Fireball

iTrader: (21)

at drop of the clutch (~6600 rpm) the car goes lean as the rpms fall...about 14.6:1 until the rpms start climbing again (as measured with a LM1)

During this time the car also seems to have a very flat spot. (notice after launch in this video)

http://home.comcast.net/bkrzewinski/10p86.wmv

Once the rpms start climbing it immediately goes to ~13.0:1

I've logged MAP, RPM and AFR and the map is the same at that point (101kPa) so I ruled out that its in a different part of the VE Table. I don't really want to try richening it up there since once the rpms start climbing...it'll go rich as it crosses that rpm.

Is is possible the decel fuel cutoff is coming in here (since there is a deceleration in engine rpm and the car has started moving). I haven't tried it yet...but I set the fuel cutoff to min of 70mph so it CAN NOT cut fuel in 1st gear

I'm out of ideas...

niphilli

I am by no means an expert, but I am wondering if 14.6 is not such a big deal in the lower RPMs. When in the RPM range does the A/F get back to 13.0? I know that these motors generally start to detonate between 35-3900 RPM (This is where the factory tune in the '98-00 cars start to pull timing), but your motor probably does not drop that far on a launch?

A friend of mine with a blown cobra had the same problem. Just thinking out loud how much fuel did you have in the tank? Could it be that the pickup could not pickup on those 1.56 short times? Maybe a boost-a-pump would help, if it is not a pickup problem?

Fireball

iTrader: (21)

I run at least 3/8 tank...fuel pressure stays up there...

This is highly reproducible...irregarless of fuel level. I have an intank 255lph pump.

its not that its detonating or anything and it stays above 4000rpm (about 4500 IIRC)...but it seems "flat" which is keeping it out of decent 60' range. It yanks the tires 6" then goes nowhere then takes off like a raped ape...hitting ~101mph in the 1/8

HumpinSS

iTrader: (1)

I dont think it would be DFCO stock that is set to 18kpa to come on and 25 kpa to go off.

have you looked at a scatter plot or some sort of the whole run. Maybe you are hitting a real lean cell while revving the car to launch it and not hitting the same cell as you cross that RPM while going down the track in gear. Either way that would still point to the ve table just in two differnt spots.

If you send me a log I can plot out the average AFR based on map and rpm in ve table format so you can better assess the issue and send it back to you for further analysis...

jimmyblue

iTrader: (11)

Check that you do not have any PE mode delay
and your enrichment rate is 1.0. There is a PE
mode delay RPM which was 5500 on my car,
PE will be held off and ramped up according to
the rate value if RPM is below. I don't know what
the rate value is on earlier years. But set the delay
RPM to 2000 or so (wherever you would sensibly
keep RPM for your "power driving style") and eliminate
that as as possible actor.

If you can log the fuel air multiplier that would indicate
what the PCM is -trying- to do vs what it is.

HumpinSS

iTrader: (1)

Good call jimmy...Always informative

Fireball

iTrader: (21)

I'll plot out the afr vs map tonight and post

as for the PE mode...I'll look at my edit file and check that out Maybe the AFR isn't turning because the engine is now accelerating...it might be the engine is accelerating because the AFR is turning...interesting...

thanks