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Injector Constant

EFI Tuning Fundamentals

Discussion and questions related to the course EFI Tuning Fundamentals

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Got through the course. Was promised to have insight on injector constant calculation. You mentioned OE systems with a nonreturnable fuelrail and etc. In my cars ECM (Bosch ME9.6) there is a valu named Injector Constant. In HP tuners it is defined as the injector constant in Milliseconds per Percent Fuel Mass(ECM 2341). If I have the dynamic flow of the new injectors at 2.5 ms opening time with 6000 impulses 100 ml, or 74 grams. So I divide it by 6000 and get a value for 2.5 ms with one impulse to be 0,01233 grams. Then divide this by 2.5 ms and multiply by 100 to get the percentage: 0,4933. Is my calculation even in the facinity of the wright value for these injectors?

I haven't dealt with that particular ECU previously, neither have I used a system which defines injector size in this manner. I would be inclined to start by doing a very basic calculation based on the size of the stock injectors and the size of your new injectors. For example if you've doubled the size of the injector from stock then it would be reasonable to expect that you would need to double the injector constant. From here you should be in the ball park and you could refine the number from the STFT & LTFT data.

Ok. I see. Where could I find the orig. injector data? I´ve no idea about their rating.