a MAF too small

[Dave Zug]

> From:          "Mark Romans" <romans at pacbell.net>
> To:            <gmecm at efi332.eng.ohio-state.edu>
> Subject:       Re: a MAF too small
> Date:          Wed, 21 Jul 1999 21:57:30 -0700
> Reply-to:      gmecm at efi332.eng.ohio-state.edu

> 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 OWN one of those mark, it's a 12.7 car with the stock stuff. I've 
read the thrasher stuff and even have one of their chips for the GN.. 
time to re-visit his page now that I understand it more. I also do 
not know what a Fuel Management Unit is. and I also need to find 
out more what "recalibrate the settings" EXACTLY entales. I beleive I 
understand what the scaled MAF tables are doing, and that changing 
the numbers by a percentage across the board would be my first 
thought.

> 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
> 
> 
> 
> 
Dave Z. www.delanet.com/~tgp