Z06 Whisperer

I'm currently having my stock C5 Z06 LS6 engined tuned and was offered the option of having my rev limiter raised. What are the pros and cons of doing so? What's the most you would raise it by?

Thank you!
Anita

John Shiels

Cons are the big bang theory Mine is at 6700 on a LS6 which is modded.

Z06 Whisperer

Yes I've had a chance to test that theory too--it's a fun but expensive ride LOL

I believe he was thinking to only go about 500 up. The main positive I could see is that it would save me from maybe having to shift into 5th, for teeny bits of time on track in places and potentially avoid a "money shift" (the kissin' cousin of the "big bang" ). Would it really be that much harder on an engine to run the revs higher for short times? (I know you don't know my driving style, but I do love my revs).

John Shiels

I don't reall bother even shifting at my redline unless a big motor is what I am running against. I try to do 6500. Squential shift light would be worth more on track than bumping the revs with no downside.

DOUG @ ECS

With a stock cam the only gain I could possibly see would be saving you a shift in an awkward turn at a track you race at regularly. Which at that point I would change my entry or something.
The power will fall off by raising the limited so there is not a power gain, the rest of the engine can handle the revs fine, except for the valve springs that were not designed for that. So personally I would leave it at or near stock.

AU N EGL

The LS6 intake and TB does not breath real well obove 6800 rpms, SO even if you do raise the limiter, it may not do much good.

Mine is 6750 so I can shift at 6700

Cobra4B

Well... w/ my cam, comp 921 springs, and yella terra roller rockers (new light design), and LS2 timing chain I have the rev limiter set at 7000 rpms. I shift at 6800 when playing and 6200ish on track. Haven't run a track event since the cam install though.

My car made power all the way to 7k w/ it leveling off after 6600, but not dropping.

davidfarmer

Per GM RAcing and Katech endurance testing:

6500rpm for 97-2000 rod bolts
6900rpm for 2001-up engine rod bolts.

In theory, if you stay below the above limits, your engine would run "forever" on a loaded dyno. Of course, "forever" is a relative term in durability testing!

***My WC engines ran easily up to 7500rpm with stock intake and TB. If you have the valvetrain lift to suck enough air in, that is***

95jersey

I had my G5X3 car with 921 Comp springs set up at 6800. I also had my stock car set up to 6800 for a couple seasons before the 921's. I would RARELY shift at these point because the stock cam is NOT making power...

But, there are DEFINATELY circumstances on certain tracks where you are just a redline, but still accelerating towards a corner and need to make a decision to upshift for 3 seconds, back off, or bump off the limiter. I had this problem at Watkins Glen going into the toe of the boot. The extra 2000 rpm was EXACTLY what I need to keep me accelerating. While I was not making lots of power, I was still accelerating and at least not coasting into the corner.

So, I understand why you want to do this...it has nothing to do with power, but releaving some uneccessary shifting. I can't tell you nothing bad will happen, BUT I did run a stock motor at this limit for 2 years...BUT I ONLY ran it to that RPM when I absolutely had to such as the toe of the boot at WG.

VetteDrmr

This is exactly the scenario I ran into at my last autocross event. Ran the course in 1st, bumping the rev limiter at three different points of the course. In the afternoon I ran with no passengers and ended up shaving 3 seconds off my best morning time, but I had to shift into 2nd for 2-3 seconds at those three points.

Video here:

http://www.youtube.com/watch?v=7QowaUEaL_A

But, even if you bump the rev limiter up 200 (I believe the 2000 referenced above is a typo), you'll still have courses where you'll be tapping the limiter.

Have a good one,
Mike

Slalom4me

Taller tires for a lower final drive ratio ?

.

0Randy@DRM

I am going to be the first to say the chains can't hold up to rpm at all. Many motors come in here with flat out broke chains, and cam bolts falling out.

Randy

LehmanZ06

My 04 Z06---that I run in ASP now----had the limiter raised to 7000 rpm----headers intake etc. By Danny Popp. His car had the limiter raised to 7300.

I am not a "Master Vette mechanic", that has his own seperate area, at a GM dealer. So I asked Danny to set mine to 7000 rpm. No problems at all since June of 05-----and I have probably run at least 50 autox's-------banging the crap out of the limiter in 1st and 2nd----every now and again.

7000 rpm no worries IMHO

David
Founder GIANT FUNGUS RACING

Bill Dearborn

I have this exact problem at the Glen. If I shift I get about 10 mph more speed before I hit the braking point for the toe. If I don't shift I bump off the rev limiter for the a couple hundred feet. The time taken doing the upshift and downshift probably cancel out any advantage I get from shifting. My decision has been to let it bump off the limiter and then back off just a shade to keep off the limiter. I am not planning on raising the limiter since I think that is asking for trouble over the long run. Now if I was in a race Vs a HPDE I probably bump the limiter. But since my car will not be worth any more when I finish an event than it was when I started the event I am not going to take the risk.

Bill

0Randy@DRM

Guys and Gals,
Please try something the next time you are out on the track.
1st, running the crap out of her. Check lap times
2nd, short shift for a couple laps. Check lap times

Auto-x I bet would be faster banging it off the limiter, maybe
Road-race My money would be on the short shifter.

Randy

jtkeller

mike - we can bump your rev limiter up in a few seconds with my hptuners if you want...

ddl6289

Randy,

I wouldn't be surprised if your right . Next time (~ 3weeks) I'm at Road America I'll try it.

Dan

VetteDrmr

Randy,

That's my theory as well. This last event was the first one where I found myself riding the rev limiter about halfway down the straight, just waiting, waiting, waiting for the next corner.

On this course from my best 1st gear only run to my first run shifting I dropped 1.1xx seconds, and ended up my best 1-2 run being 3.6 seconds faster. Frankly, I was astonished.

Justin, I might just take you up on that. I just swapped out the stock valve springs for yellow Z06 springs, so I think that would be a safe thing to do.

Randy, do you think a 200-300 bump with new valve springs would be OK on an engine with 150,000 miles on it?

Thanks for the help, and have a good one,
Mike