This is exactly how much rear wheel steering RAS improves autocross lap time
11-08-2020, 01:22 PM
#1
Pro
Thread Starter
This is exactly how much rear wheel steering RAS improves autocross lap time
This took a lot of digging to find to satisfy my curiosity. It was an Australian student engineering project which you can easily search and find, with this title:
Active Rear Wheel Steering for a Formula SAE Vehicle UNSW Canberra at ADFA
The crux is that on a standardized formula SAE autocross track the following lap times were achieved:
Two wheel steering: 54.438 seconds
Rear wheel steering: 53.883 seconds
The methodology was interesting and complex and involved high falutin’ concepts like “fuzzy logic controller design” and “membership functions” and “linguistic rules.”
I was keenly interested in the thread showing Sport Auto magazine in Germany editors tested a 992 base vs S and found the base was faster. The test lost all meaning for me however because the vehicles had both PDCC and rear axle steering. The test was really mostly separating out the PDCC contribution at slalom speeds, which had no relevance for evaluating RAS as it wasn't engaged, as pointed out in that Rennlist thread. That said the Sport Auto journalists, not to mention many others, hated the synthetic feel of the "S" and they strongly preferred the base model without RAS and felt the magic was back in the 911 for them. They were disappointed with the initial Carrera S that was provided to journalists at launch with PDCC and RAS.
This student paper is the only specific test that is objective and scientific that credibly quantifies the improvement at autocross speeds with RAS I have ever seen, without contamination of the data by PDCC, PTV, LSD etc.
Active Rear Wheel Steering for a Formula SAE Vehicle UNSW Canberra at ADFA
The crux is that on a standardized formula SAE autocross track the following lap times were achieved:
Two wheel steering: 54.438 seconds
Rear wheel steering: 53.883 seconds
The methodology was interesting and complex and involved high falutin’ concepts like “fuzzy logic controller design” and “membership functions” and “linguistic rules.”
I was keenly interested in the thread showing Sport Auto magazine in Germany editors tested a 992 base vs S and found the base was faster. The test lost all meaning for me however because the vehicles had both PDCC and rear axle steering. The test was really mostly separating out the PDCC contribution at slalom speeds, which had no relevance for evaluating RAS as it wasn't engaged, as pointed out in that Rennlist thread. That said the Sport Auto journalists, not to mention many others, hated the synthetic feel of the "S" and they strongly preferred the base model without RAS and felt the magic was back in the 911 for them. They were disappointed with the initial Carrera S that was provided to journalists at launch with PDCC and RAS.
This student paper is the only specific test that is objective and scientific that credibly quantifies the improvement at autocross speeds with RAS I have ever seen, without contamination of the data by PDCC, PTV, LSD etc.
11-08-2020, 03:08 PM
#2
This took a lot of digging to find to satisfy my curiosity. It was an Australian student engineering project which you can easily search and find, with this title:
Active Rear Wheel Steering for a Formula SAE Vehicle UNSW Canberra at ADFA
The crux is that on a standardized formula SAE autocross track the following lap times were achieved:
Two wheel steering: 54.438 seconds
Rear wheel steering: 53.883 seconds
The methodology was interesting and complex and involved high falutin’ concepts like “fuzzy logic controller design” and “membership functions” and “linguistic rules.”
I was keenly interested in the thread showing Sport Auto magazine in Germany editors tested a 992 base vs S and found the base was faster. The test lost all meaning for me however because the vehicles had both PDCC and rear axle steering. The test was really mostly separating out the PDCC contribution at slalom speeds, which had no relevance for evaluating RAS as it wasn't engaged, as pointed out in that Rennlist thread. That said the Sport Auto journalists, not to mention many others, hated the synthetic feel of the "S" and they strongly preferred the base model without RAS and felt the magic was back in the 911 for them. They were disappointed with the initial Carrera S that was provided to journalists at launch with PDCC and RAS.
This student paper is the only specific test that is objective and scientific that credibly quantifies the improvement at autocross speeds with RAS I have ever seen, without contamination of the data by PDCC, PTV, LSD etc.
Active Rear Wheel Steering for a Formula SAE Vehicle UNSW Canberra at ADFA
The crux is that on a standardized formula SAE autocross track the following lap times were achieved:
Two wheel steering: 54.438 seconds
Rear wheel steering: 53.883 seconds
The methodology was interesting and complex and involved high falutin’ concepts like “fuzzy logic controller design” and “membership functions” and “linguistic rules.”
I was keenly interested in the thread showing Sport Auto magazine in Germany editors tested a 992 base vs S and found the base was faster. The test lost all meaning for me however because the vehicles had both PDCC and rear axle steering. The test was really mostly separating out the PDCC contribution at slalom speeds, which had no relevance for evaluating RAS as it wasn't engaged, as pointed out in that Rennlist thread. That said the Sport Auto journalists, not to mention many others, hated the synthetic feel of the "S" and they strongly preferred the base model without RAS and felt the magic was back in the 911 for them. They were disappointed with the initial Carrera S that was provided to journalists at launch with PDCC and RAS.
This student paper is the only specific test that is objective and scientific that credibly quantifies the improvement at autocross speeds with RAS I have ever seen, without contamination of the data by PDCC, PTV, LSD etc.
11-08-2020, 04:11 PM
#3
Pro
Thread Starter
I don't believe we are allowed to provide links away from Rennlist. I think that is how I got a red triangle next to my name.
If you go to the website in Germany (it is a sister publication of Auto Motor Sport), it is in the February 2020 issue, and if you go to the part of the website that has the archives, you can actually read an article preview; since it's only a few pages in, you can actually see the whole test incl. the data)
You will see a red 992 in the lower left corner of the cover.
Took me a while, but here is the link to the Rennlist thread I referenced:
https://rennlist.com/forums/992/1178...-and-pdcc.html
Cheers.
If you go to the website in Germany (it is a sister publication of Auto Motor Sport), it is in the February 2020 issue, and if you go to the part of the website that has the archives, you can actually read an article preview; since it's only a few pages in, you can actually see the whole test incl. the data)
You will see a red 992 in the lower left corner of the cover.
Took me a while, but here is the link to the Rennlist thread I referenced:
https://rennlist.com/forums/992/1178...-and-pdcc.html
Cheers.
The following users liked this post:
Sim68 (02-28-2021)
11-08-2020, 04:33 PM
#4
Pro
Thread Starter
FWIW, I have been vacillating for 2 months, but I believe after much thought, and help from other Rennlisters (Pete Stout, Ipse Dixit, Politeperson, Detasinn, smiles11, Bluehighways)
the base Carrera is my preference, getting optimal sports car feel and sacrificing some of the performance of RAS.
In the bargain, you get smaller turbos with the advantages of better sound and a better simulation of being normally aspirated than the "S" due to better throttle response. That point was specifically emphasized the the Sport Auto authors.
Also, you have a full 4 degrees of slip angle and the associated feel before losing adhesion with 2WS, as opposed to RAS where you have less
warning because of only 2.5 degrees of slip angle, per an outstanding (as always) post by Petevb.
I am thinking that the improve feel of what the car is doing, and greater margin of error is advantageous when learning to be a
better and more competitive driver. Indeed, others have pointed out the Nurburgring GT2RS was done with all driver assistance aids turned off.
the base Carrera is my preference, getting optimal sports car feel and sacrificing some of the performance of RAS.
In the bargain, you get smaller turbos with the advantages of better sound and a better simulation of being normally aspirated than the "S" due to better throttle response. That point was specifically emphasized the the Sport Auto authors.
Also, you have a full 4 degrees of slip angle and the associated feel before losing adhesion with 2WS, as opposed to RAS where you have less
warning because of only 2.5 degrees of slip angle, per an outstanding (as always) post by Petevb.
I am thinking that the improve feel of what the car is doing, and greater margin of error is advantageous when learning to be a
better and more competitive driver. Indeed, others have pointed out the Nurburgring GT2RS was done with all driver assistance aids turned off.
11-08-2020, 05:15 PM
#5
I don't believe we are allowed to provide links away from Rennlist. I think that is how I got a red triangle next to my name.
If you go to the website in Germany (it is a sister publication of Auto Motor Sport), it is in the February 2020 issue, and if you go to the part of the website that has the archives, you can actually read an article preview; since it's only a few pages in, you can actually see the whole test incl. the data)
You will see a red 992 in the lower left corner of the cover.
Took me a while, but here is the link to the Rennlist thread I referenced:
https://rennlist.com/forums/992/1178...-and-pdcc.html
Cheers.
If you go to the website in Germany (it is a sister publication of Auto Motor Sport), it is in the February 2020 issue, and if you go to the part of the website that has the archives, you can actually read an article preview; since it's only a few pages in, you can actually see the whole test incl. the data)
You will see a red 992 in the lower left corner of the cover.
Took me a while, but here is the link to the Rennlist thread I referenced:
https://rennlist.com/forums/992/1178...-and-pdcc.html
Cheers.
11-11-2020, 07:18 PM
#6
Rennlist Member
Have yet to try a base 992, partly due to Covid and partly due to scheduling. But am curious.
Fwiw, and as much as I respect RAS in some models, I really like the 991.2 Carrera/T/S without RAS. While I like the precision "on rails" feeling of the car with RAS, and agree they feel a bit smaller—and they're definitely more settled on the way into high-speed turns under braking—I prefer the honesty/feel of the Carrera with 2WS. Same goes for PTV/PTV+, which I also like in heavier, more complex Porsches or front-engined Porsches but am not as crazy about in simpler 981/718/991 platforms. Don't get me wrong…once again the performance advantage is clear, but I guess I like simple cars simple.
And I like simple cars.
Tough call between a Carrera and a Carrera T. Same engine, but Carrera T adds an LSD (with PTV...) so long as you get the 7MT—along with a number of attractive features. For me, those mainly include Sport PASM, the GT4 shifter, less sound deadening, and cloth seat centers. I'm not a big fan of PSE, so that's a point in the Carrera's favor. Can go either way on the light windows and dark wheels/trim.
Fwiw, and as much as I respect RAS in some models, I really like the 991.2 Carrera/T/S without RAS. While I like the precision "on rails" feeling of the car with RAS, and agree they feel a bit smaller—and they're definitely more settled on the way into high-speed turns under braking—I prefer the honesty/feel of the Carrera with 2WS. Same goes for PTV/PTV+, which I also like in heavier, more complex Porsches or front-engined Porsches but am not as crazy about in simpler 981/718/991 platforms. Don't get me wrong…once again the performance advantage is clear, but I guess I like simple cars simple.
And I like simple cars.
Tough call between a Carrera and a Carrera T. Same engine, but Carrera T adds an LSD (with PTV...) so long as you get the 7MT—along with a number of attractive features. For me, those mainly include Sport PASM, the GT4 shifter, less sound deadening, and cloth seat centers. I'm not a big fan of PSE, so that's a point in the Carrera's favor. Can go either way on the light windows and dark wheels/trim.
The following 4 users liked this post by stout:
11-11-2020, 09:20 PM
#7
Rennlist Member
Join Date: Feb 2009
Location: Newport Beach, CA and Melbourne, Australia
Posts: 4,324
Received 2,866 Likes
on
1,509 Posts
Have yet to try a base 992, partly due to Covid and partly due to scheduling. But am curious.
Fwiw, and as much as I respect RAS in some models, I really like the 991.2 Carrera/T/S without RAS. While I like the precision "on rails" feeling of the car with RAS, and agree they feel a bit smaller—and they're definitely more settled on the way into high-speed turns under braking—I prefer the honesty/feel of the Carrera with 2WS. Same goes for PTV/PTV+, which I also like in heavier, more complex Porsches or front-engined Porsches but am not as crazy about in simpler 981/718/991 platforms. Don't get me wrong…once again the performance advantage is clear, but I guess I like simple cars simple.
And I like simple cars.
Tough call between a Carrera and a Carrera T. Same engine, but Carrera T adds an LSD (with PTV...) so long as you get the 7MT—along with a number of attractive features. For me, those mainly include Sport PASM, the GT4 shifter, less sound deadening, and cloth seat centers. I'm not a big fan of PSE, so that's a point in the Carrera's favor. Can go either way on the light windows and dark wheels/trim.
Fwiw, and as much as I respect RAS in some models, I really like the 991.2 Carrera/T/S without RAS. While I like the precision "on rails" feeling of the car with RAS, and agree they feel a bit smaller—and they're definitely more settled on the way into high-speed turns under braking—I prefer the honesty/feel of the Carrera with 2WS. Same goes for PTV/PTV+, which I also like in heavier, more complex Porsches or front-engined Porsches but am not as crazy about in simpler 981/718/991 platforms. Don't get me wrong…once again the performance advantage is clear, but I guess I like simple cars simple.
And I like simple cars.
Tough call between a Carrera and a Carrera T. Same engine, but Carrera T adds an LSD (with PTV...) so long as you get the 7MT—along with a number of attractive features. For me, those mainly include Sport PASM, the GT4 shifter, less sound deadening, and cloth seat centers. I'm not a big fan of PSE, so that's a point in the Carrera's favor. Can go either way on the light windows and dark wheels/trim.
Trending Topics
02-28-2021, 03:00 PM
#8
Pro
Thread Starter
Have yet to try a base 992, partly due to Covid and partly due to scheduling. But am curious.
Fwiw, and as much as I respect RAS in some models, I really like the 991.2 Carrera/T/S without RAS. While I like the precision "on rails" feeling of the car with RAS, and agree they feel a bit smaller—and they're definitely more settled on the way into high-speed turns under braking—I prefer the honesty/feel of the Carrera with 2WS. Same goes for PTV/PTV+, which I also like in heavier, more complex Porsches or front-engined Porsches but am not as crazy about in simpler 981/718/991 platforms. Don't get me wrong…once again the performance advantage is clear, but I guess I like simple cars simple.
And I like simple cars.
Tough call between a Carrera and a Carrera T. Same engine, but Carrera T adds an LSD (with PTV...) so long as you get the 7MT—along with a number of attractive features. For me, those mainly include Sport PASM, the GT4 shifter, less sound deadening, and cloth seat centers. I'm not a big fan of PSE, so that's a point in the Carrera's favor. Can go either way on the light windows and dark wheels/trim.
Fwiw, and as much as I respect RAS in some models, I really like the 991.2 Carrera/T/S without RAS. While I like the precision "on rails" feeling of the car with RAS, and agree they feel a bit smaller—and they're definitely more settled on the way into high-speed turns under braking—I prefer the honesty/feel of the Carrera with 2WS. Same goes for PTV/PTV+, which I also like in heavier, more complex Porsches or front-engined Porsches but am not as crazy about in simpler 981/718/991 platforms. Don't get me wrong…once again the performance advantage is clear, but I guess I like simple cars simple.
And I like simple cars.
Tough call between a Carrera and a Carrera T. Same engine, but Carrera T adds an LSD (with PTV...) so long as you get the 7MT—along with a number of attractive features. For me, those mainly include Sport PASM, the GT4 shifter, less sound deadening, and cloth seat centers. I'm not a big fan of PSE, so that's a point in the Carrera's favor. Can go either way on the light windows and dark wheels/trim.
Your impressions of the base 991.2 were fabulous. I have reread them many times.
02-28-2021, 08:23 PM
#9
Three Wheelin'
