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Old 09-22-2019, 08:01 AM
olddog olddog is offline
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A mass flow EFI system uses the engine displacement times RPM times a pumping efficiency constant. They put this in the denominator.

They measure the air flow into the engine with the MAF meter. This goes into the numerator.

The engineering units of measurement are corrected such that the units in the numerator and denominator are the same. This gives a very accurate calculation of engine load. This is what the timing is based on in an EFI system.

Before Mass Air they used speed density, which is MAP and TP sensors. Based on MAP, rpm, and TP they estimated what the Mass Air Flow was, and this was used in the numerator.

As you know speed density does a very poor estimate, when the MAP is very low at idle and increases with rpm.

Then there is a strategy called Alpha-N. It simply used the TP sensor and rpm. This is what you will be simulating. It is the least accurate of them all, but it has its better points too. It has way less complicated calculations to do and way less sensors to go bad and lie to it. Inside a MASS Flow EFI is a copy of the Alpha-N. It is used as a sanity check to verify all sensors are reading within tolerances. It is also looked at when rapid throttle position changes happens, as the Alpha-N is quick to calculate without sensors lagging reality.

So the TP you are going to use will work similar to what an Alpha-n EFI strategy would do. It is a ball park system, not a highly accurate system, but compared to a vacuum canister and weights on springs? Likely not too shabby.

Last edited by olddog; 09-22-2019 at 08:03 AM..
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