LT4 HPFP Fuel Pressure Running Away

[evolmotorsprt]

****Updated for Resolution Post #20****


We installed a forged LT4 and blower into a 2019 C7 GS and I'm having a problem with the system regulating pressure correctly. I've checked everything and had the blower on and off several times. I'm using the HPFP Tables from a 2019 Z06, and also tried the stock tables with the same result. It's showing 2-4x the desired pressure at idle, and when I blipped the throttle the engine ran away and the pressure hit 28000kpa. I had to key it off to stop it. The engine was a swap from a wrecked car, so I'm not ruling out a bad pump. This is a startup file based on a few of these conversions I've done in the past. The lifter for the pump is from an LT1 if that makes a difference.

I did notice that if I sweep the throttle pedal with the KOEO I can hear the aux pump run.

Fuel System:
LT4 injectors
LT4 HPFP w/LS7 lash cap
38% cam lobe
LT1 Low Side
DSX Aux Fuel Pump

In terms of the harness, I've checked to make sure the HPFP is hooked up and pinned into the main harness correctly. I read somewhere that the 2019 Harness is different between an LT1 and LT4, but going through the pins and checking everything showed the connections were correct.

Looking at the attached tune file and log, can anyone tell me if I'm missing something? I'm planning to swap the LT1 HPFP back in to Diag, but surely someone has seen this before.

Also codes: P0089, P228D

[TriPinTaZ]

You didn't account for the larger fuel lobe when tuning the HPFP leading edge table.

[evolmotorsprt]

You didn't account for the larger fuel lobe when tuning the HPFP leading edge table.

I?m aware of that. I scaled the axis and it made no difference. I tried the lt1 data stock and scaled as well as the z06 data stock and scaled. The pressure ran away no matter what was in the table.

Could it be something with the low side DSX fuel system?

[TriPinTaZ]

I?m aware of that. I scaled the axis and it made no difference. I tried the lt1 data stock and scaled as well as the z06 data stock and scaled. The pressure ran away no matter what was in the table.

Could it be something with the low side DSX fuel system?

No the DSX shouldn't have anything to do with it. I didn't see the pressure that far off in your log.

The correct scalar would be to take the LT4 leading edge values and axis and put in the tune. Then multiply only the axis by the cam lobe %. The tune you posted is not correct. Not sure what you've tested but I'm only advising by what I saw in the tune you posted.

[evolmotorsprt]

No the DSX shouldn't have anything to do with it. I didn't see the pressure that far off in your log.

The correct scalar would be to take the LT4 leading edge values and axis and put in the tune. Then multiply only the axis by the cam lobe %. The tune you posted is not correct. Not sure what you've tested but I'm only advising by what I saw in the tune you posted.

Got it. Here's a tune file with those values changed the way you would like to see. I tried it with these settings and it didn't make a difference. Here's a pic of the crazy rail pressure before I shut the engine off in the above log.
Capture.PNG

[TriPinTaZ]

Got it. Here's a tune file with those values changed the way you would like to see. I tried it with these settings and it didn't make a difference. Here's a pic of the crazy rail pressure before I shut the engine off in the above log.
Capture.PNG

Was this rail pressure immediately after a WOT pull? Or at idle?

please provide the timestamp in the log or export only the area in question and I'll look again.

[evolmotorsprt]

Was this rail pressure immediately after a WOT pull? Or at idle?

please provide the timestamp in the log or export only the area in question and I'll look again.

This was a free rev off idle. The engine RPMs rose on their own, and I shut off the engine before things could get out of hand. I'm wondering if the relief valve in the HPFP is seized.

[Ben Charles]

I bet I know what’s going on, when I get time later I’ll take a look!! But the free rev from idle and reving to redline is a tune issue

[Alvin]

This was a free rev off idle. The engine RPMs rose on their own, and I shut off the engine before things could get out of hand. I'm wondering if the relief valve in the HPFP is seized.

I've seen this if the DD tables have been messed with too much especially down low.

[TriPinTaZ]

OK So I think you're actually monitoring the wrong PIDs or the non Hi Res signal. When I load that log I see my gauges only show a max pressure of 1900 PSI and an idle pressure of 500 PSI which is fine. Idle pressure should be a little lower but its probably from copying the LT4 tables over so the airmass axis is slightly different.

Anyhow, I then see when you let off the throttle that the desired PSI goes to 0 PSI. This should never go to 0 PSI. So I think its actually a PID issue and not really actually happening.

See screenshot:

fr1.png
fr2.png

[Ben Charles]

I've seen this if the DD tables have been messed with too much especially down low.

I bet it’s mapped gear is modded and not stock… will do this every time.. I’ve played with DD from the start (when individuals just modded last few rows) and never have had this problem

[evolmotorsprt]

I've seen this if the DD tables have been messed with too much especially down low.

Since I grabbed the M7 Z06 VTT as a starting point I'm also using the Z06 DD as well.
LT1 to Z06 DD Compare.PNG

OK So I think you're actually monitoring the wrong PIDs or the non Hi Res signal. When I load that log I see my gauges only show a max pressure of 1900 PSI and an idle pressure of 500 PSI which is fine. Idle pressure should be a little lower but its probably from copying the LT4 tables over so the airmass axis is slightly different.

Anyhow, I then see when you let off the throttle that the desired PSI goes to 0 PSI. This should never go to 0 PSI. So I think its actually a PID issue and not really actually happening.

See screenshot:

fr1.png
fr2.png

I'll check the pids when I get back to where the car is. The thing that alerted me to there being an issue were the codes:
P0089 - Fuel Pressure Regulator 1 Performance
P228D - Fuel Pressure Regulator 1 Exceeded Control Limits - Pressure Too High

I bet it?s mapped gear is modded and not stock? will do this every time.. I?ve played with DD from the start (when individuals just modded last few rows) and never have had this problem

The mapped gear was changed to not limit on increasing, but I usually don't touch the decreasing much, if at all. I'll revert that to stock and reassess.

[GHuggins]

Don't forget catalyst heating settings for rail pressure commands. The maxed out increasing limits and mapped gear settings will affect throttle self revving - may not be your whole issue, but won't help it. You also don't want to do that on a boosted setup anyway as it can literally make them go wot with any pedal input.

[TriPinTaZ]

The mapped gear was changed to not limit on increasing, but I usually don't touch the decreasing much, if at all. I'll revert that to stock and reassess.

I believe he was talking about this table. Make sure you didn't copy the Z06 values over to the GS.

mg1.png

I just tuned an LT1 to LT4 swap in a Camaro SS and didn't run into any such issues. But in the past, I accidentally copied over this exact table and it caused the runaway rev issues and some other codes. It was a while ago so I don't recall the codes. Can you post the before and after file so we can compare what changes you made vs the old tune? (assuming it wasn't stock)

[evolmotorsprt]

I believe he was talking about this table. Make sure you didn't copy the Z06 values over to the GS.

mg1.png

I just tuned an LT1 to LT4 swap in a Camaro SS and didn't run into any such issues. But in the past, I accidentally copied over this exact table and it caused the runaway rev issues and some other codes. It was a while ago so I don't recall the codes. Can you post the before and after file so we can compare what changes you made vs the old tune? (assuming it wasn't stock)

Cool, got it. I did copy that table over. I'll revert it to stock GS. Thank you guys for catching that.

I need to get back to the car and see what I can find with the fuel pressure. I hope it's a logging issue, but the codes are telling me otherwise.

Here're the two tune files as requested.

[Alvin]

Since I grabbed the M7 Z06 VTT as a starting point I'm also using the Z06 DD as well.
LT1 to Z06 DD Compare.PNG

.

I'd try the stock DD tables just to try it. Not stock out of another car but this car's stock tables. I promise I've seen this more than once and the DD tables were the cause.

[evolmotorsprt]

I'd try the stock DD tables just to try it. Not stock out of another car but this car's stock tables. I promise I've seen this more than once and the DD tables were the cause.

Just tried that along with reverting some other tables and It's still having the HPFP Problem. I also grabbed every PID I could find pertaining to Fuel Pressure.

When I started the car cold and it ran higher pressure it was able to adjust the high side appropriately. Once the car got warmer, The pressure would not drop below ~8000kpa.

Once my buddy gets here I'm going to put the LT1 pump back in and see if it is able to control the high side pressure. If not, I'm leaning towards the pressure relief on the LT4 pump being bad.

More C7 Diag.PNG

**Also: The mapped gear table fixed the rev hang. Thanks again for that.

[evolmotorsprt]

Okay, I installed the LT1 pump and still had the pressure problem. I then took the stock file, did a write entire, and then only entered the LT4 injector and MAF data into the file. It ran like crap but the pressures were controlled and consistent. Now I need to add things back until I find the culprit.

This will probably be the last time I use the "comparison log" to copy data over. In the past I've gone table by table. I assumed, incorrectly, I could save time by copying over large swaths of info. I'm going to figure out the offending table, but it's a lesson to be more mindful of what's being copied over and the effects.

[Ben Charles]

Just tried that along with reverting some other tables and It's still having the HPFP Problem. I also grabbed every PID I could find pertaining to Fuel Pressure.

When I started the car cold and it ran higher pressure it was able to adjust the high side appropriately. Once the car got warmer, The pressure would not drop below ~8000kpa.

Once my buddy gets here I'm going to put the LT1 pump back in and see if it is able to control the high side pressure. If not, I'm leaning towards the pressure relief on the LT4 pump being bad.

More C7 Diag.PNG

**Also: The mapped gear table fixed the rev hang. Thanks again for that.

Yep been there done that ha

[evolmotorsprt]

So we were able to figure out the problem, and maybe this can help someone in the future.

The engine that we swapped in had a Katech front cover with the phaser delete. It turns out it had a re-drilled LS3 gear that had the reluctor bumps in the wrong orientation. There was a cam correlation code, but the car was running too well to have the cam out of time. I checked desired vs actual cam position and it was off by 16deg. I didn't even think to check this because the cam was locked out and the engine came out of a running car. I turned off the codes for the cam/crank correlation and the HPFP worked perfectly.

I'm pretty sure because the computer calculates fuel delivery based on the timing and stroke of the pump, that if the cam is out of range it ceases closed loop operation for high side fuel pressure.
We tore the front of the engine down and I put a stock phaser with a lockout and the stock front cover on and this has fixed the issue.

In this case it wasn't tune related. Thanks again everyone for your help.