I am running 42# delphi injectors at 68% duty cycle at 6500 rpm with 12.5:1 afr.

Ignition problems are keeping me from running to 7000 rpm at this point, so I may be near 70% in the future.

1) If you are able to adjust the size of injectors in the PCM, does it really matter if the injectors are oversized?

2) Is this duty cycle too low for the injectors to run in their optimum range?

 

Your injectors are fine. The goal is to keep the duty cycle under 80-85%. You are doing that. As long as the duty cycle is below those limits, the injectors will perform exactly the same, each time they open and close. The only possible problem would be an inability of the combination of the PCM drivers and injectors being unable to be turned down to the very short pulse widths required to allow the engine to idle. That would show up as a minor roughness at idle. No effect whatsoever at WOT. Many people have run 42# injectors on the OEM PCM and had not problem at all at idle.

I run 78# injectors. They are at 70% DC with a 300HP dry shot. Running NA, at 500HP, they are under 40% DC.

 

Thank you.

I haven't had a problem at idle but many people have questioned the size of my injectors. It always makes you nervous.

Thanks again.