but I know there's a lot of autocrossers on here. I just removed the delay valve from my 05 and now I am afraid of blowing a diff. Question is do you guys do the 6K/clutch dump/break the tires loose, or just do a normal launch? Also, if you break the tires loose does the guy behind you in line get pissed at you for kicking up debris? Thanks for the advice, Tony

 

Usually there is a low speed turn at the start of a course which makes launching a moot issue. You trigger the timing equipment after passing this point so there isn't much point in drag launching. Frankly, if you are really afraid of damaging a differential, then you shouldn't launch the car.

Just remember to remove any driveline slack when launching. Don't just sidestep the clutch from a full stop. Rev up, release the clutch a tiny bit, and then dump it when you are ready. You don't need to initially release the clutch enough to get the car rolling, you just want to prevent a situation where all of the driveline components suddenly slap together.

The purpose of the delay valve is to prevent a sudden shock from getting transferred down the driveline... Can you see a pattern here?

If the guy behind you was worried about debris, he wouldn't stop his car right behind the starter box. I wouldn't worry about it.

 

Unless there's a serious reason why you need the last tenth of a second on a course, don't bother launching at an autocross. There is exactly one event in the country that I would bother dumping the clutch at... the National Championships. And only if I was close to winning.

 

The courses in this area always have a small kink right before the timing lights, so as Jerry said, a drag launch isn't going to do much good. Now, when I was in the PAR, drag launches were often encouraged. You do gain some from entering the course at a higher speed, but you are usually making enough mistakes elsewhere that the advantage you might gain won't mean jack. And for the guy behind you getting debris kicked, he'll learn his lesson.

 

rubber chunks baby

 

Thanks much for the replies. You confirmed the idea that it's probably not worth launching at an autoX. The bit about rolling the car a bit before dumping was good too, I really appreciate your time folks, Tony

 

I am told by the experts that a "slight" launch is optimal, and not hard on the drive train. I rev to about 3000rpm, and "almost" drop the clutch, feathering it in ever so slightly.

I think that the accomplishes two things--it spins the rear tires a bit (or, unfortunately, sometimes hops the rear tires), heating them up a bit, and gets your revs up before you cross the starting line, putting you in a better part of the power band.