MAP / MAF / Grain of Salt...

[Andrew K. Mattei]

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