What is the BBTB from?? and fitting MAF from 540i

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  1. What is the BBTB from?? and fitting MAF from 540i 
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    Hi all,

    Does any one know which model of BMW the larger bore throttle body comes from for the m50 manifold conversions? 540?

    I have also read about fitting the larger MAF from a 540. I have a 97 328i is there any one that can remap my car using the 540i maf?

    Cheers

    Rob,
     
     

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    The larger throttle body is a custom made item from Alpina527, they are bored out and a new butterfly fitted.

    As for the 540 MAF (same as the Euro M3), I think the majority of people you will see with that have it done via an OBD1 / Bosch 413 Conversion.
    With the Siemens OBD2 type ECU, it'll be constantly trying to adapt and correct itself.
    It most likely is possible, but it could take a lot of testing beforehand to get it running right.
     
     

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    Quote Originally Posted by TheEnd View Post
    The larger throttle body is a custom made item from Alpina527, they are bored out and a new butterfly fitted.

    As for the 540 MAF (same as the Euro M3), I think the majority of people you will see with that have it done via an OBD1 / Bosch 413 Conversion.
    With the Siemens OBD2 type ECU, it'll be constantly trying to adapt and correct itself.
    It most likely is possible, but it could take a lot of testing beforehand to get it running right.
    so, would you reckon that a 540i MAF would work on a OBD1 325i with no mods to the software? if so, do you think there's any gain involved?
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    Thanks very much for the reply!

    My car is an obd2 model so that pretty much answers that one, do you know if any companies have remapped an e36 using a MAP opposed to a MAF, i know of a few companies that have done this with other makes just haven't read about it being done to a bmw.

    Rob,
     
     

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    Quote Originally Posted by mistreku View Post
    so, would you reckon that a 540i MAF would work on a OBD1 325i with no mods to the software? if so, do you think there's any gain involved?
    It'll still need a bit of tuning, although you might get away with just fitting the next size up injectors.
    As the tube is bigger, the sensor in the middle give one voltage, but more air gets in around the sides, and the engine/ecu doesn't realise this.

    BMW liked to keep things matched where they could, so there is a good chance the nice size up injectors would then add the 20% more fuel to match the 20% more fuel, but I wouldn't expect it to be perfect without checking them out first.

    The 540 MAF is no good for a non-vanos engine, they used a hot wire, and the only larger version was from the M5 3.8, and an M5 3.8 maf costs more than a 325 engine!
    There is a hotwire maf from some japanese car about, possibly the Mitsi 3000GT, or Nissan 300ZX.

    For the Vanos engines, the system is similar so the 3.5 inch Maf from M3s and the 540 can be used, but you'd need to either change the software or change the injectors to keep the calibration between "x fuel for y air" within reason.

    OBD1 trusts the numbers, and makes real time adjustments if needed to 3.500 rpms, OBD2 notes down any discrepancies and applies it to everything, whether it can measure it or not.

    MAP conversions - it's unlikely to be possible on a standard ECU, It's expecting a nice clear 0-5v for none to max airflow.
    The MAP pressure isn't directly proportional to airflow, so it needs more electronics to sort that out.
    It could be done with a standalone ECU, but i'm not keen on MAP control anyway, It uses pre-programmed tables of what condition leads to what airflow, and it does mean that changing parts can throw the measurements out, IE, a better flowing airfilter would give a slight decrease in the vacuum in the manifold for the same amount of air, or if the exhaust is better flowing, the Volumetric Effeciency (the percentage it can fill the cylinders) increases without the ECU being aware.
     
     

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    Cheers for the reply,

    I have had very good results using MAP sensors in FI setups, and i find them fairly easy to work with. If you know the engine capacity, the manifold pressure and the rpm you essentially know how much air you are using, you will need an air temp/coolant temp sensor to compensate for air density but you use these with a MAF too?

    When you map under WOT conditions vacuum should be close to zero(ish), using the lookup table then gives very accurate mixture control, part throttle fueling or off throttle conditions where there is vacuum reading isn't so critical, but still accurate so long as your look up tables good. I agree MAFs will be more accurate as you are physically measuring the amount of air entering the engine.

    Using your example, fitting an aftermarket air filter may reduce vacuum under part throttle conditions, but this does mean more air has entered the engine (the vacuum reading is less), if the smaller vacuum reading doesn't richen the mixture (which it should) the labda reading will.

    None of this is really relevant to the BMW lol which i know nothing about, if it can't be done it can't be done.

    Cheers again

    Rob,
     
     

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    Quote Originally Posted by TheEnd View Post
    It'll still need a bit of tuning, although you might get away with just fitting the next size up injectors.
    As the tube is bigger, the sensor in the middle give one voltage, but more air gets in around the sides, and the engine/ecu doesn't realise this.

    BMW liked to keep things matched where they could, so there is a good chance the nice size up injectors would then add the 20% more fuel to match the 20% more fuel, but I wouldn't expect it to be perfect without checking them out first.

    For the Vanos engines, the system is similar so the 3.5 inch Maf from M3s and the 540 can be used, but you'd need to either change the software or change the injectors to keep the calibration between "x fuel for y air" within reason.

    OBD1 trusts the numbers, and makes real time adjustments if needed to 3.500 rpms, OBD2 notes down any discrepancies and applies it to everything, whether it can measure it or not.
    Thanks for taking the time to get into details, it now makes more sense.

    this might work pretty good even without the remap/injector (although i have a set of pink injectors 440's at hand), as my AFR is rather low atm (car's running a bit rich, with AFR dropping to 11-11.5 in the high range of RPM).

    but i think i'll have to replace the whole intake piping and boot with a 3.5" one, in order to get the best of the MAF.
    There are only two products required to make the universe work properly: Duct tape and WD40. 


    If it moves (and it shouldn't): duct tape. 
If it doesn’t move (and it should): WD40.

    Everything else is just stuff.
     
     

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