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Old 04-14-2014, 06:49 PM   #1
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Launching a Base Box

Last Saturday I attended an autoX school and was able to complete 20 or so runs! I experimented a lot with launching the car and I don't think I ever got it down. Running BMWs in the past I didn't have any trouble using a little clutch and gasing it off idle. The Boxster's low power and high grip really struggles with this approach, I need to use a lot of clutch to make it happen. Approach 1 is dropping the clutch at 3K, and approach 2 is using a lot of clutch to prevent bogging. Who knows which is worse for the car, probably both but I'd like to stick with the clutch drop. How do these transmissions hold up under this kind of abuse? Should I change my strategy? What are you guys doing?

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Old 04-15-2014, 09:09 AM   #2
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The torque curve on the base Boxster isn't particularly impressive at low RPM, therefore I rev to 4K and let the clutch out quickly for a fast launch. Bear in mind, I do not "drop" the clutch like I would for a burn out, but I do not linger at the engagement point either: rev's to 4K and let it out quick and smooth. Your mileage may vary.
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Old 04-15-2014, 10:50 AM   #3
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I use the same technique that thstone has described, varying around 3-4K. You've got to feel it out during the first two runs to get it right, however. On cold days or slick tracks, I'll drop the revs down to keep from spinning and wasting time, but on hotter days or stickier tracks, revs can get pretty high to not bog the launch.
When my 6 speed was opened up at 142K for a 2nd gear pop-out issue, the gears themselves looked great. I've heard of lots of 5 speeds handling pretty impressive power from 3.4/3.6 engines.
Be sure the axles are nice and tight. I've heard about more problems there than with the transmissions.
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Old 04-15-2014, 12:09 PM   #4
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Hmmmm, guess the S has quite a bit more torque at the low end.

I rev to 2000 and let it out smooth and quick with full throttle immediately at full clutch engagement.

Its a very satisfying launch with full grip and control.

My autocross likes to set up the start with a 90 degree bend 10 feet from the start line so keeping grip is more important.

I've seen folks nearly swap ends 20' into the lap from overly aggressive launches.

Guess I'll see this weekend how the layout is this time.
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Old 04-15-2014, 01:44 PM   #5
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I agree with the rev to 4000 and slip the clutch quickly technique. Im running a 3.4 through a 5 spd gearbox... Just be careful not to slip it too quickly or this will happen.

Also, AutoX isnt all about drag style launches, I usually save the hard launches for the last couple of runs.
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Old 04-15-2014, 08:42 PM   #6
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Fastest launch is really easy, and very hard on the clutch.

Its all done with the left foot. You have to modulate the clutch.

Rev to 6500k. Let the clutch out until you feel it start to grab. As soon as you start to move, floor the throttle and leave it there. From then on, it's all clutch. Feather the clutch and Try to keep the revs in th power band, 5-7k rpms, don't smoke the tires and don't bog down so you are out of he power band.

Better have a big wallet. Your clutch will only handle a handfull of these launches.
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Old 04-16-2014, 02:51 AM   #7
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Quote:
Originally Posted by Bigsmoothlee View Post
I agree with the rev to 4000 and slip the clutch quickly technique. Im running a 3.4 through a 5 spd gearbox... Just be careful not to slip it too quickly or this will happen.

Also, AutoX isnt all about drag style launches, I usually save the hard launches for the last couple of runs.
Yikes, that's a new one! I just rebuilt my axles, they seem ok. Luckily you can get them pretty inexpensively on Parts geek. Looks like I just need to get quicker at swapping my clutch.
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Old 04-16-2014, 07:59 AM   #8
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I never go for the "Big launch" in AX. I rev gently and release the clutch smoothly so that I can be full throttle/clutch fully engaged as I cross the starting line. AX is for fun and clutches and axles are expensive.
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Old 04-16-2014, 10:21 AM   #9
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At my most recent autocross (my 2nd) I tried to do a launch where I revved up to around 3500 and then fed in some clutch to get going. The clutch pedal stopped about halfway up and failed to continue to release. By that time I was going pretty good and into the first left hander which was right after the starting gate. I am not sure if I used my left foot to pull it the rest of the way up or if it came up by itself, but it smelled terrible like I had been purposely slipping the clutch. I didn't have any other trouble with it after that, but it was kind of unsettling. Clutch is new in the last 10,000 miles and the car was warmed up from the 45 minute drive to the site, and I was in the first heat. For the remaining 3 launches I just did the normal start like I do at regular stoplights, except that I did maximum acceleration once the clutch was fully engaged.

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