Running Lean - First KA-T Post

[DevilMB3017]

Here's the story... After a lot of time/money/work I've been running boosted since mid November. I drive the car maybe once a week, sometimes every two weeks, depends on conditions. It's had a couple little bugs like all turbo projects will. But now the last couple of times I've had it out (1/5, 1/7, and 1/8 testing it) it runs lean after about 3K RPM, right around when boost comes on strong.

It's significantly worse at partial throttle then WOT, leading me to think it might be ECU, but I was hoping for some input as it does happen at WOT too. I checked all the couplers and IC piping and nothing is different. Any ideas on what to check next? For those who thing it might matter it was usually about 40* when I had it out and recently its been ~55*.

Specs: 91 Motor, AMS rebuild kit, Crower V2 Cams, JGS Starter Kit with T3/04E .68 a/r, 650cc injectors, Walboro 255 lph, Greddy M-Spec with HKS SSQV, BRM exhaust, Z32 MAF and Enthalpy tuned ECU. I also have an adjustable FPR, with the pressure at 36 idle.
Modified by DevilMB3017 at 11:50 AM 1/9/2008

[Florida240sx]

Do a boost leak test. Looking at coupler means nothing. I had a cut in mine that even with coupler off you couldn't see.Does it feel like the car is going lean?Possible the wideband needs to be calibrated or is going bad. Also could be an exhaust leak somewhere. I had funky reading when I had an exhaust leak on mine.

[WDRacing]

IS the ECU in open loop during exceleration or closed loop? I only mention this because it could be a bad O2 sensor. Although that usually makes thing rich.

Does it richen back up after 3k? What are the exact AFR's?

WD

[DevilMB3017]

Florida: It does feel lean, but I haven't had a chance to do a boost leak test. My boost pressure remains pretty much the same as it was, so I'm not ruiling out the boost leak but I'm doubtful of that. I'm running a PLX wideband, and they say you don't need to calibrate them.

WD: I don't know the answer about the ECU. When I get home from work tonight I'm going to check for codes and all that. The O2 sensor is pretty new, it would suck if it just went bad like that. It does not richen back up dramtically and I'm afraid to get on it to find out. The AFR acutally flashes LEAN on my PLX's output sometimes, but is around 16 or so but does flucuate quite a bit.

And thanks to both for quick replies.

[WDRacing]

16 isn't wicked bad fr cruising, but under accel its ugly...lol.

[DevilMB3017]

That's the problem WD, it is under accel and WOT as well.

Maybe I need to get in touch with the guys at Enthaply?

[Brandon93240]

Whats your base timing set at?

[DevilMB3017]

Stock 20BTDC.

I re-torqued a couple clamps and it seems to be a little better. Up'ed the fuel pressure a bit helped too.

[crzycav86]

i was gonna say..

about the 36 psi fuel pressure. was that with the vacuum line plugged in? or is that the base fuel pressure?(pressure w/o vacuum line)

unplug or pinch the vacuum line and set the fuel pressure to around 43. that will richen up the mixture in open loop.