Apr 28, 2021 3:43:44 PM
- Whoopsy
- Rennteam Moderator
- Loc: Vancouver,BC , Canada
- Posts: 16151, Gallery
- Registered on: Sep 19, 2006
- Reply to: 996FourEss
Apr 28, 2021 3:43:44 PM
I remember Audi welding an additional tip that was not connected to anything, to make what looked like a dual tip exhaust. That was decades ago, probably on an A4. Single exhaust outlet on one side, predating the trend to symmetric dual exhausts. I can't find a picture now, but I remember the Auto Motor & Sport article showing a picture from underneath and pointing out the fakery. Circa 1990's?
Its in german but if you can find someone to translate it its quite an interesting video with a manual example, informal interior walk around with AP and a timed lap with Jorge which compares with the prior 991.2 RS MR hot lap time....
https://www.youtube.com/watch?v=ejm5-xiYQbM
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2017 991.2 GT3 Manual, 2017 Alfa Romeo Giulia QV, 2017 Macan S (Petrol)
Yes. Three tenths. But Jorg was driving without any safety gear or helmet and on his second lap out. The car was just a press car so entirely factory. I believe it was wearing only the standard Cup2 (but I could be wrong as my wife stopped translating by then!). The author of the youtube clip was sure he could have hit it with some better preparation.
More encouraging than that the fact that the 992 GT3 was as fast as the 991.2 GT3 MR on this track is the simple matter of the track itself. Its far more similar to the tracks I (and Grant) drive our GT3 at than the Nordschleife.
This would indicate that the new front suspension, wider track and larger tyre patch along with the recalibrated RWS (now 2.0 degree) and the changes that have made to the rear geo will produce improved results on real world tracks with slower tighter corners than the Ring (where the aero finally really comes into play)
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2017 991.2 GT3 Manual, 2017 Alfa Romeo Giulia QV, 2017 Macan S (Petrol)
Right. Makes sense. I gathered they were commenting on how soft they were after the lap. They also look like they probably dont last that long. I assume the 991.2 GT3 MR was probably running Cup2R so I guess like for like?
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2017 991.2 GT3 Manual, 2017 Alfa Romeo Giulia QV, 2017 Macan S (Petrol)
macca993:Right. Makes sense. I gathered they were commenting on how soft they were after the lap. They also look like they probably dont last that long. I assume the 991.2 GT3 MR was probably running Cup2R so I guess like for like?
Yes, but the GT3 has 10 mm less width on each tire.
18 GT3 Manual, 73 Carrera RS 2.7 Carbon Fiber replica (1,890 lbs), 06 EVO9 with track mods. Former: 16 Cayman GT4, 73 911S, Two 951S's, 996 C2, 993 C2, 98 Ferrari 550, 79 635CSi
Correct Grant. Im not sure how that affects tyre patch (maybe -5%?). Obviously now the 992 GT3 has a 21" rear wheel and wider front and rear tyres its type patch has grown significantly over the 991.2 GT3 (15%?). It really seems they have worked some voodoo on this chassis to give the results we are rearing and reading about...
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2017 991.2 GT3 Manual, 2017 Alfa Romeo Giulia QV, 2017 Macan S (Petrol)
macca993:Correct Grant. Im not sure how that affects tyre patch (maybe -5%?). Obviously now the 992 GT3 has a 21" rear wheel and wider front and rear tyres its type patch has grown significantly over the 991.2 GT3 (15%?). It really seems they have worked some voodoo on this chassis to give the results we are rearing and reading about...
Contact patch does not change in size with larger wheels, just shape. The only variables for sq. In. of SIZE is weight of the car and tire pressure. The wider the wheel the more rectangular on one axis the patch will be but it will become "shorter" as well.
Past-President, Porsche Club of America - Upper Canada Region
May 1, 2021 6:02:35 AM
Im fairly certain that a 21" wheel using a 315 tyre on a 12" rim (992.1 GT3) will have a larger tyre patch than a 20" wheel using a 305 on an 11.5" rim (991.2 GT3) assuming the weight is not changed?
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2017 991.2 GT3 Manual, 2017 Alfa Romeo Giulia QV, 2017 Macan S (Petrol)
May 1, 2021 1:41:02 PM
macca993:Im fairly certain that a 21" wheel using a 315 tyre on a 12" rim (992.1 GT3) will have a larger tyre patch than a 20" wheel using a 305 on an 11.5" rim (991.2 GT3) assuming the weight is not changed?
Mithras is correct, the contact patch remains at the same area, assuming weight and tire pressure doesn't change. What changes is the shape of the contact patch when a wider tire is employed instead of a narrower one; area remains the same.
May 1, 2021 1:44:53 PM
Boxster Coupe GTS:
Without a full streamline analysis, it's not necessarily indicative that the cutout, while not containing a real vent, does not contribute to air flow management around the rear of the car. The Turbo S has a rear vent to assist with cooling of the turbocharged engine and the intake air charge. The demands on a normally aspired motor, of course, are different.
May 1, 2021 9:38:12 PM
You may be right but this was what Porsche published as the increase between the 991.1 GT3 and 991.1 GT3RS back in the day. Sure the shape changes but so does the size (coverage). Why is it any differenet between a 991.2 GT3 (same as the GT3 in this chart) with 20" rear on 305 11.5J and a 992 GT3 with 21" rear 315 and 12J?
Ok its not going to be a 18% rear increase or a 20% front increase but my calcs show the increase in useable contact area is going to be between 5-10% and likely more effective coverage if you could calculate for the effects of the front double wishbone set up on dynamic camber?
Im not challenging anyone just curious to the reasons why the contact patch is unchanged with the 992 GT3 vs the 991.2 GT3?
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2017 991.2 GT3 Manual, 2017 Alfa Romeo Giulia QV, 2017 Macan S (Petrol)
May 2, 2021 6:25:05 AM
May 2, 2021 6:53:53 AM
May 2, 2021 8:07:20 AM
macca993:You may be right but this was what Porsche published as the increase between the 991.1 GT3 and 991.1 GT3RS back in the day. Sure the shape changes but so does the size (coverage). Why is it any differenet between a 991.2 GT3 (same as the GT3 in this chart) with 20" rear on 305 11.5J and a 992 GT3 with 21" rear 315 and 12J?
Ok its not going to be a 18% rear increase or a 20% front increase but my calcs show the increase in useable contact area is going to be between 5-10% and likely more effective coverage if you could calculate for the effects of the front double wishbone set up on dynamic camber?
Im not challenging anyone just curious to the reasons why the contact patch is unchanged with the 992 GT3 vs the 991.2 GT3?
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2017 991.2 GT3 Manual, 2017 Alfa Romeo Giulia QV, 2017 Macan S (Petrol)
Apparently afaik while just making the tire wider will not increase the contact patch as some have already said, a larger diameter tire wheel will increase the contract patch, and using a wider rim (not just tire) probably will as well when in motion.
Also the shape of the contact patch changes with the wider tire and a wider patch, even with the same surface area, will still give you more grip in the corners too.
As you already mentioned, the new front suspension will also make that contract patch more effective as it will keep it on the ground more efficiently. So it all ads up I guess.
Are pressures the same in the 992GT3 as in the 991 BTW?
May 2, 2021 8:36:29 AM
996FourEss:If increasing the wheel diameter doesn’t increase contact patch, all other things equal , I wonder what moron at say John Deere, decided to put those large diameter wheels on their tractors.... just saying😎
John Deere, ahead of their time when it came to big rear wheel bling tuning. Top fuel drag racers and Porsche RS cars followed tune
2016 Porsche 981 GT4 | Racing Yellow
2018 Audi S6 Avant | Ibis White
May 2, 2021 12:13:33 PM
d997h:macca993:Hey, this is so f##ked up - thanks for sharing so, there is one person driving a car over a plate all day and the other sits there with a ruler ... ... ok, all computerized and wired ... in DE they always showed us a postcard to picture it ...
Just imagine now on a sportbike, it's the size of a cigarette pack with only two tires on the ground, on equilibrium, and a 1:1 power to weight ratio... most fun vehicle... ever
May 3, 2021 8:32:51 PM
I remember reading about how small the contact area of tire actually is in Auto Motor Sport many decades ago. This is why RC is always so concerned about the correct OEM N01 or factory spec tire fitment. I have come around to this thinking now as well and specifically specify N01 tires for my Porsche and R01 tires for my R8. We are speed controlled in Canada but there is something about having best contact area you can get.
May 3, 2021 9:22:12 PM
Porsche 992 GT3 Touring looking great (with the ducktail) in a stunning render...
Link: https://widebodynews.com/renderings/new-992-porsche-911-gt3-touring-rendering/
...with thanks and credit to digital artist Treston Chen!