Proper way to "Launch" in an autocross

Richard Casto · **Posted:** Thu Oct 23, 2003 11:47 am

Ok, I can at least figure out that the idea is to have the car going as fast as possible as you trigger the "start".

I have a low amount of HP and especially a low amount of low RPM torque. So getting a great launch is a challenge for me.

Right now I am trying to juggle the right RPM with clutch action to get a very slight amount of wheelspin (to prevent sudden drop in RPM as the clutch engages) in the hope that I am applying as much power to the ground in the feet before the start trigger. If I DO get wheelspin I try to make sure it it slight and to have it stopped and hooked up by the time I trigger the start. Oh, and with 106 crank HP and wide/sticky Azenis tires any significant wheelspin is a miracle.

So what seems to work well for people. No wheelspin, some, alot? Slight slippage of clutch, none at all?

Kevin Hoff · **Posted:** Thu Oct 23, 2003 12:18 pm

AWD WRX = too much traction

With street tires, I rev the piss out of it and slip the clutch, fully releasing in about .3 seconds or so. It's all but impossible to get street tires to break loose on a decent surface.

Hoosiers (at least for me) don't launch, they just spin. I launch Hoosiers by revving to 4500 and releasing the clutch quite fast, in .1 seconds or so. All 4 light up and spin for at least the first 15 feet. It gives very consistent 60' times.

--Kevin H.

Kevin Allen · **Joined:** Thu Aug 28, 2003 6:42 pm **Posts:** 3479

1. line up so that you have the most distance between where you start and where the timer starts counting - but don't sacrifice the line you need to take for the first maneuver.

2. be sure to stop as soon as the starter says "whoa."

3. if you're on an incline (going uphill), let the car roll back a couple of feet just before you launch (j/k)

4. I don't think you'd want to spin the tires too much in a fwd car, just enough to keep the revs up and not bog when you hook up.

With the RS, I used to rev to around 5k and slip the clutch pretty quick - the front tires would spin, the car would leap forward (and sometimes bog for a split second if I didn't get it just right) and be off. Now that I've worn the clutch somewhat, I just creep off the line and floor it once I'm rolling.

Richard Casto · **Posted:** Thu Oct 23, 2003 5:06 pm

Kevin Allen wrote:

if you're on an incline (going uphill), let the car roll back a couple of feet just before you launch (j/k)

Now THAT is funny. :lol:

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

With a 100hp I would think your biggest problem is not letting the car bog down when it hooks up. You need enough revs to stop that even if you spin the tires a little bit.

With my little small block chevy and 330ft/lbs all I worry about is wheel spin. I have no idea what bogging down is :lol:

Graham

Rob Keehner · **Posted:** Thu Oct 23, 2003 11:46 pm

Ride the clutch out, it's only a few times a month

.

Rev it up pretty good and slip the clutch more gradually until the weight transfers to the rear, then let it grab all the way. Your tires should chirp and wheel hop a bit when done right and keep you out of that dreaded small bore dead spot at low rpm. This way you don't break them loose and get a bunch of wheelspin when the weight transfers back. This is what my buddy Timmy does in his RSX which runs something like 12.4's in the quarter.

Jason Mauldin · **Posted:** Fri Oct 24, 2003 12:17 am

Rob Keehner wrote:

Your tires should chirp and wheel hop a bit when done right and keep you out of that dreaded small bore dead spot at low rpm.

You probably don't want to induce wheel hop on purpose. It's one of the quickest ways to destroy a transmission. I had wheel hop once, which was enough to destruct the spider gears in my center diff.

Ryan Holton · **Posted:** Fri Oct 24, 2003 7:46 am

Quote:

I had wheel hop once, which was enough to destruct the spider gears in my center diff.

Yeah, but you also refer to your car as a turd too

Ryan
*Ducking*

Jason Mauldin · **Posted:** Fri Oct 24, 2003 8:06 am

The turd doesn't have a center diff! That was in my other car. Which was probably broken almost as much as the mirage is, but was never nicknamed a turd.

Vincent Keene · **Posted:** Fri Oct 24, 2003 8:09 am

Jason Mauldin wrote:

I had wheel hop once, which was enough to destruct the spider gears in my center diff.

This is soooo true, right Ryan? Wheel-hop is what broke the differential of my 1st tranny in the Z-24. Pretty much the same POS Isuzu tranny you have Rob. Keep it up and see what happens. :stupid:

Of course when I was doing it it was on stickies which made it even worse.

You don't wont wheel-hop Richard...trust me, and Jason. :word:

Richard Casto · **Posted:** Fri Oct 24, 2003 10:13 am

Rob Keehner wrote:

Ride the clutch out, it's only a few times a month

.

My dad occasionally codrives my car. Once he let the clutch slip a good bit and upon release it kept reving. :roll:

After the end of the run my dad looked at me and I say "yeah, dad you was slipping the clutch more than you should." It has not happened since (cross fingers).

Last year I had the Kumho 712's and it would break the tires loose much easier. Now with the much sticker Azenis (which are also heavier than the 712) it has a tendency to hook up easier, so I am afraid of abusing the clutch at this point.

Rob Keehner · **Posted:** Thu Oct 30, 2003 10:48 am

Unfortunately I seem to be fixated upon rare Isuzu related products recently. Is there a shot I can get for this?? Either way unless you pull away from the line like a retired librarian, you aren't being easy on the car. I say minimal wheelspin to get you into the powerband is still the best way to go.

Carl Fisher · **Posted:** Fri Oct 31, 2003 1:21 am

I think y'all ought to launch like Kumar Viswalingam used to do at ProSolos in his Miata. 10 seconds before the tree started down, he had the motor bouncing off the rev limiter and held it there. On the 3rd yellow light, he'd dump the clutch. :shock:

Seemed to work pretty well for him...

Chuck Frank · **Posted:** Wed Nov 26, 2003 12:14 am

Max accelleration is at the point of a small amount of tire slippage. We test the traction and try to find an RPM that will not produce wheel hop, but also not spin excessively. We bring the rpms up to that point, then on the go signal we release the clutch rapidly but not "pop" it i.e. ride the pedal up, not side step it. That RPM can be anywhere from ~2800 at Sanford to 3800 at Topeka Prosolo Finale with warm weather and hot tires.
That's one of the things we test during prosolo practice starts to see what results in the quickest 60' times. Once we find the RPM our 60' times will be consistant to within a couple hundredths. If there is a slope at the line we hold the car with the handbrake so our feet can stay on the clutch and gas. We have drilled the brake release button and put a pin in it for prosolos.

Scott Johnson · **Posted:** Wed Nov 26, 2003 9:15 am

Chuck Frank wrote:

We have drilled the brake release button and put a pin in it for prosolos.

Comfort and convenience ?

Scott

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Proper way to "Launch" in an autocross

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