Slipping the clutch is always a 75% proposition at best. 75% of the time you get it right and you take off like a bat out of hell. The other 25% you burn up the clutch and it smells/feels HORRIBLE.

When I autocross and time attack (all standing starts), I simply rev to 5,000 rpm's and dump the clutch. The launch is consistent and powerful each time. I've had people ask me if I have launch control on my car (I don't, 100% stock). Every once in a while this technique doesn't work, since, depending on the surface, the tires will break away and regrip in a manner that induces crazy amounts of either axle tramp or engine vibration. When that happens it's HORRIBLE as there are LOUD banging noises. I've loosened the driver side engine mount launching like this, to the point where I feel the engine shifting through the steering wheel when cornering hard. I had to crawl underneath the car and retighen the engine mounts.

Another, more conservative way, to launch is a clutch dump at 3,500 rpms. The car jumps off the line, almost bogs, and then the turbo builds boost and off you go. This is the launch you want to do for component logevity, especially if you compete often.

 

When you dump the clutch, do you typically go WOT too? Or just hold the throttle consistent until you get going?

 

Rev to 4,500-5000 RPM. Slowly release clutch until you feel it just start to engage, dump clutch, hold on.

Cobb LC makes it much easier for the average Joe, so if you were thinking about an AP in the near future that would be a definite plus.

 

Do not drop the effing clutch.. ever.. Slip it just right and you get results. Dropping the clutch is extremely abusive. This is not a RWD or FWD car. You can not easily spin the tires and that drive-train shock has to go somewhere. Dropping the clutch is how you break isht.

In response to the OP. I have found that 5500rpm works well for me. blip the throttle repeatedly or use Cobbs LC. Slip the clutch and off the line like a rocket. Be damn ready to hit 2nd as it comes fast.

At the track, I found that 6000rpm worked for me.

 

Just one caveat about launch control, there is an increase in susceptibility of knock events when you use it. Datalog to make sure you aren't experiencing any.

 

Cobbs LC works exactly like the factory rev limiter, I doubt any knock you see would actually be knock, rather drivetrain noise. Also, being that you are under almost zero load, it wouldn't hurt even if it was (to a certain extent).

 

Really? You guys launch that low? At the drag strip I bounce revs between 5500-6k and then I floor it and do a fast slip. Bring clutch pedal right before engagement point, Floor it, Move clutch into catch point (like halfway in) and then release when the revs are about to go up. Otherwise it'll bog, gotta launch like it you're trying to break it but nothing ever broke in my car but my stock clutch, even that took a crap ton of abuse (Handful or redline clutch dumps did it in also making 320awhp and 340awtq didn't help I'm sure). Dropping the clutch causes massive wheel hop and catastrophic things can happen. I'd rather smell clutch then hear things bang around IMO.

TL: DR Make sure the loud pedal is already to the floor before you release the clutch.

 

Relatively new to the Subaru scene, but have been driving for 17 years now. I can say from experience that launching one of these cars is alot different than any other I have raced around in. In a stocker, I would raise RPM's to around 4500-5500 rpm, whatever works for you and/or the car, let the clutch out until its almost going to engage. Then, press the go pedal down a split second before you raise your clutch foot. Raise the clutch foot like you just stepped in dog poop. Pretty fast, but don't let the pedal snap up. When done properly, your rpms will drop, but no engine bog. I think this is because you presented the engine with a load by not letting the clutch snap up, just for that split second. This should provide you with a hard drag strip type launch and no clutch burn (that you can smell) hopefully.

 

great explanation.. everyone else as well- take your foot off he clutch as fast as you can without letting it drop.. got it

I think ive been letting off the clutch before WOT'ing it and ive been gettin some serious engine bog... don't even know what engine bog really is but im guessing its when you go slow as fuck off the line

thanks guys

 

best way is just to get some practice. i did it by going to the outskirts of town and going to a u-turn area where there's a sort of "merge into traffic lane" and practice launches there.

my method is to rev from 4k-5k like rev rev rev (not letting it drop below 4k) and on the 3rd or 4th rev do the "ugggghhh wtf" 'did i just step in dog dookie?' release of the clutch, usually catching the clutch early-mid rev and going WOT. Be ready to shift ASAP into 2nd.

 

I'm in no way a pro at this nor do I track my car yet, but from what I've read on here and practicing on my own, the general advice is spot on. I've seen people say different things about RPM's when launching, from 3,500 to 6,000, but personally for me I've done pretty well around 5,000. Just so long as you're building up boost. As for working the clutch, the dog sh*t method seems to be the best method in terms of good launching and least impact on the car. Instead of dumping the clutch by slipping your foot completely off the pedal, let it out until you feel it catch, WOT, then release quickly while your foot is still on the pedal, as if you stepped in dog sh*t. Just be ready to shift because it does come up fast and you'll hit redline before you know it.

Another thing for when you're starting off and practicing that I've read is to practice on some sort of loose surface rather than asphalt so like dirt, gravel, asphalt after a good rain and similar things. This should mitigate some of the impact on the car when you drop the clutch too hard or just don't get it right. It just takes some practice but you'll get the hang of it soon enough. Good luck!

 

I have LC set at 6K at the track and 5k on the streets (just in case I need it). for emergency situation. NEVER DUMP the clutch.. release it quick..

2004 Subaru STi 13.2 1/4 mile with launch control - YouTube Don't have your speakers cranked unluess you really wanna hear it

 

Wow thanks for all the input... I'll give it a shot.

But yeah I did plan on getting a Cobb access port once I have some cash on hand.

 

Double post

 

Also, would somebody please explain to me what WOT stands for? wail on throttle?

 

wail on throttle?

:rofl: sorry I couldn't help it.

What I use for launching is Cobbs Launch control feature & flat foot shifting.

I set the LC @ 5,600 +\- 100rpms depending on surface conditions & dump the clutch like I'm stepping quickly onto a curb. I have flat foot shifting set to 5,800rpms.

I also have an ACT street disc. My 168,000 mile drivetrain is finally showing signs of fatigue with what I'm assuming is a bad u joint in the driveshaft. It just started making a slight noise when I take off from roll for a split second.

 

Wide Open Throttle

 

Honestly some of the best drivers I know don't generally floor the go pedal and drop the clutch. That's for novices. If you ask me it's all about finesse and consistency. When it comes to AWD's you tend to have to slip the clutch a little especially with a turbo engine. Unlike RWD's you won't get tire spin as easily so the car will bog.

I've found it difficult to be consistent with the STI because of the clutch delay valve (the turbo lag from the OE downpipe wasn't helping either). Anyway the valve is there to prevent the unskilled from putting too much shock load through the drivetrain and is a good feature overall in my opinion. The downside is if I engage the clutch faster than the valve will allow it slows clutch engagement and throws off my timing, so I removed it. Now though if I take on co-drivers at autocross events I have to know that they know what there doing or they could damage my drivetrain. The STU class power restrictions should limit that however.

 

is it legal to remove that when running STU?

 

Hey guys I'm new to the forums but I just got my sti 3 weeks ago and I tried launching tonight at 5-6k rpm and when I did I got a knock in the rear. What could that possible be?

 

probably drivetrain shock, mitigated with stiffer subframe/rear diff bushings

 

If its got the same bushings as the GRs, you will need to upgrade the rear diff bushings. Solidifies the rear and removes the clunk.

Subframes bushings are an extra if you're a bit more mechanically inclined.


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Thanks a lot guys