Agent911

i was just doing some maths...

it has occured to me:

at <b>5000 rev/min = 83.33333 rev/sec</b> (5000/60sec)

this means <b>0.012 sec</b> is needed for <b>1 rev</b>. (1/83.3333)


since there are 4 cycles to 1 complete engine rev, i understood it that you can only insert air and fuel when the piston is "moving down" and "not moving up". which is 1/2 time of 1 rev.

so if you split that time <b>0.012 sec</b> by 1/2, you get 0.006sec or <b>6ms</b> for which the injector can open at 5000rpm.

completley different from the link below, can someone clear this one up?

he says that the max time the valve can open is 18ms or so. what I am confused is, does the pulse count for the time when the injector is closed?

i took it as open.

thx.<ul><li><a href="https://forums.audiworld.com/performance/msgs/42816.phtml">https://forums.audiworld.com/performance/msgs/42816.phtml</a</li></ul>

dingster

It takes 2 complete revs of the crank to finish all 4 cycles on a 4 cycle engine. I never said it takes 18ms for the valve to open. It takes 21.8 ms for the crank to rotate twice at 5500 rpm. The injectors don't have to fire only when the valves are open(Think about non sequetial fuel injection and throttle body fuel injection). In a sequential FI car, normally they time the injector so it opens prior to the valve opening. But at 100% duty cycle the injectors stays wide open all the time(Not a good practice). 21.8ms is the maximum possible time the injectors can stay open for all the cycle to complete, not how long the valves open. Your actual pulse width is dependant on your load. So the duty cycle is your actual pulse witch divided by max possible pulse width.

Agent911

thx for clearing it out for me.