Reply to: Cars

[Old Hack]

Get a car with over 300 lb-ft torque, and try launching it from standstill. The 4WD will take it without flinching, the rwd might slide it's rear end a bit depending on the state of tyres, and the road conditions. The FWD will then start showing signs of torque steer. You will feel like you have to grip the steering wheel tightly, otherwise the front wheels will make it wobble. It's true that many modern FWD cars come with factory fitted LSD, but that helps more in cornering and keeping traction when you come out of tight bends. Essentially, LSD allows 2 wheels to spin at different speeds, which helps on twisty roads.

Normally, a powered wheel will take the path of least resistance, so if you have one wheel parked in wet mud, or grass, it will light up, whilst the other wheel doesn't move an inch, as all power is being given to the spinning wheel. An LSD actually provides the power to the wheel with the most grip. Then you have 4WD which can have diff locks, which essentially ensure both wheels turn at the same speed; great for off roading, rubbish for on the road, as the axles suffer what is called wind up.

I don't know about VW but most Audis are full time 4WD with a Torsen centre diff.

Correct; they have a pukka 4WD system whilst VW use an electronic part time 4WD.

I thought the TT was only part-time 4WD?

They made the TT is lower power FWD, but otherwise, they have full time asychrobnous 4WD

Yes apparently the TT & A3 are, but most of them are full time 4WD with a torsen diff.

Not the TT, although the very latest one doesn't use a torsen diff, it uses a new carlos fandango one, apart from the Q7, which still has the torsen. It also has electronic diff locks.

The 4Motion system is slightly different, in that the ones that have a longitudinal engine (N-S), have a torsen diff, and transverse engines (E-W) have a haldex clutch differential which unlike the torsen, can be electronically controlled, so that you only get 4WD when you really need it. It's actually a brilliant bit of kit, saves gas, saves tyres, and emissions.

[Mich the Tester]

What do people think of volvos?

I think of them when I want to get rid of an inconvenient erection.

[Dark Black]

Yes apparently the TT & A3 are, but most of them are full time 4WD with a torsen diff.

Fair enough... i always thought part-time 4WD (controlled by the car and not the driver) was a stupid idea anyway.

[doodab]

I thought the TT was only part-time 4WD?

Yes apparently the TT & A3 are, but most of them are full time 4WD with a torsen diff.

[gingerjedi]

I see dodgy is busy making money.

[Dark Black]

I don't know about VW but most Audis are full time 4WD with a Torsen centre diff.

I thought the TT was only part-time 4WD?

[DodgyAgent]

[doodab]

Yeah. Some cars have permanent 4WD AFAIK. Case in point, a Subbie Impreza. The MPS on the other hand is a software controlled 4WD, just like the Haldex system used by VAG group, if I am not wrong.

I don't know about VW but most Audis are full time 4WD with a Torsen centre diff.

[tranceporter]

Depends on the 4WD. Mine defaults to 50 50 torque split front and rear.

Yeah. Some cars have permanent 4WD AFAIK. Case in point, a Subbie Impreza. The MPS on the other hand is a software controlled 4WD, just like the Haldex system used by VAG group, if I am not wrong.

[tranceporter]

Errr.. no, a normal diff does that, without which you'd tend to plough straight on in tight corners, especially in the wet. An LSD actually works to prevent some of the wheel spin in order to allow more power to be transmitted through the tyres. How much depends on how tight the slipper is set up.

The drift boys tend to use a welded diff on their (RWD) cars for maximum drift fun but (as said) this can cause terminal understeer in the wet.

Whereas, the rally boys () will use a proper LSD (aka slipper) to allow them to get the maximum power down on varying road surfaces and conditions.

The original type of LSD uses clutch plates internal to the diff to determine the amount of slip and is still the preferred type for most RWD applications. Later types such as ATB (automatic torque biasing) and Gripper diffs can provide better characteristics for FWD cars, although the choice is often down to your preferred driving style.

HTH

Noted! I always thought LSD allowed different wheel spin speeds, so the inside wheel could spin faster than the outside one, thus allowing one to get traction and corner at faster speed. Interesting info! Cheers!

[Dark Black]

Get a car with over 300 lb-ft torque, and try launching it from standstill. The 4WD will take it without flinching, the rwd might slide it's rear end a bit depending on the state of tyres, and the road conditions. The FWD will then start showing signs of torque steer. You will feel like you have to grip the steering wheel tightly, otherwise the front wheels will make it wobble. It's true that many modern FWD cars come with factory fitted LSD, but that helps more in cornering and keeping traction when you come out of tight bends. Essentially, LSD allows 2 wheels to spin at different speeds, which helps on twisty roads.

Errr.. no, a normal diff does that, without which you'd tend to plough straight on in tight corners, especially in the wet. An LSD actually works to prevent some of the wheel spin in order to allow more power to be transmitted through the tyres. How much depends on how tight the slipper is set up.

The drift boys tend to use a welded diff on their (RWD) cars for maximum drift fun but (as said) this can cause terminal understeer in the wet.

Whereas, the rally boys () will use a proper LSD (aka slipper) to allow them to get the maximum power down on varying road surfaces and conditions.

The original type of LSD uses clutch plates internal to the diff to determine the amount of slip and is still the preferred type for most RWD applications. Later types such as ATB (automatic torque biasing) and Gripper diffs can provide better characteristics for FWD cars, although the choice is often down to your preferred driving style.

HTH

[doodab]

What do people think of volvos?

[doodab]

99% of the time, a 4WD is not in full 4WD.

Depends on the 4WD. Mine defaults to 50 50 torque split front and rear.

[gingerjedi]

Lol. What he means to say is that 4WD can work as FWD on motorways, but turn in to 4WD when the road conditions worsen, or you floor it, or launch it from standstill, by re-routing the torque in a 40-60 or 50-50 split between front and rear wheels. But I am sure you already know it

I do appreciate what it can do (I've had an Impreza wrx and a Type-r ep9) but I guess my own priorities have changed over the years, I'm more interested in mpg and how much gear I can get in the boot these days, I'll probably end up with a Mondeo estate.

[tranceporter]

So you carry around a bunch of heavy gears and shafts for nothing most of the time.

Lol. What he means to say is that 4WD can work as FWD on motorways, but turn in to 4WD when the road conditions worsen, or you floor it, or launch it from standstill, by re-routing the torque in a 40-60 or 50-50 split between front and rear wheels. But I am sure you already know it