E Dogg

iTrader: (1)

OK first- I did search and i know the conventional wisdom....

injector time in ms divided by [(60sec/engine speed in rpm)= ms per revolution)] =% duty cycle

for example
@ 4000 rpm/10 psi, with injector time of 6.32ms

4000/rpm = 6.32/15 gives me a duty cycle of 42%

But this takes for granted my injector is spraying throughout the entire revolution, right?

Lets say my intake duration total per revolution which would be something like degrees of intake duration multiplied by the number of times a face of the rotor moves across the intake ports per revolution of the E-shaft is 60%(just a guess for the example) so that means of our 15 ms of revolution only 9ms is available for injection, which makes the duty cycle 70%!?


is this accurate, or does the easier method mentioned first work? any ideas?

E Dogg

iTrader: (1)

posted in performance, since this isn't really a general question...

jgrewe

iTrader: (1)

I think your confusing duty cycle of the injector for something else. The duty cycle is how long the injector is open to deliver the amount of fuel you want, not the time the engine gives you to get it into the combustion chamber. The formula you have on top will give you how many ms the port is open, you can spray fuel when the port is closed no problem because above a certain rpm the air doesn't stop moving.