at WOT) with a long stock feed line and no return under WOT. All 3 felt it was something physical. So while I am looking at your newest tune could you please look at the line size to the rail from the regulator. That would be very much appreciated. Unless your tune is so far off they all felt it is something in the fuel delivery. Post it and we will see. OK!!
Glad to help,
98 tigershark


Thanks tigershark. The pump definitely supports more than 278rwhp but lets put that aside.

I have tried adjusting my IFR table to reflect the cells where I drop to 52 psi. I have not had a change in WOT AFR. This leads me to believe there is something else in my tune that might be causing this. Can I please have some input on my tune to eliminate that also..?

[samh_08]

My tune is on the first page. How can the placement of the regulator by the tank be an issue when that is how they come from the factory. Pretty much all setups I've seen run their regulator within 3 feet of their tank. All hoses are 6AN or 3/8ID except for the return line which is 5/16. It is very likely that it is a mechanical problem, but I should have been able to command my injectors on for longer at WOT to compensate for less fuel pressure. How did my changes not change anything with WOT AFR?

BTW: the tune on the 1st page doesn't have the IFR change, but I attached the current one anyways.

[98 tigershark]

Hello sam_308,

Ok, What fuel are you using and I think you said you are using 36lb and hour injectors? LS7 injector is 40-42lb. The VE is really up their too. Even if you are past the 4000 rpm threshold in B0120 the PCM does kind of guess. In other words it the PCM plays catchup and I have been told that the VE is used for that to some degree. Your speed denisity stuff looks OK.
So the size inj and try to lower the VE a little but first let me know if you are still using the 36lb inj if so that is a big problem and also what fuel. ei E10 or pure gas.
OK
98 tigershark

[samh_08]

I am using resized LS2 injectors. They are resized to 36lb @ 43.5 psi which makes them 42lb at 58 psi. I know the VE is really up there but its from adding 10% for autove. It still shouldn't be up that high should it? I dont know what you mean about B0120 and the PCM guessing (elaborate please), but I do not have a MAF and this is a speed density tune.

I believe it is pure gas but it might possibly be E10..do the 10% ethanol make that much difference?

[5.7ute]

Samh 08. I was having a think on this last night. To make sure that the PCM is commanding more fuel, log IBPW with your normal & IFR hacked tune at WOT. If the IBPW increases without a change in resultant AFR you will have other issues.

[98 tigershark]

I have never heard of resizing an injector an LS2 36lb injector is already rated at 58psi. How did you do that ? You should also log both tunes the one before and red hard supras and the IBPWs. If the IBPW increases and If the IBPW increases without a change in AFR you surely have other problems. change in AFR you will have different problems too. The VE plays a role in IBPWs.
Next B0120 means the the VE table if not disabled will use the maf after that RPMs. Since your are using a SD tune it does not use the maf after 4000 rpms. Then the PCM will use the map calculated airflow and thus the IBPWs and AFR. I think you disabled tho dtc's right. I have not seen VE% that high but I have not seen every tune.
It is suppose to be impossible to have a higher than 90% VE unless it is forced induction after peak trq. I have seen as high as 109% but that is rare.
Please let me know about how you changed the injectors and you did turn off all the DTCs for a speed density tune and disabled the maf, right?
98 tigershark.

[98 tigershark]

Ignore my IBPW and afr stuff, Use 5.7utes, he said it right. I am not sure I did!
Check the inj thing please.
Thanks,
98 tigershark

[samh_08]

Will do, gotta wait for the rain to quit. The guys at FIC do all kinds of injector work and testing and they are who I got these injectors from. They told me they are 42lb with 58psi so that is what im going for. If they weren't 42lb, my VE table would be really rich the whole way though, not?

Is there any way to figure out mathematically how much lower my VE table would be if i had 36lb injectors instead? Just out of curiosity..:thumb_yello:

[98 tigershark]

Bigger settings on smaller injectors give smaller IBPWs/leaner!
98 tigershark



Will do, gotta wait for the rain to quit. The guys at FIC do all kinds of injector work and testing and they are who I got these injectors from. They told me they are 42lb with 58psi so that is what im going for. If they weren't 42lb, my VE table would be really rich the whole way though, not?

Is there any way to figure out mathematically how much lower my VE table would be if i had 36lb injectors instead? Just out of curiosity..:thumb_yello:

[5.7ute]

Will do, gotta wait for the rain to quit. The guys at FIC do all kinds of injector work and testing and they are who I got these injectors from. They told me they are 42lb with 58psi so that is what im going for. If they weren't 42lb, my VE table would be really rich the whole way though, not?

Is there any way to figure out mathematically how much lower my VE table would be if i had 36lb injectors instead? Just out of curiosity..:thumb_yello:

If the injectors were out by 10% your VE table would be out by the same 10%.
In your case if you had 36lb injectors but an IFR for 42lb injectors you would be 17% too high.

[98 tigershark]

That is what I was kind of thinking. Not thinking to well today, headache!!
98 tigershark


If the injectors were out by 10% your VE table would be out by the same 10%.
In your case if you had 36lb injectors but an IFR for 42lb injectors you would be 17% too high.

[5.7ute]

That is what I was kind of thinking. Not thinking to well today, headache!!
98 tigershark

You were 100% correct with the bigger makes leaner statement. I was using a case where the ifr was wrongly stated & "tuned" around (hacked).

[98 tigershark]

Thanks 5.7ute,

I am feeling a little rough today, a long week. Anyway I had replace a friends injectors. From 40lbs to 60lbs. I acidentally put the same injectors back in.
When I went to check it with out the WBO2 the VE% was very high. When I hooked up the WBO2 I figured out why. DAH!! not funny at the time, but now kind of! Personally I think the injectors along with the fuel supply is the main issue here. I think the pump has hit the wall w/420 rwhp. That is a heavy vehicle too so the crank HP is probably more than thought. But it would seem to me the injectors or settings are causing a problem too. What say you?
Take care and let me know.
Thanks,
98 TS

[samh_08]

Finally got around to testing this and getting some short logs.

BBL00016 = Hacked IFR table
BBL00017 = IFR calculated from spreadsheet

Please take a look at the two logs and let me know your thoughts before I share mine. I realize the IPW's did react to the changes, but let me know what else you spot.

[joecar]

Hmmm...can you also log DYNAIR and DYNCYLAIR...

[samh_08]

Yes but it would first be tomorrow. Excuse the rookie, but I thought I was logging everything I needed for speed density. What is the purpose of logging DYNAIR and DYNCYLAIR when I am already logging DYNCYLAIR_DMA?

[5.7ute]

The hacked IFR tune is definately better with the actual AFR's. This still leads to a fuel supply issue or an incorrect VE table/maf table. Since your fuel pressure is dropping the fuel supply would be the main cause for concern.(as you had already figured out).
Its a pity you cant log fuel pressure as well since I would think that it is still dropping further with the hacked tune.

[samh_08]

I know that would be nice to have a fuel pressure gauge with the ability to log it with EFIlive (I know its possible, need $$)

From my eyes, I see the AFR's looking better with the hacked IFR table, but in both tunes the AFR's are equal for a little bit after I punch it. Wouldn't the hacked IFR tune show that much more rich, no matter the RPM? Wouldn't this be a VE problem (even though my VE values are so high already??)

BTW: Both of these logs were recorded within 5 mins of each other, so they would both have the same fuel pressure.

[joecar]

Yes but it would first be tomorrow. Excuse the rookie, but I thought I was logging everything I needed for speed density. What is the purpose of logging DYNAIR and DYNCYLAIR when I am already logging DYNCYLAIR_DMA?DYNAIR (g/s) and DYNCYLAIR (g/cyl) help to show the bigger picture when comparing pulsewidth, AFR, timing, gives an idea about VE...

log either one, DYNCYLAIR or DYNCYLAIR_DMA, whichever one you like best... sorry I don't mean to make you spin another cycle...

I did look very carefully in your logs and I didn't see either one... :)

[joecar]

More $0.02 comments... :)

[samh_08]

?? Dont know why you cant see it. This is what I see...


http://i166.photobucket.com/albums/u117/samh_08/ScreenShot002.jpg

[5.7ute]

Yep. I can see dyncylair_dma in the logs. Remember puff, puff, pass Joe (Joking)
Samh 08 you cant directly reference one log to the other as they are showing different rates of accelleration at different times.The only constant area is over 5000 rpm.

[SSpdDmon]

Personally, I think fudging the IFR table is the better way to go about this (even though I think it's completely wrong from the start). Changing the MAF or VE is going to alter the air mass calculations and throw you in different parts of other tables. IFR simply adjusts IBPW, which is what you need to change.

In the end though, I'd be concerned that it's simply a supply and demand problem. Meaning, no matter how far you drop the IFR to demand more fuel @ WOT, the ability of the system to supply it simply isn't there. Whether it's a capacity issue or a restriction of some sort, it's not happening....which is why I say don't bother wasting your time "fudging" it. Fix the real issue.

[98 tigershark]

Dido that Data.
98 tigershark



Personally, I think fudging the IFR table is the better way to go about this (even though I think it's completely wrong from the start). Changing the MAF or VE is going to alter the air mass calculations and throw you in different parts of other tables. IFR simply adjusts IBPW, which is what you need to change.

In the end though, I'd be concerned that it's simply a supply and demand problem. Meaning, no matter how far you drop the IFR to demand more fuel @ WOT, the ability of the system to supply it simply isn't there. Whether it's a capacity issue or a restriction of some sort, it's not happening....which is why I say don't bother wasting your time "fudging" it. Fix the real issue.

[samh_08]

I am beginning the process of elimination on the drop in fuel pressure at WOT tomorrow.

Do these logs that I took show that my VE is off up top too?

[5.7ute]

I am beginning the process of elimination on the drop in fuel pressure at WOT tomorrow.

Do these logs that I took show that my VE is off up top too?

You wont know until the fuel issue is sorted. If your system holds pressure @58psi & actual doesnt match commanded then your VE table is off.
As SSpdDemon correctly stated, the only place to fudge this is the IFR table. Then once your fuel system is adequate you will only need to return this table to matching the injectors flow rate. Hacking anything else will just add too much work.

[joecar]

?? Dont know why you cant see it. This is what I see...


This is very strange, I see only 22 channels worth of pids... :nixweiss:... this disappoints me since I haven't been drinking nor smoking anything today...

[joecar]

Yes, I would be concerned about fuel pressure drop/delivery.

[joecar]

This is very strange, I see only 22 channels worth of pids... :nixweiss:... this disappoints me since I haven't been drinking nor smoking anything today...lol...:hihi:...let me clarify: I don't usually drink anything other than a beer every so often...:cheers:...and I don't smoke anything at all.

I might not be seeing the DMA pids because I'm running a beta scantool build...!?

[5.7ute]

lol...:hihi:...let me clarify: I don't usually drink anything other than a beer every so often...:cheers:...and I don't smoke anything at all.

I might not be seeing the DMA pids because I'm running a beta scantool build...!?

That same thought crossed my mind. I couldnt resist having a dig though.:grin:

[98 tigershark]

Unfortunately I do have a smoking addiction!! I am addicted to smoking my tires. It is a very bad habit and makes my wife mad. But I didn't inhale!!!:hihi::angel_innocent:
Any news on the WOT issue?
98 tigershark:cheers:


lol...:hihi:...let me clarify: I don't usually drink anything other than a beer every so often...:cheers:...and I don't smoke anything at all.

I might not be seeing the DMA pids because I'm running a beta scantool build...!?