Speculation on acceleration performance of 991 TTS vs. 997 TTS
07-24-2013, 02:05 PM
#1
Instructor
Thread Starter
Join Date: Jun 2007
Location: Vancouver, Canada
Posts: 180
Likes: 0
Received 0 Likes
on
0 Posts
Speculation on acceleration performance of 991 TTS vs. 997 TTS
0-60 times are only part of the sports car equation but, for the Turbo, they always grab the headlines. And so, I thought I’d explore the question: are there good reasons to expect the 991 TTS to be faster than the 997 TTS in the 0-60 mph sprint?
Unless ‘ringers’ were used in testing the 997 TTS, the times recorded where phenomenal; 2.6 seconds by Road & Track, 2.7 by Car & Driver, 2.8 by Motor Trend. These times were considerably below official Porsche times of around 3.1 seconds. That Porsche has announced the 991 Turbo S will do 0-60 in 2.9 seconds doesn’t necessarily mean actual tests will yield a 2.5 second sprint as some have suggested. IOW, 2.9 seconds could be closer to what the 991 Turbo S can really accomplish IF performance reporting is now closer to actual figures than was the case for the 997 Turbo S.
The 997 Turbo S has exactly the same torque configuration as the 991 Turbo S – 516 ft/lbs of torque. And it weighs a tad less at 1585 Kg vs 1605 for the 991 TTS. Since it’s torque and weight that make for fast 0-60 times, the 997 Turbo S could be expected to perform close to the 991 TTS. The only important intervening variable I can think of that could favor the 991’s is slightly faster PDK shifting times. It’s also possible that unsprung weight could be less for the 991 as represented by the 991’s wheels and tire weight. This would reduce rolling weight to the 991’s advantage.
That the 991 Turbo S would outdo the 997 TS on the Ring by 6 seconds doesn’t surprise me because (i) the 991 has 30 more HP which plays more of a role at higher speeds, and (ii) the ‘turning’ rear wheels fight against the all-time turbo nemesis of understeer when entering tight corners, linked to oversteer if one jerks the wheel to correct for the understeer. IMHO that is the one, single most important difference between the 991 and 997 TS.
It’s all moot, of course. Hopefully a side-by-side sprint will be arranged by some testing group. Other insights/speculation much appreciated.
Unless ‘ringers’ were used in testing the 997 TTS, the times recorded where phenomenal; 2.6 seconds by Road & Track, 2.7 by Car & Driver, 2.8 by Motor Trend. These times were considerably below official Porsche times of around 3.1 seconds. That Porsche has announced the 991 Turbo S will do 0-60 in 2.9 seconds doesn’t necessarily mean actual tests will yield a 2.5 second sprint as some have suggested. IOW, 2.9 seconds could be closer to what the 991 Turbo S can really accomplish IF performance reporting is now closer to actual figures than was the case for the 997 Turbo S.
The 997 Turbo S has exactly the same torque configuration as the 991 Turbo S – 516 ft/lbs of torque. And it weighs a tad less at 1585 Kg vs 1605 for the 991 TTS. Since it’s torque and weight that make for fast 0-60 times, the 997 Turbo S could be expected to perform close to the 991 TTS. The only important intervening variable I can think of that could favor the 991’s is slightly faster PDK shifting times. It’s also possible that unsprung weight could be less for the 991 as represented by the 991’s wheels and tire weight. This would reduce rolling weight to the 991’s advantage.
That the 991 Turbo S would outdo the 997 TS on the Ring by 6 seconds doesn’t surprise me because (i) the 991 has 30 more HP which plays more of a role at higher speeds, and (ii) the ‘turning’ rear wheels fight against the all-time turbo nemesis of understeer when entering tight corners, linked to oversteer if one jerks the wheel to correct for the understeer. IMHO that is the one, single most important difference between the 991 and 997 TS.
It’s all moot, of course. Hopefully a side-by-side sprint will be arranged by some testing group. Other insights/speculation much appreciated.
11-29-2014, 04:03 PM
#4
Yes, 991TT and TTS have rear wheel steering.
result, as stated above: The lap time for the Nürburgring Nordschleife is reduced by approx. 3 s for the new 911 Turbo models thanks to the rear-axle steering. A significantly higher average speed can also be achieved in the obstacle avoidance test (110 m) and slalom test (36 m) with rear axle steering.
They says: The rear axle steering is standard on the new 911 Turbo models. The system comprises two electromechanical actuators, which are installed on left and right of the rear axle instead of the conventional toe control arms. Using these actuators, the system steers the rear axle of the new 911 Turbo models either in the opposite or same direction as the steering angle at the front axle with an interval of +3 degrees to -1.5 degrees, depending on speed.
The steering angle at the rear axle thus depends above all on the steering angle at the steering wheel, the driving situation and the driving speed.
And they say: Up to a speed of approx. 50 km/h (30 mph), the system steers the rear wheel in the opposite direction to the steering direction of the front wheels (opposite steering).
In terms of geometry, this results in a virtual shortening of the wheelbase by approx. 250 mm and ensures both greater agility and day-to-day usability. This facilitates manoeuvring and parking and the turning circle is reduced by over 0.5 m.
At speeds of over approx. 80 km/h (50 mph), the system steers the rear wheels parallel to the front wheels (same direction). In terms of geometry, this results in virtual lengthening of the wheelbase by approx. 500 mm and increases driving stability, particularly at high speeds. As a result, fast lane changes on motorways, for example, are even smoother and safer. At speeds of between 50 and 80 km/h (30 and 50 mph), the system continuously switches between steering in the same and opposite direction, depending on the driving situation.
result, as stated above: The lap time for the Nürburgring Nordschleife is reduced by approx. 3 s for the new 911 Turbo models thanks to the rear-axle steering. A significantly higher average speed can also be achieved in the obstacle avoidance test (110 m) and slalom test (36 m) with rear axle steering.
They says: The rear axle steering is standard on the new 911 Turbo models. The system comprises two electromechanical actuators, which are installed on left and right of the rear axle instead of the conventional toe control arms. Using these actuators, the system steers the rear axle of the new 911 Turbo models either in the opposite or same direction as the steering angle at the front axle with an interval of +3 degrees to -1.5 degrees, depending on speed.
The steering angle at the rear axle thus depends above all on the steering angle at the steering wheel, the driving situation and the driving speed.
And they say: Up to a speed of approx. 50 km/h (30 mph), the system steers the rear wheel in the opposite direction to the steering direction of the front wheels (opposite steering).
In terms of geometry, this results in a virtual shortening of the wheelbase by approx. 250 mm and ensures both greater agility and day-to-day usability. This facilitates manoeuvring and parking and the turning circle is reduced by over 0.5 m.
At speeds of over approx. 80 km/h (50 mph), the system steers the rear wheels parallel to the front wheels (same direction). In terms of geometry, this results in virtual lengthening of the wheelbase by approx. 500 mm and increases driving stability, particularly at high speeds. As a result, fast lane changes on motorways, for example, are even smoother and safer. At speeds of between 50 and 80 km/h (30 and 50 mph), the system continuously switches between steering in the same and opposite direction, depending on the driving situation.
