Awd, X, 4matic, 4motion.... - Page 2

Snake Vargas · 09-30-2005, 01:34 PM

Not sure what Lambo use, but VAG (btw, that's Volkswagen Auto Group) also use some Torsen systems, probably most notably in the RS4. I'm not sure whether or which ones, but some 4Motion badged vehicles may also be Torsen - ie. 4Motion doesn't necessarily mean Haldex.

Just_me · 09-30-2005, 01:49 PM

Quote:

Originally Posted by Snake Vargas

Not sure what Lambo use, but VAG (btw, that's Volkswagen Auto Group) also use some Torsen systems, probably most notably in the RS4. I'm not sure whether or which ones, but some 4Motion badged vehicles may also be Torsen - ie. 4Motion doesn't necessarily mean Haldex.

Here is the link again.

- ONLY REGISTERED AND ACTIVATED USERS CAN SEE ALL LINKS - CLICK HERE TO REGISTER

Alx · 09-30-2005, 01:53 PM

OOOOOOOOooooooooooh...... Bugatti Veyron is on the list.

Didn't think they made their AWD system too.

Lots of performanc cars on the list....

Great find Just_Me.

Maserati · 09-30-2005, 01:59 PM

SV: thanx man .. so actually Audi's quattro is not supplied by a single vendor ... but it depends on the model ...

this is interesting ..

Alx · 09-30-2005, 02:23 PM

That list is pretty impressive, from super cars to minivans.

Must be one of the better AWD systems i suposse.

martinbo · 10-01-2005, 02:59 PM

That Haldex coupling is a brilliant unit no doubt - it has to be because it has its work cut out for it! The reason I say this is because the typical Haldex system drives only two wheels in normal driving conditions. However, as soon as the system detects wheel-spin it needs to direct a great portion of the total engine output to the rear or opposite axle. So guys, though the Haldex coupling is state-of-the-art, this does not mean that this is the most complete AWD package.

I could go on forever about grip and four-wheel drive and all but I'd just end up boring you to tears. So, here's martinbo's concise and abridged appreciation for what is all-wheel drive in road cars:*1

There are 3 main types of AWD on any given vehicle and their fundamental behavior is governed by the single most important component of any AWD system: the centre differential.

1. Semi-permanent, reactive AWD
You'll notice the list of cars in that Haldex page, most of them are FWD cars and the Haldex LSC acts as a limited slip centre differential that reacts to front wheel slippage (very quickly mind you) to send torque aft to the rear axle. Once the slipping stops, so does the all-wheel drive. So, the ultimate benefits of AWD *2 aren't attained and the car behaves predominantly in much the same way as its FWD counterpart might do i.e. the vehicle has a natural tendency to understeer quite dramatically when pushed close to the limits of adhesion. Examples are the Audi S3, Golf R32 and Volvo XC70 Cross Country.

2. Permanent, reactive AWD
This is a much better system - especially if the torque split is 50:50 or close to that - as the benefits of AWD are already in place and working for the driver. Because the torque split is so even, the wheel that has the most grip is doing most of the work and so, even in the event of wheel spin the limited slip device such as a viscous coupling has much less work to do in terms of apportioning a percentage of torque to the axle with most grip. It's quite simple: take a powerful car like an R32 with 320 Nm and divide that between the two front wheels = 160 Nm per tyre. Take a US spec STI with 400 Nm divide by all four wheels = 100 Nm per tyre. So the limited slip diff has a more even spread of torque and thus has less to do when moving it from front to rear. The LSD reacts to losses in grip at a given axle. Subaru is a prime example of this system as is Porsche and to a lesser extent, BMW's x-Drive which uses electronic sensors to signal the transfer of torque. Such a vehicle has a natural tendency to understeer when pushed beyond the limits of adhesion.

3. Permanent, proactive AWD
The ultimate AWD systems, the most notable example being Torsen as found in the Audi S4, RS4 and RS6 for example. It takes the above concept of AWD to a different level. The Torsen centre differential is a worm / planetary gear arrangement that is a mechanical work of art. It's name is derived from TORque & SENsing because really that's what it does: senses which axle has the most torque based on the frictional co-efficient or the amount of grip that that axle has. It reacts early on to subtle changes in torque before grip is lost. Hence, my term proactive. This is the ultimate in LSD technology in my opinion.

So there you have it. Please ask more questions but remember that eventually you will reach my level of technical incompetence.

*1 I say road cars simply to eliminate other types of 4x4 systems on off-road utility vehicles like pick-ups and heavy duty off-roaders for the purposes of this discussion

*2 The primary benefit afforded by true all-wheel drive is to halve the amount of power being sent to any one axle. Quite simply, in a good AWD system the power is divided permanently between the front and rear axle up to a perfect 50:50 front to rear ratio. This effectively halves the force of the engine output acting on a wheel reducing the potential for loss of grip.

Maserati · 10-02-2005, 01:57 PM

martinbo: thanx .. well said and explained ..

BMW_Dude · 10-02-2005, 01:58 PM

Martin, I've just noticed you are a mod, I'm sure you'll make a great mod, with your unbaised views and great technical knowledge!

Just_me · 10-02-2005, 02:09 PM

Quote:

Originally Posted by BMW_Dude

Martin, I've just noticed you are a mod, I'm sure you'll make a great mod, with your unbaised views and great technical knowledge!

Probably the reason why HoH is leaving

Maserati · 10-02-2005, 02:11 PM

Quote:

Originally Posted by Just_me

Probably the reason why HoH is leaving

Yes i thought the same ..

09-30-2005, 01:34 PM	#11
Snake Vargas Fanatic Join Date: Sep 2005 Location: Sydney, NSW, Australia Posts: 1,201 Thanks: 0 Thanked 4 Times in 4 Posts	Re: Awd, X, 4matic, 4motion.... Not sure what Lambo use, but VAG (btw, that's Volkswagen Auto Group) also use some Torsen systems, probably most notably in the RS4. I'm not sure whether or which ones, but some 4Motion badged vehicles may also be Torsen - ie. 4Motion doesn't necessarily mean Haldex.

09-30-2005, 01:53 PM	#13
Alx Connoisseur Moderator Emeritus Join Date: Sep 2005 Location: --Poconos, PA.-- 2005 Aston Martin DB9 Posts: 6,012 Thanks: 1,243 Thanked 662 Times in 316 Posts	Re: Awd, X, 4matic, 4motion.... OOOOOOOOooooooooooh...... Bugatti Veyron is on the list. Didn't think they made their AWD system too. Lots of performanc cars on the list.... Great find Just_Me.

09-30-2005, 01:59 PM	#14
Maserati Advocate Join Date: Sep 2005 Location: UAE Posts: 994 Thanks: 245 Thanked 266 Times in 115 Posts	Re: Awd, X, 4matic, 4motion.... SV: thanx man .. so actually Audi's quattro is not supplied by a single vendor ... but it depends on the model ... this is interesting ..

09-30-2005, 02:23 PM	#15
Alx Connoisseur Moderator Emeritus Join Date: Sep 2005 Location: --Poconos, PA.-- 2005 Aston Martin DB9 Posts: 6,012 Thanks: 1,243 Thanked 662 Times in 316 Posts	Re: Awd, X, 4matic, 4motion.... That list is pretty impressive, from super cars to minivans. Must be one of the better AWD systems i suposse.

10-01-2005, 02:59 PM	#16
martinbo Fanatic Moderator Emeritus Join Date: Sep 2005 Location: Johannesburg Posts: 1,701 Thanks: 324 Thanked 531 Times in 269 Posts	Re: Awd, X, 4matic, 4motion.... That Haldex coupling is a brilliant unit no doubt - it has to be because it has its work cut out for it! The reason I say this is because the typical Haldex system drives only two wheels in normal driving conditions. However, as soon as the system detects wheel-spin it needs to direct a great portion of the total engine output to the rear or opposite axle. So guys, though the Haldex coupling is state-of-the-art, this does not mean that this is the most complete AWD package. I could go on forever about grip and four-wheel drive and all but I'd just end up boring you to tears. So, here's martinbo's concise and abridged appreciation for what is all-wheel drive in road cars:1 There are 3 main types of AWD on any given vehicle and their fundamental behavior is governed by the single most important component of any AWD system: the centre differential. 1. Semi-permanent, reactive* AWD You'll notice the list of cars in that Haldex page, most of them are FWD cars and the Haldex LSC acts as a limited slip centre differential that reacts to front wheel slippage (very quickly mind you) to send torque aft to the rear axle. Once the slipping stops, so does the all-wheel drive. So, the ultimate benefits of AWD 2 aren't attained and the car behaves predominantly in much the same way as its FWD counterpart might do i.e. the vehicle has a natural tendency to understeer quite dramatically when pushed close to the limits of adhesion. Examples are the Audi S3, Golf R32 and Volvo XC70 Cross Country. 2. Permanent, reactive* AWD This is a much better system - especially if the torque split is 50:50 or close to that - as the benefits of AWD are already in place and working for the driver. Because the torque split is so even, the wheel that has the most grip is doing most of the work and so, even in the event of wheel spin the limited slip device such as a viscous coupling has much less work to do in terms of apportioning a percentage of torque to the axle with most grip. It's quite simple: take a powerful car like an R32 with 320 Nm and divide that between the two front wheels = 160 Nm per tyre. Take a US spec STI with 400 Nm divide by all four wheels = 100 Nm per tyre. So the limited slip diff has a more even spread of torque and thus has less to do when moving it from front to rear. The LSD reacts to losses in grip at a given axle. Subaru is a prime example of this system as is Porsche and to a lesser extent, BMW's x-Drive which uses electronic sensors to signal the transfer of torque. Such a vehicle has a natural tendency to understeer when pushed beyond the limits of adhesion. 3. Permanent, proactive AWD The ultimate AWD systems, the most notable example being Torsen as found in the Audi S4, RS4 and RS6 for example. It takes the above concept of AWD to a different level. The Torsen centre differential is a worm / planetary gear arrangement that is a mechanical work of art. It's name is derived from TORque & SENsing because really that's what it does: senses which axle has the most torque based on the frictional co-efficient or the amount of grip that that axle has. It reacts early on to subtle changes in torque before grip is lost. Hence, my term proactive. This is the ultimate in LSD technology in my opinion. So there you have it. Please ask more questions but remember that eventually you will reach my level of technical incompetence. 1 I say road cars simply to eliminate other types of 4x4 systems on off-road utility vehicles like pick-ups and heavy duty off-roaders for the purposes of this discussion 2 The primary benefit afforded by true all-wheel drive is to halve the amount of power being sent to any one axle. Quite simply, in a good AWD system the power is divided permanently between the front and rear axle up to a perfect 50:50 front to rear ratio. This effectively halves the force of the engine output acting on a wheel reducing the potential for loss of grip. Last edited by martinbo; 10-01-2005 at 03:05 PM..

10-02-2005, 01:57 PM	#17
Maserati Advocate Join Date: Sep 2005 Location: UAE Posts: 994 Thanks: 245 Thanked 266 Times in 115 Posts	Re: Awd, X, 4matic, 4motion.... martinbo: thanx .. well said and explained ..

10-02-2005, 01:58 PM	#18
BMW_Dude Aficionado Join Date: Sep 2005 Location: England Posts: 4,472 Thanks: 368 Thanked 495 Times in 283 Posts	Re: Awd, X, 4matic, 4motion.... Martin, I've just noticed you are a mod, I'm sure you'll make a great mod, with your unbaised views and great technical knowledge!

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode