Blown Yellow

Hello,

I am dyno tuning a 1998 Camaro that I just installed PRC heads and a Magic stick cam in. The problem I am having is that the car keeps on going off the chart rich as soon as it hits 4,800.

I of course started tuning the car to nail down the fuel trims and have got them nicely in the -2 to -3 range. I then did a WOT run and the result was a table that needed a little tuning down low but was below 10:1 after 4,800.

No matter what changes I make in PE mode, I just can't get the thing to lean out!! I have tried comanding crazy lean WOT A/F's like over 18 and it just does not lean it out after 4,800.

I have already verified my dynojet is reading properly by testing another vehicle, anybody have any suggestions, my customer is starting to doubt me.

Thanks,

Martin

O'dell

iTrader: (1)

Try and mess with the maf table, I had the same problem when I first started tuning mine, just couldn't get the PE table to do anything. As soon as I started making small adjustments to the maf table, it was very obvious on the dyno...just start with small increments.

slow

iTrader: (7)

check for COT to be disabled, my car woudl dump tons of fuel when it went into cot protection.

Ryan

Blacker

iTrader: (3)

I had a similar issue and the COT was the culprit. It will dump extra fuel in at WOT to save the cats. I have had mine disabled and have no issues.

Blown Yellow

Thanks for the suggestions guys, the COT table was one of the first things I changed and it still had no effect. It is a very repeatable problem, It just goes completely and instantly fat at around 4-4500 rpm I have tuned quite a few H/C LS1's and have never experienced this problem.

This problem is frustrating, I wish it was a lean problem so I could at least start looking at things like injectors and fuel pump. Any chance the injectors are hanging open on the top end? The car is seeing normal fuel pressure, Dang this sucks.

I guess I will start playing with the maf tables but it just bugs me that I have never had to do that before for WOT tuning.

Thanks again,

Martin

slow

iTrader: (7)

what does the commanded air fuel ratio read, does it change during the run?

how did you chance the wot fueling before if you never adjusted the maf?

Ryan

Blown Yellow

VIA the PE VS RPM table.

Blown Yellow

Here is the graph

txhorns281

iTrader: (12)

Try this, find out how many lbs/min your MAF is pulling right when you start to richen up all nasty like. Convert that value to g/sec (1 lb/min = 7.58 g/sec) and then look at your MAF table. Find the closest value in g/sec that you have corresponding to your calc, and highlight that cell and every one above it. Now, multiply that portion of the table by .9 (90% downward scale) And then run the dyno again. If that doesn't lean you out, then I dunno WTF your car is doing....

Also, have you verified that your IFRs are of good nature?

MNR-0

Checked your O2 sensors lately? No bullshit. Bad O2 sensors will cause PE tuning to go haywire only because of the uncontrollable fuel charge going into WOT.

gameover

check you openloop fuel table as well, the PCM will use the richer of the PE table and the openloop table. A lot of cals have this number set quite high as the temp gets close to 100degC

TT_Vert

iTrader: (12)

yep check open loop F/A. The computer will use the richer of the two ( PE and open loop FA tables) My Open loop F/A tables were 1.13 so anything past 4800 RPMS was using the richer of the commanded AFRs which wasnt my PE) So i set all my open loop F/A tables to 95-100 KPAS in any temp id be in at the trace track to 1.00.

Dave