lean issue on WOT pulls, need advice or help on what to look for

[ej25subie05]

hey all, having an issue with my 2005 STi that me and a good friend of mine have been tuning for a bit now. We are using the cobb v2 access port with cobbs tuning software (access tuner race). We are stumped by the issue we are having and hoping to get some insight form someone that knows cobbs tuning software pretty well. He's used to the older version of Cobbs tuning software so access tuner race is new to him in a few ways.

Before i go on we are trying to tune for Speed density. just to make that clear

the reason i am trying to do this with my friend is because i have built the car myself (except engine) and there is no reason for me not to learn how to tune my own car as well. i want to learn everything i can.

Issue we are having.

Car runs great, but as soon as we do a WOT pull (3rd gear for instance) it holds a solid 11* afr till about 5400 rpm in most cases then starts going lean. it starts going lean around 4,500rpm in some gears and 2nd won't do it till around 5800rpm

Do a part throttle pull in 1st-4th gear (didn't do 5th-6th for excessive speed lol) and you can go to redline with a beautiful 11.3 afr.

I am new to tuning, this is my first car i have ever tried to do it with a friend to learn as much as i can. but does any one with knowledge of the access tuner race software have any ideas. maybe I'm missing something. Or maybe its a mechanical issue???

here is a list of mods to show the extensive work done on the car, its no ordinary engine.

K1 billet crankshaft
K1 rods
Cosworth forged pistons
Arp rod bolts, arp head studs
Headgames port and polished heads
GSC S2 cams
ferrea valvetrain
ATI fluid dampner pulley
cosworth oil baffle
killer b oil pickup
TGV deletes (stock welded)
3mm tgv spacers
id1000cc injectors
custom stainless steel fuel lines with aeromotive fuel rails and aeromotive for
custom 3" intake
SPEED DENSITY
Cobb map adapter with AEM 3.5 bar MAP sensor
Perrin fmic
perrin blow through pipe for SPEED DENSITY
Grimmspeed ebcs
pas hard turbo inlet
blouch 3.0xtr 10cm exhaust with 2.4" inlet
perrin catted downpipe
agency power unequal length headers
grimmspeed ewg uppipe
tial bov
tial ewg 38mm with external dump
emissions system delete

if you need to know any other mods specifically please lmk i may have missed something.

appreciate any help. really want to start getting somewhere with the tune. as far as city driving car is perfect. starts like stock, idles like stock (higher rpm) same drivability etc. afrs cruising stay at 14.7-14.8 far

 

[Alin]

[MENTION=9]HolyCrapItsFast[/MENTION] [MENTION=1069]35r[/MENTION] [MENTION=3516]zax[/MENTION] [MENTION=3416]WRB_STi[/MENTION]

:tup:

 

[Spamby]

I'm not a tuner so I won't be much help with the tuning part (learning this as well), more of a mechanics guy. I didn't see a fuel pump listed? Getting enough fuel, maybe?
Logs will probably be requested by the tuners, I'm sure. So if you have some logs, post those up.

 

[ej25subie05]

have a in tank walbro 255. it should flow enough for this turbo.

lmk what y'all want data logged and ill do it.

 

[Alin]

I have the generic list of what needs to be logged but in this situation im sure holycrapitsfast would want different parameters monitored.

 

[ej25subie05]

ill wait for them to chime in then with what they want logged. had issues with hooking up afr to my laptop (i monitor via aem wideband and ecu) so hopefully i can get those setup for these logs

 

[HolyCrapItsFast]

At first glance it sounds to me like it might be a fuel delivery problem as Spamby suggests and the walbro my not be enough. It could still be tuning and more specifically the SD map needs more work. You hit vastly different load cells from gear to gear so fueling in fourth gear may not hit the same VE as first gear.

Do you have a fuel pressure gauge you can refer to?
Is this full speed density or hybrid MAF/SD?
Is the MAF still installed?

As for log parameters I might suggest the following in first gear and one in fourth gear. Stop the pull when it starts to go lean. No need to destroy your motor while we figure this out.

Injector Duty Cycle
SD VE Commanded
SD Air Flow Pre and Post
Mass Airflow voltage (if MAF is still installed)
Manifold Rel Pressure
Throttle Position
Calculated Load
Engine Speed
Commanded Fuel Final
Your wide band AFR gauge
Feedback Knock Correction
Fine Knock Learned

 

[ej25subie05]

isn't the walbro 255 good for at least 500hp? i am getting fuel, at least to the fpr i havnt checked beyond that.

i can check the fuel pressure on idle but not while driving (don't have a gauge that i can monitor in cab)

tune is full SD but we are using MAF sensor in blow through tube as IAT sensor (instead of a gm sensor or the such) could this maybe cause issues?

I'm still thinking its in the tune honestly. we maxed out the fuel delivery (once to see what it would do) and it was pig rich all the way to that certain load and it went lean again. its like there is a limiter set, and something is cutting off the fuel. we have double and triple checked. but as mentioned I'm new to this and he's not used to the newer software so we may have missed something.

 

[ej25subie05]

i appreciate y'all trying to help out. really do. Never expected tuning to be this complicated

 

[HolyCrapItsFast]

The Walbro 255 is not sufficient for 500+ IMO. You would think about getting an Aeromotive 340 or a Deatchwerks 300 or even a Walbro 400. If you are not monitoring fuel pressure then you will never know. Gauges are cheap on Ebay and you can probably mount one temporarily, if not taped to the hood, but it has to be ruled out.

If it is tuning then I feel it is in the VE table. The only limiters that might affect this is load limit and max airflow. I usually just set these to max load of 5 and max air flow 500gS. I believe these parameters are under "Miscellaneous limits".

I did run into this same thing once before with open source where the SD logic was still referencing the the MAF limits in hybrid mode and the only way for me to fix it was to go to full speed density. However the Cobb logic is vastly different and this would be the first time I experience a limit wit SD on a setup like yours with Cobb on full SD.

 

[ej25subie05]

i will get a gauge to rule out fuel pump and fpr.

my load limit is set at 2,000g/s for SD like cobb tuning guide stated. but i could not locate the max airflow you mentioned. could it be known as something else in cobbs software?

would you happen to have access tuner so you could look at what we have setup? one extra pair of eyes may do the trick.

 

[HolyCrapItsFast]

I do but I have to wait till tonight when I get home to refer to it. I'm at work right now. :tup:

If you want to send me your latest rom then send it to my email. brodix32@gmail.com

 

[ej25subie05]

thank you sir!
sending it over shortly.

 

[HolyCrapItsFast]

Got it thank you! I will have a look tonight when I get home.

 

[ej25subie05]

okay so i did some digging that i didn't even think about till today because i was so set on it being in the tune.

got a fuel pressure gauge and the fuel pressure was acting really, really strange lol

turn key and it hits almost 40psi but won't hold 40psi drops down to 0-5psi right after pump stops cycling (explains why i have to crank car a bit to get it to fire at times)... start the car its around 35psi, let it run a minute or so and it drops down to 26psi and stays there. so i was like okay fpr may be bad... took the top off with spring and diaphragm, looks like new with no rips or cracks.

took pump out and everything looked okay, tried swapping in a stock pump but it wouldn't even prime (pump most of seized just wanted to see if i could get a good fuel pressure at idle with another pump) so now i guess my only option is to purchase another fuel pump?

or does anyone have some ideas on how to rule out a fuel pump???

 

[HolyCrapItsFast]

Okay I had a look and nothing jumps out at me regarding any limits that might be causing your issue. :tup: There are other aspects of the tune that could be touched beyond stock values but nothing related to your issue IMO. I notice you are using stock latency but the ID1000's are vastly different than stock. That will create a string of other issues as you are compensating with the VE table. Also your per cylinder injector trims should all be zeroed. There is more but I would rather focus on the fuel issue first.

What MAP sensor are you using? The scaling suggests an Omni 4 bar.
Can you post or send a log with the prescribed parameters?

Thank you for the opportunity to help!
George

 

[HolyCrapItsFast]

okay so i did some digging that i didn't even think about till today because i was so set on it being in the tune.

got a fuel pressure gauge and the fuel pressure was acting really, really strange lol

turn key and it hits almost 40psi but won't hold 40psi drops down to 0-5psi right after pump stops cycling (explains why i have to crank car a bit to get it to fire at times)... start the car its around 35psi, let it run a minute or so and it drops down to 26psi and stays there. so i was like okay fpr may be bad... took the top off with spring and diaphragm, looks like new with no rips or cracks.

took pump out and everything looked okay, tried swapping in a stock pump but it wouldn't even prime (pump most of seized just wanted to see if i could get a good fuel pressure at idle with another pump) so now i guess my only option is to purchase another fuel pump?

or does anyone have some ideas on how to rule out a fuel pump???

I do agree that it should maintain pressure after the pump primes. You need to check the base pressure first and to do that you idle the car and remove the vacuum line from the FPR (clamp it off). The pressure should be around 43.5 psi and be stable. Then when you re-attach the vacuum line, the pressure should drop by manifold relative pressure. So if your relative pressure at idle is -7psi the fuel pressure should be roughly 36psi. Adversly if you go into boost the fuel pressure should increase by that much as well so if manfold pressure is 17psi then fuel pressure should be around 60psi.

Besides a bad FPR it could also be a manifold vacuum leak or a bad fuel pump still.

 

[ej25subie05]

Okay I had a look and nothing jumps out at me regarding any limits that might be causing your issue. :tup: There are other aspects of the tune that could be touched beyond stock values but nothing related to your issue IMO. I notice you are using stock latency but the ID1000's are vastly different than stock. That will create a string of other issues as you are compensating with the VE table. Also your per cylinder injector trims should all be zeroed. There is more but I would rather focus on the fuel issue first.

What MAP sensor are you using? The scaling suggests an Omni 4 bar.
Can you post or send a log with the prescribed parameters?

Thank you for the opportunity to help!
George

We were just trying to create a base map at first, i will pass on the info to my buddy. i am running a aem 3.5 bar map sensor with cobbs map adapter

 

[ej25subie05]

sorry forgot to mention that i did clamp the vacuum line to try to set the base psi. but it just wasn't gonna have any of it haha. it wouldn't even move which is very strange. i screwed it in practically all the way and practically took the screw out with car running (vacuum line clamped) and gauge wouldn't budge.


anyone here have a extra fuel pump they don't need that they would sell? something bigger than a walbro 255
if not I'm looking at the aeromotive 340 right now. just need to find someone to overnight it.

 

[HolyCrapItsFast]

We were just trying to create a base map at first, i will pass on the info to my buddy. i am running a aem 3.5 bar map sensor with cobbs map adapter

Oh right you mentioned the aem map sensor.... My bad.

sorry forgot to mention that i did clamp the vacuum line to try to set the base psi. but it just wasn't gonna have any of it haha. it wouldn't even move which is very strange. i screwed it in practically all the way and practically took the screw out with car running (vacuum line clamped) and gauge wouldn't budge.


anyone here have a extra fuel pump they don't need? something bigger than a walbro 255
if not I'm looking at the aeromotive 340 right now. just need to find someone to overnight it.

Post in the "Request a Quote" thread... http://igotasti.com/vBforum/forumdisplay.php?288-Request-A-Price-Quote, Our vendors offer great prices.

Also do you think you could also post a picture of your engine bay focusing on the fuel lines and rails?