hey guys i own a 1997 baja 272 with a 454 mpi. i am looking at buying a whipple for it and the guy has a mefi 4a ecm. what is the difference between a mefi 4a and 4b. i have looked all over and can not find any comparisions.
also will the 4a work fine for my application? oh ya my engine is completly stock.
thanks

E-mail Todd peterson here:

http://www.racepak.com/Road_Racing/index.php

He has worked for the GM factory teams and knows everything there is to know about the MEFI computers.

Jeff

You may or may not have a Mefi3 on yours. If you do, it will work just fine as well.

my stock ecm is a mefi 1.

Being a 97, it should be at least a Mefi2. Mefi3's were out in 07 as well.

mefi 1 is horrible get rid of it

the mefi 1 is not horrible, however, conquest30' is correct, it is not able to do any above 1 bar tuning. You CAN re-pin your harness to handle the mefi4.... for your application the 4b vs 4a offers no advantage. There are a few more controls available in the 4b, but none that matter at your(I assume) hp and injector size level.

What do you want to know?

My 97 was a mefi 1. I bought the harness ends from AZSM and converted mine to mefi 4b. Make sure you're tuner has the capability to tune a 4. I don't think M3 software works(?)

yea what rich said is what i mean haha, no 2 bar map sensor and cant set the fuel curve over 5100, it uses some weird spark cable multiplier or some crap, im re-pinning mine also to mefi-4

Mefi 4, 4a, and 4b are all pinned the same. You need to use the correct software level for each one. The 4b breaks the fuel and spark tables down to be more precise. I have new mefi 4 harnesses it is a lot of work to convert a mefi 1 harness over. Tyler