2016 Camaro SS with LT4 pumps erratic fuel pressure
Hello,
I wanted to share my issue and everything I've done to try to correct it. On my 2016 Camaro SS, I have the LT4 high and low pressure fuel pumps. What I'm seeing is that the low side pressure fluctuates considerably up and down anywhere from 10-20psi. This is at idle while the car is not moving. I also have fluctuations in part throttle driving. High side is maintaining desired pressure fine but low side is not steady at all. The car generally drives ok. I've searched for other threads of similar issue and I came across two other threads where tuners/owners have the exact same issue and their logs posted look the same as mine for low side pressure! These threads were non LT4 vehicles that had the LT4 fuel parts added. These threads unfortunately were left open ended with no real evidence of a solution.
This got me thinking on how rare this issue is so I actually started looking for random other threads where people had added LT4 fueling but were posting for totally unrelated issues on their setups, just so I can see their log files and what their pressures looked like. Surprisingly, in a 5 minute search I saw a number of other people have this occurring in their setups and don't even realize it. Some were struggling with idle tuning, cam tuning, drivability, etc. but their logs of low side fuel pressure were just as bouncy as mine.
List of things I've tried to figure out this issue:
with and without oem check valve near hpfp
routing the lt4 lpfp to a surge tank in trunk then feeding the hpfp with an external pump
tried a different external pump
wiring the external pumps to the fpcm for pwm control
hardwiring the external pumps (yielded very high pressure to the pumps relief valve opens at 112psi)
adding a regulator and return with external pump set at 75psi engine off (smaller fluctuations in pressure (~10psi or less) but still there and visible in the scanner)
I've done so many experiments on the low side that I just ordered a new hpfp to see if there's something wrong with my current hpfp causing these pulses and at $700 this is a very expensive "experiment". After seeing so many others with this issue I may not even "try" the hpfp and may just return it.
I get the feeling my tuner is getting annoyed and is ready to just try to tune as is but I'm a little worried that this can turn out to be a bigger problem as we progress into WOT and big boosted power levels.
What are you guys's thoughts around this kind of issue? Is this hardware or software driven? I feel I've changed everything I could on the low side, what are the chances a bad hpfp could cause this? What would you possibly try next?
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