RobertEarl

Your at your local autocross, you are approaching a 90 degree turn after a long straight, you start hitting the rev limiter before you reach your braking point. Question, how long do you run on the rev limiter before you shift instead.

I have gone as long as 2 seconds. Does it hurt anything to keep on it a little longer? What is a good amount of time before you are better off shifting than hanging on the rev limiter????

Reb

Chuck A

I also have a question am i not hitting the rev limiter bad, due to i have heard you should bring it up rather near the high, i usually shift when i hit maybe 4000 rpms, and does anyone know the speeds when you should shift, like the speed for first what should be the tops, maybe 20-30mph, then 2nd 30-50 etc etc etc

davidfarmer

pretty much every c5/c6 engine has a very high HP curve, and the "ideal" shift point is at redline, or even above. Therefor, don't shift unless you are going to be in the higher (lower torque) gear long enough to actually gain significant speed, as the time you lose doing the shifts will hurt you more than the slight hp gain you get.

I'm no autocrosser (never enjoyed it very much), but on the road course, upshifting/downshifting also commonly causes people to overbrake, so they end up carrying less speed through the following corner than they would have just coasting/light braking into it.

It won't hurt anything to hit the rev limiter, however depending on your setup, raising the rev limit a few hundred rpm might solve the problem AND make you go faster. 97-00 safe to 6500rpm stock, 01-up safe to 6900rpm......this according to GM longevity testing, or so I was told by their racing contact back in my World Challenge days.

LehmanZ06

I set mine to 7000 rpm----about 200 autox events NO PROBLEM

04 Z06

the blur

I often wondered if banging off the rev limiter jolted the timing chain too much. certainly not too smooth when the motor starts bouncing at high RPM's.

sometimes I forget to upshift, and the limiter is an instant reminder

Bill Dearborn

Most autocross courses aren't long enough to ride on the rev limiter for too long. At the Glen I ride the limiter or just below where it cuts in on one straight for a distance of ~ 500 ft.

Bill

VetteDrmr

If I'm on the limiter for 2-3 seconds (seems longer in the heat of battle), I'll just breathe the throttle once the revs "sound" like the limiter is close. This may cost me a bit of speed, but the car is smoother and less distracting.

If I'm only hitting the limiter for a short time then I just let it hammer.

I know you asked about autocrossing, but out at MSR recently I tried leaving the car in 4th coming into Big Bend instead of downshifting into 3rd. It allowed me to hit the brakes (probably too much), turn in, and be WOT before the apex. Pulled 1.5 seconds off my lap times with that technique.

HTH, and have a good one,
Mike

autoxer6

I actually ran into this debat this past sunday. Three of us at a Milwaukee autocross in Z06's were hitting the rev limiter about 8-10 "pings" in second. The DL-1 data showed that it was a wash shifting into third. This was because there was a little time lost downshifting in the next corner.

Bill Dearborn

Isn't the time lost during the upshift when the wheels aren't being powered? You can downshift during braking so shouldn't lose any time other than for over braking.

Bill

autoxer6

Good point.

In this particular case the "braking zone" was short and just a tap on the brake just to plant the front of the car to turn in. The corner was more like 45 degrees.

mikahb

For me, 2 seconds was about the limit before I'd be trying plan B. I always found it hard in autoX to try to get a heel-toe downshift in smoothly from low rpm 3rd into 2nd. Pretty course dependent as to how much the downshift will hurt you.

Rev limiter on my new motor (stock LS6) is set at 6900 because at 6600rpm plus, the injectors are maxed out at 93% duty cycle, so I go lean at the top.

waktasz

What car are you driving and what gear are you in on the limiter? I know some Corvette drivers like to keep it in first for as long as possible. I use first for as long as I can into the first turn or two, then keep it in second of the rest of the run. Even in super low speed corners I won't downshift.

If you're hitting the limiter in second and debating about using third, I want to come autocross with you guys . We never have courses like that, even on our 1/2 mile long runway.

VetteDrmr

Mineral Wells, TX. Here's our last event, although this one was quick even for our group. No audio because I forgot to power up my mic:

http://www.youtube.com/watch?v=K6BZl6L3OwE

I was in third gear three times on this one.

Have a good one,
Mike

TedDBere

You should have come up to Corvette Day last weekend! I was on the rev limiter on three sections of the course and into 3rd once. All this on a 65-70 second course. E-town road course set-up.

waktasz

I had to work! Emergency datacenter downtime

(and it was PECO's fault)