Launching @ 4Krpm problem .... need tips

[Loren]

Better shocks should help. Specifically, more rebound damping in front and more compression damping in the rear to resist the rapid transfer of weight to the rear on launch. Stiffer rear springs would probably help, as well, for the same reason.

Grippier tires will actually make wheel hop worse unless they don't spin at all. Less-grippy tires will just spin and not grab and hop. Add grip and the tire tries to hang on, but can't quite do it. Every time they grab, you get a jolt of rearward weight transfer (rear goes down, front goes up -- hence the suggestion for rear compression damping and front rebound damping) and when they spin, you get a little less of a jolt in the opposite direction.

In the extreme, you dump the clutch, you have enough grip to start a launch, but all the weight immediately transfers HARD to the rear, leaving the front tires light... the front tires spin, the acceleration ceases, the weight transfers back to the front, the tires hook up again... and the same thing happens again several times.

Keeping the suspension movement more controlled (not STIFF, just controlled) will help minimize hop.

There is much you can do to try to address the problem, but probably the biggest thing is to just launch smoother. Slip the clutch a little, maybe launch at 3500 instead of 4000? Try to keep the front tires hooked up so that they don't hop.

Toyota Starlet... you can't compare. It's RWD. When you launch a RWD car, the weight transfer to the rear HELPS the car to hook up.

Simplest/cheapest thing you can do is fit a set of adjustable shocks. For hard launches, set the front shocks somewhere in the middle and the rear shocks full stiff. Then adjust your technique to fit the car. Not every car is going to launch well at 4000 rpm!

[Parmas]

Thanks Loren for the deep info on topic...

So what Brand and type of shock do you recommend for my Vitz 2001 NCP10?

Originally Posted by Loren

There is much you can do to try to address the problem, but probably the biggest thing is to just launch smoother. Slip the clutch a little, maybe launch at 3500 instead of 4000? .

I am building a car to drag race... this must launch above 5K for a good start. Of course I have to be able at 4K before

Toyota Starlet... you can't compare. It's RWD. When you launch a RWD car, the weight transfer to the rear HELPS the car to hook up.

I was comparing to the 1990+ Starlets which any of them aren't RWD.

[Loren]

Originally Posted by Parmas

I was comparing to the 1990+ Starlets which any of them aren't RWD.

Ah, okay. The Starlet was only sold in the US in the early 80's... as RWD.

Any adjustable performance shock is going to be better than your stock shocks. None of them are designed for drag racing, though. They're generally going to be valved for road course use or for "agressive street" driving. But, you can use their adjustability to your advantage. As I said, probably something like full-stiff in the rear and a little (maybe even a lot) softer in the front.

The ideal setup would be custom valved shocks/struts with matched springs all set up by a suspension engineer who knows FWD and has drag racing setup experience. But that's gonna cost big bucks. Probably well over $2000.

[Blown_xa]

suspension upgrades like springs, coil-overs and shocks won't solve the problem.

Motor mounts help. Best thing to do is to upgrade the A-arm bushings to urethane or spherical bearings. Wheelhop is causeed by rotational movement of the A-arms.
The other thing you can do is to make traction bars, this will eliminate wheelhop all together.

this is what a traction bar set-up looks like for a fwd car, it links the front control arms to the lower core support.....

http://www.full-race.com/catalog/pop...7756e08be3c159


you may even be able to make a Honda set-up work with some fabrication