Robert56

iTrader: (2)

Getting the new style 315 bfg dr and need some input on launch rpm and suggested burn out. I plan so far on launching at 4500rpm to start with, this is with stock Z06 clutch (good shap for now). Don't have a strut brace yet or hardened shaft and trying not to break anything. I was getting 1.9x/2.02 60's on stock gy 295's at lower rpm's.

Coach 02 A3 Z/28

iTrader: (10)

On the burnout. When you start to see somke in the mirrors count 1001, 1002, 1003 let go of the line lock and let the car feather out. I would try launching the car the same way as you did before.

Coach

Robert56

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Thanks

00Vette

iTrader: (4)

I just asked this Q on a thread in my regional forum. I got this great reply. Hope it helps!!!!

Here's a quote from a 2001 post by the Bowerboy, a famous Corvette drag racer.

With an old/stock clutch your options are limited. You will have to hold your RPM's below 3K and slip it slightly. If you had an upgraded clutch (not stock or Z06) I would recommend launching at 3500 to 4000RPM with a slight slip. The type of Tire you will use will also drive your launch.

If you are running stock tires, keep your launch below 2500 RPM regardless of clutch type. If you are running a drag radial, make sure you sufficiently heat them with a burnout before staging. Either way make sure your stage shallow.

The following is a description of staging shallow: The are 2 yellow lights which indicate the staging area. They are separated by 7 inches. When the track worker waves you up you approach the lights and as your car rolls you will turn on the top light first (pre-stage). As soon as the first light goes on, stop. Then slowly nudge your car forward until the second light goes on (staged). Stop immediately! When you launch your car, the clock does not start until you break the beam of both the pre-stage and stage lights (the starting line).

As soon as both lanes are staged (The staged light in each lane is lit), the first of three large yellow lights will light. On the third yellow light begin your launch. With a shallow stage. your car will have a few inches to begin rolling before the stage lights are triggered indicating you official start.

Once under way, quick shifts improve ET and MPH. Be sure to max out your RPMs without hitting the rev limiter. I shift at red-line minus 300 rpm. On your 1st to 2nd shift, power shifting (leaving your foot on the gas to the flow as you depress the clutch and make your shift) is not recommended do to traction. The 2nd to 3rd shift can realize a significant gains with a power shift however, this is the trickiest to maneuver (directional angle of the path between 2 and 3). The 3rd to 4th shift is the easiest to power shift.

Here's a link that provides some useful info:

NHRA Drag Racing Basics


"Ideal Launch RPM" defined by the Corvette Program Office

First an optimum launch rpm must be established which is a function of ambient temperature, sun load, track surface, tire temperature, vehicle loading .... An optimum launch will allow enough wheel spin so that when the tires "hook up" to the pavement there is not a loss in vehicle acceleration."


Launching a Z06 on Stock Tires

Here is what I do. No claim it's the best way.

Competition mode. AC and audio system off. Windows up. Tire pressure 44-48 psi (front); 24-28 psi (rear).

Try 2800 rpm. Increase or decrease the rpm 200-300 each run until you find the sweet spot for your conditions.

Engage the clutch over the first 2 to 10 feet of movement depending on conditions. Go WOT ONLY once the tires are hooked, and do so by squeezing the pedal progressively to the floor.

If you do some practice on old blacktop and ambient outside temp is around 75, you ought to be able to launch leaving only about 10 feet of rubber.

Another key is on the 1st-2d shift. Ease the throttle just enough to avoid a lot of wheel spin, which will hurt your time. When I began drag racing the Z06, I shifted to 2d at an indicated 6200, 3d at 6300-6400 and 4th at 6400. Objective is to shift as high as you can without hitting the rev-limiter.

What you are after is developing the launch "touch" combining input from all yours senses. I can feel the tires spin in the steering wheel, clutch pedal, and seat of the pant. Sight and sound help too. But the F1SC tires don't make much of a squeal when they spin.

I use Competition mode rather than "AH/TC off" because I want AH to intervene should the rear get substantially out of line. Just some insurance to limits "the worst that can happen."

Two last things you probably already know. Be sure your oil is above 155 degrees (preferably above 170) before you do launch practice. Also choose your spot wisely.


Why I ALWAYS Run in "Competitive Driving" Mode

I posted this in Feb 2002

I've alway run in COMPETITIVE DRIVING mode at the drags. Do it on principle...It has no effect whatsoever on my times unless my rear end gets seriously out of line, at which point active handling will be invoked, thereby saving my a $ $. In such a moment, my ET would be the last thing on my mind.

Today I narrowly averted a disaster that was not of my making. AH saved my butt and vindicated my practice of running with it turned on.

I made eight passes at Capitol Raceway in Crofton Maryland. On the fourth pass, I was next in line behind a highly modified car that spewed tranny fluid on the track just after the 60_ mark. Unfortunately, no one, including me, noticed the spill as it occurred. AND, I was next.... I had my best launch of the day (1.82) and slammed 2d gear hard amidst his tranny fluid...whereupon my rear end moved violently right...toward the wall. Fortunately, Active Handling engaged and queued me to back out of the throttle immediately upon recognizing my predicament...but not before I had come within just a foot or so of the wall.

Had I turned AH off (as many people do), I surely would have hit the wall HARD. Wouldn_t have been my fault; but certainly would have spoiled the day. When that occurred, the last thing on my mind was my ET...which was a 12.81...in a day of 12.04 and a bunch of 12.1Xs, plus one trap of 118.1...all in COMPETITVE DRIVING mode.

Here is the full thread. Toward the end is a hair raising story that turned out BAD and underscores the need to keep AH ON at the drags. COMPETITIVE DRIVING Mode at the Drags--Disaster Avoided

Another post about my "wall incident":

The "queue" from AH means that within fractions of a second (literally) (1) my rear end moved violently right toward the wall and (2) AH immediately invoked counterveiling action. Both produced sensory inputs that deviated from the norm and I backed out of the throttle. The car came straight again nearly against the wall. It had moved right about 12 feet. Total time of the event was around half a second.

I also made some steering correction, but AH played two roles (1) its pulsing actions queued my senses and (2) it took psoitive counterveiling action to correct the out-of-line condition. Given that AH makes corrective adjustments many times in a tenth of a second, it certainly was the dominant factor in my staying off the wall. True, I backed off the throttle, but not until the accumulating sensory inputs caused me to recognize my predicament; but in those crucial tenths of a second AH had already been in action.

Lota folks can recover from just "loose." But few (without AH ON) can recover successfully from "violently loose." You may be one who can, I'm not.



Burn-out of BFG Drag-radials without a line-lock

Here is what I'm doing; no claim it's the best way.

Back into the waterbox if possible and immediately spin the tires just enough to get a full rotation of them, but NOT enough to throw (much) water up into the wheel wells.

Roll forward out of the water few feet; but do NOT roll so far as to put the rear wheels onto the rubber/VHT prepped area.

Make sure you're in COMPETITIVE DRIVING mode. Put the 6-speed in 2d gear.

Drop the clutch and feed the throttle and (if necessary), quickly lightly apply the brakes with your left foot. I donŐt usually need the brakes but some folks find it helpful for keeping the rear end from walking sideways.

Bring the rpm to about 6000 until the tires smoke strongly and start to grab and the rpm starts falling. At that point, back out of the throttle and (if applied) release the brake, and you'll roar forward. The tires are heated. I don't count seconds but just spin them strongly until they grab hard.

Takes a little practice. But remember, if you botch the burn-out, DON'T retry it with dry tires. Doing that will likely glaze the clutch...or worse.


Launch on BFG Drag Radials

I hold the launch rpm (usually starting with 3600-3900 on an average prepped track) and then quickly but smoothly releasing the clutch with a full engage occurring over the first 4-10' of movement. I try not to feed it more throttle until I think the tires are hooked. There is a delicate balance to find. But it entails squeezing the throttle progressively to the floor between 10-25 foot off the lights. Drag radials will take throttle more quickly than stock tires, but it's still a "squeezing" action rather that a "stomp." Another big advantage of DRs is that they do a great job holding the shifts to 2d, 3d, and 4th without spinning (much). Most of my sub-12 runs have comes when the shift to 2d little wheel-spin and the car feels as though it jumps forward on that shift. Ditto the shift to 3d.

Robert56

iTrader: (2)

Thanks good info and I remember Bowerboy, but haven't seen a post from him lately.