Power to Weight my2c

[Munro]

This week I got my R34 GTR corner weighted & wheel aligned.

It weighs 1658 kg.With 2 average to fat people in it thats around

1850 kg or 4000 pounds.That is one heavy car.All the 4WD gear,

hicas,bracing etc really adds up.Even with 270 rwkw (360hp) which at a 20% loss through the driveline equates to around 340

kw at flywheel (450hp) it has to work hard to move off the line & pull hard to decent speeds.The 4WD system definately helps to get it off the line but the extra weight is a disadvantage.

A GTSt with the same power would need very good tyres & suspension to hook up off the line like the GTR, but once moving

would pull away from the GTR due to the 100kg or so less weight.

Obviously the GTR would handle better through corners due to attessa system but once again physics comes into it.More weight

(or inertia) makes it harder to change directions.

The R33 was also corner weighted.It weighs only 1270 kg!(without me in it - add 100kg) This car has over 450rwkw @20psi

(600hp) At 30 psi it should make over 500rwkw(670hp) so again,

at 20% loss should be roughly 840hp at flywheel.2kg/kw.Hmmm.

The R34 has 4.8kg per kw.Same as a ferrari 360 modena.GT2 has

4.2kg/kw.Lamborghini Diablo 4.01kg/kw.

A GTSt with 340kw(450hp) at 1500kg = 4.4kg/kw.Looks like pretty

good value to me! Of course the weight/power ratio of my R33 is

insane, but to get it that light we had to strip all the creature comforts out of it & it has turned into a race car.No mirrors,no gauges,no air,power steering,stereo, etc,etc.The door windows are perspex so I cant wind them down.I do drive it on the street,

but it gets pretty hot in there,& I do miss the mirrors!

So the point of all this - weight is the enemy.More power is great,

but if you cant modify your engine, pull some weight out from somewhere.Just dont go too far or you will end up with a race car like me.

[Steve]

Thanks for that Munro, some really interesting points, and some pretty bloody insane ponies for a street car - must be fun.

Just one question - wouldnt the extra weight help the car to hook up and therefore have better control? Or does it come down to the driver and his level of control. Would a lighter car be more predictable with regart to wheels spin and power oversteer? I ask because sometimes I find it difficult to get traction when the right foot goes down, sometimes it seems somewhat unpredictable (spose road surface contributes a bit here) and can give me a bit of a wake up call. Do you have any tips for getting the power down?

Cheers

Steve

[Munro]

It all comes down to the rubber.You can adjust driving styles,suspension,etc, but ultimately it's where the rubber meets

the road that matters.The technology used in new tyres now gives a good selection of compounds etc for each application.So

for drifting & general fun leave some old hard tyres on, but if you want to get serious get a set of big,soft,sticky boots like RE540s

or similar.

[Duncan]

Another thing is, you only have to start once from a standing start in a race, not as big a deal as in drag racing where launch is a huge % of your time. In circuit, its helps to get a good start, but you can always make it up later , particularly if you're faster down the straights.

[Clint32]

now imagine a stripped 32 gtst, with 1270kg stock i think i could get that down to about 1150 with the aircond rear seats carpet gone, now with 270 rwkw or 340fly you would have 3.38 kg/kw and still be pretty comfortable and a weapon if you can get traction.

I still cant decide weather i should get a 32gtr in 12 months or go extreme on the gts.