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  1. #1

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    Boost limit of stock MAP sensor / ECU

    Ok folks, I did a bit of research today and found this.

    My stock Bosch MAP sensor is a part number 0 261 230 049. According to. . .

    http://partfinder.smpeurope.com/inde...10&value=16829

    . . . it crosses over to a Bosch 0 281 002 510 and is used in many European turbocharged small cars, but none in the US.

    According to the datasheet for a Bosch Motronic MS3. . .

    http://64.233.167.104/search?q=cache...lnk&cd=1&gl=us

    . . . that sensor is a 2.5 bar sensor. That means that no matter what ECU you put on it, you won't get any additional fuel beyond 22 psi boost unless you change the MAP sensor.

    Now, the next question is. . . does the stock ECU have a fuel table that goes all the way to 22 psi? I know my turbo Z28's MAF sensor will continue reading higher and higher as the boost rises, but the ECU will not comprehend anything higher than 511 gm/sec.

    Mike


  2. #2

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    I really like to see GOOD questions like that one! I don't have a clue.

  3. #3
    bttek1's Avatar
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    Hello Mike,

    The stock (RXP) Bosch sensor is a 2 bar sensor with a max 5v output at max boost.


    Quote Originally Posted by engineermike View Post
    Ok folks, I did a bit of research today and found this.

    My stock Bosch MAP sensor is a part number 0 261 230 049. According to. . .

    http://partfinder.smpeurope.com/inde...10&value=16829

    . . . it crosses over to a Bosch 0 281 002 510 and is used in many European turbocharged small cars, but none in the US.

    According to the datasheet for a Bosch Motronic MS3. . .

    http://64.233.167.104/search?q=cache...lnk&cd=1&gl=us

    . . . that sensor is a 2.5 bar sensor. That means that no matter what ECU you put on it, you won't get any additional fuel beyond 22 psi boost unless you change the MAP sensor.

    Now, the next question is. . . does the stock ECU have a fuel table that goes all the way to 22 psi? I know my turbo Z28's MAF sensor will continue reading higher and higher as the boost rises, but the ECU will not comprehend anything higher than 511 gm/sec.

    Mike

  4. #4

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    Quote Originally Posted by bttek1 View Post
    The stock (RXP) Bosch sensor is a 2 bar sensor with a max 5v output at max boost.
    If that's the case, then the stock, Riva, and Rotax Racing ECU's will all go "dumb" over 15 psi boost.

    Mike

  5. #5
    bttek1's Avatar
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    The bosch map sensor will see 29.5 lbs/5v so technically you can call it a 3 bar sensor but I have always referred to such sensors at 2 bar...


    Quote Originally Posted by engineermike View Post
    If that's the case, then the stock, Riva, and Rotax Racing ECU's will all go "dumb" over 15 psi boost.

    Mike

  6. #6
    HORSEPOWER JUNKIE 9secZO6's Avatar
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    Let's not forget the rising rate regulator.....let the ecu go dumb, A/F gauge is king, timing is another story.

  7. #7

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    Quote Originally Posted by bttek1 View Post
    The bosch map sensor will see 29.5 lbs/5v...
    29.5 psiA or psiG? If it's 29.5 psiG, then it would be a 3 bar for sure.

    Mike

  8. #8
    bttek1's Avatar
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    psiG


    Quote Originally Posted by engineermike View Post
    29.5 psiA or psiG? If it's 29.5 psiG, then it would be a 3 bar for sure.

    Mike

  9. #9
    Website may not be suitable for small children WOT's Avatar
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    If the stock ECU does not have a fuel table above say 15 psig, we could run a potentiometer inline with the MAP sensor so that we effectively calibrate the MAP to be within the fuel table of the ECU. That way you could run larger fuel injectors (maybe 50's or 55's) and not have it be rich down low, but still maintain the proper AFR at higher boost levels. And, it wouldn't be as much as a guessing game: the computer would continue to add injector pulse width with boost (not just with higher rpm). That would also allow a simple pot to turn to adjust AFR on the fly.

    This is very doable. We need a simulator to hook an ECU up to to play with. This should be an easy mod to get the proper AFR with the stock computer.

    I can't remember, does the MAP resistance go up with manifold pressure or down? I think it goes down with increasing pressure. Time to start rigging up a test fixture.....

  10. #10
    Quote Originally Posted by WOT View Post
    If the stock ECU does not have a fuel table above say 15 psig, we could run a potentiometer inline with the MAP sensor so that we effectively calibrate the MAP to be within the fuel table of the ECU. That way you could run larger fuel injectors (maybe 50's or 55's) and not have it be rich down low, but still maintain the proper AFR at higher boost levels. And, it wouldn't be as much as a guessing game: the computer would continue to add injector pulse width with boost (not just with higher rpm). That would also allow a simple pot to turn to adjust AFR on the fly.

    This is very doable. We need a simulator to hook an ECU up to to play with. This should be an easy mod to get the proper AFR with the stock computer.

    I can't remember, does the MAP resistance go up with manifold pressure or down? I think it goes down with increasing pressure. Time to start rigging up a test fixture.....
    The resistance goes down with increasing boost.

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