Injector PW vs Duty Cycle

Injector PW vs Duty Cycle

Posted by Mario Velotta on Mar 27th 2023

Injector PW and Duty Cycle

Some may already know this and some may not. So lets go!

The injector pulse width is how long the injector is open during an engine cycle. This open time is in milliseconds. The duty cycle is how long the injector is open vs. how long it can be open per a given engine RPM.

For those visual learners out there, I have put this data into a graph. The Blue trace is a linear engine RPM, and the Orange trace is the available PW per engine RPM. As you can see the time you have to inject your fuel shrinks as you gain engine speed and this is where the duty cycle comes into play. The Yellow trace represents a fixed 18ms pulse (you wouldn't have this at idle).

At 1000RPM this pulse is only about a 15% duty cycle. But at 8000RPM that same fuel pulse is 120%. Once you reach 100% your injector is open 100% of the time, you cannot inject any more fuel. At this point, you would need to resize your injectors about 30% larger to get a 90% duty cycle at full load. I hope this helps you in your EFI journey :D

#aircooledefi #dubshopproducts #4injectorsatatime