a MAF too small

[Mark Romans]

Hi Dave:  There are a number of options.  First I would say that the maf
will flow 750 cfm at 28".  So the maf sholdn't be  a flow restriction.  If
you go to http://www.thrasher-ep.com/
Look at the ECM Secrets and Tuning Hints.  They have a ton of good info.
The buick Turbo's run a maf and have no problem.  I would suggest that once
the maf is maxed you add fuel based on rpm (At wot) and also use a FMU.
This should resolve any problem with fuel flow at wot and also allow stock
driveability at part throttle.
I suppose also if you "HAD" to you could adapt a larger Porsche 928 maf,
which is also by Bosch and recalibrate the settings in the ecm to match up
with the larger maf.
Mark
-----Original Message-----
From: Dave Zug <dzug at delanet.com>
To: gmecm at efi332.eng.ohio-state.edu <gmecm at efi332.eng.ohio-state.edu>
Date: Wednesday, July 21, 1999 11:38 AM
Subject: a MAF too small


Heres a brief intro to my project, for those new:

I have an 89 5.7l Iroc, 165 ECM, ARAP (vette) binary. I have put a
supercharger on it and the computer has no idea what airflow is
coming in after about 3000 rpm cause the MAF reads 255 right about
there.

The definite solution is to go to a MAP system. I dont want to hack
the wiring apart and have to use a binary that I'm not skilled enough
at to tune from scratch.

Heres my thoughts as to a solution to the MAF max problem:

If I drill holes PAST the maf sensor, effectively forcing it to
read 75% of the actual air entering the engine.. I can alter the MAF
tables to re-compensate. If it works, I can wrap foam around the
holes and lube with K&N oil for now.. until I can get a pipe made.

Voila.. don't have to buy a twin MAF, dont have to use a translator,
don't have to go to a MAP system. only trouble is at idle, the
resolution might make idle quality suffer. If (there should be)
there is a fairly linear relationship between volume thru the
sensor and unmeasured volume into the "post sensor holes" or larger
single  "post sensor hole", it should work.  one snag is the
difference between the filter restrictions but it may be neglidgable
enough to tweak the MAF values at WOT manually using an EGT or O2..


Am I missing an easier solution? Do I even really care what's going
on at WOT above 3000 rpm?  I MAY max the MAF at 70% TPS and 3500 rpm
so my thinking is I DO care.

I have a few more days and I'll have the alum heads, 28#
Buick GN injectors (12.7 ohms (??)) and new fuel pump on so the
problem is about to get worse.  PS I blew the head gasket probably
from being lean so my mission is that much more critical now with
1200$ heads to warp 8-(

Dave Z. www.delanet.com/~tgp