FW: MAF Upgrad

[lkurek at smtpgate.anl.gov]

     The GM MAF is a Bosch unit.
     
     So, you say I can cut away the 3" tube and replace it with a 4" one, 
     which would result in a 78% increase in flow area and compensate with 
     an increase in fuel pressure and/or injector size, in order to use the 
     same fuel map in the ECM? (I know...I could get a programmable unit, 
     but hey...I'm trying to be creative here :) ).
     
     So, assuming my current fuel map was set with 22lb/hr injectors 
     @43psi, I could bump my fuel pressure to 76psi (please bare with 
     me...I know I could get into an injector lock problem here), or go to 
     40lb injectors (or a combination of both), and this would correlate 
     with the decreased MAF input to the ECM?
     
     Anything else? What about low speed resolution? What about setting a 
     code for inadequate GPS flow at a given RPM? How linear is the flow 
     rate to MAF area?
     
     TTYL!
     
     Larry


______________________________ Reply Separator _________________________________
Subject: Re: FW: MAF Upgrad
Author:  <diy_efi at efi332.eng.ohio-state.edu> at Internet
Date:    2/24/98 1:28 PM


I don't know about GM MAFs, but Bosch MAFs sense flow only in a portion 
of the body.  That is, the same sensor is used for many different flow 
capacities, just different bore diameters.  The ECM is only reading 
frequency, that is RELATIVE flow, which you should be compensating for 
with fuel pressure and injector size anyhow.  I know some aftermarket 
 ECM suppliers make huge MAF bodies.
     
John Bucknell is jb24 at chrysler.com
---------------------- Forwarded by John R Bucknell/JTE/Chrysler on 
02/24/98 12:40 PM ---------------------------
     
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        02/24/98 12:31 PM
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Subject: Re: FW: MAF Upgrad
     
>case.  It might be easier to just have one MAF supply voltage (and the 
>other is a dummy) and just change your tables to compensate.  i.e. 
assume
>that twice the amount of air is entering the engine as the MAF says 
 there is.
     
The advantages of doing this is its very simple to devise - bolt on a 
 few
MAFs and connect them up.  But, with my desire to run twin turbo's, this 
introduces more potential for problems, as I'd have to have the ECM be 
aware of one turbo is boosting higher than the other...  I debated for a 
while, physically mounting the turbo's in such a way that I could put a 
shaft rod between them to ensure they boost at the same level, but I 
 dunno.
 I started making my manifold anyway, though the front of the intake log
plenum has an open face - I'll be welding on a panel with either one 
 hole
or two depending on how I'm going - I have two MAFs, two ThrottleBodies, 
and using two, allows more flow with cheap OEM junkyard parts.
     
     
Frederic Breitwieser
Bridgeport, CT 06606
http://www.xephic.dynip.com/
     
1993 Supercharged Lincoln Continental 
1989 4-Door Softtop Humvee (Hummer)
2000 Buick GTP (Mid-engine track car)
     
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