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Best launch technique? 850

Automatic? From a standing start? Just hold your car with the brakes and run the engine up against the torque converter. Then release the brakes n' let it rip. This is best done with a leased car or a rental http://www.ag.auburn.edu/users/gparmer/articles/neon/, but don't let that stop you. Manual? Run the RPMs up, then dump the clutch. Your mechanic (or Volvo dealer) will LOVE you especially if he has a boat payment to make or kids in college.....

Street racers do "rolling starts" to avoid a lot of the strain on the drivetrain and to avoid tosee flashing brake lights that so interest the police. At least that's what I'm told. I really wouldn't know.

From:

http://www.therangerstation.com/dragracing.htm

Launching:

Here, more often than not, the race is won or lost. Every car likes a little bit different launch technique, so the methods presented here are a starting place (pun intended), not the final word. Experiment! And be aware that any change in your setup or the conditions may radically alter what works best. The only way to get good at it is to practice. Unfortunately, this can be somewhat hard on your car, but it’s really the only way to become consistent, and consistency is the difference between being a punk-ass has-been who beat a fast guy once, and actually being that fast guy.

There are two main variables that will effect your basic launch technique: What kind of transmission you have, and which wheels are doing the work. In a car with a manual transmission, the idea is to avoid the extremes of uncontrolled wheelspin on one end, and bogging the motor on the other. Every engine has an RPM range in which it produces the most power. In a perfect world, you would be able to keep the engine in this ‘sweet spot’ from the moment you launch to the end of the race, without any of the power being wasted. Unfortunately, the world is decidedly imperfect, so starting from a dead stop something has to slip. In dragracing, this can be either the clutch, the tires, or a combination of the two. Regardless of what is slipping, it’s easy to see that this is lost power. Although it’s inevitable, sometimes having a narrow power band means that the fastest launch includes a lot of wheelspin or clutch slipping. The only way to know for sure is to experiment at the track with various RPM levels at the launch to see what gives you the best results.

Manual Transmission Tip:
Use the factory line lock (parking brake) to keep your car from rolling out of the lights once you’re staged. Unless you have an extra leg to operate the brake pedal, this is the only way to keep your car stationary while you work the clutch with one foot and the throttle with the other. That way, you can use your free hand to disengage the parking brake as you launch, and you won’t redlight because your car crept forward after you staged.

Although automatic transmissions have a reputation as being power-robbing slugs, they do have one big advantage for dragracing – the brake-torque launch. Simply put, this launch method involves holding the car in place with the brakes while running the engine up against the torque converter. This effectively preloads the entire drivetrain, and allows the engine to operate closer to its power peak from a stop. In a turbocharger-equipped vehicle, it also allows boost to build before the launch. The only disadvantage is that it puts a lot of stress on the transmission, causing it to heat up pretty quickly. Unless the car is wildly overpowered for the tires it’s on, a brake-torque launch usually won’t spin the wheels because of the shock-absorbing nature of the automatic transmission. Surprisingly, brake-torqued launches are actually easier on the rest of the drivetrain, because instead of a massive shock load, everything from the brake rotors back to the transmission has the torque applied more slowly instead of one huge jolt. The penalty is that automatic transmissions lose more power later on down the track, and generally don’t shift nearly as aggressively as you can with a stickshift. There are ways to get around this and to tune the performance of an automatic for use on the strip, but that’s beyond the scope of this article.

Automatic Transmission Tip:
If you have power brakes, once you’ve staged, put the transmission in neutral and press HARD on the brake pedal. Rev the engine once, and quickly get off the throttle. The idea is to ‘snap’ the throttle plate shut. This will cause a manifold vacuum spike and you’ll feel the brake pedal sink further to the floor. This greatly increases the holding power of the brakes, and will allow you to rev the engine up higher against thetorque converter and give you a harder launch. Just don’t forget to put the transmission back in gear!

Which wheels are doing the pushing also makes a difference in your launch technique. Most FWD cars are traction-limited because of the way a sudden start transfers weight off of the front wheels. The current trend towards wheelie bars on FWD race cars isn’t to prevent wheelies – the bars actually help keep the front suspension pressed to the ground. You may have to launch using less than full throttle to avoid wheelspin or hop, and tip in to it as you gain traction. Rear wheel drive vehicles usually have more available traction off the line, so you may find you need to slip the clutch more to keep the engine from bogging because spinning the tires isn’t an option. All-Wheel-Drive cars often have more traction than they can use, and unless equipped with an automatic transmission, full-power launches can be very hard on their clutches and drivetrains.






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New Best launch technique? [850]
posted by  someone claiming to be Speed  on Thu Nov 7 17:59 CST 2002 >


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