94SLUG

How does the car react? Is there a break up or does it just shut down? Does the power just drop off? I was thinking this might be my problem after 6000rpms or blowing spark out. I will have to check MAF/plugs tonight. I know its not fuel and i think im clear on the ignition.

94 NO TOP Z

It will run leaner and leaner the faster you spin the engine past where the MAF maxes out. I don't know how much boost you are running but, mine maxes out at 5,000 rpm with the little P600 blower. I wouldn't run it anymore until you can scan it and see the MAF reading or get it on a wide band. The breaking up could be because its running so lean.

94SLUG

So if this is my problem whats the solutions? Should i send pcm back out to be reprogramed to add fuel when MAF maxes @XXXXrpms. Would it matter if the MAF is on the blow/suck side? Thanks for reply. Its about time to start learning LT-1 edit i guess .

Camaro_SS/R

For my car, the MAF limit problem occur starting at 4900 rpm on the dyno and it leans out like crazy (baseline dyno tuning A/F at 4900 - 11.7 531rwhp then 5000rpm 14.7 439rwhp). Your car will feel like it hits a brick way and power will drop. If you continue pushing above that, your car will blow.

However, this only occurs (AFAIK) for the OBDII computer not on an OBDI. Look at the OBDI section in the following writeup by LJ at http://para.noid.org/~lj/PCM%20Tutor...reviations.htm for more information.

Have you dyno tune your car to see if it is running properly and the A/F is good. Are you sure that it is not fuel (FP or injectors) or ignition (amplifier or coil)

One stupid question just in case - is your stock rev limit taken out.

Definitely learn LT1 Edit.

Good luck

94SLUG

Very cool write up, I want to learn as much as i can before i buy LT-1/edit /tunercat. So im in the clear having OBD-1, but how do i fix the problem if the MAF is maxen? I have searched several other topics on MAF MAXING and 94 obd-1 ECMs have had this problem too. I have not been to a dyno yet because its like 6hr drive, and i dont think the problem is in the fuel system. I have 42lb injectors, GSS340intank, and a boost a pump(FP65psi WOT). Dew module and opti are new. The coil could be a problem considering its a MSD. Rev Limit is set at 6500rpms. The mechanical part of engines is not a problem for me, but my knowledge with the ECM aspect is very small. Thanks for reply and or ideas.

So when you went to a 94 ecm you problem was gone. Could
this be in the tune i have? So what i got from the artical the MAF wont go into limit mode (speed density) on obd-1? Sorry for all the questions.

Thanks Bill

10secz

OBDI or OBDII?

OBDI cars just need "normal" tuning. OBDII cars need to be tricked because of the high-MAF code which (AFAIK) causes an instataneous switch to speed-density mode.

My MAF is max'ed from the second I engage the transbrake until I let off in the traps. Fueling is controlled by the PE tables (coolant and rpm). You'll have a steep increase in the PE vs RPM table starting near the RPM where your MAF maxes. Or do what Hugh did: use the Voltblaster to increase fuel flow at WOT, which resulted in a less-steep PE vs RPM curve.

The best way to dial in the PE tables is on a dyno with a wideband O2 sensor.

94SLUG

sorry by voltage blaster do you mean a BAP?

10secz

My turn to be sorry - what's a BAP? This is a VoltBlaster:
http://www.ramchargers.com/cgi-bin/n...890&cat2=26891

I just ordered one for my car. My O2s are just barely rich enough with the PE vs RPM table max'ed out and the PE vs Coolant table set to 50%. That's not enough headroom for me, and I'd rather not bump the fuel pressure cuz the street driving BLMs are pretty good right now.

EddieP

A BAP (boost-a-pump) is basically the same thing as the voltblaster, but only only feeds juice to the fuel pumps (or whatever you wire it to) at WOT instead of the entire electrical system.

Ultra_Dog

During my dyno, I found AFR shoot way up around 4400 RPM. In monitoring the fuel pressure for the FMU, the pressure did not get up as high as advertised (55psi vs 90psi). Until I can confirm my fuel pump and hoses are set properly, there isn't much else I can do.