Once you've made some passes at the dragstrip, you'll be looking for ways to run faster without harming the clutch or driveline of your Corvette. From my experience in making 570 passes at the track, here are five areas that merit close attention.
Burnout procedure for heating the rear tires without a line-lock
A proven way to improve traction on the launch and shifts at the dragstrip is heating the stock rear tires by doing a burnout. Drag radial tires, used by some owners, must be heated by a burnout if they are expected to outperform stock tires. Here's the burnout procedure.
Put the car in Competitive Driving mode (C5) or Traction System Off (C6).
Drive around the water.
Back into the damp area, not the wet area. Move back far enough to put just a very small amount of water on most of the tread. Don't spin the tires in the water. It helps to open the door and visually verify the desired rear-wheel position in the damp area; keep the door open until you pull forward and verify the correct position for starting the burnout. That spot is just forward of the leading edge of the damp area. Do not spin the rear wheels in the sticky rubber area that is heavily coated with VHT traction compound. Doing so risks breakage.
Put the transmission in Second gear. Because the tires are damp, they spin easily in Second and will heat faster than in First gear. Some drivers prefer First gear.
Bring the motor to 3,500 rpm and pop the clutch, feed the throttle, and immediately apply the brake pedal lightly with your left foot. The brakes keep the rear from walking sideways. The car should start and finish the burnout with no more than one foot or so of forward movement. Don't worry about brake wear. Four seconds on the brakes during a burnout is like braking from 70 mph to 20.
Bring the rpm to about 5,000 and hold it there until the stock tires make first smoke and drag radials make strong smoke. At that point, lift the throttle and release the brakes. The car will roar forward. Push the clutch in. The tires are heated.
In monitoring the volume of smoke produced, it is helpful if the driver's outside mirror is adjusted to provide a view of the left rear wheel. That mirror setting can be stored in memory as part of the race preset.
Warning. If you botch the burnout, don't redo it without rewetting the rear tires.
This burnout procedure takes practice to perfect synchronization of the foot movements. To that end, you can practice burnouts away from the track in any level asphalt parking lot using water from a couple gallon jugs. Draw some lines with chalk to help establish an alignment guide. Pour out two or three gallons of water generally at the rear wheels. This constitutes a pseudo water box for practice.
Shifting drills to improve speed and accuracy
Conduct these drills with the car parked and engine off. But before beginning, drive the car to warm up the driveline, particularly the transmission fluid, for which an oil temperature of 100 degrees is a good surrogate benchmark.
Wear your shifter glove and racing shoes. Restore the driver's seat and steering wheel toyour preset race positions. With those preparatory actions completed, you are ready to start the drills.
Check and adjust your hand position on the shifter.
My advice is to keep your thumb off the shifter. Missed shifts often result from a driver's five-finger death grip on the shifter, which introduces unintended lateral movement that misses shift gates widely.
Pull the shifter with cupped fingers, no thumb.
Push the shifter with the heel of the hand, no fingers.
To make the First-to-Second shift, pull the shifter straight back; remember cupped fingers and no thumb.
To make the Second-to-Third shift, push the shifter toward the radio; remember heel of the hand and no thumb. This will allow the shifter's strong centering device to find the Third gear shift gate.
To make the Third-to-Fourth shift, pull the shifter straight back; remember cupped fingers and no thumb, same as the First-to-Second.
Conduct shifting drills, using the Step 1 hand positions.
The key to strong shifts under heavy acceleration without missing them is practice.
During fast shifting, the left foot goes on the clutch with the heel in the air, not on the floor. The left foot is always either suspended over the clutch preparing to shift or on the clutch executing a shift. Again, the left heel never touches the floor.
For each shift, there are five movements: clutch-in, and throttle-lift; gear-change; clutch-out, and throttle-down. It takes practice to get the moving parts of each shift synchronized, integrated, and executed in minimal time.
Now do the full shifts with complete movements: First-to-Second, Second-to-Third, Third-to-Fourth...pause. That constitutes one repetition. I suggest five repetitions per set and two sets per session.
I do at least 20 sets of this drill per week, usually two sets at each end of my daily commute, and two sets in the staging lanes at the dragstrip before each pass. This routine embeds muscle memory and makes each shift a preparatory cue for the next. Consistent practice will put an end to missed shifts for most drivers, and make each shift much faster and nearly automatic. That in turn will free the mind to focus on shift points.
Tips for shedding a few more tenths
Once you are comfortable staging, launching, and shifting the car, the following small adjustments will help improve your e.t. and trap speed.
Increase the front tire pressure to 40 psi. This will reduce rolling resistance. Tires without pressure sensors can be set to 45 psi.
Manage the engine coolant temperature to ensure it is 195 degrees or less when staged. This generally requires cooling the car between passes and minimizing time spent at idle. The engine management computer progressively retards timing as the coolant temperature rises above about 195, reducing effective engine power.
Heat the stock rear tires by doing a burnout. This will improve traction on the launch and shifts.
Intensify your shifting drills to further reduce shift times. This includes doing more sets in the staging lanes between passes.
Focus strongly on attaining correct shift points. This is easier to accomplish once the shifts themselves are essentially automatic.
Make a logbook and faithfully record your performance. On arrival back in the pits after each pass, write down your impressions while they are fresh. Study the entries later to identify and correct patterns of technique inconsistency and wastage. Not everyone has the discipline to keep a logbook, but if you do, I guarantee it will help make you a faster, more consistent driver.
Taking care of your clutch
C5 and C6 Corvettes driven aggressively often fall prey to clutch pedal issues during or following high-rpm shifts. The general symptoms include a clutch pedal that becomes lazy, hard, soft, hangs midway up, or sticks to the floor. These behaviors are commonly called clutch pedal woes. I struggled with this problem on my '01 Z06. Chevrolet's solution for my car involved swapping out all the clutch and hydraulic components. Despite that, my pedal woes returned within weeks. It was clear to me a better approach was needed.
I found through experimentation that keeping the clutch fluid fresh and clean solves the problem and precludes its recurrence. And I became an advocate of what is now sometimes termed the "Ranger clutch fluid protocol."
Why is it necessary? Clutch fluid degrades when subjected to high heat that accompanies aggressive driving and to water absorption. The sign of bad fluid is a change in its color from clear to dark and murky. At that point, the fluid needs to be cleaned up. If not done, normal operation of the clutch hydraulics will be disrupted under high-demand circumstances. This can provoke incomplete disengagement of the clutch during high-rpm shifts, which often leads to missed shifts that damage the transmission.
A consistent preventive maintenance routine of keeping the clutch fluid fresh and clean will preclude most pedal issues. And if the clutch pedal is already misbehaving badly, cleaning up the fluid should be the first step in remediation and usually resolves the issue.
With that as background, here is the Ranger clutch fluid protocol.
Step 1 Inspect the fluid in the clutch master cylinder reservoir. If it's not clear and clean, move to Step 2.
Step 2 Change the fluid in the clutch master cylinder reservoir.
Draw out the discolored fluid with a syringe, keeping the corrosive fluid off your paint.
Wipe down the reservoir and the rubber fitting on the cap using a clean, lint-free towel.
Refill the reservoir to the fill-line with fresh fluid specified in the owner's manual.
Replace the reservoir cap tightly.
Step 3 Pump the clutch pedal strongly and rapidly 20-30 times. This causes fluid in the hydraulics to flow, blending the new and old fluid, and revealing the color of blended fluid. It also helps to scour crud from the clutch actuator (slave).
Step 4 Inspect the fluid in the reservoir again. If it remains clear and clean, you are finished. If it's not, restart at Step 2.
Inspect the clutch fluid each time you add gasoline or prepare for spirited driving, including the track. If the fluid is not clear and clean, then restart at Step 2.
Even badly degraded, dirty clutch fluid can be substantially cleaned up in 10-15 reservoir changes. That takes less than an hour, costs less than $10 for fluid and a syringe, and doesn't involve a visit to the dealer. I recommend this protocol for every C5 and C6 Corvette with a clutch that sees any form of aggressive driving. If you follow this protocol, you very likely will avoid clutch pedal issues. that is a very important assurance because the car's performance depends on a clutch that is operating properly.
Avoiding driveline breakage at the track
Driver error is the primary cause of breakage among stock Corvettes at the dragstrip. The following are classic mistakes to avoid.
Turning off Active Handling. Doing this provides no straight-line performance benefit whatsoever and denies the driver badly needed help if the rear end gets loose when hitting oil, transmission fluid, antifreeze, or any other slick substance on the track surface. Damage from striking the wall, usually ten feet or less from the side of the car, is normally not covered by a driver's insurance policy.
Failing to reduce rear tire pressure before launching the car. This transfers maximum shock to the driveline, threatening the axles and differential.
Getting the rear wheels hopping on launch or the First-to-Second shift, and then staying on the throttle. This is a great way to break an axle or the differential case.
Performing a burnout with dry rear tires rather than wetting them first in the water box. This torture threatens the axles and differential.
Botching a burnout and redoing it without reapplying water to the rear tires. This can glaze the clutch or break an axle or the differential.
Heating the tires by a burnout and then goosing the throttle repeatedly on the way to the line. This is another great way to break an axle or the differential case.
Brutalizing the transmission with strong missed shifts near redline. This can bend shift forks and damage synchronizers in the transmission.
Failing to heed the warning presented by the onset of clutch pedal woes and continuing to do strong shifts anyway. This is a leading cause of transmission issues in C5s and C6s.
Finally, keep in mind that fast driving is a sport. And like any sport, you will improve your driving performance by commitment, adoption of proven techniques, and practice, practice, practice.
Editors Note: John "Ranger" Armstrong is producing a DVD on the aforementioned techniques for maximum acceleration in Corvettes. Scheduled for release via his web site (www.rangeracceleration.com), the DVD is intended to help any Corvette owner get the most from their cars in a straight line, on the street, and at the dragstrip.