[Rayscott]

I just got my 228i and the dealer located it in another state. It was missing a 2nd key and the owners manual. I should have both soon. I own an X3 so most of the controls are similar. I was scrolling through eco, comfort, sport and sport+ and the all wheel drive selection came up. Now I cant get it to come up. I thought the car was in all wheel drive all the time.??

[EuroDude]

Interesting Ray, did you try and post up on the X3 forum?

[Cyberdemon]

What do you mean by "all wheel drive" selection?

Are you simply referring to the graphic they show that looks something like this?



If so that does not mean all wheel drive. That's just how they visually indicate that the drivetrain (which means throttle response and transmission logic) are in "Sport" mode now. I can see the fact that it highlights all 4 wheels might make you think it did something else.

[Zooks527]

Originally Posted by Rayscott

I just got my 228i and the dealer located it in another state. It was missing a 2nd key and the owners manual. I should have both soon. I own an X3 so most of the controls are similar. I was scrolling through eco, comfort, sport and sport+ and the all wheel drive selection came up. Now I cant get it to come up. I thought the car was in all wheel drive all the time.??

It is full-time AWD. The rear wheels are hard-connected to the transmission output shaft. The system has a clutch-based transfer case that's used to match the speed of the front axle to the rear axle. The clutch is initially set so that there's a 40/60 front/rear torque split on a dry road moving straight ahead.

It tightens and loosens the transfer case clutch as the dynamics of the situation change. Front wheel slip results in the clutch being loosened (biasing the torque to the rear until the fronts stop slipping) and rear wheel slip results in the clutch being tightened (moving torque forward until the rears stop slipping).

"100% torque to rear" occurs when the front wheels are slipping completely (or the car is making a tight turn at low speed, plus one or two other conditions) such that the clutch is fully released

The "100% torque to front" condition can only occur when the rear wheels are on a "frictionless" surface with at least one front wheel having traction. In that situation, the rear wheels are spinning at the same rate as the front wheel providing thrust to the car.

[Rayscott]

Originally Posted by EuroDude

Interesting Ray, did you try and post up on the X3 forum?

Sorry, I meant the 228i

[Rayscott]

Originally Posted by Cyberdemon

What do you mean by "all wheel drive" selection?

Are you simply referring to the graphic they show that looks something like this?



If so that does not mean all wheel drive. That's just how they visually indicate that the drivetrain (which means throttle response and transmission logic) are in "Sport" mode now. I can see the fact that it highlights all 4 wheels might make you think it did something else.

Yes, the 4 wheel drive symbol came up once and I have never seen it again. I don't know how it happened.

[Rayscott]

Originally Posted by Zooks527

It is full-time AWD. The rear wheels are hard-connected to the transmission output shaft. The system has a clutch-based transfer case that's used to match the speed of the front axle to the rear axle. The clutch is initially set so that there's a 40/60 front/rear torque split on a dry road moving straight ahead.

It tightens and loosens the transfer case clutch as the dynamics of the situation change. Front wheel slip results in the clutch being loosened (biasing the torque to the rear until the fronts stop slipping) and rear wheel slip results in the clutch being tightened (moving torque forward until the rears stop slipping).

"100% torque to rear" occurs when the front wheels are slipping completely (or the car is making a tight turn at low speed, plus one or two other conditions) such that the clutch is fully released

The "100% torque to front" condition can only occur when the rear wheels are on a "frictionless" surface with at least one front wheel having traction. In that situation, the rear wheels are spinning at the same rate as the front wheel providing thrust to the car.

Thank you for that excellent explanation. Does AWD enhance handling and acceleration. Never had it in a car, only in a Jeep and SUV.

[Grentz]

Originally Posted by Rayscott

Thank you for that excellent explanation. Does AWD enhance handling and acceleration. Never had it in a car, only in a Jeep and SUV.

Yes it does, hence why the xDrive versions are actually a bit quicker in the 2 series. They are able to put more power down vs. full RWD.

There are different AWD/4wd systems as well. The one in our cars is more performance based and designed to put power down and retain some of the RWD bias dynamics that BMW is known for. Other systems like those in an off roader are designed more to maximize traction on non-traditional terrain and get vehicles "unstuck".

[Zooks527]

Originally Posted by Rayscott

Does AWD enhance handling and acceleration.

As Grentz notes, off-the-line acceleration is faster in an AWD once the HP/torque get above the maximum amount of power that can get down to the road through only the rear wheels. In a RWD, at some point you'll get wheel spin. In an AWD car, the energy used to spin the wheels gets shifted to the other axle and applied to the road. This effect is undisputed, although by the time you get into the 1/4 mile range, the ~150 lb increase in the weight of the car from the AWD system can / does result in lower top speed and increased elapsed times for the AWD car.

Does it enhance handling? Well (warning, flame war in 3 ... 2 .. 1 .), if you know what you're doing, it can. If you don't know what you're doing, it can. In fact, you'll often see comments about how AWD helps "inexperienced" drivers drive faster in various situations. If you ask why this increased ability doesn't transfer over to "experienced" drivers, you'll find that it doesn't because shut up. After all, it's so clear that there can't be a positive effect with a "good" driver that they've had to prohibit it in some racing series to keep people from wasting their time giving it a try.

[jgoldstein2000]

Lol

[Xi-Xi]

Brilliant.