injector pulse width max?

[pero648]

hi all, can anybody tell me what my injector pulse widths should stay under? at the end of the drag strip i am at 99% injector duty cycle ( time to ungrade i know) and 17.945ms pulse width. pulse width reaches 17ms at around 87% duty cycle. what would normal pulse width be? thanking all pete

[redhardsupra]

it depends solely on RPM. at what RPM did you get the 17ms IPW?

[joecar]

You should be looking at duty cycle, which is maximum at 100% (and above that is the same as 100%).

It is recommended to run no higher than about 80% for various reasons.

[joecar]

17ms at 87%dc comes out to a period of 19.45ms which is 6141rpm...

your PW is 17ms, the maximum PW is 19.45ms at 6141rpm.

(6000rpm is a period of 20ms).

[swingtan]

As stated, maximum injector pulse width is dependent on the RPM of the motor. The basic formula is...

1 / RPM / 60 = "cycle time" in seconds

However, the LSX motor fires the injector twice per cycle, so the formula changes to...

1 / RPM / 60 * 2 = "max injector pulse time" in seconds

To convert the result to mS ( milliseconds ) just multiply by 1000. This will give the maximum amount of time that the injector can be open for before it overlaps the into the next cycle of the motor.

The accepted maximum duty cycle is 90% of the maximum so you need to multiply the the result above by 0.9 to get the maximum time the injector pulse width "should" reach. Here's a quick graph showing the maximum times from 4900 RPM to 7000 RPM.