2016 C7 Corvette Fuel Rail Pressure

[TSerna0331]

Fuel Rail Pressure Drops off.hpl Hi guys and gals, I am having an issue with this 2016 C7 Corvette. We have a procharger kit on it as well as headers and exhaust and in the attached log you will see towards the end of the pull my injector MS goes up as well as INJ DC and the fuel Rail Pressure drops off drastically. Has anyone ever had this issue before and if so was it a tune related issue or a mechanical issue. Also take note the car also has Z06 Injectors and the Z06 HPFP installed also. Thanks in advance.

[Ben Charles]

Yea... means you are out of fuel

[TSerna0331]

The car isnt making over 600hp so I find it very unlikely that I am out of fuel. Thanks for the input, is there anything else that you could think of or recommend checking as far as tune wise or mechanical wise. Thanks.

[Higgs Boson]

you didn't post your tune so no one will be able to identify anything.

[TSerna0331]

you didn't post your tune so no one will be able to identify anything.

More Boost Attempt 3.hpt Sorry about that thought i did attach it with the log file but here it is. Thanks again for any input.

[veee8]

You need to start with getting the ZO6 fuel pump settings in the tune. The LT4 runs at a lot higher pressure then the LT1, and the ECM will need to be told to run at that via the tune.
You will also want to command more from the low pressure pump as well. LT1 drops fuel pressure as rpm and load increases.

[big_sapper]

You need to start with getting the ZO6 fuel pump settings in the tune. The LT4 runs at a lot higher pressure then the LT1, and the ECM will need to be told to run at that via the tune.
You will also want to command more from the low pressure pump as well. LT1 drops fuel pressure as rpm and load increases.

Well that's interesting. I've always wondered if the LT4 pump needed to be programmed and I think I've asked that specific question (elsewhere) and IIRC was told it wasn't required.

[Ben Charles]

Of course it needs programmed... who ever said it doesn?t, doesn?t know what there talking about

[TSerna0331]

You need to start with getting the ZO6 fuel pump settings in the tune. The LT4 runs at a lot higher pressure then the LT1, and the ECM will need to be told to run at that via the tune.
You will also want to command more from the low pressure pump as well. LT1 drops fuel pressure as rpm and load increases.

The log file that I attached in the original post is a WOT pull with all the data for a Z06 pump as well as the injectors the last tune was just a test to see if there would be any differences with the stock fuel pump data in the tune and it made no difference same thing everytime... Could it be a bad LT4 Pump that we got? I know thats a stretch, but ive seen dumber stuff lol. And ill try to see what I can do about commanding more from the low pressure side to see if that makes a difference or not. Ill post up another log when i get it back on the dyno. Thanks again for the help guys.

[Ben Charles]

Look at the HPFP when logging... of hitting desired it?s not the pump

[TSerna0331]

Look at the HPFP when logging... of hitting desired it?s not the pump

Its not hitting desired FP which in WOT range is set to 2100ish psi and its dropping to 1000 and into 900's and im not make near the amount of power to be running out of fuel so some back history on the car we put the procharger on it stock pump, injectors just headers and procharger and made 580's to 600. Came back for the z06 pump and smaller pulley and have been having this issue had a buddy from another shop come take a look and he said i was running out of injector so we put z06 injectors in it and still having the same issue but its not making power so we swapped the pulleys back to the way the were originally setup and cars makes 590 consistently with no issues put the smaller pulley back on and power drops off completely from 5900 and up. So it could not be the pump or it could be it was just the HPFP that I seen first that was consistently falling off so its just leading me to think that maybe the HPFP is bad? since that and the injectors were the only thing mechanically changed with the car besides the pulley of course and checked plugs they are fine and also went ahead and put brand new oem plug wires on as well.

[Ben Charles]

My vote is HPFP... did you add a lash cap by chance??
If you did hope you measured... probably sheared the 2 10mm bolts

[veee8]

The HPFP pressure drop goes hand in hand with the commanded lower pressure from the LPFP, along with the extra demand.

[TSerna0331]

My vote is HPFP... did you add a lash cap by chance??
If you did hope you measured... probably sheared the 2 10mm bolts

No Ben we did not add a lash cap to the HPFP.

[TSerna0331]

The HPFP pressure drop goes hand in hand with the commanded lower pressure from the LPFP, along with the extra demand.

We are going to add a BAP to the LPFP to see if that fixes the issue that we are having and if that doesnt work then we will be replacing the HPFP with another new one to see if maybe we just got a defective one? I know thats a far fetched idea but going off what you guys are saying plus others ive kept in contact with that do more c7s then me its the only thing i can come up with right now but ill have it back on the dyno this afternoon and let you guys know what happens. Thanks again for the replys and help.

[Ben Charles]

I’ve seen 2 random HPFP lt4 failures... lost pressure just like your seeing

[veee8]

Make sure you up your requested LP here, and log requested/desired low pressure.

[TSerna0331]

Make sure you up your requested LP here, and log requested/desired low pressure.

I will make sure it is done if not already done thanks for the info and the help

[TSerna0331]

I’ve seen 2 random HPFP lt4 failures... lost pressure just like your seeing

interesting im wondering if im having that same issue but we will find out soon enough thanks again

[TSerna0331]

Alright guys I got the car back on the dyno and added a boost a pump to the low side and the low side is holding at 70ish psi and this run in particular at 5000 rpm my HPFP drops from 2900ish to 2100ish and after that it drops from there at 5700-5900rpm it drops straight down to 1000psi. Take into account i did switch the HPFPump back to the lt1 pump and the car went lean and dropped pressure just for testing purposes and when we put the same HPFPump (Z06) we did put a LS7 Lash cap to see if that would help the pressure from dropping off and it didnt so im wondering if the Z06 pump that we got is faulty? and were basically getting (valve float) but in the pump and on the spring, sorry thats the only way i can describe it lol but yea thats where im at now......