HOW TO LAUNCH FOR AUTOCROSS

[Purist]

Hey all, just wondering how you guys launch off the line for good autox times. Low revs high revs, dump the clutch ? Use OFT or Ekutek 'launch control' (which isn't even launch control)...?

My hillclimb has a conctrete startline, super slippery, and the first corner is really soon after.

[doggieboy09]

It depends. While I personally like to launch at around 4-5k, a lot of fast autocrossers don't even launch the car at all. In your case I don't even think an aggressive launch would even help at all. Only at drag race starts does launching matter. Even then you wouldn't win a race because you had superior launches because you still have to drive the course.


[ame="https://www.youtube.com/watch?v=h3jV_vNLAkw"]SCCA Pro Solo Practice starts @ Crows Landing 4-24-15 Subaru BRZ MY2013 - YouTube[/ame]

[Submarinesonce]

I disagree, I always describe autox as drag racing with corners. some layouts don't lend themselves to hard launches, but on layouts with a good run to the first element, you could pick up .5 secs or so just based on launching hard and getting to race pace vs pulling away gently. all that said, I set the OFT LC to about 4000 RPM and slip the clutch when I can launch hard at an autox.

[Imp]

Most starts for non-proSolos are designed (*are supposed to be designed) to remove drag starts so one car wouldn't have an advantage over the other because of the start favoring more powerful or traction favored vehicle. After the start, before the lights or near the lights is supposed to be a turn that removes any advantage to a fast start.

Most (again, not all - YMMV) should be just a brisk start to get up to speed, but shouldn't require high revs or anything that should accel wear.


Do a search for Roger Johnsons Course Design Handbook, essentially listing the golden rules for *safe* and good course design parameters.

--kC

[justint5387]

I use the ECUTEK "launch control" for maximum wheel spin at Pro Solo, which is not the fastest way.

For regular autocross, I almost never launch it unless it's a national event and the course calls for it.

[Lex_K]

I find that the car gets off the line best at around 4K with mild clutch slip then letting off to get a little wheel spin.

[Purist]

Originally Posted by justint5387

I use the ECUTEK "launch control" for maximum wheel spin at Pro Solo, which is not the fastest way.

For regular autocross, I almost never launch it unless it's a national event and the course calls for it.

I tried the OFT version but it goes to normal rev limit at something like 20km/h so no point IMO.

[trippinbillies40]

Even at national courses with a 90 degree bend at the start, I rarely find myself having to lift at the first corner that was designed to prevent a drag race start. Something about our cars not having much power...

FWIW, I was a 4k rpm launcher until I was getting crushed by David Marcus at the '15 Wilmington Pro off the line. He said bump it up to 5k which I did, ended up matching his 60' times. I think it all depends on surface and tire selection.

[hpde_addict]

Originally Posted by doggieboy09

It depends. While I personally like to launch at around 4-5k, a lot of fast autocrossers don't even launch the car at all. In your case I don't even think an aggressive launch would even help at all. Only at drag race starts does launching matter. Even then you wouldn't win a race because you had superior launches because you still have to drive the course.

I noticed 0.5-1s difference at a BMW club Mariana Airport event with launching vs. no launching. That being said, I think launching is pointless unless you are fast enough to win your class and willing to pay for axles :P

[Stang70Fastback]

Originally Posted by hpde_addict

That being said, I think launching is pointless unless you are fast enough to win your class and willing to pay for axles :P

I've been launching my car from 3-4k RPM at every autocross event for 3 years now (2 of those years on 245 section RE71Rs) on a lowered car, and have yet to experience any axle issues. I don't completely dump the clutch. Just a really quick release that results in some minor wheelspin/shudder.

[trippinbillies40]

Hmm, I launched the shit out of my FRS for 3 years and never broke one. But I was never the lowest kid in grid either.

[G_Ride]

Originally Posted by hpde_addict

I noticed 0.5-1s difference at a BMW club Mariana Airport event with launching vs. no launching. That being said, I think launching is pointless unless you are fast enough to win your class and willing to pay for axles :P

It depends on the course and club whether or not launching makes a difference.

Originally Posted by Stang70Fastback

I've been launching my car from 3-4k RPM at every autocross event for 3 years now (2 of those years on 245 section RE71Rs) on a lowered car, and have yet to experience any axle issues. I don't completely dump the clutch. Just a really quick release that results in some minor wheelspin/shudder.

Try doing regular autox on grippier surfaces

You're also not as low as some other cars.

[TrqlessWonder]

I'm starting season 5 with this car in CS trim. Lotsa side-step launching, first season was on A6s, rest on 235/245 bridgestones, still on the OE axles at ~77k.

IIRC, the guys breaking things were a bit more than "lowered"...closer to #stancenation levels of low.

That being said, I think launching is pointless unless you are fast enough to win your class and willing to pay for axles :P

If you launch the car harder/get going aggressively, I think you'd be pleasantly surprised how much closer to the front you get with just that change.

There absolutely are times when it would provide no benefit whatsoever. But, those are the exceptions to get depressed by, not the norm to expect.

Think of the courses where your first press of the brake pedal is like two worker stations in. If *everyone* is full throttle from the start lights to the entry of the same slalom/turn/other speed-scrubbing element, those going that extra foot/sec faster when they came across the start lights get there sooner. Manage to not make a mistake and give that time back, and you get to the finish lights sooner, too.

[Submarinesonce]

Originally Posted by TrqlessWonder

I'm starting season 5 with this car in CS trim. Lotsa side-step launching, first season was on A6s, rest on 235/245 bridgestones, still on the OE axles at ~77k.

IIRC, the guys breaking things were a bit more than "lowered"...closer to #stancenation levels of low.



If you launch the car harder/get going aggressively, I think you'd be pleasantly surprised how much closer to the front you get with just that change.

There absolutely are times when it would provide no benefit whatsoever. But, those are the exceptions to get depressed by, not the norm to expect.

Think of the courses where your first press of the brake pedal is like two worker stations in. If *everyone* is full throttle from the start lights to the entry of the same slalom/turn/other speed-scrubbing element, those going that extra foot/sec faster when they came across the start lights get there sooner. Manage to not make a mistake and give that time back, and you get to the finish lights sooner, too.

all of this. go as fast as you can, as often as you can.