Poll: Who has ever hit the rev limiter?

[edram454]

the question was,, can it damage your car?? well just yesterday I met up with a nice guy in my neighborhood with a 1991 z, he seems like a very handy person with lots of equipment in his garage, welders, press etc.. he had just powder coated and ported his top end and his cam covers.... but on the side of his garage on a crate stood a wrapped up lt5. he just bought that engine used because he over-reved his engine and damaged it. he turned it on and it make some bad noises internally. he thought it was maybe damaged lifters so he replaced some of them. he decided to replace the whole engine so he bought a long block. he was driving around while his tach was not working and over-reved it and lost his motor. I know when I have hit the limiter on my c5 it just drops cylinders and stumbles. maybe the lt5 will do the same but again we are doing many more rpms than a c5 would be doing so the damage is more iminent. I would say not a good idea bumping that limiter too many times. by the way, this friends zr1 had 130k miles on it and still was running as strong as a bull.

ed ramos #3028

[cadillac531]

Originally Posted by Paul Workman

Around 6400 ya think? Hmmmm....

Pete and I were discussing the topic of where to shift for performance (on a stock ZR-1) with Jim (Jingles) Inglals (sp?). (Jim was the Corvette engineer that established - among other things - the drag strip numbers for the then new ZR-1) As I recall he recommended POWER shifting the Z at around 6300-6400 rpm (no throttle let-up between gears).

I think Pete and I agreed that neither of us is going to do any POWER SHIFTING as long as its on our dime if something breaks! But, to your comment regarding the UPSHIFT light coming on at 6400 for performance(?)...makes me wonder if it isn't more than just a "koinkeedink"

But, here's the thing: If Jim power shifts at around 6400, according to the tach, the actual rpm might well be at least a few hundred rpm higher than 6400, especially in the lower gears.

Just muddying the waters a bit...

Yeah, you may be right on that. I don't watch the tach very closely anymore except for the hole shot, where I bring it to 4000 off the line.

I just grab the next gear when the shift light pops, and in my peripheral, it looks like the needle is around that 6400 mark. The car is dead on consistent shifting with the light, though.

To the power shifting comment:

I power shifted it once on the street, and without a prepped surface, it blows the tires off on the 1-2 shift. That shifter has such a long throw though, that you really have to train that clutch leg to stay in long enough to complete the shift. I haven't, nor am I interested, in power shifting that 3-4 shift.

No worries on the muddy water...it makes things interesting.

[cadillac531]

Originally Posted by edram454

the question was,, can it damage your car?? well just yesterday I met up with a nice guy in my neighborhood with a 1991 z, he seems like a very handy person with lots of equipment in his garage, welders, press etc.. he had just powder coated and ported his top end and his cam covers.... but on the side of his garage on a crate stood a wrapped up lt5. he just bought that engine used because he over-reved his engine and damaged it. he turned it on and it make some bad noises internally. he thought it was maybe damaged lifters so he replaced some of them. he decided to replace the whole engine so he bought a long block. he was driving around while his tach was not working and over-reved it and lost his motor. I know when I have hit the limiter on my c5 it just drops cylinders and stumbles. maybe the lt5 will do the same but again we are doing many more rpms than a c5 would be doing so the damage is more iminent. I would say not a good idea bumping that limiter too many times. by the way, this friends zr1 had 130k miles on it and still was running as strong as a bull.

ed ramos #3028

Yeah, on a traditional pushrod motor, hitting the limiter can cause valve float. When that happens, the valves could contact the piston **BANG**.

In our LT5's, the movable valve train weight should be less, since there's no pushrod, so I would think the force would need to be much higher to get the valves to float. That sudden stop in accelerating RPM's still creates forces within the engine that attempt a valve float.

That's why aftermarket rev limiters try to soften that stop, like MSD's soft touch rev limit.

[WydGlydJim]

I've bumped it a time or two.......best I can tell the Lingenfelter is set at 8200.

[tf95ZR1]

Originally Posted by Kevin

just saw this old post,
90 is the one only that has the shift light for performance, the rest have it for fuel economy

Originally Posted by cadillac531

Not true, my 91 lights up for performance, and mine is all stock. I don't remember the actual rpm it lights up, but some where around 6400 I think.

Does anybody with a MY 1994/1995 have a OEM "Shift Light"? I have an aftermarket,
but never noticed or saw one that would have come with the car.

[WARP TEN]

Originally Posted by edram454

the question was,, can it damage your car?? well just yesterday I met up with a nice guy in my neighborhood with a 1991 z, he seems like a very handy person with lots of equipment in his garage, welders, press etc.. he had just powder coated and ported his top end and his cam covers.... but on the side of his garage on a crate stood a wrapped up lt5. he just bought that engine used because he over-reved his engine and damaged it. he turned it on and it make some bad noises internally. he thought it was maybe damaged lifters so he replaced some of them. he decided to replace the whole engine so he bought a long block. he was driving around while his tach was not working and over-reved it and lost his motor. I know when I have hit the limiter on my c5 it just drops cylinders and stumbles. maybe the lt5 will do the same but again we are doing many more rpms than a c5 would be doing so the damage is more iminent. I would say not a good idea bumping that limiter too many times. by the way, this friends zr1 had 130k miles on it and still was running as strong as a bull. ed ramos #3028

Hi Ed--
We have a good FBI friend named Al who ran into a little problem at last year's half mile races. Here is a video of what happened to his motor due to a little over revving: http://www.youtube.com/watch?v=bgQiABT05tM --Bob

[Paul Workman]

Originally Posted by edram454

the question was,, can it damage your car?? well just yesterday I met up with a nice guy in my neighborhood with a 1991 z, he seems like a very handy person with lots of equipment in his garage, welders, press etc.. he had just powder coated and ported his top end and his cam covers.... but on the side of his garage on a crate stood a wrapped up lt5. he just bought that engine used because he over-reved his engine and damaged it. he turned it on and it make some bad noises internally. he thought it was maybe damaged lifters so he replaced some of them. he decided to replace the whole engine so he bought a long block. he was driving around while his tach was not working and over-reved it and lost his motor. I know when I have hit the limiter on my c5 it just drops cylinders and stumbles. maybe the lt5 will do the same but again we are doing many more rpms than a c5 would be doing so the damage is more iminent. I would say not a good idea bumping that limiter too many times. by the way, this friends zr1 had 130k miles on it and still was running as strong as a bull.

ed ramos #3028

The limiter is there to prevent over-reving the motor, and in and of itself isn't going to cause any catastrophic issues. After completing the "FBI 500+" package, including the Fidanza FW and before installing a shift light (on my 90) I often bumped the limiter. It is nothing more severe than miss firing/sputtering or missing (read: pretty soft, but no drivetrain shock).

Before I had my rev limiter bumped to 7600 and a shift light installed, I'd hit it quite often - Here is an example of how soft the limiter is:

This is Pete's Green Monster. Notice the little misfire on his second burnout at about 1:05.

http://www.youtube.com/watch?v=SFNFOhGGlR4

Nothing to worry about...BTDT many times, w/o issues - NO crashes of gears or anything like that. Very soft.

P.

[edram454]

I understand it is to prevent over-reving of the motor but there are only so many times a motor is going to let you bust its gut until it busts yours. they are definitely great engines and durable but they are not indestructible. My friends lt5 had 130k miles until it blew up. he bought the car with 120k miles. those are miles that could have been done a 1/4 mile at a time. I understand bumping the limiter during a grudge match or something. i dont understand just bumping it every time you go for a drive.

I dont like to be hard on my equipment and that is why I have never had catastrophic failures even in race engines. I use it and get what I need out of it at the time and leave it. I wont just beat on it for kicks. everybody has different driving habits and of course if the owner wants to rev it every time then its ok. I just think engines that are thrashed continually will one day bite you in the rump. that guys zr1 in the video is a monster. 11.30 at 129 mph and no power adder. Great car and great power.

ed ramos #3028

[5ABI VT]

Bumped it about 10x last week when I took it out. have to get a feel for where it is on the tach because they aren't exactly accurate. Pretty much figured it out now. I have no fear with this motor at all. if it blows up oh well stroker time

[Paul Workman]

Originally Posted by 5ABI VT

Bumped it about 10x last week when I took it out. have to get a feel for where it is on the tach because they aren't exactly accurate. Pretty much figured it out now. I have no fear with this motor at all. if it blows up oh well stroker time

Tach calibration is a relatively easy DIY fix for anyone familiar with basic electricity; just soldering in a resistor in place of the deteriorated, printed one.

I believe Dynomite (our club's Archive guru) has the procedure captured in his archive. Check there first. Or, I have a copy of the article I wrote on it...somewhere around here if you need me to dig it up for ya!



Course too, with any analog meter (tach in this case) there is a certain % of lag which increases with changing (rpm) rate; naturally there's more in first gear especially. SO...a shift light is recommended. And, in the archives too is procedures for installing one. (I installed a Raptor light which is small enough to be hidden behind one of the vent grills. All seven LEDs wink on and off in sequence when the ignition is first turned on - as a test mode.)



In the book, "Heart of the Beast" there was a problem discovered when a single chain was used. But, the cure was the double chain that the LT5s have now. In the book, it describes how Lotus engineers tested the motor by alternating the engine between peak torque and 7000 rpm for a little more than a week w/o issues. So, I don't think occasionally hitting the limiter at approx 7200 is "pushing it" at all, long as it hasn't been run out of oil or the like. It ain't no pushrod motor!