gives a total of 5 x 5 x 3 x 2 = 150 VE tables and then you still have a giant interpolation mess to deal with at the end. the old way being conservative assuming 5 VE tables for each cam position, three differnt states for the manifold switch and a couple of states for DoD. For example, to do this the traditional way would require multiple VE tables for each camshaft, then some mehtod to mix the result and then another set of VE tables for each depending on the switched manifold state, not to mention you have DoD thrown in as well. Now most of you are wondering, why, for the love of god, would anyone think this is a better system than before? The answer is simple really, this mathematical approach gives a highly accurate result in the new multidimensional space created by adding the exhaust, intake camshaft and also the variable intake systems. If you open an early E38 file, under Engine Airflwo, Dynamic Airflow you will see the zone mapping thresholds and numbering.įor the later code they eliminated the ability to map the zone #'s but the convention is the same as below. VE = Constant + KMap².MAP² + KMap.MAP + + + + KRpm².RPM² + KRpm.RPM + + + KRpm.RPM + KEx².Ex² + KEx.Ex + KExIn.Ex.In + KIn².In² + KIn.In Here's the full formula for those that are interested: For those 4cyl guys who have variable camshaft your world is another 2 orders of magnitude more complex) becuase the Intake and Exhaust cam terms are not zero. It is completely non-intuitive, but you could construct a spreadsheet or something to calculate the VE value at given RPM and MAP values for any set of coefficients (using the formula above). that then churns out the filter coefficient matrix, which is then put into the calibration tables. Then put that into a math package like Matlab etc. in this case the multi-dimensional VE table). The way this kind of thing is typically done in a mathematical sense is you create the solution matrix that they are trying to achieve (ie. Kxxx is the coefficient from the current zone VE = Constant + KMap².MAP² + KMap.MAP + + KRpm².RPM² + KRpm.RPM The simplified equation is (leaving out all the variable cam stuff that isn't used): Bascially the engine operation is divided up into 30 "zones" and then there is a coefficient for each zone that forms an equation for the PCM to calculate the VE value (instead of looking it up in a traditional table).
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