Gtr Tuning Issues - Keeps Leaning Out

[zachscalais]

Hi all, having a bit of a problem tuning my gtr. Both the tuner and I are stumped so would love any input. Ill try and give all relevant detail, but if I miss something feel free to ask.

My main issue is that its leaning out around 5000rpm at 20psi. I'll go through and explain all the details. The Ecu is a pfc.

When it first leaned out we pulled the fuel pump, and it was the stock one still. I had never bothered checking it because I was told it was a nismo item (the previous set up had a hks ta45, log mani ect and had always held fuel pressure fine)

I replaced that with a walbro gss 342 that I had at home (recommended by the tuner over a 040, also personal preference, people say it will be to small, but when I see a pressure drop I'll believe it) – It still leaned out

Put a fuel pressure gauge on the end of the fuel rail, pressure did not drop at all

The injectors are only at 65% duty (so they're not the issue)

I have twin 25afm's which are confirmed by part numbers, and both sending equalish voltage signals (have tested these, one reads 0.2v lower then the other at idle regardless of what branch of the Y-pipe its on, but under no load at 2000rmp the are close to equal voltages) – I'm confident that these are not the issue.

The airflow map is maxed out at 5500rpm (5v)

Now its easy to say "get bigger afm's", however its proven many times that twin 25's on a 26 with a 35r will have enough resolution up to making 400rwkw.

Despite the afm map being maxed, we should have been able to tune around this using all the rpm axis cells to at least prove that it was the afm's fault. All the cells in the appropriate section were given an overall correction of 30%, (I think ended up trying even higher) and it still leaned out at the exact same point.

I've searched the net for many hours and there's not one mention of any issue like this. I've seen numerous setup with the same afm's and a turbo that flow much more air then mine with no issues.

so in short,

-the afm's are reading correctly

-the fuel pressure is remaining constant (meaning fuel pumps big enough, not blocks in the filter, the line is adequate diameter and the injectors aren't using more fuel then they are receiving)

-the injectors are large enough

The only idea we have at the moment is that there's an issue with the PFC. No one I know has an ecu that they are willing to lend to test this, so it seems my only option is to get a new ECU to try. If I do, I will be going down the map sensor route as well.

Power wise, with a fair bit of timing pulled out and no work done to the fuel map, cam gears not set up, it still made 390hp atw at ~5000rpm.

My set up

Edited February 3, 2011 by zachscalais

[Beer Baron]

replace the power FC. I've had a similar problem and I believe it was the power FC. just borrow one first if you can to test.

[zachscalais]

that sucks, I dont know of anyone with another pfc I can borrow unfortuantly. Slowly saving for another ecu though, the track car is getting most of the money at the moment, its much more fun.

Thanks for the info though

[STATUS]

IM in vic where are you? i have a d-jetro 4sale atm if your trust worthy i may lend it for a day or so.

[Sunkist]

This is why status tuning are fkn great!

[Beer Baron]

yeah I've hard this weird issue with a power FC before. car was fine till I fried the ecu. ecu was repaired and appeared to work perfectly fine, tune was still in there etc. but the car was lean as hell. would barely run unless I dialled in massive fuel correction. drove it like that for a while just dialling in fuel correction each time. got it in a dyno and apprently regardless of changing the tune the car would not respond. replaced it with a nistune and everything was fine.

[DVS JEZ]

thats weird beer baron, but if its been fried i suppose anything is possible,

Zach, do you know what sort of numbers the power fc is seeing in the fuel table? what injectors?

Have you tried rescaling the AFMs?

[zachscalais]

yeah I've hard this weird issue with a power FC before. car was fine till I fried the ecu. ecu was repaired and appeared to work perfectly fine, tune was still in there etc. but the car was lean as hell. would barely run unless I dialled in massive fuel correction. drove it like that for a while just dialling in fuel correction each time. got it in a dyno and apprently regardless of changing the tune the car would not respond. replaced it with a nistune and everything was fine.

i had it tuned at godzilla with the old 550cc's and old turbo setup, and had no issues using the same afm's and ecu. And he didnt mention that I was nearly maxing out the table then, so im assuming it was fine a year ago. (even though that turbo would have been flowing a heap less air, probably similar on WOT to this 35r at 5000rmp.)

IM in vic where are you? i have a d-jetro 4sale atm if your trust worthy i may lend it for a day or so.

hey thanks for the offer, but im in Bundaberg QLD

thats weird beer baron, but if its been fried i suppose anything is possible,

Zach, do you know what sort of numbers the power fc is seeing in the fuel table? what injectors?

Have you tried rescaling the AFMs?

injectors are delphi 1000's. i cant rember the fuel table figures off the top of my head. in a different town to the car atm. We didnt rescale the afm reference table because we added fuel to every reference point corresponding with the 5v in the fuel map but even that didnt help, which is leading more towards an ecu error rather them afm/afm table setup

Edited February 3, 2011 by zachscalais

[SATO GTS]

Are you sure your ignition sys is up to scratch to be able to burn all the air fuel mix at boost pressure??

Especially with 1000cc inj's there seam to be alot of work to burn it all .

Just a thought.

Cheers

[zachscalais]

yeah pretty confident with it, got super spark coilpacks. Its not breaking down or missing as it ramps up. It makes power nicely untill that one point. Plugs are brand new, gapped to .8. Pretty standard stuff. If it was blowing out spark it should be getting richer if anything?

[SATO GTS]

if the fuel is not being burnt then there will be excess air that the meter is picking up on hence why lean mixture.

[zachscalais]

yeah true, but at the same time there should be something in the curve that would show that happening? and we should also be able to alter the severity of it by changing the values, none of this changed the point at which it happened. There was no excessive unburnt fuel smoke around the point.

We could have ran lower boost which would have helped fault find, but didn't think of it at the time.

[STATUS]

TRy some known coil packs ive had some issues with all the cheapies, and if you want email me the tune file and i will check out the AFM scale.

[zachscalais]

I'll see if i can get my hands on some different coils, no one around here has a 26 willing to help out though ill also try and get a copy the tune off the tuner. Even if it is coils-packs, I still have an issue somewhere to be saying the afm's are maxed out correct?

[VB-]

is fuel pressure increasing with boost? line hasnt popped off the reg or anything silly like that?

[MrStabby]

is fuel pressure increasing with boost? line hasnt popped off the reg or anything silly like that?

+1, or the regulator may have died.

You said "Put a fuel pressure gauge on the end of the fuel rail, pressure did not drop at all" but did you see it rise following the boost rise? ie you had 20psi more fuel pressure in the rail at 20psi boost?

[badhairdave]

It's probably not your problem now but once you sort this issue it will be

the walbros are rated 246l/h@50psi, basically at 1 bar boost your base pressure plus boost pressure is going to be near enough to 50psi. 246/60 is 4.1L/min

1000cc/m injectors x6 x.65 duty gives 3.9L/min

You're marginal