My car is at a shop right now getting a blower installed with a forged 383 and fuel system, FMIC etc. They are saying the 94-95 pcms are limited to about 550rwhp. I thought they could handle more HP and that rpm was the limiting factor. Can the MAF tables be changed to handle more then 550hp? I want to run about 15#s of boost and if possible avoid the fast/BS3 setups. Is there anything I can do? Thanks,
Randy

 

There are a few making 1000 rwhp with the stock PCM and many more making 700+ rwhp with the stock pcm. You are correct in that the PCM is limited to around 7000 RPM, but you dont need any more RPM to make power with boost. I would recommend some kind of tuning software and appropriately sized injectors. People have made big power with the FMU and timing retard, but it's not anywhere close to being as accurate as actual tuning.

 

I think the fact that the MAF maxes out at 470 or 512 or wherever it is can cause problems with air density on a non-speed density setup. So while you can program the pcm for fuel enrichment, if atmospheric changes happen, the A/F mix might not be the same as it was when you tuned it since the MAF is pegged.

 

I could be wrong, but I was under the impression that the MAF had nothing to do with fuel enrichment at WOT. The PCM relies solely on the PE tables during WOT to supply the correct AF ratio, and WOT is the only time you're likely to see enough airflow to max out the MAF.

 

at WOT the PCM uses the MAF airflow reported and the PE tables to modify the MAF inptu to acieve the AF desired. There are ways to run 2-3 bar setups with MAF and make big hp.

 

Can you elaborate, please?

 

Yeah thanks for clearing that up for me. I would gladly absorb any more knowledge you have on this.

 

that would require giving away a hard earned trade secret. I will talk it over with the powers that be.

 

while the MAF will be pegged out around ~550ish RWHP, you can instead tune with only speed density, no MAF. This requires runnign a 2 or 3 bar MAP sensor and rescaling all your MAP tables (your fuel enrichment table, MAP vs. RPM is the big one here) so that the computer still thinks its a 1 BAR sensor when in fact it is not. The computer output in a scan program will only read up to 1 Bar, so you have to know your re-scaling factor to know exactly where it is by the scan program... of course you should have a boost guage anyway to tell you this.

bottom line, it IS possible to tune for BIG HP with stock lt1 pcm...just kinda a PITA to make it work.

look into the megasquirt standalone system, i got mine up and running for about $400, completely boost sensative, wideband compatable, real time tuning.

www.diyautotune.com
www.megasquirt.info

 

What i will be doing is using a Pro-M MAF with it... its completely tuneable...That will ocver the maf limit...

Use a 2bar, first, map sensor and rescale everything. In all it can be done.

With all the stuffs you are going to be using as add ons...

Versafueler,
LTCC,
Pro-M Maf
etc...
Sometimes i think its a better idea to run a standalone.

If i could somehow make a 24x crank sensor that i could adapt to my lt1, i would run an ls1 with the 2 bar map sensor and versafueler and call it a day.

 

I run a 10# Vortech with custom programming by Jeff Creech using my stock 1995 computer. My MAF maxes out at around 4,500 rpm and Jeff tuned a nice flat AFR of 12, allowing me to put down 593 rwhp.

 

would you mind telling me how you have the ignition being controlled and what not??? Seeing how the pcm is starting to become a bigger and bigger limiting factor with my future plans... I may have to go to megasquirt (though i think the sniffers will hate me if i move somewhere with emissions...)

 

sorry for hi-jacking this...haha i just read your sig, ive seen your can in that mag., i was laid up in a hospital bed in may of 05 and my parents brought me that mag. for reading material...you dont know how many times i read that article...lol

and tuning like you are can be done, obviously, but unless the tuning is done on a dyno with a wideband, its kind of like shooting in the dark, the computer is in open loop, with no self correction of any kind based on MAP, or MAF readings because they will both be maxed out. It can be done though, after all, guys who run carbs and tune by seat of pants driving and checking sparkplugs are more in the dark than we are in this case... just food for thought

 

sure thing, the megasquirt II pcm has an on board ingition driver circuit that can be installed during the assembly. i am just using an old school cylinder 12 volt coil driven off the MSII. Im using an obdII crank sensor (for misfires on an OBDII car), which is a 4x even pulse crank sensor. this is used for rpm input on my MSII in the hall sensor setting. because of the uneven slots in the opti wheel, the opti cannot be used as a trigger input with the MSII, so i retrofitted this crank sensor.

the MS can preform just as well as the stock pcm, so as long as your emissions guy doesnt know its there, it can and will pass emmissions with the proper tune... lucky for me, no emissions where i am.

im goin to make a write up soon on my car domain page on how to install a MS on an LT1 since nobody else has been able to figure it out.

BTW, mine is piggy backed on my stock pcm, the stocker is just running guages and reverse lockout...

 

So let me get this straight, with the stock PCM, tuning on your own past 550 or so RWHP, is pretty difficult, if not nearly impossible. However, am I understanding things correctly, that it can be tuned properly by a dyno tuner when the power could be over 600-650 RWHP?