Quote:
Originally Posted by Senna-F1
So I decided to take my car to SOHO Motorsports to figure out why my duty cycle was 80-90% on pump. Fuel pressure was about 41 psi at idle. They set it to 50 from what I hear, I think this what they normally set it at?? and re-tuned the car for pump. Duty cycle is now 60 or so, or in the 60’s, not sure. I don’t have logs, this was just a late night conversation at the shop after being awake more than 30 hrs so I wasn’t all there  . But we went from having a conversation when I first showed up very much like you had, talking about lowering rev limit, getting 1300’s, to there now being no issue with moving ahead with e85. Raising fuel pressure alone this amount does not account for this dramatic of a drop in duty cycle according to what I’ve read. In fact when I was still working with Eugene, I went to the trouble to try and figure out what it would take to go e85 based on my high duty cycle, and came up with it would take 64.5 psi at idle. If raising fuel pressure to 50 alone was a fix for all my fuel troubles, I think Eugene would have simply asked me to raise fuel pressure and we would have done some pulls. So, I think there may be something in either the tune or in how duty cycle is being calculated that’s not quite right. And BTW, this was in the 550 WHP and 425 TQ range. |
Sorry I missed this post. I am curious to know what happened as well, when you've had a little more sleep of course haha.
Without knowing the correlation between pressure and flow exactly, if they set your pressure to 50psi at idle, with the hoses connected, then they did raise your pressure. Roughly guessing, 50 at idle would correlate to near 60 at atmospheric. This would lead to a reduction in duty cycle, given the same injector size.
There is only one thing that can change your duty cycle for a set AFR and injector. Injectors are set because you install them. The AFR piece is for your tuner to play with and is arguably set at a certain value for safety, so I consider this arguably not a variable. This leaves the variable to be pressure. After that comes the issue of the pump being able to support the flow.
I have the CJM S1-SE fuel system with ID 1050x injectors from an Aeromotive 340lph pump with pressure set at 51psi at atmospheric pressure. Looking at my most recent logs, my injector duty is 51%, tuned on 93 octane, while around 11psi.
EDIT: I uploaded a picture of a log to show where my car is at right now for the respective parameters.