MAP Questions...

[David Doddek]

>    Well, now that I know a ton about MAF. I came to a great revolation. I 
>checked the minimum air flow specs and I'm not even close to the turn on
flow at
>full power!!!!!
>    So much for the power of a briggs and stratton. But a MAP sensor is the
next
>bet, or any Barametric Pressure Sensor. Does anyone know of any good ones?
>    What are the dimesions of you average MAP? <asking for something like 
>hieght, width, etc>
>    What is the output type, and range? <Analog voltage,frequency,PWM etc> 
>Analog Prefered of course.
>    Lastly how exactly can it tell me how much air is flowing in the engine?
>
>               Thanks....
>                     Jim Staff
>
>
Jim,

A map sensor from a gm car will work just fine.  It has a 0v (0kpa absolute)
to 5V (100 kpa absolute) analog signal.  One thing to remember about the
briggs, is that the small displacemant 1 cylinder will not develop a stable
vacuume signal.  You may need to make an intake with some type of volume,
say equal to the engine displacemant to act as a buffer.  Or else use a very
fast a-d converter and average or filter the signal in software.  As has
already been mentioned, the amount of air in the engine can be defined by
the ideal gas law.  Think about it this way, If there is little air
pressure, then there is little air.  A lot of air pressure means that there
is a lot of air.  Since the ratio of fuel to air is to be pretty much
constant, the amount of fuel is related to the air pressure in the intake.
This is pretty general, but is a start.  The dimensions of the gm map sensor
are roughly 1" by 1.5 " by 4" and uses a 3 pin packard connector operating
on 5 volts.

David J. Doddek                                          |pantera at dris.com
Owner SGD Electronics & Development Engr for Caterpillar |h 309 685-7965
Formula SAE Team Sidewinder 94-95                        |w 309 578-2931
89 T-bird SC,  69 Fairlane w/SGD EFI                     |fx 217 428-4686
74 Pantera w/Electromitive Tec-II Twin turbos and Nitros |
Hey, If you are going to go fast, go REEEAAL FAST.       |