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  • #31
    Alpha-n is the description of the way the ecu runs/controls fueling without the mass airflow sensors. Fueling in Alpha-n is controlled or metered via throttle position sensor rather than mafs. A good mapper can get this to work every bit as smooth and well as oem. Just have to remember to have spare throttle position sensor in the car just in case!
    Black S50

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    • #32
      It sounds a little complicated to take in at this time of the day!

      So OEM ECU stays in place, new carbon airbox is added and the MAF taken away?!
      2002 '52 S54 - Titanium Silver with 18" BBS LMs, AP Racing BBK, KW V3, H&R anti roll bars & ACS flippers (previously 2000 'X' S50 - Arctic Silver)

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      • #33
        Originally posted by Spooks View Post
        It sounds a little complicated to take in at this time of the day!

        So OEM ECU stays in place, new carbon airbox is added and the MAF taken away?!
        Thats it.

        The OEM ECU is programmed to ignore the MAF (or lack of one) and instead determine fueling based on the throttle position sensor.

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        • #34
          Originally posted by topgeartom View Post
          Thats it.

          The OEM ECU is programmed to ignore the MAF (or lack of one) and instead determine fueling based on the throttle position sensor.
          2002 '52 S54 - Titanium Silver with 18" BBS LMs, AP Racing BBK, KW V3, H&R anti roll bars & ACS flippers (previously 2000 'X' S50 - Arctic Silver)

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          • #35
            saw this on another forum,

            http://www.bmw-driver.net/forum/showthread.php?p=482989

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            • #36
              The MC's ECU uses different sensors to measure the air entering the system (Mass Air Flow sensor and Intake Air Temperatrure sensor) so that an appropriate amount of fuel can be injected into each cylinder, dependent upon the requirements from the Throttle Position Sensor. The Oxygen sensors then monitor the exhaust gas as it flows through the cats to ensure that the fueling was correct with regard to emissions.

              An airbox like the CSL or MacMotoren, is almost akin to the throttle bodies being completely open to atmosphere with virtually no restriction except for the filter, but the MAF represents a restriction within the intake system. So if you remove the MAF, then fueling is regulated by the angle of the throttle position sensor without actually measuring the amount of air entering the engine and this is termed Alpha-n tuning.

              The MAF and IAT sensors obviously help the ECU to accurately calculate the density of air and not just its volume, so must be more accurate method of fueling than Alpha-n since a TPS cannot work out the mass of air flowing into the engine. The screens within the MAF occupy about 20% of the cross-sectional area of the MAF, but they are there to ensure that the airflow can be accurately measured so removing them doesn't help. Fitting larger MAFs could help and I've even read of using tandem MAFs but both these alternatives would require some recalibration of the signals they send to the ECU.
              Last edited by exdos; 31-07-2012, 05:26 PM.
              /// Exdos ///
              "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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              • #37
                Originally posted by exdos View Post
                Fitting larger MAFs could help and I've even read of using tandem MAFs but both these alternatives would require some recalibration of the signals they send to the ECU.
                I was thinking about this earlier. Whilst I am sure there would be some connector and ECU programming issues, a big old MAF from something mahoosive combined with a similarly large silicone hose that connects to the inlet manifold must yield appreciable gains.

                I guess the cost per hp/gain ratio must be pretty close to/worse than cams or a carbon airbox which might be why its not been done before, but it would mean the drivability isnt affected.

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                • #38
                  Originally posted by topgeartom View Post
                  I was thinking about this earlier. Whilst I am sure there would be some connector and ECU programming issues, a big old MAF from something mahoosive combined with a similarly large silicone hose that connects to the inlet manifold must yield appreciable gains.

                  I guess the cost per hp/gain ratio must be pretty close to/worse than cams or a carbon airbox which might be why its not been done before, but it would mean the drivability isnt affected.
                  BMW use the same MAF as used by the MC in several of its models, including the M6 (S85) which has two air intakes and a MAF in each one, so this would be a possibility with a redesign of the MC's air-intake before the plenum and some electronic modulation of the signals from 2 MAFs. I wouldn't know how to do that though.
                  /// Exdos ///
                  "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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                  • #39
                    Originally posted by exdos View Post

                    The MAF and IAT sensors obviously help the ECU to accurately calculate the density of air and not just its volume, so must be more accurate method of fueling than Alpha-n since a TPS cannot work out the mass of air flowing into the engine. The screens within the MAF occupy about 20% of the cross-sectional area of the MAF, but they are there to ensure that the airflow can be accurately measured so removing them doesn't help. Fitting larger MAFs could help and I've even read of using tandem MAFs but both these alternatives would require some recalibration of the signals they send to the ECU.
                    So on the actually M3 CSL then, how did BMW do it as I assume the MAF is removed?
                    2002 '52 S54 - Titanium Silver with 18" BBS LMs, AP Racing BBK, KW V3, H&R anti roll bars & ACS flippers (previously 2000 'X' S50 - Arctic Silver)

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                    • #40
                      Originally posted by Dave P View Post
                      Interesting read. No prices though?
                      2002 '52 S54 - Titanium Silver with 18" BBS LMs, AP Racing BBK, KW V3, H&R anti roll bars & ACS flippers (previously 2000 'X' S50 - Arctic Silver)

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                      • #41
                        Originally posted by Spooks View Post
                        So on the actually M3 CSL then, how did BMW do it as I assume the MAF is removed?
                        There is no MAF. The fueling is all relative to the angle of the TPS - that's what is called "Alpha-n".
                        /// Exdos ///
                        "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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                        • #42
                          Originally posted by exdos View Post
                          There is no MAF. The fueling is all relative to the angle of the TPS - that's what is called "Alpha-n".
                          So from what I have read its a less sophisticated method but does the trick?!
                          2002 '52 S54 - Titanium Silver with 18" BBS LMs, AP Racing BBK, KW V3, H&R anti roll bars & ACS flippers (previously 2000 'X' S50 - Arctic Silver)

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                          • #43
                            Originally posted by Spooks View Post
                            So from what I have read its a less sophisticated method but does the trick?!
                            I'd agree with that.
                            /// Exdos ///
                            "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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