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Thread: MAF vs. MAP

  1. #1
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    MAF vs. MAP

    a mass air flow (MAF) sensor and manifold absolute pressure (MAP) sensor are two different ways of feeding fuel to an engine. some cars use a MAF and some cars use a MAP, but i get the impression a MAP system is preferred for turbo use. can anyone explain why?

    here's some comments from the SDS standalone computer site:

    http://www.sdsefi.com/tech.html#FAQ


    Q. What is a MAP sensor and why are there 3 different ones?

    A. A MAP sensor senses the pressure in the intake manifold. When combined with rpm information, it allows the ECU to compute airflow and supply the correct pulse width to the injectors.

    We sell 3 different MAP sensors to cover engine applications with different boost levels.

    The 1 Bar sensor is for naturally aspirated engines.
    The 2 Bar sensor is for engines running up to 15 psi boost.
    The 3 Bar sensor is for engines running up to 30 psi boost.

    Map sensors are referenced to an absolute vacuum internally so they compensate for altitude and barometric changes automatically. MAP sensors simply connect to your intake manifold with a length of vacuum hose.

    Q. Can SDS use an airflow meter?

    A. No. Since SDS is fully programmable and designed to work on almost any engine, we decided to use the speed/density method of load sensing. Installation of airflow meters on many vehicles, especially turbocharged ones, is often awkward because of their size. Airflow meters also represent a flow restriction which is not conducive to making hp on performance applications.

    any supporting/contrary comments? thx.

  2. #2
    get out im naked! deckedoutmp5's Avatar

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    good thoughts and post, i use a 2 bar map but after 15 i guess i need a 3 bar?

    juan is this true?
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  3. #3
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    I think I may have a 2.5 Bar sensor soon. I think that should hold me over...
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  4. #4
    264 chipmunks at 12 psi Little Beavis's Avatar

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    Yes, but isn't a MAF more accurate?

    (Don't get me wrong, they have their issues and most days I wish I didn't have one, but if the MAF worked for the full range of air flow. . .I don't see the problem.) On that note, is the Mazdaspeed MAF different? Why does ours max out if the MSP doesn't? Or does ours not max out. . .damn, I apparently have confused myself. . .I know not what I say. . .
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  5. #5
    Registered Member PaulMP3's Avatar
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    MPI has a larger MAF
    (bluemp3)
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  6. #6
    MOTM Winner Jan '09 Kooldino's Avatar
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    Originally posted by LinuxRacr
    I think I may have a 2.5 Bar sensor soon. I think that should hold me over...
    What kind/where from?
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  7. #7
    Super Moderator LinuxRacr's Avatar
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    Originally posted by Kooldino
    What kind/where from?
    Not sure I will have it yet....I must wait and see. The system I am getting will also be able to use the stock sensors.
    Last edited by LinuxRacr; 10-02-2003 at 11:36 AM.
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  8. #8
    Are you threatening me? stef_nz's Avatar


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    sure a maf is more accurate but aftermarket computers are usually designed to use map (for the reasons below) and they are much better at it now than they once were.

    try finding a maf that a) is big enough to cause no flow restriction, and b) doesn't mind if you have a bov venting to atmosphere....

    if you vent to atmos with a maf, heaven help you - measuring flow at the maf which doesn't get to the engine, what happens then? very annoying i'd imagine....

    oh, and afaik, map sensor specs are for vacuum as well as boost, so two bar = 1 bar each side of 0, three bar is for up to two bar boost etc.....

  9. #9
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    thx for the feedback.

    Originally posted by stef_nz


    try finding a maf that ... doesn't mind if you have a bov venting to atmosphere....

    if you vent to atmos with a maf, heaven help you - measuring flow at the maf which doesn't get to the engine, what happens then? very annoying i'd imagine....
    .....
    it's a little bit greek to me, but here's a post that suggests using a SAFC to make it work:

    http://www.hyundaiperformance.com/fo...ic.php?t=35963

  10. #10
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    MAF is the only way to go for any street car and should be used race cars. The MAF will read how much air is going into the motor. The MAP has been seen as the end all for years due to the fact that OEM meters were small. For over the last 15 years the 5.0 Ford market has lived with MAF meters and it opend the door to making big power without all of the problems that came with aftermarket computers. With 100,000s of Fords on the street with MAF meters the aftermarket was forced to that a look and do something about it. You then saw a few companies start making larger MAF meters. Some were junk and they are no longer around. With the G-M running MAP sensors they were forced to use aftermarket computers for big power. With the Ford you could still keep the stock EEC-IV or the EEC-V.

    We built and ran a Ford Ranger ProRWD truck for the last two years. It had a 2.3 Turbo that would have made over 1000hp if it could be tuned right. One of the main sponsors is Electromotive. They did all of the tuning for us on and off of the track. The TEC-III will not work with a MAF so we stuck and had to take a trip back in time and use a MAP sensor. They would tune it this week and next week the air got colder and the tune was off. After a retune we would go back to the track in a few weeks and this time the air was hotter, now it needs to be retuned again.

    This is a very common problem with the MAP system and aftermarket computers. The MAF meter will read the airflow into the engine. If it is a hot day the air is different they on a cold day. The same is true on a dry day or a rain day. All of the factors will be seen by the MAF but not the MAP. Once you dial in a MAF system you can leave it alone. With the MAP you will need to retune as the weather changes.

  11. #11
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    What is the hangup with BOVs. You can get by-pass valves for upto 40lbs of boost and 500hp. Also a by-pass will help spool the turbo faster when you shift. How much are you looking to run?

    We stock two Mazda meters that will work from 300 to over 425hp. How much are you looking to make?

    We sell an aftermarket computer that does use a MAF sensor, it will run upto 12 injectors, 4 coils or your stock Mazda coils, boost control and turbo launch control. It also has Windows based software and it is easy to tune.

    Thanks again


    Later......Nick

  12. #12
    MOTM Winner Jan '09 Kooldino's Avatar
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    Originally posted by stef_nz
    sure a maf is more accurate but aftermarket computers are usually designed to use map (for the reasons below) and they are much better at it now than they once were.

    try finding a maf that a) is big enough to cause no flow restriction, and b) doesn't mind if you have a bov venting to atmosphere....

    if you vent to atmos with a maf, heaven help you - measuring flow at the maf which doesn't get to the engine, what happens then? very annoying i'd imagine....

    oh, and afaik, map sensor specs are for vacuum as well as boost, so two bar = 1 bar each side of 0, three bar is for up to two bar boost etc.....
    Yup, 'tis all true, AFAIK. Long time no see, stef. WB.
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  13. #13
    Registered Member TiGrayMsp716's Avatar

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    Ok since MAF sensor don't like BOV because they vent air into the astmosphere why don't they move them post BOV and elimiate that problem... I know it sounds too simple but I'm not understanding the difference between MAP and MAF
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  14. #14
    Registered Member YuYuRena's Avatar

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    Originally posted by MPNick
    MAF is the only way to go for any street car and should be used race cars. The MAF will read how much air is going into the motor. The MAP has been seen as the end all for years due to the fact that OEM meters were small. For over the last 15 years the 5.0 Ford market has lived with MAF meters and it opend the door to making big power without all of the problems that came with aftermarket computers. With 100,000s of Fords on the street with MAF meters the aftermarket was forced to that a look and do something about it. You then saw a few companies start making larger MAF meters. Some were junk and they are no longer around. With the G-M running MAP sensors they were forced to use aftermarket computers for big power. With the Ford you could still keep the stock EEC-IV or the EEC-V.

    We built and ran a Ford Ranger ProRWD truck for the last two years. It had a 2.3 Turbo that would have made over 1000hp if it could be tuned right. One of the main sponsors is Electromotive. They did all of the tuning for us on and off of the track. The TEC-III will not work with a MAF so we stuck and had to take a trip back in time and use a MAP sensor. They would tune it this week and next week the air got colder and the tune was off. After a retune we would go back to the track in a few weeks and this time the air was hotter, now it needs to be retuned again.

    This is a very common problem with the MAP system and aftermarket computers. The MAF meter will read the airflow into the engine. If it is a hot day the air is different they on a cold day. The same is true on a dry day or a rain day. All of the factors will be seen by the MAF but not the MAP. Once you dial in a MAF system you can leave it alone. With the MAP you will need to retune as the weather changes.
    The problem would be corrected if you tune the car to standard day, and run all your pressure and speed corrected to standard day.

  15. #15
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    I am a little lost as to what you trying to say. Do you mean that if you tune on a prefect day the car will always be in tune?

    Thanks again


    Later.........Nick

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