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Thread: injector duty cycle question

  1. #1
    Advanced Tuner
    Join Date
    Sep 2010
    webb city, mo

    Question injector duty cycle question

    I've got a '99 C5 with a 223/231 112 cam and a D1SC procharger making about 8.0-8.5psi. The tune definitely needs scaled but i've just been roughing it in to get the car running good enough to drive around.

    I put it on the dyno today and it maxxed out the MAF so i switched over to SD to dial in the VE (2bar OS). It's maxing out dynamic airflow, 67.7lb/min, at about 5,200 rpm. It has 72lb (750cc) fuel injector connection injectors in it and they're going up to 90-95% duty cycle by 6,500 rpm.

    Every online calculator says those injectors should be plenty for this combo. It's on 91 octane.

    Is this high duty cycle a result of the tune not being scaled and maxing the airflow out or do you think this combo actually needs more injector? It has a stock fuel pump but also has the A&A Corvettes single external pump that kicks on at 3psi via Hobbes switch. I haven't verified exact fuel pressure but the Hobbes switch and pump ARE working, so there should be enough pressure to feed everything.

    I'm going to verify pressure during a pull next if i can set the gopro up on my gauge and go ahead and start working on scaling the tune...just wondering if i need to order bigger injectors because i didn't think i would have to.


  2. #2
    I would definitely check into the fuel pressure prior to buying more injectors. What size fuel line and are you returnless or no? Not familiar with those combos.