MAP / MAF / Grain of Salt...

[Greg Hermann]

>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...

Well--if you must go MAF (would not be my choice) why not run two identical
ones in parallel, but only hook up one of them to the ecm. The second one
could even be a dead one (CHEEP), (it's spring, the birds are coming back!)
Then just run injectors twice as big as what the ecm is expecting! (Double
air flow=double fuel flow.) Then just fine tune the ecm to fit your app.
You could run one to each turbo, but use an H-pipe crossover, like on
exhausts, to even out any pulsing. If you do this, be sure all the ducting
is match or mirror of its twin, and watch out for inlet swirl going into
the turbos--which would be one of the more likely culprits if things do not
want to balance..

Regards, Greg
>
>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