Overrev
02-14-2019, 07:47 PM
#62
Le Mans Master
02-14-2019, 10:12 PM
#63
02-14-2019, 11:55 PM
#65
Le Mans Master
02-15-2019, 12:13 AM
#66
Pro
Thread Starter
02-15-2019, 08:28 AM
#68
The logging frequency in the PDR for RPM data is 83.33 Hz. I have definitely had issues with the tach and shift lights lagging when accelerating in lower gears and hitting the hard limiter before the first blue light shows up on the HUD so I don't know how much I trust what you were able to see on the tach and that is why I would not assume you only spun it to 6900 RPM. I have missed the 4-5 shift on the track and hit 3rd and the data showed only about 6800 RPM but those are different ratios and I typically short shift in to 5th because I have to shift before a bend on the straight.
I'll offer one more anecdote but unfortunately I can't find the thread. Several years ago forum member JD blew a built LS7 on track. Jason went back to a prior video he had posted that showed where he zinged the motor on an early downshift going in to a corner. The motor continued to run fine for a while even on track. I don't agree that the LS7 and LT4 are that different in this regard, fatiguing the metal in a valve spring by overstressing it is the same in both cases. I mentioned this previously but that is why when I had a mechanical overrev in my own car I took a few evenings to pull the valve covers and replace the valve springs.
If you don't plan to track it and have a warranty go ahead and drive it. If you're going to track it I'd do everyone out there with you a favor and replace the valve springs. A buddy just totaled a brand new 991 GT3 Cup car at the track because another guy who knew he had a weak motor went anyway and blew his motor on track and oiled it down. My buddy was a passenger once he hit the oil and hit the wall so hard the motor came out of the back of the car.
I'll offer one more anecdote but unfortunately I can't find the thread. Several years ago forum member JD blew a built LS7 on track. Jason went back to a prior video he had posted that showed where he zinged the motor on an early downshift going in to a corner. The motor continued to run fine for a while even on track. I don't agree that the LS7 and LT4 are that different in this regard, fatiguing the metal in a valve spring by overstressing it is the same in both cases. I mentioned this previously but that is why when I had a mechanical overrev in my own car I took a few evenings to pull the valve covers and replace the valve springs.
If you don't plan to track it and have a warranty go ahead and drive it. If you're going to track it I'd do everyone out there with you a favor and replace the valve springs. A buddy just totaled a brand new 991 GT3 Cup car at the track because another guy who knew he had a weak motor went anyway and blew his motor on track and oiled it down. My buddy was a passenger once he hit the oil and hit the wall so hard the motor came out of the back of the car.
02-15-2019, 08:53 AM
#69
Le Mans Master
I dont disagree with what you are saying Poor-sha, but i think it unlikely. while being absolutely possible, i still think damages would ive been right away. Metal fatigue in valve springs is unlikely from 1 '' small'' overrev, not talking about a full blast at 9000RPM!! Of course there is no way to be 100% sure without opening it up, if it was mine i wouldnt, but that is OP decision!
Last edited by timmyZ06; 02-15-2019 at 08:53 AM.
The following users liked this post:
Poor-sha (02-15-2019)
02-15-2019, 09:40 AM
#70
Great advice from Poor-sha, replacing the springs is very cheap insurance against what could easily happen from over-stressed springs.
Ignoring what happened and hoping for the best reminds me of a line in a Stephen King novel where the character "treated" his blood in the urine issue by peeing in the dark.
Ignoring what happened and hoping for the best reminds me of a line in a Stephen King novel where the character "treated" his blood in the urine issue by peeing in the dark.
02-15-2019, 11:30 AM
#71
Does the Corvette ECU log over-revs? I know from past experience a majority of performance brands (BMW, Porsche, Mazda, Subaru...etc) logs mechanical over-revs and will deny warranty claims related to motor damage (valve train, crank bearing...etc). I'd be surprised if the mechanical over-rev wasn't stored in the ECU.
02-15-2019, 01:48 PM
#72
The logging frequency in the PDR for RPM data is 83.33 Hz. I have definitely had issues with the tach and shift lights lagging when accelerating in lower gears and hitting the hard limiter before the first blue light shows up on the HUD so I don't know how much I trust what you were able to see on the tach and that is why I would not assume you only spun it to 6900 RPM. I have missed the 4-5 shift on the track and hit 3rd and the data showed only about 6800 RPM but those are different ratios and I typically short shift in to 5th because I have to shift before a bend on the straight.
I'll offer one more anecdote but unfortunately I can't find the thread. Several years ago forum member JD blew a built LS7 on track. Jason went back to a prior video he had posted that showed where he zinged the motor on an early downshift going in to a corner. The motor continued to run fine for a while even on track. I don't agree that the LS7 and LT4 are that different in this regard, fatiguing the metal in a valve spring by overstressing it is the same in both cases. I mentioned this previously but that is why when I had a mechanical overrev in my own car I took a few evenings to pull the valve covers and replace the valve springs.
If you don't plan to track it and have a warranty go ahead and drive it. If you're going to track it I'd do everyone out there with you a favor and replace the valve springs. A buddy just totaled a brand new 991 GT3 Cup car at the track because another guy who knew he had a weak motor went anyway and blew his motor on track and oiled it down. My buddy was a passenger once he hit the oil and hit the wall so hard the motor came out of the back of the car.
I'll offer one more anecdote but unfortunately I can't find the thread. Several years ago forum member JD blew a built LS7 on track. Jason went back to a prior video he had posted that showed where he zinged the motor on an early downshift going in to a corner. The motor continued to run fine for a while even on track. I don't agree that the LS7 and LT4 are that different in this regard, fatiguing the metal in a valve spring by overstressing it is the same in both cases. I mentioned this previously but that is why when I had a mechanical overrev in my own car I took a few evenings to pull the valve covers and replace the valve springs.
If you don't plan to track it and have a warranty go ahead and drive it. If you're going to track it I'd do everyone out there with you a favor and replace the valve springs. A buddy just totaled a brand new 991 GT3 Cup car at the track because another guy who knew he had a weak motor went anyway and blew his motor on track and oiled it down. My buddy was a passenger once he hit the oil and hit the wall so hard the motor came out of the back of the car.
We shouldn't confuse the sampling rate of the PDR or any scanning devise with the broadcast rate to the tachometer.
Information provided to the PDR or a scanner is considered "polling data".
Polling data is by nature latent data because it has to be requested from the original source and then provided to the requesting source.
This process provides snap shots of past events. And it takes approximately twice the bandwidth to display.
The data presented to the tachometer display is from what is considered "broadcast data".
Broadcast data rates are not nearly as "latent" as "polling data" rates. They are a live direct feed from the source as it happens.
An analogy between the two would be the difference between siphoning water through a hose and getting water full blast from a spigot.
Couple of points I am making here.
1. Even at 83hz (83 times per second) a PDR RPM event would have to last less than half that time in order not be recorded at all.
This is because in order to miss an "over rev" and display some lessor rpm the rev's have to both climb to a peak rpm AND subside from that peak RPM in less than 1/83rd of a second.
In layman's terms the event would have to happen in less than 1/83rd of a second and be missed twice within that time frame. (Once on the way up to max rpm and once on the way down from max rpm). This simply aint going to happen.
2. One above was the PDR which uses "polling data".
The tachometer in the car with the "high rev marker" that was left at 6900 rpm is fed with broadcast data which should have sampling rates much faster than the PDR polling rate of 83hz.
This makes it even less likely an "over rev" event will be displayed as some lessor RPM.
Regardless of all the above, I don’t believe an engine can go from 6900rpm to let's say a conservative 7500rpm and back down to 6900rpm in 1/83rd of a second.
This is why I say if the OP's tach marker maxed out at 6900rpm, that's about what the max rpm was.
02-15-2019, 03:17 PM
#73
Racer
So I messed up a bit and threw 1st instead of 3rd at the higher end of 2nd. Maybe like 75-80. Felt the higher than normal rev and the fuel cut off hitting immediately which dropped my speed with a quickness. I also kicked the clutch into neutral. The afterimage of the rev limiter showed 6800-6900. No lights or wired sounds just yet, thoughts?
02-15-2019, 03:46 PM
#74
So I messed up a bit and threw 1st instead of 3rd at the higher end of 2nd. Maybe like 75-80. Felt the higher than normal rev and the fuel cut off hitting immediately which dropped my speed with a quickness. I also kicked the clutch into neutral. The afterimage of the rev limiter showed 6800-6900. No lights or wired sounds just yet, thoughts?
02-15-2019, 04:18 PM
#76
Race Director
02-15-2019, 04:24 PM
#77
Pro
Thread Starter
That's literally not true technically. As soon as that clutch is pushed in, the transmission un-couples from engine engagement. The only thing is the car will say first fear but you're not actually in it until you engage the clutch.
02-15-2019, 06:33 PM
#78
Le Mans Master