OriginalSterm

We were out tuning my Dad's 951 the other day and were hitting over 90% duty cycle on the injectors. He has the older style (2 ****) LR MAF kit with the duty cycle/AFR gauge. At WOT we were touching up ~12.5 or so AFR and could not get it any richer. I was concerned the duty cycle was too high and didn't want to try and richen up the mixture any more for fear of burning up the injectors or the DME. He has Guru chips and the 3 bar FPR, so I don't want to turn up the fuel pressure anymore.

Is there anything we can do to get the mixture a little richer and/or run a lower duty cycle?

Matt H

55 lb/hr injectors?
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OriginalSterm

We are planning on bigger injectors when we go bigger turbo. Depending on how big the turbo is, will 55 lb/hr be enough?

I was hoping that there was an alternative in the meantime. Or hoping someone may know of a reason for the injectors getting so close to static so soon.

Matt H

I have no clue if 90% is considered high on the 944s. I am going to 72 lb/hr (as soon as they are off backorder so I can finish this GD car). I will be running a T04E at about 18psi, with a HR Stage (something) MAF.
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TonyG

If it is in fact running at 90% duty cycle, then you are too high.

You're not going to burn up the DME or the injectors, but you risk the injectors not functioning properly (opening up or closing properly). And if that happens, you will have a problem for sure (engine related).

TonyG

OriginalSterm

I've seen a lot of data on power made with 80% duty cycle. Is this considered the rep rate at which maximum performance is achieved without the injectors being way oversized?

rhesus

Since you have the Guru chips I believe all you have to do is change to bigger injectors and then flip a switch on the chips & you should be running the same as before, except with a lower duty cycle