2015 Silverado 6.2 Rebuild

[sappje]

New to the forum and by no means a tuner. Just hoping to get a little insight to what may be going on. A few months ago I swapped out my Gen V 5.3 for a 2017 Gen V 6.2. Prior to doing so the 6.2 was rebuilt with a BTR 220 cam with VVT limiter. New rods, pistons, valve job, headers, coils, wires, plugs, injectors, torque converter among other items. I did not install a new HP fuel pump. Anyway after several trips to the tuner we ended up with a running truck that is drivable and has plenty of power, but still has issues. I have been getting LT fuel trim rich errors on both banks and there is a slight hesitation when starting from an idle. In addition if I go WOT while cruising it falls flat on its face between 4,500 and 5,000 rpms. However WOT from an idle will run through the power band up to mid 5k rpm to 6k rpm with no issues.

I have been doing lots of troubleshooting on the fuel trim issue with no luck and I am down to replacing the HP fuel pump as I have seen where lots of folks having issues with internal fuel leaks causing the LT trim issues with fuel/vapors in the oil.

Any ideas on what could be causing the WOT issue when cruising vs WOT from idle?

[GHuggins]

A log would do better. You can use the attached channels to log with. Gen V's aren't easy to tune in for changing temperatures. In fact I would say a lot of tuners don't bother or know how. As long as you don't smell gas in the oil, I doubt your hpfp is leaking.

[sappje]

Here is a short log from this morning. I tried to get a log from idle to WOT but got an error and the computer lost connection. I will figure out what happened and get that logged as soon as I can. In the meantime here is cruising to WOT. Thanks for the look and suggestions.

Cruising 55mph to WOT.hpl

[GHuggins]

Just from what little I could see in that log, I'm willing to bet that your fueling wasn't dialed in at temp. As long as you're not getting fuel into the crankcase via the hpfp which is easy enough to diag - just change the oil and see if trims shift a bunch and you've still got a good working crankcase ventilation system and the purge valve isn't sticking open (you did have a 6% shift in that log due to purge) then it's showing to be 22ish % rich on your VE and 25ish % rich on your MAF. In fact, in that log you didn't even get things up to temp enough for my filters to allow VE logging for my vehicles that run colder Tstats (yours is 170F in the log - needs to be able to hit 187F).

Because there are so many multipliers for fuel in these things to keep them happy for the EPA and balanced in general, it makes it to where it is very easy to dial things in incorrectly and just get more and more out of whack. The base fueling and multipliers alike really need to be dialed in on top of the torque model and so on.

[sappje]

Just from what little I could see in that log, I'm willing to bet that your fueling wasn't dialed in at temp. As long as you're not getting fuel into the crankcase via the hpfp which is easy enough to diag - just change the oil and see if trims shift a bunch and you've still got a good working crankcase ventilation system and the purge valve isn't sticking open (you did have a 6% shift in that log due to purge) then it's showing to be 22ish % rich on your VE and 25ish % rich on your MAF. In fact, in that log you didn't even get things up to temp enough for my filters to allow VE logging for my vehicles that run colder Tstats (yours is 170F in the log - needs to be able to hit 187F).

Because there are so many multipliers for fuel in these things to keep them happy for the EPA and balanced in general, it makes it to where it is very easy to dial things in incorrectly and just get more and more out of whack. The base fueling and multipliers alike really need to be dialed in on top of the torque model and so on.

Thanks for the information. I will check with the tuner to see if he had it at temp. I have noticed that this engine runs a lot cooler coolant temps in the truck than the 5.3 did. The 5.3 was consistently at 210 degrees and I don't think I've seen the 6.2 above 180 degrees yet. When I saved this log the truck had been running for about 20 minutes and it was only at 170ish.

[GHuggins]

The 6.2's do take a touch longer to get to temp, but should get there nonetheless.

If you're running an AM Tstat in particular then those seem to have problems with getting hot in colder temps. I would advise a new Tstat and then re-tuning the base fueling at full operating temperature. Injector temp needs to be between 60 and 74 degrees Celsius and coolant around full operating temperature to make corrections to the base models. Then, even though I don't know of anyone dialing them in other than Jason or myself although I'm sure some might, the multipliers need to be dialed in as best as possible to keep fueling right from there.

You need to verify you don't actually have a fuel saturation problem before doing any of that though.