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GM powertrain specifies the maximum recommended RPM as 6600 for the LT1 and LT4. How much over this the typical LT1/LT4 can go without damage is another question as is how strictly GM wants to stick with the specified limit. If they want to play hardball, they can (and perhaps are) stating that 6,500 is marked redline on the tach giving you a 100 RPM buffer before hitting maximum recommended and you went beyond this RPM. I wouldn't care for that reasoning but I wouldn't want to try to fight it in court.
Since you have the PDR data, you can download Pi Toolbox from Cosworth and show a graph of the precise RPM for any PDR data that you have. It would be interesting to see what Pi Toolbox shows for the actual RPM compared to the peak RPM on the LCD display tach. I suspect that the ECM captures the maximum RPM the engine has seen over its lifetime and that may not have been at this track event or on this specific lap.
Here is a screen capture of Pi Toolbox. Moving the cursor across the graph will show the precise value in the data box for that point on the timeline.
I downloaded the program, where do you download from a PDR? It talks about adding an outing but I can't find a PDR download. Unless you need a more advanced version, I downloaded the Lite version
You can work your way through it using the Pi Toolbox manual but this is a great video that a Corvette owner posted to YouTube that makes it very simple to get started:
You are right! The OP shows us a film covering minutes of a cars life that has over 5,000 miles on it. The minutes just happen to occur on a race track which apparently was not the first time it was used for that purpose. GM, who designed the engine, built it, and warranties it, looks at the tear down and has the audacity to say it was an over-rev situation.
Now you, with your extensive experience with these matters, calls BS and knows GM is simply trying to dodge their responsibility. But, you have a lot of company chiming in. Never seen the car nor really know anything in reality but not their money so GM should certainly pay!
Now is the time though to find that attorney everyone has on retainer!
Yeah, and I'm sure any day now GM will own up to their z06/Gs wheel problem and their A8 problems, right? Because they would never try to dodge responsibility, right? LOL - you can keep trusting GM to act honorably, and I'll keep living in the real world and understand they are a soulless corporation that only cares about profit margins.
Don’t these motors have a rev limiter preventing the engines from over revving and burning out?
if you read the entire thread and watch the video, you will see this is a manual car, and the over-rev is during a downshift.
Nothing can prevent human error of forcing a downshift too early and thus over-revving the motor.
Yes, there is a rev limiter for fuel when accelerating that will prevent it from increasing in rpm beyond redline, but that is not the same as downshifting too early.
While the video shows very slight time in the red, I do agree that if the car can't take 100rpm over, and that GM didn't include some buffer there, then this is a hard pill to swallow.
I don't see how just getting the VIN and tearing the motor down provides what they need to know to stand firm on over-rev. They probably looked the vin up and saw it was a manual car and decided at that moment that it can be over revved and they were done.
I am not an engineer but you can't tell me that when they set the red line at 6500 that the true red line is not higher. I relate this to the gas gauge, when you hit empty on newer cars empty is really not empty a cushion is built in. When there is a highway off ramp listed at 30mph, one can definitely go 40mph without damage. If dipping into the supposed redline for less than a second is enough to blow this "bullet-proof" engine then this will be the last corvette I ever consider buying. I buy expensive tools with warranties that state if I drop the tool and it breaks its covered. I haven't heard back from GM yet but I know what the answer will be. Is this "high performance" car only good for traveling around the town? Sorry, this whole thing just doesn't make sense to me.
This thread is seriously making me reconsider my C8 purchase. I'm in the same opinion that if 100RPM is all it takes, then I probably need to move on.
This thread is seriously making me reconsider my C8 purchase. I'm in the same opinion that if 100RPM is all it takes, then I probably need to move on.
Why? there is no need to ever redline an engine. Not even on a race track, as its usually not optimum to shift that high as you are getting out of your torque curve.
Also a 1x redline bump wont grenade a stock engine. repeatedly redlineing one will. OP is only providing video for going past redline by 100-200rpm 2x. What about what happened for the other track events and the other 5000 miles. How many times in the past has there been a missed shift or a downshift instead of upshift event.
Why? there is no need to ever redline an engine. Not even on a race track, as its usually not optimum to shift that high as you are getting out of your torque curve.
Also a 1x redline bump wont grenade a stock engine. repeatedly redlineing one will. OP is only providing video for going past redline by 100-200rpm 2x. What about what happened for the other track events and the other 5000 miles. How many times in the past has there been a missed shift or a downshift instead of upshift event.
If I might make a suggestion. All these films and discussions of what will and won't make an engine blow are certainly interesting. The problem still remains that GM had the engine torn down and after actual physical inspection, declared over rev the cause of failure. Were it my $25,000, I would be looking for an independent engine expert to look at the torn down engine and offer an opinion of what they see. That expert could be a certified Corvette tech from another store, a respected independent shop owner from the area, a local education facility person, etc.
If I hired another opinion and they confirmed the original opinion, game over and let me find a used engine. If they can offer another alternative scenario, I want an attorney.
"Good morning. I have spoken to the Field Warranty Representative about your case. He let me know that he had came to the dealer to look at your vehicle personally, and he has involved all the district representatives. What was found during inspection was that all the valves had hit the pistons, and the vehicle had went over the recommended RPM. He says this is caused when you downshift too hard, and it causes the engine to over revv. Though the vehicle is considered track ready the owner's manual tells you precautions to be aware of when racing. I found on page 194 of the owner's manual it says that When downshifting, if more than one gear is skipped, or the engine is racing when the clutch pedal is released, the engine, clutch, driveshaft or transmission could be damaged. Unfortunately, the engine damage that was caused is not a manufacturer defect, and it will not be covered. Good morning. I have spoken to the Field Warranty Representative about your case. He let me know that he had came to the dealer to look at your vehicle personally, and he has involved all the district representatives. What was found during inspection was that all the valves had hit the pistons, and the vehicle had went over the recommended RPM. He says this is caused when you downshift too hard, and it causes the engine to over revv. Though the vehicle is considered track ready the owner's manual tells you precautions to be aware of when racing. I found on page 194 of the owner's manual it says that When downshifting, if more than one gear is skipped, or the engine is racing when the clutch pedal is released, the engine, clutch, driveshaft or transmission could be damaged. Unfortunately, the engine damage that was caused is not a manufacturer defect, and it will not be covered."
I have asked GM for any documentation or data that definitively shows the engine was over-revved, and so far they will not provide.
Their response to my request:
"I will see if I can get that information, but I don't think I can. Once the representatives comes to a resolution it doesn't change. "
Well that certainly sux. I thought one of the computer modules stored a history of max revolutions on these cars. If that is true, then you need to find someone with equipment to read that bit of history. That could either validate or invalidate GM's premise. I think you would have a hard time beating GM's case unless you had such information. And remember that GM defines redline at 6500RPM, so technically you've already proven their case with your video of the RPMs at 6700 briefly 2 times that I saw. Agreed that shouldn't be enough to grenade one of these engines, sadly in your case it appears that it was. Maybe time to figure out your next steps and move on. All the best and I hope whatever direction you go works out for you in the end.
I hate to play devil's advocate here, as this certainly sucks, but from watching the short video, I think the original poster spends far too much time close to red line. There is just no need for it, especially if you expect the motor to last. The first time I tracked my '15 Z51, I felt I was spending too much time between 5000 and 6500 rpm only to review the video and see I was more like 4500 to 5500 or so. While the Corvette is a great car, no motor is going to last when driven at max rpm so frequently. When downshifting, there should be no reason to be at or above 6500 in the next lower gear, or you are downshifting too soon. Hit the brakes more, then downshift, so that when rev-match kicks in, it's around 6k or lower, not 6700. You're just asking for trouble spending that much time around 6500 rpm.
Again, sorry this happened, breaking a motor sucks and I hope you get it back on the road soon.
06-13-2019, 07:08 AM
