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Old 27th April 2014, 08:39 AM   #12 (permalink)
Little Nismo
Little Nismo is A Pickled Cabbage seasoned Member
Join Date: May 2002
Location: Hamilton New Zealand
Cars owned: Nissan Skyline R33 GTR, 402kw @ 1.75bar
Posts: 110
Originally Posted by borat52 View Post
That's the appeal of downforce, going back to our friction equation it increases R (reaction) with zero increase in mass so we can counter any given momentum or kinetic energy with more friction.

Also a weightless car in theory has zero mass so would require an infinitely small force to go infinitely quickly (ke = 1/2mv(squared) so it's not something that makes sense in the real world.

Your ute is a function of bad design, it has significant mass to accelerate but only a small mass over the drive wheels and hence the Reaction force and friction over the drive wheels is small. Iff all of its mass was over the drive wheels it would be as quick to accelerate as any vehicle with the same mass and same tyres.

The GTR is quick simply because of the efficiency in which its able to manipulate its power through the 4wd system maximising the friction on each tyre at all times coupled with a chassis and suspension set up which helps to ensure the tyres are generating lots of friction all the time.

Its weight is really a consequence of its design, not an objective in itself.

I stand by it that losing 500kg would make it significantly quicker. Yes it would spin the wheels easier but remember less mass means we need less energy to accelerate/brake so less power from the engine would give the same acceleration.
Ok not a weightless but a very light car. The point was really asking is there a cross over point at which your vehicle is too light for the power and the selected wheel size?

Ie if the gtr weighed 1200kgs is that too light? What about 1000kgs? 900, 800.

Of course I don't deny that light can be good the lotus formula of 800-900kgs and 250hp makes for great track cars.

I'd be interested in whether you believe the weight has no advantage in snow ice wet at low speeds and on launch?

If I hear you right you are saying making a 4wd road gt car means that you will have to have 1800kgs or I'm guessing make it expensive (carbon fibre) and the rest of the specs are all to overcome that weight? You are saying there is no trade off for less weight in low downforce situations?

Yup that's certainly a possibility but why would they make up porkies about it? It seems a little pointless. Why not just say that the weight is a function of the car dimensions engine and 4wd drive and the power wheel size suspension etc are selected around this.

Which I guess is the point of this thread.

Is it that now engines with massive power and torque can be made so manufacturers look to make the most of this. But to have a 1200kgs car with 600hp is gomna be a handful in amateur hands in adverse conditions?
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