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How to launch a stock all-trac?

Sat Feb 20, 2010 11:36 pm

I haven't had my celica too long... i'm taking it easy on her, but i did test to see what its got, and i'm impressed, but i haven't tried launching her yet.

what is the best way to launch her off in a drag application (without engine or tranny damage)?
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Re: How to launch a stock all-trac?

Sun Feb 21, 2010 9:08 pm

(and) launch = (some) damage...
Now lets talk about the amount of damage...

Most of the damage is to the clutch (which is usually the weakest point in the power train).
And this is good and natural...
As hard as the launch will be as more wear to the clutch.

2nd is the tires... and I don't need to explain here...

3rd is the tranny, as fast as you release the clutch to move the power to the tranny (and differential on AWD)...

4th is the engine... no need to explain here too...

Now, basic fast launch is done by holding the engine at 3000 RPM (a point that the engine can produce boost and quite a lot of power) and releasing the clutch while increasing the throttle...
If the hear the tires then you left the clutch too fast.
If the engine RPM drops, then too less throttle (or you release the clutch too much but you have a tires with very high grip (eg. very wide, semi-slicks...)).

There are others here how race in drag races that probably can tell you more...

Re: How to launch a stock all-trac?

Sun Feb 21, 2010 11:40 pm

I feather the gas real fast at around 3.5k and drop my foot and let out the clutch only alittle faster than you normally would you'll be slipping the clutch more than a usual launch but at the same time you wont bog or spin the tires.
thats all your stock all-trac really needs to leave your friends 20g talon in the dust... 8)

Re: How to launch a stock all-trac?

Mon Feb 22, 2010 6:46 pm

thank you... very informative

Re: How to launch a stock all-trac?

Tue Feb 23, 2010 7:12 pm

or in drag races...
the better launches i've seen live around 5K rpm.

Re: How to launch a stock all-trac?

Tue Feb 23, 2010 10:16 pm

After launch at 5K RPM you can smell the burned clutch all the way home... :)

Re: How to launch a stock all-trac?

Wed Feb 24, 2010 12:33 pm

AvivB wrote:After launch at 5K RPM you can smell the burned clutch all the way home... :)

Depends on the surface and how sticky your tyres are.

For auto-x I usually let it fly between 4500-5500, but that's because I'm on 200 or so threadwear tyres and there's a bit of loose stuff on the asphalt usually, since we do not have a dedicated auto-x track and what we use is really a large car park.

Re: How to launch a stock all-trac?

Fri Mar 19, 2010 6:57 pm

Launching a completely stock, and probably well worn car is not terribly smart. You'll put a lot of wear on a lot of things simply because a number of bushings and other components are not in good repair, or are approaching 20 years old in some cases.

If you're going to be launching the car with any regularity, you want:

- Stiffer, or at least new engine mounts. Poly is best.
- Stiffer, or at least new front crossmember bushings.
- Stiffer, or at least new rear subframe and diff bushings.
- CV shafts in good repair.
- Driveshaft in good repair (they're hard to break, but if you have driveline vibrations, it's probably out of balance)

... at a bare minimum. If those items are not in good repair all you're going to do is bounce things around in the driveline and generally make the car unhappy.

That said, if those items are in good repair, in all cases you want to:

- Warm the clutch by slipping it at ~3k for a few seconds.

- Once staged/stationary, bring the revs up to your launch rpm, and PRE LOAD the driveline. That means barely engage the clutch so as to take up the lash and slop in the driveline. This is how you avoid breaking things.

- Depending on your setup, either drop the clutch and feed the power in (twin plate, unsprung puck clutch), or engage the clutch rapidly (about one full second to fully engaged) while feeding in a moderate amount of power, going to full power once the clutch is locked up (sprung or stock-ish clutch).

As to launch RPM, depends largely on your turbo setup and power level, but for a rough guideline:

- Street tires on pavement, ~4,500.
- Slicks on pavement, ~5,000-5,500.
- Slicks on prepared track (sticky goo), ~6,000.
- Anything else on dirt, snow, etc: ~3,500.
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