GS AWD System Superior to the Germans?
04-17-14, 11:49 PM
#1
Pole Position
Thread Starter
GS AWD System Superior to the Germans?
Is the Lexus/GS AWD system superior in snow compared to the German sedans aka BMW/MB/Audi? This 2 part analysis seems to suggest that (if you read between the lines of the article) :
LUXURY SEDAN AWD SYSTEM REVIEW :
Part 1 : http://youwheel.com/2014/04/04/luxur...review-part-1/
Part 2 : http://youwheel.com/2014/04/04/luxur...review-part-2/
After reading this article, these are my preliminary thoughts :
1) Lexus and Audi systems provide the most grip in snow since they can divert full power to the non-slip wheels.
2) The Audi system's advantage over the Lexus (doesn't require a bulky separate transfer case for the center differential unlike the Lexus) is offset by the fact that this requires the engine to be 100% in front of the front axle ie a Front Wheel Drive layout. Hence the FWD-based Audi tends to be nose heavy and this spoils handing.
3) Those GS350 AWD owners who complain that the Lexus AWD transfer case intrudes on the driver's right leg in the footwell may take some measure of comfort in that the small inconvenience is an acceptable trade-off for increased security and mobility in snow. Since that "intrusive" transfer case allows for a much more robust AWD system in their car compared to BMW/MB.
4) The AWD system in the GS seems to be criminally under-rated since Lexus hardly bothered to advertise the benefits and abilities of its AWD.
LUXURY SEDAN AWD SYSTEM REVIEW :
Part 1 : http://youwheel.com/2014/04/04/luxur...review-part-1/
Part 2 : http://youwheel.com/2014/04/04/luxur...review-part-2/
BMW xDrive:
it does not have a “real” center differential at all. .... it uses an electronic controlled multi-plate clutch coupling system to act like a center differential.
...when the car is not going a straight line, the clutch plates are rotating at different speed, which generates friction and abrasion, (hence) this system cannot be partially engaged for long time (which will create excessive wear to the clutch plates)...
.. This means mostly the BMW xDrive system works in an on-demand basis. Once the computer sense you are cornering or not going straight, it will disconnect the clutch and sends all power to the rear wheel.
it does not have a “real” center differential at all. .... it uses an electronic controlled multi-plate clutch coupling system to act like a center differential.
...when the car is not going a straight line, the clutch plates are rotating at different speed, which generates friction and abrasion, (hence) this system cannot be partially engaged for long time (which will create excessive wear to the clutch plates)...
.. This means mostly the BMW xDrive system works in an on-demand basis. Once the computer sense you are cornering or not going straight, it will disconnect the clutch and sends all power to the rear wheel.
Mercedes-Benz 4Matic:
...But perhaps unknown to many people, the limited slip device MB used on their car based 4Matic system, can only handle an upper limit of 50Nm (36.9 lb-ft) torque only. This is really a small amount of strength, so it means the 4Matic AWD system is mainly to get you on the road when your parking spot is blocked by a pile of snow. If you want spirited AWD driving, then the car’s ABS or stability control system may help you more than the LSD....
The CLA class AWD is different. It uses the Haldex system, which belongs to the on-demand type. Under normal driving conditions it acts like a FWD; only if the front wheel is slipping, then the multi-plate clutch will be engaged and use the coupling effect to transmission power to the rear wheels. Similar to BMW’s xDrive, because of friction and abrasion, extensive long time transmitting power to rear wheels will cause excessive wear to the Haldex system.
...But perhaps unknown to many people, the limited slip device MB used on their car based 4Matic system, can only handle an upper limit of 50Nm (36.9 lb-ft) torque only. This is really a small amount of strength, so it means the 4Matic AWD system is mainly to get you on the road when your parking spot is blocked by a pile of snow. If you want spirited AWD driving, then the car’s ABS or stability control system may help you more than the LSD....
The CLA class AWD is different. It uses the Haldex system, which belongs to the on-demand type. Under normal driving conditions it acts like a FWD; only if the front wheel is slipping, then the multi-plate clutch will be engaged and use the coupling effect to transmission power to the rear wheels. Similar to BMW’s xDrive, because of friction and abrasion, extensive long time transmitting power to rear wheels will cause excessive wear to the Haldex system.
Lexus:
the IS250/350 AWD and GS350 AWD are using a planetary-gear center differential, plus a wet-type multi-disc clutch control to act as slip control. This is a very advanced and complex design.
Because the multi-disc clutch can be 100% locked, it means Lexus’ AWD can handle the case that even front or rear wheels completely lose traction, than the rest side of the two wheels still have full power.
The disadvantage of this design is it is complicated and the parts take space. Actually the IS/GS AWD are similar to an off road SUV – they have a separate transfer case to enclose the differential and the limit slip clutch unit.
Please note that here the clutch control mentioned in the Lexus section is act as limited slip function, it should not be confused with the BMW xDrive’s coupling purpose. They are two totally different things.
Although with such advanced and sophisticated design, Lexus seldom advertise their AWD system, or claim this is their selling point (I cannot even find an cutaway illustration of the Lexus AWD system). Perhaps Lexus vehicles are so well build that the Lexus management decided it is not necessary to add an extra selling point?
the IS250/350 AWD and GS350 AWD are using a planetary-gear center differential, plus a wet-type multi-disc clutch control to act as slip control. This is a very advanced and complex design.
Because the multi-disc clutch can be 100% locked, it means Lexus’ AWD can handle the case that even front or rear wheels completely lose traction, than the rest side of the two wheels still have full power.
The disadvantage of this design is it is complicated and the parts take space. Actually the IS/GS AWD are similar to an off road SUV – they have a separate transfer case to enclose the differential and the limit slip clutch unit.
Please note that here the clutch control mentioned in the Lexus section is act as limited slip function, it should not be confused with the BMW xDrive’s coupling purpose. They are two totally different things.
Although with such advanced and sophisticated design, Lexus seldom advertise their AWD system, or claim this is their selling point (I cannot even find an cutaway illustration of the Lexus AWD system). Perhaps Lexus vehicles are so well build that the Lexus management decided it is not necessary to add an extra selling point?
Audi:
The A3 is using the Haldex system as mentioned in Mercedes-Benz CLA class.
Before 2010, the Audi Quattro system is using a Torsen center differential. Some may not know, Torsen technology is owned by JTEKT, which is a subsidiary of the Toyota Group...
Maybe Audi consider the development cost or licensing cost from Toyota is unnecessary, or Audi consider their own invention may be better. Starting from 2010 Audi RS5, they started to use Crown Gear Differential as the center differential, which is developed within the VW group. The crown gear differential has similar functionalities as Torsen. To be simple, you can treat Torsen and crown gear differential are substitution of each other.
One thing should be noted is that, Audi managed to integrate the center differential inside the transmission assembly, without using a separate transfer case like the Lexus. But the tradeoff is it must place the whole engine 100% in front of the front axle, which is exactly a front wheel drive layout. Such layout will cause heavy car nose, not an optimal weight distribution. This is also the reason why some of the Audi cars has front wheel drive version (because it is actually a FWD layout!). To your surprise, in European market the flagship sedan A8 even has a FWD trim available.
The A3 is using the Haldex system as mentioned in Mercedes-Benz CLA class.
Before 2010, the Audi Quattro system is using a Torsen center differential. Some may not know, Torsen technology is owned by JTEKT, which is a subsidiary of the Toyota Group...
Maybe Audi consider the development cost or licensing cost from Toyota is unnecessary, or Audi consider their own invention may be better. Starting from 2010 Audi RS5, they started to use Crown Gear Differential as the center differential, which is developed within the VW group. The crown gear differential has similar functionalities as Torsen. To be simple, you can treat Torsen and crown gear differential are substitution of each other.
One thing should be noted is that, Audi managed to integrate the center differential inside the transmission assembly, without using a separate transfer case like the Lexus. But the tradeoff is it must place the whole engine 100% in front of the front axle, which is exactly a front wheel drive layout. Such layout will cause heavy car nose, not an optimal weight distribution. This is also the reason why some of the Audi cars has front wheel drive version (because it is actually a FWD layout!). To your surprise, in European market the flagship sedan A8 even has a FWD trim available.
1) Lexus and Audi systems provide the most grip in snow since they can divert full power to the non-slip wheels.
2) The Audi system's advantage over the Lexus (doesn't require a bulky separate transfer case for the center differential unlike the Lexus) is offset by the fact that this requires the engine to be 100% in front of the front axle ie a Front Wheel Drive layout. Hence the FWD-based Audi tends to be nose heavy and this spoils handing.
3) Those GS350 AWD owners who complain that the Lexus AWD transfer case intrudes on the driver's right leg in the footwell may take some measure of comfort in that the small inconvenience is an acceptable trade-off for increased security and mobility in snow. Since that "intrusive" transfer case allows for a much more robust AWD system in their car compared to BMW/MB.
4) The AWD system in the GS seems to be criminally under-rated since Lexus hardly bothered to advertise the benefits and abilities of its AWD.
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04-18-14, 04:26 AM
#2
Instructor
Wow, good info! My cousin lives in Michigan all the way up in the upper peninsula where snow is really bad in the winter. He has owned several Audis Quattros and sometimes get stuck. But ever since he bought a Lexus LS Awd has never been stuck. Both his Audis and lexus had snow tires. That says alot about Toyota Awd.
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RichardB23 (09-20-19)
04-18-14, 06:32 AM
#3
Pole Position
Excellent info, and it matches what I learned a little earlier this year by digging through some of the AWD system documentation published on the TechInfo site. I agree Lexus really under-sells the AWD system and its capabilities. The marketing material seems to only say the GS system is a 30/70 torque split and can go to 50/50 in low traction situations. When really it can fully lock the center differential, which is very different (and much better) than a 50/50 torque split.
In terms of the hardware, the GS AWD system seems to be very similar to modern Subaru products, and everyone raves about their AWD capabilities. Being all computer controlled these days, we can't tell if the software that controls the system is as good.
In terms of the hardware, the GS AWD system seems to be very similar to modern Subaru products, and everyone raves about their AWD capabilities. Being all computer controlled these days, we can't tell if the software that controls the system is as good.
04-21-14, 07:13 AM
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well audi uses two different awd systems.
haldex and torsen
Subaru uses different types of awd depending on the model, the best system is in the WRX STI and then goes down in features from there based on price of the vehicle.
the H6 Legacy, Outback, and Tribeca bearing the 3.6R designation are still use a version of Symmetrical AWD that uses Variable Torque Distribution (VTD) of 45/55 rear bias.
the cvt's use a variation of the VTD with a 60/40 front bias
wrx sti uses 2 differentials. One is electronically controlled and grants the Subaru's computer fine control over the front-to-rear torque split. The other is a mechanical unit that is capable of reacting more quickly to stimuli than its electronic counterpart -- the driver can bias the system toward either of the center differentials via the electronic Driver Controlled Center Differential (DCCD) controls.
I use to own a 2010 3.6R legacy, and locking the center diff was fun in snow and required during uphill starts on icy/slippery stop light intersections.
haldex and torsen
Subaru uses different types of awd depending on the model, the best system is in the WRX STI and then goes down in features from there based on price of the vehicle.
the H6 Legacy, Outback, and Tribeca bearing the 3.6R designation are still use a version of Symmetrical AWD that uses Variable Torque Distribution (VTD) of 45/55 rear bias.
the cvt's use a variation of the VTD with a 60/40 front bias
wrx sti uses 2 differentials. One is electronically controlled and grants the Subaru's computer fine control over the front-to-rear torque split. The other is a mechanical unit that is capable of reacting more quickly to stimuli than its electronic counterpart -- the driver can bias the system toward either of the center differentials via the electronic Driver Controlled Center Differential (DCCD) controls.
I use to own a 2010 3.6R legacy, and locking the center diff was fun in snow and required during uphill starts on icy/slippery stop light intersections.
04-23-14, 08:39 AM
#6
Lexus Fanatic
I don't know anybody with a BMW X Drive sedan that I've had a conversation with about how good it is in the snow. I know that one of my salespeople has a C300 4MATIC that he raves about how good it is in the snow, and as I said this winter my GS is awesome in the snow. In les than say 5 inches I actually think my GS drives more solidly than my Jeep...above 5 inches obviously its a matter of ground clearance.
I do think Lexus needs to advertise their AWD system more, perhaps give it a "name" like "XDrive" or "4Matic" to make it easier to market.
I do think Lexus needs to advertise their AWD system more, perhaps give it a "name" like "XDrive" or "4Matic" to make it easier to market.
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04-25-14, 10:08 PM
#8
How good any AWD system is in snow is a combination of how it's set up by the manufacturer and the tires on the car. Any comparison between driving characteristics on two different cars with different tires is a broad generalization.
The AWD system on the Evo 9 & 10 as well as the GTR is pretty advanced and optimized for handling and traction but without proper snow tires even the best engineered AWD system is useless in snow. A RWD GS350 with winter tires will have more traction in snow in most circumstances than an AWD GS with all season tires.
The AWD system on the Evo 9 & 10 as well as the GTR is pretty advanced and optimized for handling and traction but without proper snow tires even the best engineered AWD system is useless in snow. A RWD GS350 with winter tires will have more traction in snow in most circumstances than an AWD GS with all season tires.
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04-26-14, 05:32 AM
#11
Instructor
Wow I didnt know Acura SH Awd is that good. Maby its better because its really a front wheel drive based with awd capability? Id still get a rwd based vehicle with awd hardware.
04-26-14, 07:15 AM
#12
Lexus Fanatic
The RX has a pretty different system than the RWD Lexus vehicles too I believe.
04-26-14, 09:13 AM
#13
Lexus Champion
Videos like this make me so skeptical. If there was such a black and white difference wouldn't it drive all other carmakers to implement a similar AWD system? Nevertheless, it was cool seeing the Acura climb the grade with ease. Also confirms that I'll never live anywhere where it snows. 
04-26-14, 09:19 AM
#14
The RX iAWD if you're on the freeway say can deliever 100/0 on a straight but when a turn or poor weather comes into play it sends power to the rear wheels as needed. The RX350 has a locking differential whereas the RX450h does not since it's AWD (rear wheels) are powered by electric motors.
04-26-14, 09:49 AM
#15
Pole Position
Thread Starter
It's minus 32 at the Mecaglisse test track, 90 minutes from Montreal. Lexus Canada invited 24 Drivers to put the 306-hp GS 350 AWD F SPORT through some extreme winter driving challenges.
Equipped with snow tires, they conquer the skid pad, cornering, slalom, accident avoidance, and more. Watch their reactions as they put GS’s rear-biased all-wheel-drive control with sport performance to the test.
Equipped with snow tires, they conquer the skid pad, cornering, slalom, accident avoidance, and more. Watch their reactions as they put GS’s rear-biased all-wheel-drive control with sport performance to the test.
I know that this was a promotional video but still impressive nonetheless.
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