[normally_crazy]

guys,
have a small confusion.

during a drag , at the start ..the engines are revved to the redline before they take off ..this results in wheel spin before the cars actually move....

my question is doesnt the wheelspin waste precious seconds ?? i mean if we take off without the wheel spin the times will be faster

cheers

[Jaggu]

yup to keep the motor in power band engines are revved.. so that when u dump the clutch the revs dont fall too much.. the problem is wheel spin and ideally it has to be limited, thats where proper practice comes into scene and helps save precious seconds..

in a professional track burn outs are done and a layer of rubber is laid at the start up to improve the traction during final run..

[RJK]

Yes..Wheelspin wastes time. The idea is to get a perfect launch. Minimum wheelspin=Max acceleration. There was an Esteem at the Speedrun which had a perfect launch..obviously it won against another Esteem.

[Rtech]

Hey NC,

The start is the most important aspect of drag racing. Knowing your car/bike intimately is essential for a good start. You have to know at what rpm to dump the clutch at to get that perfect balance between too much or not enough wheelspin. Too much spin and you waste time, too little spin and you bog the engine down.

A car needs to spin its wheels a bit. Ideally, yes, whenever the wheels are spinning, power is being wasted as you are not really moving forward as fast as you could be. But, in the real world, a bit of wheelspin is essential to avoid breaking your driveshafts. If your tyres are too large and grippy, and your engine does not have enough power, its just gonna slow you down at best or snap your driveshaft at worst as the shaft cannot handle the sudden load on it.

A little bit of wheelspin basically eases the transition of load onto the driveshaft preventing it from breaking. Thats why its really hard to launch 4WD vehicles properly, especially if they are not too powerful. You then have to slip the clutch a lot on these cars.

Rt

[GTO]

NC,

As has already been elaborated, its a very thin fine balance between too much wheelspin and getting the right start.

On the team-BHP drive back from panchgani, we had a couple of 0 - 100 sessions using my Gtech pro as the timing equipment. With the skinny 175mm tyres, the Vtec was wheelspining all over the place. It was just too darned difficult to get the right launch. Some of the earlier launches were completely wasted with times varying between 9.4 and 10.5 seconds.

Finally I settled at a launch of 2700rpm which resulted in a time of 8.93 seconds!!! Wait till I get better rubber....will improve this time by atleast .5 seconds.

Originally Posted by [b

Quote[/b] ]But, in the real world, a bit of wheelspin is essential to avoid breaking your driveshafts

Rtech, would this not be restricted to only rear wheel drive vehicles? Though I am pretty sure horrible launches could ruin the transmission of a front wheel drive too.

GTO

[Rtech]

Originally Posted by [b

Quote[/b] ]Rtech, would this not be restricted to only rear wheel drive vehicles?

No GTO, its applicable for any vehicle...rear, front or All wheel drive. On a FWD, you would damage the transaxle. With Indian cars though, I doubt we will ever have that problem coz of the low power.

Infact, in the Indian context, I would say the driveshafts are easier to break by spinning the wheels too much with the steering turned. I've seen it happen many times in autocross's...the guy is in a tight corner (dirt track), floors the accelerator, wheels (or wheel actually as there's no LSD), and then POP....driveshaft breaks!

Rt

[GTO]

Correction. It was not 0 - 100 km/h but 0 - 60 mph which is 97 km/h.

GTO

[normally_crazy]

gee thanx guys,

for all the info....

cheers

[shravan316]

What about the Gear shifts for drag races?? Do you double clutch or shift gears with only one time clutch press??

[Rtech]

Originally Posted by [b

Quote[/b] ]What about the Gear shifts for drag races?? Do you double clutch or shift gears with only one time clutch press?? *

Double clutching (DC) in a drag? Not really a good idea IMO.

Firstly, all modern cars have syncromesh box's that does away with the need to DC while upshifting. Yes, DC will reduce the wear and tear on your gearbox...if only by a miniscule bit in the real world. And if you are dragging, I'm sure that tiny difference in the wear of your box is insignificant to you. Also, DC takes up too much time. Even an expert driver cannot complete a DC upshift as fast as a regular shift.

On a circuit it may be more useful, but again really only on older cars or race cars without syncromesh. Even then, I used to shift up directly on the F2000's without using the clutch, much quicker.

Rt

[Rehaan]

Hey N_C,

Great topic. Let me try and add some more stuff to what ppl have aldready explained.

Ideally and theoretically, you would want ur engine to be at peak HP RPM (or above, so that if revvs drop a bit you still have a bulk of the peak HP to go thru). And you would want almost no wheelspin.
Now this would require some incredible clutch control (as well as a "perfect clutch&quot , which is not humanly or mechanically possible (due to properties of friction and their effect on how the smoothly the clutch transfers power from 0%-100%...(perfect clutch being a linear curve).

But as said above...all this aint happening....lol....... and hence the best ways are described above in other peoples replies.
The launch makes a hell of a difference in a drag.... in the US they call it "hooking up (off the line)"....

I remember a friend telling me that TopGear once did this episode in which they launched cars with wheelspin... and launched cars the "granny way"..ie letting of the clutch slowly...and the granny way was much better...... DOES ANYONE HAVE THIS EPISODE? or did anyone see it? cld u shed more light on the whole thing...

Originally Posted by [b

Quote[/b] ]What about the Gear shifts for drag races?? Do you double clutch or shift gears with only one time clutch press??

Shravan, chk out this thread.....i think its from b4 u joined TBHP!
Whats Double Clutching & Whats the Reason to Use it ??

cya
R

[Shan2nu]

Yup, a wheel-spin-less launch is anyday better and faster than spinning the wheels.

It all depends on yor gear ratios, tyres, road surface etc. If a car with launch control were to be launched on Ice, it would take it's own time to get to speed but it'll make sure it doesn't spin the wheels and unsettle the car. Incredibly, it would still be the fastest way to accelerate the car on Ice.

If you know how to slip the clutch then you shoudn't have much trouble launching a car, you just need to balance the revvs using the clutch and the gas pedal. But even pro drivers never manage exact times each and every time, it's just not possible.

Regards..
Shan2nu

[shravan316]

Thanks Shan2nu! That cleared the doubt, so what the 'Fast n Furious' guys were talking is all crap rite??

[ajmat]

Just been reading in the latest CAR about the drag between an Ariel Atom and a CL55 - power to weight vs sheer power. The Ariel shear the drive shaft on the second try but it ran the Merc close.
The drag experience

Ariel - raise the revs, hold tight , let the clutch out , shift up at 3000, rear end twitches with each upshift

Merc - floor the accelerator gently, tum tee tum tee taa, engine hums , oh ...already there !

[Rehaan]

Originally Posted by [b

Quote[/b] (ajmat @ Aug. 31 2004,21:35)]Ariel - raise the revs, hold tight , let the clutch out , shift up at 3000,

3000 rpm upshift ? why??