help! went to the track, my car kept getting leaner each pass!

[ryans1000]

ok, so I went to the track, with newly installed dual walbros, fuel line, injectors and e85. humid 85 degrees out. Made 4 passes. Pass 1 , the wideband showed pretty close to what was commanded. After that run I richened the boost ve table up about 5% at full boost (175kpa, 11psi) . Pass 2, afr's looked good except for the very top of 4th gear got lean. So I richened it up another 5% and on pass 3 it got leaner all through 3rd and 4th gear. Didn't change anything after pass 3. Pass 4 got even leaner!

So I get back home and install a fuel pressure sensor and log fuel pressure, I am still having a lean problem but the fuel pressure is stable right where it should be rising 1:1 with boost.

I'm stuck. My fuel pressure is looking good so the only thing I can think of is my wideband is not right or something in the tune or meth injection (already tested it and no clogs , seems to be working fine) . My setup is in my signature.

pass 1
http://importevolution.com/temp/logs/run1_11-7_bad_launch.jpg


pass 4
http://importevolution.com/temp/logs/run4_10-5.jpg

[ryans1000]

Here are the logs and the two track tunes. I have a plx wideband setup in the log.

11878
11879
pass 1 11880
pass 2 11881
pass 3 11882

[joecar]

Is your FPR MAP-referenced (air hose to manifold)...?
Is your fuel rail pressure steady as MAP changes...?

[ the correct answers to those two questions based on your tune should be "yes" and "no" ]

Also check for airleaks.

[slows10]

Noticed a few things, may not have nothing to do with your question. But did you have the pedal all the way to the floor during that run in the first log I think I looked at. It showed only about 95% tps as max I think. Also started the run at apprx IAT 112deg F and ended up over 150 at 115 mph. Seems like a big increase, noticed no intercooler but meth. Was the meth used?

[ryans1000]

joe, yes fpr is map referenced. Now that I'm logging fuel pressure I have verified it while doing wot pulls 58psi base + 10psi of boost and for the most part it will be at 68psi in that scenario. Sometimes it is off by 2-3 psi, kind of fluctuates but I wouldn't think it would be enough to make it go that lean. checking for air leaks is a good idea, haven't done that yet.

slows10: yea my throttle hits the carpet and needs to be adjusted, it has never opened all the way to 100%. The IAT's look fairly normal compared to my last times at the drag strip. Meth injection just can't keep it cool enough without an intercooler from what I've seen, contrary to what you might hear claims on. Although I will say without the meth the temps would probably be around 300 degrees.

[joecar]

In your case fuel pressure should be 58 psi (400 kPa) minus BARO plus MAP...

i.e.
- in kPa: FP should be: 400 - {SAE.BARO.kPa} + {SAE.MAP.kPa}
- in psi: FP should be: 58 - {SAE.BARO.psi} + {SAE.MAP.psi}

[ note that BARO - MAP is MANVAC ]

Do you have a FP pid (what input are you using to read FP)...?

Can you also log BARO and FP and post the logs (post your calc_pids.txt file).

2-3 psi variation is ok.

[joecar]

Your base pressure of 58 psi was measured with the FPR exposed to barometric pressure (i.e. reference hose temporarily removed), right...?

[ryans1000]

yea base pressure was set with reference hose removed. At the drag strip I wasn't able to log fuel pressure. After this problem I bought a fuel pressure sensor. I can post a log with fuel pressure test runs on the street later tonight.

[ryans1000]

actually are air leaks likely to cause an issue on a speed density car?

[ryans1000]

here is the pass 4 video just for kicks http://importevolution.com/temp/videos/2011_shootout/ryan_10-58.wmv

[ryans1000]

timing looks steady to me except between shifting gears

[joecar]

actually are air leaks likely to cause an issue on a speed density car?Yes, it causes MAP to be wrong, this causes the PCM to compute the wrong cylinder airmass, different than actual cylinder airmass (which is the same with or without leak).

[ryans1000]

what about clogged injectors? is there anything I can look for in efilive to trouble shoot a clogged injector?

[ryans1000]

is it possible this issue could be caused by slight misfires that I wouldn't be able to notice but my afr's would show a little lean? misfire due to plugs perhaps? I don't notice a misfire but I'm running out of ideas?

[joecar]

Dirty injectors can only be diagnosed by having them flow tested and cleaned... this service is not expensive and turn around time is quick.

[joecar]

is it possible this issue could be caused by slight misfires that I wouldn't be able to notice but my afr's would show a little lean? misfire due to plugs perhaps? I don't notice a misfire but I'm running out of ideas?Yes, very good observation...

misfires cause unburnt fuel and unburnt oxygen to go past O2 sensor, the O2 sensor sees the oxygen so it reads lean.

Do a CASE relearn and then monitor the misfire counters.