2018 Procharged LT1 Corvette 6,000 RPM issues

A little back story, last summer the car had a procharger installed. Baseline numbers where normal, the Procharger is installed and it goes back on the dyno. Now I that point (I went back and looked again), I had tuned 73 stock LT1 vehicles with and without boost and many more built LT1 based built vehicles, with many into the 4 digit club. I setup my calibration for a stock LT1 with a Procharger and first pull was about normal, everything looks good so I add some timing and go for pull number 2. This time the car looses about 50 rwhp. I see right around 5500-6K it pulled timing for knock, I was low at only 8 or 9 to began with, so I removed the two I just added and did pull number 3, this time I'm down 70 rwhp. I do a compression test and two cylinders are low on compression but the car runs good, idles, no smoke. So it comes apart and broken ring lands on two cylinders. I'm amazed because after all these LT1 engines I have never seen a stock piston failure and this was with low timing just starting on tuning. So the pistons are replaced, see nothing wrong, but also replace those two injectors and go back on the dyno. Low power and its not really responding after half a day, we check compression again and one of the same cylinders is low on compression. Not as bad as before and only one cylinder. So it comes back apart and broken ring land. This time we pull the engine, go drop in pistons and rods, replace all the injectors with LT4 and an LT4 HPFP. Put it all back together and it idles ruff on start up, but smooths out when warm. Installed Meth as an extra safety and went back on the dyno. Almost every pull on the dyno was low on power and at 5500-6K the car would loose power and pull timing. Some runs it would pull almost nothing and I would get a decent pull to 6500, still loosing power by 6K. Other runs it would pull 2-12 degrees possibly more. My best runs on the dyno where with knock disabled, meth on and timing at 17 degrees. Power was still low in the low 500 range when I would normally see high 500 to low 600 range on my dyno. The car came off the dyno and timing was set to 13 degrees on the top end. Better to be safe, not a power house but it would do. A year goes by and the car comes back with a few issues. First the car will idle so ruff after start up for the first few minutes until warm it will set a random misfire. This started after the lT4 parts went in, so possibly I have something set wrong. Once warm and the car was being driven around it had this surge feeling, looking into it the car was pulling max fuel. If I turned off fuel correction all the surging was gone and it ran perfect. Looking over the tune, I had swapped over the LT4 SOI and EOI and they are completely different from the LT1. Changed them back and fuel correction went back to normal and the surging was gone. I was thinking this would also fix the cold start misfires but it didn't. The owner of the car doesn't normally drive it his wife does so its normally not taken to redline. well he started hammering on the car and at 5500-6K the car hits a wall and falls on its face. This happens 90% of the time, however 10% it will make a clean pull. During a drive yesterday I got on it twice. At 5500 you can feel the car start breaking up and by 6K it just wont pull anymore. The pcm pulls lots of timing at this point in the last three days I have seen anywhere from 2-16 degrees pulled. I don't have lots of timing to start with Have confirmed the meth is spraying. Its the same problem as last year, with meth, without meth, with old injectors, with new injectors. Anyone have any ideas.

thank You
Bad383TA

I can't look at the log or tune if you posted them at the moment. I've only got my phone with me. This really sounds like a torque management or Torque model related issue. I've seen torque models on a few occasions result in random cylinders to drop and even bank to bank fueling to be off which sounds like what you've got going on with random cylinders being leaned out and damaging Pistons but like I said I can't confirm the tune settings or anything else at the moment. This is just what popped into my head when I was reading it. If you can post up a good driving log with idle and going through all the gears. 30 minutes long if it'll let you.

I assume you know there's a lot of things not dialed in or set up correctly such as the VVE table and the 1 bar map?

I only made changes to the 7.5 cam position - figured it was close enough to 10 to see if it was going to do anything.

Why would you even attempt to tune it with a 1 bar map? I remember when PC released the P1SC kit 20yrs ago with a fuel management unit claiming to run 8psi on stock timing...just crank the fuel pressure up and send it. This isn't much if any better.

Procharger- You need to include a breakout harness and LS9 map with your gen5 LT1 kits.

Greg, this was just a stock 12K mile LT1 with a base Procharger System making 6 psi. It was a complete system provided by the customer and as you know they don't upgrade from a 1 Bar. Being stock, the original VVE tables work with good drivability Its not ideal but works with a stock LT1. The crazy thing is last year at the same time this car came in another C7 of the same year, received the same Procharger system with the same starting calibration. No problem pulling straight to 6500 and it made 596 at the tires and no meth, this has problems pulling past 6,000 but not always and I think only made 642 with meth. I tried your calibration and didn't see or feel any real change. I did notice that at 5500-6,000 I did get a flashing check engine light, that was new. I drove the car for about 30 minutes just before the rain and have attached the log file.

Thank You
Bad383TA

It went straight to 6200 every time in that log. There are some other background tables that control the rev limiter and you can clearly see the controller taking over trying to kill rev the first wot pull - 18 degrees of spark knock/timing pull. I would clean the MAF curve up and since it's a manual dial in the torque model however you like. I can do this later, but right now have my own tunes to take care of.

Problem is as I'm sure you're aware is GM changed a lot. You can't just take a tune and put it into another anymore and things need to be more in line and correct now more than ever. That includes having components right on the builds. Older OS's you could do whatever. These newer ones require pretty much starting from scratch each time.

^^ Greg hit it on the nose. GM changed some stuff on these cars behind the scenes for tables that are not defined by HPTuners. I can't tune a 2022+ ZL1 the same way I tune a 2017-2018 and some 2019s. At some point something changed and you have to tune later model years differently.

Here's another one to try out. I dialed in the torque model as best I could off of the logged data. I will say it's showing you've lost torque in the lower rpms vs the stock tables, but I assume you went with lower compression pistons? In fact a lot of it even in boost isn't much different than factory other than the 15 cam position. I also killed a lot of the map and correlation codes.

There's a bunch of other tables I'm waiting to change for you that can affect limiting. Let me know if this does anything first.

Greg, it did go straight to 6200 in the log but if you look it pulls straight to 5500 or so and then it almost stops and the tach will flat line or even move back and fourth. If I stay in it the engine will eventually make it past 6,000. I installed your calibration and I did feel some difference. Looking at the attached log you can see it went straight to 6200 in first, had a hard time getting to 6200 in second and in third it hit a wall at 5400 and just would not move past it, even staying into the throttle.

Thank You
Bad383TA

Just for testing do you by chance have an ls9 map or even a lt4 map you can throw in it for a quick run? I'm wondering if it being pegged ins't what's causing the ecm to go into the "the hell you say" state :) Wondering this because it's acting like the accel threshold tables are still in play. Usually only does that when it's seeing something wrong... Otherwise I'm still waiting on the other tables to get coded to try for you.

Open and do a write entire. Don't know if it'll fix your problem, but one table appeared to possibly be an issue. Also changed some other minor things in the cal that I had overlooked.

If this works - not saying it is or isn't going to, but if it does work your torque model will need reworking again with good data that doesn't include the timing being chopped out of it.

Will still couldn't find a couple of tables I was hoping to get, but I don't think they would have helped much anyway. It may even be some knock noise settings that need to be tweaked in case it's actually picking something up and not just A cutting power scenario...

Greg, Its been a few day as I was waiting for a break in the weather. I installed a ZR1 Map sensor and went for a test drive, exactly the same as before.

Bad383TA

Is that the latest with a write entire? Or just the ls9 map? Never mind I checked. This one doesn't have the modified tables in it. Do a write entire with the last one I posted.

This one has the knock noise thresholds updated - tread carefully with it. You might want to go back to stock lt1 knock settings. I do believe you're detuned enough, especially with the forged pistons but either way... I also updated the settings for the ls9 map. Again, just open this and do a write entire. This one also has the other updated tables that were in the previous one.

Greg, The Vette has been on the back burner and I still have problems. Same issues as the beginning of the post but a little more info. After trying your tune changes the car did the same thing hit a wall in the 5-6k range. I noticed a flashing check engine light and tried again. This time monitoring Misfires in the engine. I had a very specific cylinder 3 misfire at 5500, over and over again. It hits 5-6K rpms and cylinder 3 goes from 0 to 100 plus misfires immediately and timing is pulled into the negative. Its a non dod cylinder, changed plug wire coil and injector twice, along with compression test and leak down. Leak down is under 5%, two different injectors (went from new Lt1 to all new Lt4). Same cylinder that broke multiple times with stock pistons, thank god it has a forged drop in setup. Oh, I even changed valve springs on that specific cylinder.

Bad 383 TA

You did write entire on the tunes? I'm tuning one right now that's hitting 6400 without knock or anything. I did tune in the torque models, VE, MAF and density tables though.

For it to be killing it like that then it's seeing something it doesn't like and cutting cylinders. I just had this discussion with DDtech this last week with one he was having some trouble with. These torque controlled ecms will cut fuel, timing, throttle or anything if something isn't dialed in fairly close or it's seeing something it doesn't like. These newer OS's seem to be a whole lot worse about it. There's a lot of knock in your logs. Something has to be causing it whether you have to change settings for it or something is causing it. I would say focus on that and the problem will start to resolve itself. The last tune I posted had LT4 knock noise settings changed in the background. It should have had the reported knock a whole lot lower as long as you did a write entire - in other words opened and flashed entire without trying to copy things over or anything like that.

Ever figure this one out?

Quote:

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Originally Posted by GHuggins

Open and do a write entire. Don't know if it'll fix your problem, but one table appeared to possibly be an issue. Also changed some other minor things in the cal that I had overlooked.

If this works - not saying it is or isn't going to, but if it does work your torque model will need reworking again with good data that doesn't include the timing being chopped out of it.

Will still couldn't find a couple of tables I was hoping to get, but I don't think they would have helped much anyway. It may even be some knock noise settings that need to be tweaked in case it's actually picking something up and not just A cutting power scenario...

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What are you talking about here Greg where you had to do a Write Entire to fix some tables?

Older hpt software required you to do write entire to change the background settings that I had changed for this guy or maybe I'm mistaken on that. Either way newer software doesn't. I had changed some torque settings for his that made a difference but didn't fix his issue. Something I've run into even just recently on one was where hpt left out the max map settings for the torque model. I had to get those defined so the airmass side of the torque model would continue to report above the 150 kpa limit. I was experiencing horrible knock on one because it wasn't able to see the torque increasing with rpm and boost. Changed that one setting and got rid of about 80% of the knock this one truck was seeing. Misfires will show horrible knock too as the piston is just rattling around. Anyway, that's what I was referring to.

I love how HPT sells a product incomplete and expects us to beta test and fix it all the time for us