FAST tuning on an n/a LT1 stroker

[Birdzilla]

Gentlemen, I am looking for suggestions and some help.
I just put a FAST system on my 383 LT1 in my '93 f-body. The car previously had a custom eprom in it tuned by myself using Tuner Cat software. The car ran well (11.90's) even being forced to short shift it below the ceiling of the factory pcm. I wanted to getaway from having to burn chips and needed to break the 7000rpm ceiling of the factory ecm because of my high-reving valvetrain. The combo should be good for mid to low 11's.

I transcribed my previous VE and spark tables into the C-Com software and setup fuel calc parameters for my 383 w/ 30# injectors. The AE/TPS tables are setup quite different so I tried to go by examples listed on this forum to get them in the ballpark.
To say I'm struggling now would be an understatement.

Idle & cruise drivability is fine, very happy with that.
Slowly rolling the loud pedal into the upper rpm's seems ok as well, with an occasional miss above 5500rpm's.

Stomping it is a whole different story unfortunately... the car lunges off the line like an animal and pulls hard till it quickly hits 5500rpm, then it starts to miss. It will pull on through this up into the upper 6000's rpm's, missing and stumbling. It feels like the motor is trying to pull the car but something is holding it back. It is NOT too lean and I believe the problem is actually that I'm choking it with too much fuel on acceleration. I just don't know what tables and how to manipulate those tables to sort out this problem. I've been trying to get it right for days.


It always happens above 5500rpm, the faster you bring the rpms to 5500, the worse the problem is. Brrr-ba-bbr-ba-brrrr-brr-ba-brrrr. I'm hearing it in my sleep. ANY advice would be greatly appreciated. If anyone might be so kind as to like to take a look at my gct file i'll email it off to them.

 

[bobc455]

Have you verified that your VE tables are pretty close? Does your target A/F match your actual A/F? Does it take a lot of O2 correction to get there?

What A/F ratio are you aiming for?

What are your high/low RPM limits?

Are you supercharged/turbocharged?

What ignition setup do you have?

-Bob Cunningham
bobc@gnttype.org

 

[Birdzilla]

The system I purchased was wideband delete. Its an upgrade option however. Given that I am reading volts off of my stock O2 sensor which I realize is far from optimal. I can if necessary upgrade to that, but since my stock system didn't use it & I successfully tuned it, I figured this should be actually easier. Dosen't seem to be the case so far. Anyway...

I am aiming for a 12.7 ratio under power.

My rev limits are 7600/7400 rpm.

Its naturally aspirated.

Ignition consists of gm optispark, msd 6al, blaster coil, msd 8.5mm wires, ngk plugs. (plugs & wires are new)

I have the ability to swap in & out my stock(reprogrammed) computer at will. I determined the high rpm miss under load is not there with the stock computer. It puls hard right up to 7000rpm then hits the stock computer's ceiling.

So the issue is definately in my FAST programming. The VE tables are right on in the stock ecm as are the spark. The tables map out MAP vs. rpm vs VE identically. I'm just lost with the FAST acceleration tables.

 

[Birdzilla]

Found it

FYI:
I finally found the problem- a bad MSD-6AL. Disconnected it from the loop and not only did the idle improve, but my stroker revved like it supposed to.

Amen.