Track performance - AWD vs RWD
08-12-2018, 04:27 PM
#16
RL Community Team
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It's the hybrid system that makes it AWD. Don't forget that the base engine in the 918 is a NA 4.6L making only 600hp. The reason the GT2RS is faster around the 'Ring is because the hybrid system runs out of battery juice in the 918 over the course of the lap resulting in the car only being powered by the base engine. Swap that engine with the current GT2RS monster of an engine with a massive torque curve and hp, and the story changes quite a bit.
In high HP cars, I'd say more often than not, the AWD car will be faster even given the weight penalty because it can put more power down everywhere. However, faster does not equal more fun to drive.
In high HP cars, I'd say more often than not, the AWD car will be faster even given the weight penalty because it can put more power down everywhere. However, faster does not equal more fun to drive.
But as as to high HP cars benefiting from AWD, while I tend to agree, McLaren seems to do ok with the 720S and the Senna.
08-12-2018, 04:39 PM
#17
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Also, for track use (and on race cars) don't forget that lighter cars handle better, there is a slight penalty in speed on straights because of higher AWD friction losses.
... should also mention that my comments are directed at the scope of the original post, which did not include 918s or 919s or other hybrids.
Last edited by PCA1983; 08-12-2018 at 05:07 PM.
08-12-2018, 04:51 PM
#18
The reason the GT2RS is faster around the 'Ring is because the hybrid system runs out of battery juice in the 918 over the course of the lap resulting in the car only being powered by the base engine. Swap that engine with the current GT2RS monster of an engine with a massive torque curve and hp, and the story changes quite a bit.
The key to the GT2’s ‘ring time isn’t power or rear wheel drive, it’s focus and tires. The 918’s tires were developed over 4 years ago, and they were tuned in part for low rolling resistance to help the car achieve 3 liters per 100 km on the European cycle. The GT2RS’s consumption in over 3x higher because economy is no part of its mission. Speed around a track is, and hence drag, rolling resistance and usability are all secondary. Put the GT2’s Cup 2 R tires on the 918 and there’s zero question it could retake the record... but what would be the point?
Technically
08-12-2018, 07:46 PM
#21
AWD is just a tool to help put down the power rapidly just the way a limited slip / smart (PTV/PSM) rear differential is. The current GT cars have an rear NA engine, smart diff, tall gears, revs high, and really wide tires that allow it to smoothly put the power down, so AWD may not be necessary. I'm sure AWD would make it put down the power even better (see plenty of vids drivers losing traction), but apparently Porsche doesn't think its needed (or worth adding). Who knows maybe its not compatible with the engine, there isn't enough room, or its just a marketing decision. Maybe Porsche knows that GT3s end up as fun weekend toys, track cars, or garage queens so AWD doesn't suit the design (similar to how they decided that giving Targa sport PASM doesn't fit its character).
The Turbo S on the other hand output some serious rapid torque and they only offer it with AWD. Pretty sure they had to give it AWD as a tool that so it can use its power.
The 991.2 has a lot of torque, but its still linear. You don't *need* AWD to put the power down, but it can help in real world conditions (rain, poor pavement, worn tires, slick lane markers, etc). In the base, S, and GTS lineup, Porsche is marketing AWD as a 'better' version of the car because its faster, more expensive, wider rear, LED strip, etc.
Traditionally AWD made a car slightly slower, but now with the advancements in the latest generation AWD systems (and the crazy high torque cars can do), AWD cars are even quicker than RWD. Porsche is shifting to mostly turbo engines, so my guess its going to make its way into the next gen GT cars. I wouldn't be surprised if next GT3 is turbo as I'm pretty sure the next GT4 will be. GT3 will eventually start generating rapid torque similar to a turbo s and probably require AWD just a turbo s.
I'm not a mechanic, but AWD in most other cars can't handle being engaged 100% otherwise it over heats. Possible that's what happens when they tested it in harsh track conditions so Porsche determine it shouldn't be offered in GT cars marketed to be 'street cars that can be used on the track.' If I floor C4S, its doing 50% torque up front...hard to imagine the system can maintain that for too long.
4S PDK is 3,329 and 2S PDK 3,219, so its over 100 LB more heavy, but this weight is mostly up front and low center of gravity so I don't think its that significant. GT3 PDK is 3,153 for reference. The weight difference isn't important because the AWD cars accelerate faster, meaning weight isn't a limiting factor... traction is.
I personally wouldn't want to take a 150-200k high powered car on a track. If I did, I'd want AWD to have my back because I'm no pro driver...I wouldn't feel confident in pushing the car hard without it due to 'snap oversteer + spin' I experienced plenty in my 'lower powered' 981 bosxter. If all wheels are on perfect surfaces all the time, AWD doesn't do much, but that is not reality in normal driving (track or street). Aside from increased complexity, I can't think of any downsides NOT having AWD for any kind of driving...the single argument I read is 'its not as fun,' but that doesn't apply to me because I don't find anything fun about losing traction.
So in summary, AWD is great. GT cars don't offer it for other reasons. All other 911 models have for years and I'm sure plenty take them to tracks with great success.
The Turbo S on the other hand output some serious rapid torque and they only offer it with AWD. Pretty sure they had to give it AWD as a tool that so it can use its power.
The 991.2 has a lot of torque, but its still linear. You don't *need* AWD to put the power down, but it can help in real world conditions (rain, poor pavement, worn tires, slick lane markers, etc). In the base, S, and GTS lineup, Porsche is marketing AWD as a 'better' version of the car because its faster, more expensive, wider rear, LED strip, etc.
Traditionally AWD made a car slightly slower, but now with the advancements in the latest generation AWD systems (and the crazy high torque cars can do), AWD cars are even quicker than RWD. Porsche is shifting to mostly turbo engines, so my guess its going to make its way into the next gen GT cars. I wouldn't be surprised if next GT3 is turbo as I'm pretty sure the next GT4 will be. GT3 will eventually start generating rapid torque similar to a turbo s and probably require AWD just a turbo s.
I'm not a mechanic, but AWD in most other cars can't handle being engaged 100% otherwise it over heats. Possible that's what happens when they tested it in harsh track conditions so Porsche determine it shouldn't be offered in GT cars marketed to be 'street cars that can be used on the track.' If I floor C4S, its doing 50% torque up front...hard to imagine the system can maintain that for too long.
4S PDK is 3,329 and 2S PDK 3,219, so its over 100 LB more heavy, but this weight is mostly up front and low center of gravity so I don't think its that significant. GT3 PDK is 3,153 for reference. The weight difference isn't important because the AWD cars accelerate faster, meaning weight isn't a limiting factor... traction is.
I personally wouldn't want to take a 150-200k high powered car on a track. If I did, I'd want AWD to have my back because I'm no pro driver...I wouldn't feel confident in pushing the car hard without it due to 'snap oversteer + spin' I experienced plenty in my 'lower powered' 981 bosxter. If all wheels are on perfect surfaces all the time, AWD doesn't do much, but that is not reality in normal driving (track or street). Aside from increased complexity, I can't think of any downsides NOT having AWD for any kind of driving...the single argument I read is 'its not as fun,' but that doesn't apply to me because I don't find anything fun about losing traction.
So in summary, AWD is great. GT cars don't offer it for other reasons. All other 911 models have for years and I'm sure plenty take them to tracks with great success.
08-12-2018, 11:48 PM
#22
Rennlist Member
This may be a noob question.
Thinking about this recently...all the Porsche track oriented cars (GT3, GT3 RS, GT2 RS) are RWD but most people talk about merits of AWD in cornering and putting down power especially with higher torque engines. So why does Porsche make their track oriented cars only in RWD? Please educate me. Thanks!
Thinking about this recently...all the Porsche track oriented cars (GT3, GT3 RS, GT2 RS) are RWD but most people talk about merits of AWD in cornering and putting down power especially with higher torque engines. So why does Porsche make their track oriented cars only in RWD? Please educate me. Thanks!
I track a 4S pretty regularly. I have a lot of fun w it and it's pretty fast in typical track day field, but there are definitely issues w it:
- Having axles and diffs upfront complicates front suspension geometry and inevitable mods
- Front tires both steering and trying to put down power, the feedback you receive from the steering wheel/car a bit less pure, less informative
- Heavier
- Understeers more, unless you sort the setup proper
- More loss to wheel hp
- It gets you really used to going back to throttle in any kind of trouble. The kind of driving (plenty of throttle through corners and at corner exit) I do w this car, especially on corner exits, I'd probably spin two out of three times in a GT3.