5 Generations of 911 GT3 - Auto Motor und Sport Test Data
08-27-2013, 01:22 PM
#16
Roughly makes sense to me. Yes, the engine dropped about 55 lbs, but between the 7 speed, PDK and the rear wheel steering they added nearly that much back in, all over the rear axle. I also suspect this car was tested with the smaller standard gas tank, which when full pulls about 50 lbs off the front axle. That's a 1% shift in the wrong direction all by itself, and that plus passengers might explain why some numbers might be quoted at 58% on the rear- both could be correct. Older gen cars seem to have a slightly larger tank (by only a gallon) helping their weight distribution slightly when at full fuel.
Last edited by Petevb; 08-27-2013 at 02:24 PM.
08-27-2013, 01:24 PM
#17
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The braking tests 62mph to 0 are really only a reflection of the tires and ABS (any GT3 has brakes strong enough to lock the wheels from that speed). Any real test of braking needs to be done at much higher speeds and for prolonged periods.
That being said, I suspect that the new 410/390mm PCCB's are a big improvement.
That being said, I suspect that the new 410/390mm PCCB's are a big improvement.
PCCBs shouldn't contribute to improved stopping distances IMO.
08-27-2013, 01:40 PM
#18
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I agree from 62mph, but from higher speeds (and repeated braking) the additional brake torque (larger rotors mean higher braking power from longer lever applying the force) and heat dissipation may be reflected in better numbers.
08-27-2013, 03:23 PM
#19
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Roughly makes sense to me. Yes, the engine dropped about 55 lbs, but between the 7 speed, PDK and the rear wheel steering they added nearly that much back in, all over the rear axle. I also suspect this car was tested with the smaller standard gas tank, which when full pulls about 50 lbs off the front axle. That's a 1% shift in the wrong direction all by itself, and that plus passengers might explain why some numbers might be quoted at 58% on the rear- both could be correct. Older gen cars seem to have a slightly larger tank (by only a gallon) helping their weight distribution slightly when at full fuel.
08-27-2013, 04:06 PM
#20
Three Wheelin'
Magazine test for stopping distance from 70 to 0 ...
z06 vs. ZR1
160 145
150 142
164 143
146 142
150 140
152 144
The ceramics were more consistant, however the tire difference between the two cars likely made the difference in overall stopping distance, Z06s came with Goodyear Supercar Runflats, ZR1s with Michelin PS2s ZPs (also runflats).
Ryan
08-27-2013, 04:15 PM
#22
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Not always - it depends on the speed, pads, calipers, tires and track condition, downforce, etc...
Larger diameter rotors mean more braking torque (potential braking power). As you said, that can't always be used before locking a wheel.
If the track is hot, you're using slick racing tires, the racing brake pads are just starting to fade, and you're traveling 170mph on a smooth and high-friction surface, and you have aerodynamic downforce, then you may have much less braking power than tire adhesion (at least on initial bite).
On ice, never going to have less brakes than tire adhesion...
Larger diameter rotors mean more braking torque (potential braking power). As you said, that can't always be used before locking a wheel.
If the track is hot, you're using slick racing tires, the racing brake pads are just starting to fade, and you're traveling 170mph on a smooth and high-friction surface, and you have aerodynamic downforce, then you may have much less braking power than tire adhesion (at least on initial bite).
On ice, never going to have less brakes than tire adhesion...
Last edited by GrantG; 08-27-2013 at 05:14 PM.
08-27-2013, 04:17 PM
#23
Race Director
The difference shown in this vid could be significant, or not, since the two cars were tested at different times under possibly very different conditions. One thing that was pointed out when this vid appeared in another thread was that GT3 had a passenger who can be seen filming while the 4.0 may or may not have had one. The comparison is interesting but not conclusive.
08-27-2013, 05:04 PM
#25
My estimates of changes to the rear weight bias from the 997 GT3 would be:
Move engine and trans fwd: -.4%
RWS +~22 lbs rear only +.3%
PDK vs 6 speed +~55 lbs +.6% (assumed: PDK is 20 kg heavier than the manual 7 speed, 6 speed is likely ~5 kg lighter than that?)
Lighter engine -55 lbs -1.0% (engine behind the axle has a larger effect)
Lighter 991 chassis +.2% (weight reduced from both front and rear equally changes weight balance)
This list would make the 991 GT3 have .3% less weight on the rear than the 997, so not quite correct (the table shows .1% less) but it shows you wouldn't expect a dramatic change with the numbers we roughly know. Take out the RWS and PDK and you'd have a noticeable difference, so you could say the lighter and shifted motor allowed them to add the RWS and PDK without a major negative impact.
Last edited by Petevb; 08-27-2013 at 05:30 PM.
08-27-2013, 05:39 PM
#26
Burning Brakes
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08-27-2013, 05:52 PM
#27
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Overall the weight distribution was as I expected. The increased wheelbase has only changes the Polar Moment of Inertia. The brake performance and in gear flexibility was a little better than I expected and the past generations weight tested was way worse than I expected. Essentially the 991 GT3 in any form of real world trim looks in reality to be one of the lighter GT3s developed in the last 10 years if we assume those in the test were all of similar specification.
After all the "weight crucifixion" on this board in the early days that was a surprise.
After all the "weight crucifixion" on this board in the early days that was a surprise.
08-27-2013, 06:29 PM
#28
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Can you imagine they made it 3050lbs (My 4.0's real weight) and manual?
It would still be awesome and more fun!
Bah, they should have just kept making 4.0's till the end of days, it would have depreciated to a very palatable and trackable $125K by now....
God, my new 991RS is gonna be fast though..
It would still be awesome and more fun!
Bah, they should have just kept making 4.0's till the end of days, it would have depreciated to a very palatable and trackable $125K by now....
God, my new 991RS is gonna be fast though..
08-27-2013, 09:02 PM
#29
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