HCI LS3 hot start stumble

[Action_Balser]

Hey folks,

I searched as best as I could but wasn't finding anyone with a similar situation/problem as mine.

For context, this is on my 2008 C6 Corvette with an H/C/I LS3 that I've had tuned and running strong since last April.

The issue I'm having involves hot starts, but only after the car has been sitting for around an hour. The normal hot start / cold start is about 2 seconds of cranking and then it will fire and climb to idle RPM, as it normally should. However after sitting for about an hour when I've been out driving, it will crank for about 1/2 a second, catch and fire for 1/2 a second, then either die or barley sputter to life without throttle intervention.

I'm assuming this issue has something to with heat soak, because if I park the car for the hour its off with the hood open, this doesn't happen. Additionally even if the car is heat soaked and IAT's are hot from sitting in traffic, if shut it off and start again a few minutes later, it starts normally without issue.

Attached is a log of the catch and sputter to life scenario, and my current tune.

Hotstart.hpl

Current Tune June 2024.hpt

Any input is appreciated, thanks!

[danmw2003]

Under Spark/Advance Startup Cranking. Make the coolant temp rows 176 and higher all 5 degrees. See how that works out. You're pulling -10 degrees in some of thise cells for some reason.

[Cringer]

Hey folks,

I searched as best as I could but wasn't finding anyone with a similar situation/problem as mine.

For context, this is on my 2008 C6 Corvette with an H/C/I LS3 that I've had tuned and running strong since last April.

The issue I'm having involves hot starts, but only after the car has been sitting for around an hour. The normal hot start / cold start is about 2 seconds of cranking and then it will fire and climb to idle RPM, as it normally should. However after sitting for about an hour when I've been out driving, it will crank for about 1/2 a second, catch and fire for 1/2 a second, then either die or barley sputter to life without throttle intervention.

I'm assuming this issue has something to with heat soak, because if I park the car for the hour its off with the hood open, this doesn't happen. Additionally even if the car is heat soaked and IAT's are hot from sitting in traffic, if shut it off and start again a few minutes later, it starts normally without issue.

Attached is a log of the catch and sputter to life scenario, and my current tune.

Hotstart.hpl

Current Tune June 2024.hpt

Any input is appreciated, thanks!

I had the same issue on my LS3:
https://forum.hptuners.com/showthrea...Restart-Issues

Follow Up Video explanation:
https://youtu.be/Sz878VXfYD8

New tune attached for you to try.
Current Tune June 2024 - Cringer.hpt

[Action_Balser]

Odd, I checked my backup factory tune and its the same there. Will try this tomorrow. Thanks!

[Cringer]

Under Spark/Advance Startup Cranking. Make the coolant temp rows 176 and higher all 5 degrees. See how that works out. You're pulling -10 degrees in some of thise cells for some reason.

The -10* is OEM GM shenanigans.

[danmw2003]

When you mod the engine, stock values arent always suitable.

[Cringer]

When you mod the engine, stock values arent always suitable.

I agree. If you see the tune I posted I fixed the -10*.

[danmw2003]

Ive run into this before as well. Making those rows all 5 degrees helps it considerably to light off and start.

[Action_Balser]

When you mod the engine, stock values arent always suitable.

Definitely, I was just surprised to see such odd values for this item lol

I agree. If you see the tune I posted I fixed the -10*.

Just looking through the tune and watching your video now, TONS of awesome info, thanks very much for this!