[Gmecm] ZZ4 and Accel DFI

[Carlos A. Martinez]

Don't know if anyone on here has used one of Accel's DFI systems?  I 
got some questions about it.  I did an engine coversion on my '88 Fiero 
about a year ago.
The engine used is a new SBC crate ZZ4 with Sallee chevrolet installing 
the LT4 HOT cam in in and the GMPP 1.6 Roller rockers.  Many people 
have used this engine in this configuration with great success in 
Fieros, so I decided to go with that.  I didn't want to go with a stock 
Camaro/Firebird TPI system because the runners and everything about it 
is too tiny to really handle the almost 400 horsepower generated by 
this engine.  So the Plug and Play 350 Accel DFI system fit the bill.  
At the time that I bought it they (Accel, by talking to them) claimed 
it was only designed to work with a normal 350, and that using on a ZZ4 
would require reprogramming the computer quite a bit.  That was fine 
with me I'm up for a challenge anyway, and am pretty familiar with how 
and why engines works, and what to do and not to do for the most part.  
Reading through Accels like 50 page manual on the DFI system is a great 
additional learning for me as far as tuning is concerned.  Since then, 
from what I see on Accels website, thee new 350 plug and play system is 
programmed to work with a stock ZZ4.  I have emailed them regarding 
obtaining that ECU file if possible, if indeed it is different than the 
one my older (same Gen 7+) ECU carried back then.  They have not 
responded in over a week, which is strange because their tech support 
was always excellent whenever I had any questions.

My current problem is that it runs extremely rich.  All the injectors 
are verified to be OK by Accel, I had them check'em for good measure.  
Even with the pressure turned way down to like 30 psi i still runs 
rich.  Also, the timing is obviously totally wrong for this engine.  
More than about 1/2 throttle at over 2000 rpm causes some serious 
knocking so I assume it's advancing too much.  The Plug and play 
computer is not reprogrammable (timing, injector pulse width, etc.) 
without what I understand is some "standard key" or "pro key" that you 
hook up to your PC allowing more extensive programming of the ECU.  
Before go all nuts with all this, I wanted to see on this list to see 
if anyone has a ECU file for an Accel Gen 7+ ECU that they are using 
with success on a ZZ4 in my configuration.  ZZ4's are pretty popular so 
I figured it wouldn't hurt to ask first before attempting any 
reprogramming on my own.

This is one issue I want to tackle.  The second issue is to figure out 
why the darn engine vibrates at almost any RPM.  I still need to check 
compression.   All external electronics have been checked, double 
checked and or replaced.  The vibration seems to get worse at about 
1800 rpm gets really bad (engine is on solid mounts, can't do it any 
other way) at about 2300 rpm or so, and sorta smooths out (harmonics 
with the chassis or something) and gets to a faster  vibration over 
3500 rpm.  Many have told me it's the flywheel, but It really cannot be 
(doubtful at the very least), because there is only ONE flywheel you 
can use for this engine conversion and it's made by Centerforce for 
V8Archie (from who I got the conversion kit)  It is an externally 
balanced flywheel with drilled divets on the inside of it to counter 
weight it.  I has the same number of divets in it as all the other 
Centerforce flywheels, so it would be doubtful it is unbalanced.  
Unless the divets were accidentally drilled to a different depth on my 
flywheel for some odd reason.
I've adjusted and installed roller tip rockers before on my Fiero when 
it had the 2.8 V6  and it was simple, you just needed to make sure they 
were turned in 1.5 turns from no lash with the lifter in the lowered 
position.  It worked fine.  How much of a role could the rockers being 
in or out of adjustment play in my problem (possible bad cam ??).  Most 
have told me not much.  From what I've heard the GMPP full roller 
rockers only need like 1/2 turn from zero lash or something like that. 
If someone could enlighten me on this matter it would be great.

This thursday, hopefully I'll get a chance to lift the car up and pull 
the plugs and check the compression on this thing.  I can't wait to get 
this as smooth as silk.  Other V8 Fiero owners with the same engine 
tell me it's as smooth as silk.  I just with mine was.

Thanks,
Carlos