Haltech f7c map sensor info...

[Kris Weldy]

Wow !Thank you very much Chris!It almost appears as if haltech was in fact
correct.DOH!I was hoping it would be as easy as a simple map sensor
change-but go figure!Im not all about making another one work with some
other circuitry that i have to build-not lack of effort-just lack of
knowledge,nevertheless thanks for all the great ideas.I may just go ahead
with a cut off raiser from Mcmaster Carr  and a one way check valve to fool
the map sensor.Details can be found at
http://pages.cthome.net/gus/cutout.html
.I figured this could possibly lower the signal or air pressure of air going
to the map sensor,thus allowing me to tune the car to run above 22psi of
boost,my goal is 30psi.Does this sound feasible?
If not ill have to resort to nitrous,unless anyone else has any other
ideas,Thanks.--
Kris Weldy (AIM: VolvoFam3)
Arlington, TX
'87 760ti, 20psi w/B23FT, TO3/04E turbo, many mods



> At 04:11 PM 1/21/01 -0800, Kris Weldy wrote:
>
> >I finally got the info from my haltech map sensor.The goal of this
project
> >is to change the haltech f7c map sensor(mounted onto the chip)from a
22psi
> >map sensor to a 3 bar map sensor(roughly 40psi?).
> >
> >merely a letter "M" with a circle around it.then follows two rows of
number
> >below it-the first row of numbers is:
> >mpx2200ap
> >the second row reads:
> >94    40
>
> This is the Motorola MPX2200. The -AP refers to the case style. See:
>
>
http://e-www.motorola.com/webapp/sps/prod_cat/taxonomy.jsp?catId=M9393462190
36
>
> That page lists the Moto sensors in that family, incl. the 2200. You
> can d/l the datasheet incl. pinout, etc. 9440 is probably a date code,
> 40th week of 1994.
>
> The bad news is that this is an non-signal conditioned sensor, which means
> you can't just drop in a normal 3 wire, +5v conditioned output sensor.
It's
> a raw bridge. It takes a drive V from 10-16V and outputs a low level
> signal, ~40mv full scale.
>
> Moto does not seem to offer a similar unit above 2 bar. (The MPX2200 is a
> 2 bar absolute unit, good up to ~14.5 psi of boost.)
>
> The ideal would be another sensor that's electrically similar, but which
> reads 3 bar at a nominal 40mv output. Somebody out there may have one,
> time to hit the catalogs and websites.
>
> A less ideal solution would be to build a little circuit to regulate
> the sensor drive down to +5v, drive a normal 3 wire conditioned unit,
> and use a voltage divider to cut it's output down to 40mv full scale.
> You'd also need to convert that signal into a fake differential signal,
> roughly in the middle of the V+/ground range set up by the sensor
> drive voltage. Should be the work of a few resistors and op amps,
> but you'll need good precision parts for the resistive divider, noise
> may be a problem, accuracy may suffer, etc. (Insert the usual EE
> booga-booga warnings here.)
>
> A quick look thru the Digikey catalog (www.digikey.com) shows that
> they offer a few sensors which might be usable. You need one that
> outputs 40mv at your desired max boost. The promising ones look like
> 100mv FS at 100psi (absolute). This will deliver 40mv (the full scale
> the Haltech will "see") at 40psi. This is p622-624 of the Oct-Dec 2000
> catalog, SenSym and Measurement Specialities. Prices range from $25 to
> $100++.  You also need to make sure the new sensor can handle the
> voltage (MPX2200 is listed at 16v max, or you could measure what the
> Haltech is actually providing), and that the bridge resistance is
> ballpark similar.
>
>
> >3 bar sensor i can use to replace this one?Someone also said the software
> >would change if i changed the map sensor-i got the impression they were
> >implying that the motherboard would "know" and then the software would go
up
> >to the 3 bar setting.Is this true?
>
> It won't know by itself. There may be a software setting where you can
> tell it, but if the swap is done right the box will have no idea what
> was done.
>
>
>    Chris C.
>
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