MAP sensor

[Mark Pitts]

Just a note:

The sensors you are talking about have a nipple for a push fit hose, or =
two nipples in the case of the differential ones.  If you want to get a =
pipe thro' a metal box (shielding or whatever), look at the tank =
fittings for model airplanes... they are handy, especially the bulkhead =
ones with a threaded bit in the middle and a nipple on each end, so that =
you can build a box with all the local electronics inside, and not have =
to open it t connect/disconnect the pressure hose.

Just an idea

Mark

----------
From:  tom cloud[SMTP:cloud at peaches.ph.utexas.edu]
Sent:  Friday, September 13, 1996 3:20 PM
To:  diy_efi at coulomb.eng.ohio-state.edu
Subject:  Re: MAP sensor

>> I would like to add MAP sensing to my system.  What's a good MAP to =
use,
>> how much is it, where does one get it (if it's for a vehicle, I =
suppose
>> a parts house), and how does it work?

Alex Cazin replied:

>The Ford EEC-IV MAP sensor is a good one. It is a "smart" sensor,=20
>with on-board signal processing and it has digital output, a "near"=20
>perfect square wave (49-51 % duty cycle). It is rugged and it lives=20
>well in the engine compartment and a long vacuum hose from the=20
>intake manifold does not bother it.
>
>Square wave output makes it easy to process. Output frequency is from=20
>about 159 Hz at 0 in. vacuum (key ON, engine OFF or wide open=20
>throttle, same as baro pressure output) to around 102 Hz at 21 in.=20
>vacuum (idle).
>
>Frequency vs. vacuum output is pretty linear for a good sensor.
>

Thanks, Alex.  Now, I'll just need to find out how much it costs,
what it looks like, how it mounts, etc.

To followers of the thread, Todd Knighton recently posted:

"Newark Electronics has the Motorola Sensors.  They're not to be put in
"the engine compartment.  They're not ruggedized.  We've been putting
"them inside the Motronics unit inside the car and they've worked well.=20
"the MPX4250A is a 2.5 bar absolute sensor, so it's good to about 20psi
"and absolute vacuum.  They make a MPX4100A, I think that's the number,
"for normally aspirated vehicles, never ordered that one.  These are all
"temperature trimmed and compensated sensors so they aren't affected by
"different temps like most MAPs are."

The data sheets for these are on the Motorola web page,
(http://motserv.indirect.com/) and they're listed in the Newark catalog
for about $26.  They have a linear voltage output (not freq), are
small and have different methods for connecting them to the pressure
source to be measured (probably via a hose).

Now, which to use -- and what does one do with the data re EFI ??
The analog output might be ideal for me to augment the control on
the Holley aftermarket system I already have.  For a digital
system, will simply A-D.

Now, the frequency output of the OEM unit -- seems that
that would entail either an F-V convertor and then A-D or an
interrupt driven timer circuit that would return a number of counts
proportional to the period of the sensor output.  Any suggestions?

Tom