Guys:

I think Porsche understimated the power on the new GT3 at 380Hp.

Car and driver tested weight on the GT3 was 3219 lbs. The Ferrari Challenge Stradale ($200k) was 3157 lbs.

The Ferrari comes with the new 40v V8 rated at 425Hp (45 hp more). BTW, Ferrari claims that the Stradale is a 2800 lbs car (probably with Lexan all around, no oil, no gas, etc).

Results: The Porsche matched the Ferrari in every single acceleration test, with the exception of the 1/4 mile where the Porsche beat the Ferrari 12.3 vs. 12.4.

The GT3 did a 1.03g at the skipad in street tires, and it beat the Ferrari on a racetrack. The Ferrari was fitted with R compound tires (PZero Corsa).

Do you imagine how faster the GT3 was going to be fitted with R-compound tires as well rather than street tires (MPS)?

The GT3 ran 0-60mph in 4.0 sec and 0-100 in 9.7 sec.

Karl's car ran 37x Hp at the dyno.

I have one of this weight to power calculators, and there is no was a 380 Hp car can run a 1/4 mile in 12.3 with 3200 lbs.

What do you think?

 

I was going to bring this article up this morning on this board here.

What does everyone feel about the placement of the car in the final standings. C/D has always liked the Marque, but I think they felt the car was just too bland compared to the other two. Maybe thats not the best way to describe, but....

 

Don't know about your calculator, or the accuracy of this one but it seems to be possible according to this:

http://www.turbofast.com.au/Drag.html

I get 11.85 ET with 3200lbs and 380 hp

I have some more references at home but I don't see much to be suspicious of here - acceleration times are subject to wide variances...

 

If you pipe RWHP into that calculator the times are much, much closer to what C&D achieved.

 

That's what I was just thinking...there's no instructions with the calculator but if you reverse engineer it 12.3ET with 3200 = 340hp

So what's drivetrain loss on these cars?

 

Yeah right!

Regular stock C5 running low 12s.

Stock Z06 running 11.6 ?

Advice: Don't use drag racing calculators. They consider 1/4 mile time in a sticky drag way with drag race tires.

How can you explain that C&D tested the GT3 against a lighter, 45Hp more powerful Ferrari Stradale in more sticky tires and they got practically the same acceleration times?

The same magazine has tested the Z06 vette multiple times not getting that kind of 1/4 mile times.

For me, this car probably has 400Hp and Porsche didn't want to hurt Turbo image and sales. In the same way the X51 has 350-360Hp but Porsche claims only a 25 Hp increase.

 

OK, so what's your formula for calculating HP based on ET?

FWIW, I found about 10 other sites that hit the same number as that calculator. Not saying they are right but I'm not sure that any of these take into account tires, gearing, driver skill level, temperature, etc which are all major factors... Thus my comment that they are subject to wide variances.

 

i thought Karl had 358 RWHP?

 

I love it when I write in the 996 based forums. Its like I'm talking to myself. Into nothingness. I can say things and there is never a ripple of a response. Funny.

 

yeah, I think that was it...IMHO these exercises are a lot of mental ma$terb@tion... too many unknown variables to come up with anything accurate

 

Watt:

You're right.

358.8 hp stock and 368.8 with the adjusted ECU (the figure I had in mind).

If you take 358.8 hp at the wheels, that's way over 400Hp at the wheels.

There is no such thing as a 996 with 10% or less losses from flywheel to wheels, specially considering 18" wheels, transmission, L S D, etc.

bob_dallas:

When using those calculator we have to consider the following:

- To add the driver's weight to the car weight, or take the weight of the car with the driver inside.

- Some of them work based on Wheel Hp and others in Flywheel Hp. The 380Hp figure is at the flywheel.

My estimation is that the GT3 is around 400+Hp.

Consider that the 3.4 996 runs around 250Hp at the wheels. www.Evoms.com claims a 17% loss on a 996 drivetrain and they have some dyno runs on stock 996s showing 248.8 - 252 Hp. There are more web sites showing dyno runs on 3.4/3.6 996s.

If the GT3 generates 108 hp at the wheels more than the 3.4 996, and the 3.4 996 is rated at 296Hp/300Hp, then how is it possible to have 84/80Hp more at the flywheel when it should be 108 + 17% = 126Hp more?. BTW, the 02 Z06 rated at 405 Hp runs around 355Hp at the wheels.

 

so the calculator is semi-useful for another variable in the comparison but I don't see how they can get accurate HP from a weight and ET...too many other car-dependent variables. Think about the acceleration differences that different gearing make on a car. I bet you could easily drop the 1/4mi time .5 sec or more with different gears but the weight and HP would stay the same... see my point?

That aside, I do agree that 358 at the rear wheels should = more than 380 at the flywheel but I don't have a good way to calculate that on the car either.

 

Brendan - to your comment...I thought it was a very strange comparison for several reasons and extremely subjective. Some of the comments were strange (like the Stradale being easier to drive at the limit?)... no time to comment more right now though

 

The Challenge Stradale is only available w/the F1 transmission. Perhaps the acceleration times from a standstill are hampered by this setup which is why the GT3 is better. Did they report any in-gear acceleration times for the cars?

Greg A

 

Bob

Power, by definition, is work per unit time. Work is defined as the product of force acting over distance.

The MINIMUM power requirement can be calculated to shift 3200 lbs a distance of 1/4 mile in 12 sec.

So (working in metric units) we have:

mass, m=3200lbs =1454.5 kg
time, t=12 sec
distance, s = 400 m

work= force x distance

but FOrce = mass x acceleration

Basic newtonian kinematics tells us:

s = u x t + 1/2 x a x (t)^2 where u=initial velocity = 0 for standing start

so, s = 1/2 x a x t^2 OR

a = 2 x s / t^2

So, substituting this into our equation for work:

w = m x [2 x s / t ^2] x s, OR

w =m x 2 x s^2 / t^2

now, power = work / t

so, power = m x 2 x s^2/t^3

If you plug in hte numbers (in metric) that we know, mass, time and distance we get:

Power = 269 359 watts (kW)

= 361 HP.

Not so far off , without even allowing for ANY losses. Physics rules!