duty cycle over 100%
duty cycle over 100% I have a cam + bolt on's ls1 with the white 36lb injectors in it (which I just installed because my stockers were going to a DC of 140% per my hp tuner, wideband was showing afr going up to 15.5 under WOT) and I am still having a issue with my DC going to 100% right at redline, my AFR is mid 12's now which is good but I am wondering why I am pushing a 100%DC on what should be a 380rwhp motor and plenty of injector? The only thing I can think of is that my Fuel Pressure is dropping, any other ideas?
TECH Enthusiast
Joined: Nov 2006
Posts: 620
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From: Katherine N.T Australia
Im not surprised at all that you are over 100% with the 36's due to being at 140% on the stockers which is huge for your power. Get a fuel pressure gauge on there ASAP to verify but it certainly sounds like its caused by low pressure. As above mentioned 58psi +- a couple of psi is where it should be.
What is red line for you? If you are spinning it too fast, the inj's can't keep up and have to stay open pretty much the whole time until the RPM's drop. At high RPM, anything over 80% and the injector is pretty much open non stop. If you are at or over 80% at higher RPM's and believe the inj's are plenty big enough, I would bet your theory is right about the fuel psi. Maybe a dirty filter?
Last edited by b.d.d.; Jul 19, 2009 at 03:56 PM.
Sounds like it is in the tuning to me (at least now with the new injectors). How would the PCM know the fuel pressure is droping at WOT? It is no longer looking at the NB (not that they would work). I do not think the PCM would know what the AFR is actually at at WOT, hence why we have to use the WB to tune WOT. Now I am talking only of the duty cycle, it is a calculation of what data we put in the tune right? I understand he verified the AFR was lean with a WB. I am just asking if there is a way other then the data we put in the tune that the PCM uses to calculate the IDC. If not then I would make sure the tune is correct. Can you post up your tune?
My VE table is pretty nutty at WOT, redline is 6500, I set the flow rate correctly with it increasing slightly with more vacuum.
My VE table at 95KPa goes something like this
5200 5600 6000
178 192 211
BTW this is a 255lph Walbro in tank with a Vette Fuel Filter (built in regulator)
My VE table at 95KPa goes something like this
5200 5600 6000
178 192 211
BTW this is a 255lph Walbro in tank with a Vette Fuel Filter (built in regulator)
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