How To Run 10s In A Stock Z06 - Maximum Acceleration, Part 2

Learn how a stock Corvette with a manual transmission and skilled driver can easily out accelerate one with fifty more horsepower piloted by an average driver.

John "Ranger" Armstrong Dec 1, 2007 0 Comment(s)

The Launch Has Three Components
1 ::: The launch rpm is held steady during release of the clutch. This pre-selected rpm is the maximum you believe prevailing track conditions will reward. An ideal launch rpm will produce just a small amount of wheelspin before the tires hook. A higher rpm would produce too much wheelspin, and a lower rpm would cause the motor to bog. With stock rear tires, the launch rpm will generally be in the range of 2,400-3,300. If you are unsure, start at 2,400 and, based on the results, adjust upward or downward in 200-300-rpm increments on the next pass. After a few runs, you will find the sweet spot that gives the right balance between wheelspin and bog.

2 ::: The clutch release should be very fast, but less than a pop or side step. The clutch pedal should be out fully before the car has moved more than 3-to-5 feet. Some drivers favor a literal pop of the pedal, termed a clutch dump. I find this more likely to break driveline parts than my approach. Other drivers prefer a slow release of the pedal to produce significant intentional clutch slip and keep the rpm elevated during the launch. I also avoid this approach because it increases clutch wear and generates unwelcome heat that can glaze the clutch entirely or cause pedal woes during the pass. This is a particular concern on the C6 Z06 because the LS7 clutch is intolerant of intentional slip at an elevated rpm.

3 ::: The throttle squeeze requires modulation and calibration to track conditions. The instant the clutch release is complete-and not before-quickly squeeze the throttle to the floor. This motion is not a stab or stomp, that would provoke excessive wheelspin, something to definitely avoid since it will slow you down and greatly increase risk of driveline breakage. Rather, the motion is a firm, deliberate squeeze with your senses focused on what the clutch and rear wheels are doing. The goal is to have the initial wheelspin from the clutch release transition quickly to a rapid rise in engine rpm without a loss of momentum or bog. Once the tires are hooked, you want the fastest squeeze achievable without provoking renewed wheelspin. The faster the squeeze, the faster the launch and 60-foot time will be. Generally, the throttle is on the floor within 20-30 feet of forward movement, depending on track conditions.

Using this three-element launch procedure, an average Corvette driver will attain 60-foot times in the 2.0s. With practice to synchronize these movements and react correctly to feedback from the car and track surface at the ragged edge of traction, a good driver will dip into the 1.9s and an excellent driver into the 1.8s.

Gear shifting should be performed fast and at the correct rpm, but more on that in a moment. A fast shift of a Corvette manual transmission can be completed in about 200 milliseconds (two-tenths of a second). So three fast shifts in a quarter-mile run (the 1st-to-2nd, 2nd-to-3rd, and 3rd-to-4th) consume six-tenths of a second with the clutch disengaged and the car not accelerating. In contrast, an average driver without the fast-shifting skill will need 400-500 milliseconds per shift, consuming 1.2-to-1.5 seconds for the three shifts; that is six- to nine-tenths slower than the fast shifter. The way to avoid the slow-shifting penalty is to practice until the act of repetitive shifting is fast, precise, confident, and, essentially, automatic.




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