Consolidated 991RS thread
11-12-2014, 05:11 PM
#2536
Surprised by no RWS as well. However it can't all add up- if the "50% improved traction" bit is even half true it's going to be a monster at the track RWS or not. That downforce will let it carry speed, those tires, 10% better power to weight ratio... And only 7:20?
Porsche "likes to be fastest". When the GT-R published a video lap doing 7:29 at the ring, Porsche green-lighted project code 727 - the GT2 RS - to put them in their place. By whatever means necessary. Today Nissan boasts of 7:08, and while we all know the Nismo is so tuned for the 'Ring that it can't run anywhere near that well anywhere else, Porsche must again feel the need to respond. The 458 Speciale and ZR-1/ upcoming Z06 must also be on their radar.
The GT3 RS is the car Porsche has to respond with at the moment, and 7:20 seconds doesn't seem like a "suitable" response, "homologation" of the RWS be damned. Thus I'd be surprised if it wasn't quicker- call it 7:15 or better. Like any good engineers Porsche designs to targets, and they do what's required to hit those targets. As yourself- if you were in their shoes choosing a 'Ring target for the RS, what would it be?
Macca- why work from German pricing if he's in Italy?
Porsche "likes to be fastest". When the GT-R published a video lap doing 7:29 at the ring, Porsche green-lighted project code 727 - the GT2 RS - to put them in their place. By whatever means necessary. Today Nissan boasts of 7:08, and while we all know the Nismo is so tuned for the 'Ring that it can't run anywhere near that well anywhere else, Porsche must again feel the need to respond. The 458 Speciale and ZR-1/ upcoming Z06 must also be on their radar.
The GT3 RS is the car Porsche has to respond with at the moment, and 7:20 seconds doesn't seem like a "suitable" response, "homologation" of the RWS be damned. Thus I'd be surprised if it wasn't quicker- call it 7:15 or better. Like any good engineers Porsche designs to targets, and they do what's required to hit those targets. As yourself- if you were in their shoes choosing a 'Ring target for the RS, what would it be?
Macca- why work from German pricing if he's in Italy?
11-12-2014, 05:13 PM
#2537
Italian and German prices are not so different...
About the lack of RWS...don't know what to tell,but two different sources tell the same thing...hope they are wrong,but with RWS slicks are not allowed,maybe without yes?!?!
I read somewhere that the ring time seems far better than 7.20
About the lack of RWS...don't know what to tell,but two different sources tell the same thing...hope they are wrong,but with RWS slicks are not allowed,maybe without yes?!?!
I read somewhere that the ring time seems far better than 7.20
11-12-2014, 05:16 PM
#2538
I'm not saying it'll get RWS- the rumors may well be correct that it won't. I'm simply saying that if they felt they needed it to hit their targets (and it's the customer's perspective that really sets the target) then they'd use it. And since I'd guess at <7:15 as a logical target, I think they'll hit that. RWS or no...
11-12-2014, 05:32 PM
#2539
I'm not saying it'll get RWS- the rumors may well be correct that it won't. I'm simply saying that if they felt they needed it to hit their targets (and it's the customer's perspective that really sets the target) then they'd use it. And since I'd guess at <7:15 as a logical target, I think they'll hit that. RWS or no...
11-12-2014, 07:38 PM
#2543
Rennlist Member
I know the tax rate in Germany, but I dont in Italy. The base price for the 991 GT3 was 137500 Euro IIRC in Germany so the difference appears to be destination charges/transport and maybe tax. Based on the 991 GT3 Germany pricing in Germany the 991RS will retail for around $185K Euro...
In the USA the base price before tax was basically dollar for Euro against the German pricing (thus in effect 25% discount). Therefore I would assume if 991 GT3RS headlines in Germany at 185K E base then it will be 180K USD as has been previously elluded to.
In the USA the base price before tax was basically dollar for Euro against the German pricing (thus in effect 25% discount). Therefore I would assume if 991 GT3RS headlines in Germany at 185K E base then it will be 180K USD as has been previously elluded to.
11-12-2014, 08:01 PM
#2544
Have any cars with significant downforce been produced with RWS? Is it possible it reduces the amount of downforce can be added? I've heard the no RWS from several sources and it seems to be getting confirmed.
11-12-2014, 08:42 PM
#2545
The question is would the benefits of RWS increase or decrease? I'm not sure, and I can make arguments either way.
On the plus side for RWS one of the big issues with high downforce is ride height: as aero load increases ride height decreases. Very high downforce cars need to use stiff springs or sophisticated linked suspensions to maintain ride height, but at street car downforce levels you usually stiffen springs slightly and deal with it.
As the rear suspension compresses, however, it toes the rear wheels in, meaning as speeds increase in a high downforce car your alignment is effectively going off. RWS would seem to offer a good way to counter this, especially useful for autobahn running.
On negative side for RWS, however, it's possible that with careful tuning, tires and application of downforce the other benefits of RWS would be reduced.
RWS largely helps the car rotate at low speeds while adding stability at high speeds. Careful downforce tuning, however (higher rear downforce vs front) can effectively do something similar, allowing a car to be "loose" at low speed and then using aero loads to plant the rear end as speed increases.
The toe-in described above would be a natural side effect that would compound this effect, as toe-in also increases high speed stability. Thus with aero and suspension kinematics working together it's possible that the new package is getting benefits similar to RWS.
Finally the RS's bigger tires operate at a lower "slip angle", and I'd therefore expect the RS to use less rear steering angle if RWS is retained. At some point, however, the steering angles needed would be so small that the weight and complexity of RWS might not be worth it. Perhaps they've managed to juggle the other elements of the design enough that this is the case in the RS.
So it's a complex question that probably needed some cool simulation and testing to answer properly. I'd love to ask them- it'd be very interesting to learn the truth.
11-12-2014, 09:09 PM
#2546
Three Wheelin'
No cars with RWS and more downforce than the 918 Weissach that I know of, but how many cars have been made with RWS period? RWS would certainly be possible for the RS. The loads from aero will go up marginally, but that's easy to handle- if you can design for 2000 lbs it's straightforward to design for 2400.
The question is would the benefits of RWS increase or decrease? I'm not sure, and I can make arguments either way.
On the plus side for RWS one of the big issues with high downforce is ride height: as aero load increases ride height decreases. Very high downforce cars need to use stiff springs or sophisticated linked suspensions to maintain ride height, but at street car downforce levels you usually stiffen springs slightly and deal with it.
As the rear suspension compresses, however, it toes the rear wheels in, meaning as speeds increase in a high downforce car your alignment is effectively going off. RWS would seem to offer a good way to counter this, especially useful for autobahn running.
On negative side for RWS, however, it's possible that with careful tuning, tires and application of downforce the other benefits of RWS would be reduced.
RWS largely helps the car rotate at low speeds while adding stability at high speeds. Careful downforce tuning, however (higher rear downforce vs front) can effectively do something similar, allowing a car to be "loose" at low speed and then using aero loads to plant the rear end as speed increases.
The toe-in described above would be a natural side effect that would compound this effect, as toe-in also increases high speed stability. Thus with aero and suspension kinematics working together it's possible that the new package is getting benefits similar to RWS.
Finally the RS's bigger tires operate at a lower "slip angle", and I'd therefore expect the RS to use less rear steering angle if RWS is retained. At some point, however, the steering angles needed would be so small that the weight and complexity of RWS might not be worth it. Perhaps they've managed to juggle the other elements of the design enough that this is the case in the RS.
So it's a complex question that probably needed some cool simulation and testing to answer properly. I'd love to ask them- it'd be very interesting to learn the truth.
The question is would the benefits of RWS increase or decrease? I'm not sure, and I can make arguments either way.
On the plus side for RWS one of the big issues with high downforce is ride height: as aero load increases ride height decreases. Very high downforce cars need to use stiff springs or sophisticated linked suspensions to maintain ride height, but at street car downforce levels you usually stiffen springs slightly and deal with it.
As the rear suspension compresses, however, it toes the rear wheels in, meaning as speeds increase in a high downforce car your alignment is effectively going off. RWS would seem to offer a good way to counter this, especially useful for autobahn running.
On negative side for RWS, however, it's possible that with careful tuning, tires and application of downforce the other benefits of RWS would be reduced.
RWS largely helps the car rotate at low speeds while adding stability at high speeds. Careful downforce tuning, however (higher rear downforce vs front) can effectively do something similar, allowing a car to be "loose" at low speed and then using aero loads to plant the rear end as speed increases.
The toe-in described above would be a natural side effect that would compound this effect, as toe-in also increases high speed stability. Thus with aero and suspension kinematics working together it's possible that the new package is getting benefits similar to RWS.
Finally the RS's bigger tires operate at a lower "slip angle", and I'd therefore expect the RS to use less rear steering angle if RWS is retained. At some point, however, the steering angles needed would be so small that the weight and complexity of RWS might not be worth it. Perhaps they've managed to juggle the other elements of the design enough that this is the case in the RS.
So it's a complex question that probably needed some cool simulation and testing to answer properly. I'd love to ask them- it'd be very interesting to learn the truth.
Great thorough thoughts!!!! I think it would be cool to have one of the dozen unused buttons be there to turn the RWS on/off.
11-13-2014, 04:20 PM
#2547
Rennlist Member
No cars with RWS and more downforce than the 918 Weissach that I know of, but how many cars have been made with RWS period? RWS would certainly be possible for the RS. The loads from aero will go up marginally, but that's easy to handle- if you can design for 2000 lbs it's straightforward to design for 2400.
The question is would the benefits of RWS increase or decrease? I'm not sure, and I can make arguments either way.
On the plus side for RWS one of the big issues with high downforce is ride height: as aero load increases ride height decreases. Very high downforce cars need to use stiff springs or sophisticated linked suspensions to maintain ride height, but at street car downforce levels you usually stiffen springs slightly and deal with it.
As the rear suspension compresses, however, it toes the rear wheels in, meaning as speeds increase in a high downforce car your alignment is effectively going off. RWS would seem to offer a good way to counter this, especially useful for autobahn running.
On negative side for RWS, however, it's possible that with careful tuning, tires and application of downforce the other benefits of RWS would be reduced.
RWS largely helps the car rotate at low speeds while adding stability at high speeds. Careful downforce tuning, however (higher rear downforce vs front) can effectively do something similar, allowing a car to be "loose" at low speed and then using aero loads to plant the rear end as speed increases.
The toe-in described above would be a natural side effect that would compound this effect, as toe-in also increases high speed stability. Thus with aero and suspension kinematics working together it's possible that the new package is getting benefits similar to RWS.
Finally the RS's bigger tires operate at a lower "slip angle", and I'd therefore expect the RS to use less rear steering angle if RWS is retained. At some point, however, the steering angles needed would be so small that the weight and complexity of RWS might not be worth it. Perhaps they've managed to juggle the other elements of the design enough that this is the case in the RS.
So it's a complex question that probably needed some cool simulation and testing to answer properly. I'd love to ask them- it'd be very interesting to learn the truth.
The question is would the benefits of RWS increase or decrease? I'm not sure, and I can make arguments either way.
On the plus side for RWS one of the big issues with high downforce is ride height: as aero load increases ride height decreases. Very high downforce cars need to use stiff springs or sophisticated linked suspensions to maintain ride height, but at street car downforce levels you usually stiffen springs slightly and deal with it.
As the rear suspension compresses, however, it toes the rear wheels in, meaning as speeds increase in a high downforce car your alignment is effectively going off. RWS would seem to offer a good way to counter this, especially useful for autobahn running.
On negative side for RWS, however, it's possible that with careful tuning, tires and application of downforce the other benefits of RWS would be reduced.
RWS largely helps the car rotate at low speeds while adding stability at high speeds. Careful downforce tuning, however (higher rear downforce vs front) can effectively do something similar, allowing a car to be "loose" at low speed and then using aero loads to plant the rear end as speed increases.
The toe-in described above would be a natural side effect that would compound this effect, as toe-in also increases high speed stability. Thus with aero and suspension kinematics working together it's possible that the new package is getting benefits similar to RWS.
Finally the RS's bigger tires operate at a lower "slip angle", and I'd therefore expect the RS to use less rear steering angle if RWS is retained. At some point, however, the steering angles needed would be so small that the weight and complexity of RWS might not be worth it. Perhaps they've managed to juggle the other elements of the design enough that this is the case in the RS.
So it's a complex question that probably needed some cool simulation and testing to answer properly. I'd love to ask them- it'd be very interesting to learn the truth.
I wish we had a 'general contact' at PAG. The CEO, AP, Q&A, Engineering dept., etc...that we could forward ideas & comments to. This is one of those posts that deserves a forward to a decision maker.
11-13-2014, 04:45 PM
#2548
Thanks, but don't kid yourself. I'm a rank amateur, and know what I don't know. Those guys are pros, and will have covered all those angles and more. With some car companies I couldn't say that with full confidence, but with Porsche, absolutely. One of the reasons we appreciate them...
11-13-2014, 04:50 PM
#2549
Racer
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Incredible post. I just hope Porsche engineers have done the math & thought this through as much as you have.
I wish we had a 'general contact' at PAG. The CEO, AP, Q&A, Engineering dept., etc...that we could forward ideas & comments to. This is one of those posts that deserves a forward to a decision maker.
I wish we had a 'general contact' at PAG. The CEO, AP, Q&A, Engineering dept., etc...that we could forward ideas & comments to. This is one of those posts that deserves a forward to a decision maker.
I think we can count on the Porsche engineers doing 'the math' - what worries me is the marketing department.
In my track experience the 991 GT3 tends to understeer at low speed and slightly oversteer at high speed. More rear downforce and bigger tires sound like they would help balance that out. Removing the RWS would have the opposite effect and I hope they don't do that in some misguided marketing 'homologation' ploy.
11-14-2014, 12:12 AM
#2550
Rennlist Member
Thanks, but don't kid yourself. I'm a rank amateur, and know what I don't know. Those guys are pros, and will have covered all those angles and more. With some car companies I couldn't say that with full confidence, but with Porsche, absolutely. One of the reasons we appreciate them...
I think we can count on the Porsche engineers doing 'the math' - what worries me is the marketing department.
In my track experience the 991 GT3 tends to understeer at low speed and slightly oversteer at high speed. More rear downforce and bigger tires sound like they would help balance that out. Removing the RWS would have the opposite effect and I hope they don't do that in some misguided marketing 'homologation' ploy.