I'm intentionally posting this in the racing forum in the hopes of actually having an intelligent conversation about the topic, and since Autocrossing usually involves launching, I figured it should be acceptable.

I know common practice for a "fast" launch on a stock s2k is sidestepping the clutch at high rpm and hoping and praying your rear end doesn't detonate. Also, the reason why you can't slip the clutch on a launch is because the clutch just isn't strong enough and you'll roast it.

My question, however, is for those of us running upgraded clutches (via the standard HD Pressure Plate/OEM friction disk/Lightened flywheel recommendation), can we intentionally use a bit of clutch slip to save the drivetrain and prevent destroying expensive parts?

If you Launch at 6k, but feather the clutch a little bit *With an upgraded clutch*, can we get a good launch without breaking things or glazing clutches?

 

You have enough power to overcome a soft launch. Take it easy on the clutch and rearend and make it up later. Most of the course setups out here don't require a hard launch from what I've seen. Focus on your driving and the .05 you could gain on launchs will be nothing but an after thought.

 

I dissaggree. Rip that bish a new orafice on every start. I've got over 250 high rpm clutch drop launches on my 2000 with race tires and no blown diff yet. If you blow it, get another. There is probably at least .5 seconds in the launch to lose if you bog.

The way I see it, something has to slip on the launch because we have no torque. You can slip the clutch or the tires. I would rather replace tires. By breaking the tires loose I theorize that you're lessening the shock on the diff.

 

If you can slip the clutch at 6-7k RPM without having it wilt, it's possible to launch without tire slip. Getting a clutch to do that seems to be the trick...

 

See his thread here: FI forum

He won't need to launch at 6-7k making that kind of power and again our courses out here very seldom have any type of drag launch without an immediate corner or the start beems after a little bend with a running start so no hard launch is needed. This will be his first time racing and should not worry about the couple tenths he might be able to save on the start line.

 

I'm not well-versed in FI but it seems like low- to mid-range torque will still require a significant clutch dump. Of course, if you can get the tires spinning at a lower RPM and have the additional torque keep them spinning, even increasing the engine speed while spinning, it's good enough. Only testing would tell this.

 

I only autox 3 to 4 times per year, and even with the RA-1s on the car I can get a nice little rear wheel spin and I'm not coming off the clutch at much more than 3,000 to 3,500 rpms. I autox for fun and that is about all the pounding I choose to do on the drivetrain.

I'll be the 1st to admit that glagola1 is right in the fact that a bog at the start can cost you some serious time. But I also agree with l8brakr when he says you can make up for lost time in other places. I know when I watch others autox I can't believe the number of people who seem to let up just before the final timing light; not me. I charge all the way past that sucker, and then figure out how to stop.

 

So, what constitutes the "ideal" launch? Just a tiny hint of wheelspin with no bogging?

With my setup, I'm pretty sure I can do that with a full throttle launch at about 3k or so with a "moderate" letup of the clutch. (NOT a drop).

I guess the point of my question was that I just don't drive that way on the street (actually I don't really ever do full throttle launches), but were I to practice, I'd wan't to make sure I wasn't going to turn my rear end to mush.

The clutch should absorb enough of the shock from a launch described here without any risk of damage, right?

 

An ideal launch is one that gets you down the pavement the fastes. For a low-torque, high traction car like the S, that means dropping the clutch at high RPM to keep the engine in VTEC. It may well be slower in the first 60 feet than other cars but the loss of acceleration due to bog is greater than loss by (seemingly) wildly spinning the tires. Look at old road tests where they used lower RPM launches for acceleration runs - times were 1-1.5 seconds slower. If you can get a clutch that will clamp well after slipping it rather than the tires to keep the engine in VTEC, you'd be eliminating almost all the shock that folks worry about. I haven't heard of such a setup yet.

That said, many auttocross launches are followed by an immediate sharp turn so the launch can be much softer. With gearing and/or torque, you can get the tires spinning and have more torque applied to the wheel to keep the engine in the sweet spot. Low traction surfaces "help", too.

The clutch will absorb only what the clamping allows. Due to the inability to slip the clutch sufficiently while getting it to clamp well once you're going means that you need to transfer a major shock all the way down the drivetrain. The clutch is the least of it except for the clamping/slippage issue...

 

Im sorry, but I"m very new to the world of Auto-X, but very anxious to learn. I plan on running bone stock at the local tracks around here for the first time this season. I'm trying to learn as much as I can before I go.

What do you guys mean when you talk about putting damage to the "rear"?

Any tips for first timers on the track?