LT-1 Rev Limiter??
Thread Starter
Racer
Joined: Dec 2004
Posts: 429
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From: Midddleburg FL
LT-1 Rev Limiter??
My car is a 95 and, as far as I know, completely stock. From what I've read as LT-1's redline is 5500 rpms, which is where the rev limiter kicks in. Last night when I left work i pulled out of the parking lot and stood on it, WOT. At around 5500 rpms the car shifted into second. The instant that it shifted I saw the tach pass 6000 for a split second. The rev limiter didn't kick in, and now I'm curious if this is actually a "quirk" (for lack of a better word) of the tach itself. This isn't the first time I've seen it do this. So I'm wondering, anyone else ever see something like this before?
Le Mans Master
Joined: Apr 2000
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From: Amateur driver on open course.
At higher RPM's, I found my tach to be off by 700 RPM. Alot of other folks here experienced the same thing. I would guess yours is a bit off too. A dyno run can tell you for sure.
Melting Slicks
Joined: May 2002
Posts: 2,670
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From: Severna Park MD
Originally Posted by tm1995c4-LT1
My car is a 95 and, as far as I know, completely stock. From what I've read as LT-1's redline is 5500 rpms, which is where the rev limiter kicks in. Last night when I left work i pulled out of the parking lot and stood on it, WOT. At around 5500 rpms the car shifted into second. The instant that it shifted I saw the tach pass 6000 for a split second. The rev limiter didn't kick in, and now I'm curious if this is actually a "quirk" (for lack of a better word) of the tach itself. This isn't the first time I've seen it do this. So I'm wondering, anyone else ever see something like this before?
The stock rev limiter is 5850. It acts by cutting off fuel, and there is a delay until the pressure goes down in the fuel rails. You can overrev the limiter in 1st and 2nd on a 6 speed, then it will seem to cut off at lower revs in 3rd and 4th. Time is the factor here. The engine revs so quick in 1st that the tach is farther behind than it is in 3rd and 4th. So you aren't seeing a true reading on the tach. I believe my tach is close to right on in 3rd gear going through the 1/4.
I have my limiter bumped to 6400 and try to shift at 6200 by the tach. I don't normally hit the rev limiter going through the 1/4, I only bounce off it when there is horrible traction.
Race Director
Joined: May 2001
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Originally Posted by FELNGR8
The stock rev limiter is 5850. It acts by cutting off fuel, and there is a delay until the pressure goes down in the fuel rails. You can overrev the limiter in 1st and 2nd on a 6 speed, then it will seem to cut off at lower revs in 3rd and 4th. Time is the factor here. The engine revs so quick in 1st that the tach is farther behind than it is in 3rd and 4th. So you aren't seeing a true reading on the tach. I believe my tach is close to right on in 3rd gear going through the 1/4.
I have my limiter bumped to 6400 and try to shift at 6200 by the tach. I don't normally hit the rev limiter going through the 1/4, I only bounce off it when there is horrible traction.
I have my limiter bumped to 6400 and try to shift at 6200 by the tach. I don't normally hit the rev limiter going through the 1/4, I only bounce off it when there is horrible traction.
5850 is stock and the factory tach can only move so fast. Thus your rev limiter will appear to be different places depending on what gear you're in and how far you've got the pedal to the floor.Question though? I know the factory limiter works by dropping fuel. Wouldn't it do this by cutting the injectors, thus it would be instant. Cutting the fuel pump would take a LONG time to have a noticeable effect.
Anyway, I've got an MSD digital 6 set at 6500 RPM's and the factory limiter is programmed out of the way. For the track I have a shift light that comes on at a preset RPM no matter what the tach actually reads.
Thread Starter
Racer
Joined: Dec 2004
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From: Midddleburg FL
Originally Posted by 95AquaC4
At higher RPM's, I found my tach to be off by 700 RPM. Alot of other folks here experienced the same thing. I would guess yours is a bit off too. A dyno run can tell you for sure.
I've seen this happen in my car a few times. I was a little concerned, but more curious than anything.
Thread Starter
Racer
Joined: Dec 2004
Posts: 429
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From: Midddleburg FL
Originally Posted by Nathan Plemons
5850 is stock and the factory tach can only move so fast. Thus your rev limiter will appear to be different places depending on what gear you're in and how far you've got the pedal to the floor.Question though? I know the factory limiter works by dropping fuel. Wouldn't it do this by cutting the injectors, thus it would be instant. Cutting the fuel pump would take a LONG time to have a noticeable effect.
Anyway, I've got an MSD digital 6 set at 6500 RPM's and the factory limiter is programmed out of the way. For the track I have a shift light that comes on at a preset RPM no matter what the tach actually reads.
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Melting Slicks
Joined: May 2002
Posts: 2,670
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From: Severna Park MD
Originally Posted by Nathan Plemons
:Question though? I know the factory limiter works by dropping fuel. Wouldn't it do this by cutting the injectors, thus it would be instant. Cutting the fuel pump would take a LONG time to have a noticeable effect.
It makes sense that the PCM has knowledge of the rpms and has full control of the injectors, so that's the correct way to cut off some cylinders. If the injector is not fired at all then there is no lean condition to harm the engine.
Lord knows, as much as Mojo hits his limiter he should have blown it up by now if there was a problem.
I swear I got well beyond 5850 by the tach in 1st when i hit the rev limiter, but got cut off at 5850 in 3rd. I never have hit it in 4th or 5th so I don't know what happens in those gears.