MAP / MAF / Grain of Salt...

[Mark Romans]

Tpis also says a modified maf will flow 750 cfm and I have flowed one on a
superflow 600 and modified maf flowed 796 cfm (589cfm at 11").  I show 255
grams/sec (Which is the max it will measure) at 4600-4700 rpm's.  As long as
peak torque is below the max flow you should be able to tune the engine to
run fine with a 165 ecm.
Mark
-----Original Message-----
From: Andrew K. Mattei <amattei at mindspring.com>
To: gmecm at esl.eng.ohio-state.edu <gmecm at esl.eng.ohio-state.edu>
Date: Saturday, March 27, 1999 8:44 AM
Subject: Re: MAP / MAF / Grain of Salt...


>Frederic Breitwieser wrote:
>>
>> For my engine, 431 stroked cubes and 10lbs boost max, I was
>> hoping it was okay.  I still don't "get" which is better,
>> MAP or MAF for my boosted application.
>
>Unfortunately, I'm not qualified enough to jump in to the MAP vs MAF
>debate. ;) Nor do I wish to start one...
>
>Here's what I *know*. The MAF sensor that accompanies my 165 ECM is a
>Bosch unit, with a 2 3/4" opening (3 1/8" OD, 2 3/4" ID). The
>restrictions inside include the large heat sink fins (which some people
>shave for performance), and the loop for the wire sensors. I'm not sure
>of the "maximum flow" through this unit, but my "guesstimation" would be
>in the range of just under 600 cfm. (I have a book that quotes TPIS as
>saying that it "is capable of flowing only 529 cfm stock" - of course,
>they sell modified MAFs, so, take with a grain of salt...). While this
>would likely get your 431 rolling, it would prove to be a restriction
>later down the road.
>
>Now here's a thought (one from the peanut gallery - or as Bruce would
>say, "Sleepy says..." ;^D ). Has anyone ever tried two MAF sensors? This
>book I have ("How to Tune and Modify Chevrolet Fuel Injection", Ben
>Watson, Motorbooks Series) states that the Bosch MAF gives a signal
>range of 0-5 volts output based on airflow (low->low, high->high) (not a
>frequency based unit like the later Delco 2 found on LT1/LT4 cars). Some
>creative circuitry (op amps) could combine the two MAF signals in to one
>for the ECM... That is, if you max out the initial MAF. Just a
>thought... Of course, I'm still on my first cup of coffee... <G>...
>YMMV...
>
>FWIW, I can't decide whether to go MAF or MAP either... I have my 730
>ECM sitting on top of my 165... Probably go MAF, because that's what my
>wiring harness is set up for... I have a lot more work before I actually
>get the thing running, though...
>
>-Andrew (ported my heads this week, though ;^D) M
>