LS2 GTO: Bad hesitation on throttle tip in

[LS1FREEK]

Car runs great otherwise, but seemed to get significantly worse after going SD tune. Car is an 06 GTO, A4, Texas Speed iron 408ci, PRC 245cc heads, T-rex cam, Fast 102 inyake, NW 102 TB. I've been through the tune quite a few times, can't find what might be causing this other than the TB is so big it let's too much air in too fast and the ecm can't get fuel to it fast enough? Only does it when you slam it to the floor, wideband says it goes completely lean, about 1 sec then fuel catches up and works great. Anyone else ever had this problem?

[LS1FREEK]

I'll upload my crappy tune when I get home lol. This is my first SD tune on an E40 ecm

[LS1FREEK]

It still did it when it was MAF tuned, but only about half as bad

[joecar]

Post tune file and most recent log file.

Is your FPR manifold-referenced or un-referenced...?

What was measured rail pressure (measure with reference hose temporarily removed)...?

[joecar]

Also, did you check FAST intake for leaks (did you use the special valley cover bolts)...?

[LS1FREEK]

19044

19045

[LS1FREEK]

I didnt build car, am only tuning it for a friend, I'm pretty certain FPR is not referenced, and I believe the regulator is in the tank right? Fuel pressure hasnt been messed with.

[joecar]

Ok, I'm not an expert on LS2/E40, but this is what I see:
- B0141: is set to EQR 10, this is way rich, should be set to around EQR 1.00 in warmed up engine range, and somewhat richer in cold engine range.
- B0143: same comment as for B0141.
- B0155: is set to 1200 rpm, meaning PE won't kick in when TP is opened from an idle (I don't really know about this one).
- I think some of the idle parameters/tables don't look right, but I'm not sure which.
- think burst knock may be getting involved.


Do you have the stock file that was on this car (to compare against)...?

[joecar]

Ok, I found the stock tune for this, there are a lot of changes, some of them not needed.

[joecar]

Hmmm, it looks like it's set to run from the MAF only, and MAF is known to not catch up when throttle is snapped open.

[LS1FREEK]

Ok, I dont know what you mean when you say I have it setup to run on MAF only?? It has no MAF on it, I took it off because it was doing this:

19047

Watch the MAF HZ

[LS1FREEK]

Will the MAF Patch fix this?