S15, How Do I Get My S15 To Launch Hard

[den001]

i have a s15 with a big setup, rb30/26 1100 hp turbo, and its still manual.... rb25 box, strengthened....

i have also added a r32 gtr complete rear end to the car,

i have hsd coilovers and now i would like to set it up to get off the line hard, like gt autosound or devilsh.....

what would i need to do, do these cars still run irs or have they been converted to some type of 4 ling system, id rather not convert anything as it is still a street driven car ocasonally..

regards

denis

[-==L=a=N=c=E==-]

remove the coilovers and go back to the stock suspension.

If you want a compliant drag like rearend setup, make the suspension as loose as possible. 90/10 shocks in the front. 50/50 in the rear. stock springs, shouldn't be a problem.

[R33Turbo]

serious? i got 2.1 60 ft time with coil overs so with stock suspension i can do better?

[R33Turbo]

BTW can't you just adjust the dampers for drag race purposes if u need to be soft?

[NYTSKY]

Get some HKS Drag coilovers in the rear, MT drag tyres and slip the clutch a little.

[10MinuteCar]

whats slipping the clutch? riding it?

[NYTSKY]

Riding the clutch is what learner drivers do to hold the car on a slight hill because they cannot use the handbrake,accel and clutch at the same time.

To slip the clutch is engage the clutch gradually but quickly. This is so the car has some momentum before stepping off the clutch completely. Allows you to get off the line without errupting into wheelspin.

It takes practise to get it right,too much clutch and you will either bog down or spin the wheels. Not enough and your clutch plate will just grind on the flywheel,resulting in a slow launch and a flywheel with heat spots in it.

1-2 seconds of clutch slip is what you want to aim for.Depending on your setup.

[limpus]

With that kind of power the stock suspension probably will not cope...and if its too soft its gonna squat on its arse and the camber will open right up hampering traction even more...

[Ronin 09]

In the most basic terms:

people are saying to use soft/stock rear suspension because of weight shift. If the back is soft, as you launch, the weight shifts backward onto the rear wheels. More weight, more traction, more grip, better launch.

If you have 12kg rear springs of a circuit car, then there is no large rearward weight shift, less traction, less grip, wheelspin hell.

think about it.

[NickR33]

With that kind of power the stock suspension probably will not cope...and if its too soft its gonna squat on its arse and the camber will open right up hampering traction even more...

that's why with a drag setup you would run some positive camber at the rear

[Sydneykid]

In regard to setting up a 2wd drag Skyline, I posted this recently (that's why the Search button is so handly) and it all applies to an S15;

You want no more then 3 kg/mm rear springs, around 2.5 kg/, is better. You want rear shocks with very little low frequency bump valving but a large amount of low frequency rebound damping. If the shocks are a decent brand then you can leave the high frequency valving alone. The soft spring rate allows the rear to squat and absorb the torque hit, the large amount of low frequency rebound damping holds the rear down for maximum weight transfer onto the rear tyres. The problem is you get a lot of dynamic negative camber when you get enough squat, so you need to set the static rear camber slightly positive (around 0.5 deggres). A rear subframe alignment kit installed in the "Maximum Traction" positions is also a must.

Around 3.5 to 4.0 kg/mm front springs are OK (hardly "hard"). You want front shocks with a large amount of low frequency bump valving but with very little low frequency rebound damping. Similarly to the rear, if the shocks are a decent brand then you can leave the high frequency valving alone. The limited amount of low frequency rebound damping allows the front suspension to extend therebye reducing the weight over the front and hence more effective weight transfer to the rear. The reasonable front spring rate helps to hold the front tyres onto the track, you may need to steer at some point. The front suspension geometry is pretty much irrelevant, just make sure the wheels are pointed straight ahead (zero toe) so they don't provide too much drag.

In a general sense the average Japanese aftermarket coil over kits are not suitable for drag racing and the standard suspension is better. But (there is always a "but") the problem with the rear standard shocks is that they don't have anywhere near enough rebound damping. That's when they are new, let alone 15 or so years old. So you get bad axle tramp, the kind that breaks drive shafts. The more power the car has, the worse this problem becomes. In a standard'ish Skyline (boost up, FMIC, exhaust etc) you might just get away with it (standard shocks) on street tyres. But drag radials or slicks and decent power don't mix well with poor rebound control. You will spend more money/time replacing drive shafts than you will spending the extra on buying the right shock spring combo.

I did this type of set up for BU5TER and his R33GTST which did a 1.5 for 60' first time out.

Cheers

Gary

[Granthem]

serious? i got 2.1 60 ft time with coil overs so with stock suspension i can do better?

My car managed 2.0 with coil overs lol!

the secret?

5psi in the tires...

Nice smokey burnout.

4000rpm drop

(my mate drove it this run)