Basal Skull

Hey Felix if you use my rational, it works out pretty similar to your calculation ie. 1043HP !

(much more math though aargh...)

300km/hr = 83.33 m/sec
deceleration 83.33/6.8 = 12.25 m/sec (squared)

1500kg car
1500x12.25 = 18382 Newton

tire diameter say 26” = 66 cm=0.66 m
r= 0.33

18382x0.33=6066 nm



so rpm of wheels
0-300 so average speed assuming constant (average deceleration) 150km/hr = 41.67m/sec

26” wheels = 66cm dia -> 0.66x3.14 = 2.07m circumference
so 41.67m/sec x 6.8 sec = distance travelled =283.6 m
so rotations = 136.9
RPM = 136.9 rotations/6.8sec=1207.8 RPM

RPMx2pi/60 = 1207.8x2x3.14/60= 126.4 radians/sec

126.4x6066 = 766742.4 watts

766742.4/735=1043 hp

Felix

Good point - adding aero drag would mean less energy dissipated by the brakes

Hey Brian, I is just a failed engineer - wimped out and joined management!

Jean

I think the key might be here:
Maybe braking capability and measured braking are not the same thing! This car might have braking capability of 2000 HP given the right conditions.

As tested by Sport Auto, the 993TT goes from 62mph to 0 mph in 34 meters, that is ~1.2Gs of deceleration and about 2.5 seconds. This is about the limit of traction for street tires. If you move to slicks and test on a sticky surface, you can well see above 2Gs of braking force, your braking distance will be cut almost by half and time required as well..

If you factor a heavier weight (2 + 2 people on board + luggage), you can be adding about 300kgs of weight.

Given that the claim is that they have "capability" to brake at 2000HP, it might be justified one way or another.

ALl of the above is meaningless...let's get those GPS devices.

Felix

This might be the source of that 2000 horsepower brakes quote - bottom of page 222 of Bruce Anderson's 911 Performance Handbook