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Master injection time

EFI Tuning Fundamentals

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Hi

I did not quite understand what the master injection time is based on.

is it supplied by the ECU once the information on the injectors and on the AFR has been recorded in its parameters?

when André says 100kpa, he speaks in absolute pressure or in nanometric pressure?

This parameter is only relevant for ECUs that use an injection time fuel mode. Basically this calibrates what a number of 100% in the fuel table means. For example if the master injection time/pulse is 6 ms, then this would be what the ECU would supply with a number of 100% in the fuel table. BUT, this is before background compensations are applied. The ECU will also alter the delivered pulse width based on MAP. This works on the basis that if we double MAP, we need to double fuel to get the same AFR. The ECU will also apply compensations to the final pulse width based on IAT/ECT compensations too.

With respect to MAP then, I quoted that the master pulse width is at 100 kPa and this is absolute. As explained above, if the MAP value dropped to 50 kPa, the ECU would halve the pulse width and if it was 200 kPa the pulse width would double.

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