[harrywillson204]

I have both the engine, but next 2 will be better

[CanadianGatorBacon]

Originally Posted by Zooks527

All the references I've seen say they're all rear-biased, including the X1. Granted, "what I've seen" is not dispositive, but I can't find a reference for the X1 that says otherwise. Since the system can send anything up to 100% of the torque to whichever axle it wants, or up to 50% of the torque to any one wheel, there's no need to keep the same bias conditions as a 2WD version.

For example, from the BMW USA site:

"Unlike other all-wheel drive systems, we've built xDrive, BMW's intelligent all-wheel drive system with rear-wheel bias for surefooted grip on slick or uneven roads, without sacrificing the feel of rear-wheel drive. It smartly sends power to the wheel or wheels with the surest footing—and it does so in milliseconds. That means under normal conditions, drive forces are spread out with a rear-wheel bias. But the moment the system senses excessive wheel slip, it subtly shifts torque to meet the changing conditions, offering maximum available traction and superior handling on all surfaces—despite the weather conditions."

http://www.bmwusa.com/Standard/Conte...ng/xDrive.aspx

That's somewhat reassuring, although I wonder if there are different chassis requirements between a FW biased and a RW biased AWD system, and if there are similarities between the FW biased AWD system and the FWD car that will make it too tempting to cut costs by sharing components. I'm not automotive engineer or suspension expert, but is seems reasonable (from a business perspective) that BMW would do this instead of making RW bias AWD system.

[Zooks527]

Originally Posted by CanadianGatorBacon

[That's somewhat reassuring, although I wonder if there are different chassis requirements between a FW biased and a RW biased AWD system, and if there are similarities between the FW biased AWD system and the FWD car that will make it too tempting to cut costs by sharing components. I'm not automotive engineer or suspension expert, but is seems reasonable (from a business perspective) that BMW would do this instead of making RW bias AWD system.

Well, there's no cost difference to BMW to changing the bias.

xDrive works with a central transfer case no matter what. There will be driveshafts to both front and rear axles, and the clutch pack transfer case can load them however it wants. That's different from other systems such as Audi's Haldex-based system (which runs FWD until slip occurs) or their older Torsen system (which had a fixed split all the time). Those systems are truly "biased" from a mechanical perspective, whereas BMW shoves it around at will via the ECU.

Weight distribution may not cooperate, however, if you get a nose heavy design as a function of a base FWD car.

[scrape1]

Originally Posted by Zooks527

Well, there's no cost difference to BMW to changing the bias.

xDrive works with a central transfer case no matter what. There will be driveshafts to both front and rear axles, and the clutch pack transfer case can load them however it wants. That's different from other systems such as Audi's Haldex-based system (which runs FWD until slip occurs) or their older Torsen system (which had a fixed split all the time). Those systems are truly "biased" from a mechanical perspective, whereas BMW shoves it around at will via the ECU.

Weight distribution may not cooperate, however, if you get a nose heavy design as a function of a base FWD car.

It's probably going to be the system from the active tourer. From the below, it sure looks to me that it's FWD unless wheel spin is detected. May not be mechanically identical to Haldex, but I bet it feels pretty similar.

http://www.autoevolution.com/news/bm...ned-89358.html

The xDrive models weigh just 61 kg more than FWD ones

The Active Tourer range is aiming at offering both space and luxury and the BMW badge and all that should come with it. That means drivers will expect the car to handle in a certain way. FWD doesn’t allow the car to be particularly dynamic, but with all-wheel drive things change.

The xDrive system for the car weighs just 61 kg (134 lbs) and features technology that allows to save the amount of losses per the drivetrain to a minimum.

Power from the front drive to the rear axle is transferred thanks to an angular gear on the front differential and a two-part cardan shaft that are called ‘Power Take-Off’. The heart of the entire system is an electro-hidraulic multiple-disk clutch (Hang-On) fitted inside the rear axle drive. Its job is to vary the torque distribution between the front and rear wheels via a hydraulic pump.

Power Take-Off

We know BMW likes to use all sorts of weird names for its technologies so we had to know what Power Take-Off actually meant. As far as we can tell, it’s an angular gear mounted behind the engine, on the automatic transmission and crankcase.

The input shaft is a hollow shaft construction and directly connected to the front axle differential. This way, part of the drive force is transferred from the differential basket to the cardan shaft via the hollow shaft, the crown wheel and the pinion shaft.

Hang-On

As far as ‘Hang-On’ goes, this is the multiple disk clutch located in the rear axle drive. It directs a proportion of torque to the rear wheels, depending on the driving situation. It can send up to 100 percent of the power to one axle and is operated by a hydraulic pump which, in turn, is controlled by a pulse-width-modulated signal from the ECU.

What makes this system stand out compared to others is that the pressure inside the pump is not measured by a sensor but rather by means of voltage and power alignment.

The cars are front-wheel drive when all-wheel drive is not needed

In order to be as efficient as possible, the xDrive system deactivates the pump that controls the multiple disk clutch when all-wheel drive is not needed, turning the car into a front-wheel drive vehicle. Thanks to a spring-loaded valve, the oil level in the clutch is lowered, reducing friction losses, making the car run even more efficiently.

[Zooks527]

Originally Posted by scrape1

It's probably going to be the system from the active tourer. From the below, it sure looks to me that it's FWD unless wheel spin is detected. May not be mechanically identical to Haldex, but I bet it feels pretty similar.

http://www.autoevolution.com/news/bm...ned-89358.html

Ugh, that's depressing! Yeah, that's just the way Haldex works.

[BentZero]

Originally Posted by scrape1

It's probably going to be the system from the active tourer. From the below, it sure looks to me that it's FWD unless wheel spin is detected. May not be mechanically identical to Haldex, but I bet it feels pretty similar.

http://www.autoevolution.com/news/bm...ned-89358.html

The xDrive models weigh just 61 kg more than FWD ones

The Active Tourer range is aiming at offering both space and luxury and the BMW badge and all that should come with it. That means drivers will expect the car to handle in a certain way. FWD doesn’t allow the car to be particularly dynamic, but with all-wheel drive things change.

The xDrive system for the car weighs just 61 kg (134 lbs) and features technology that allows to save the amount of losses per the drivetrain to a minimum.

Power from the front drive to the rear axle is transferred thanks to an angular gear on the front differential and a two-part cardan shaft that are called ‘Power Take-Off’. The heart of the entire system is an electro-hidraulic multiple-disk clutch (Hang-On) fitted inside the rear axle drive. Its job is to vary the torque distribution between the front and rear wheels via a hydraulic pump.

Power Take-Off

We know BMW likes to use all sorts of weird names for its technologies so we had to know what Power Take-Off actually meant. As far as we can tell, it’s an angular gear mounted behind the engine, on the automatic transmission and crankcase.

The input shaft is a hollow shaft construction and directly connected to the front axle differential. This way, part of the drive force is transferred from the differential basket to the cardan shaft via the hollow shaft, the crown wheel and the pinion shaft.

Hang-On

As far as ‘Hang-On’ goes, this is the multiple disk clutch located in the rear axle drive. It directs a proportion of torque to the rear wheels, depending on the driving situation. It can send up to 100 percent of the power to one axle and is operated by a hydraulic pump which, in turn, is controlled by a pulse-width-modulated signal from the ECU.

What makes this system stand out compared to others is that the pressure inside the pump is not measured by a sensor but rather by means of voltage and power alignment.

The cars are front-wheel drive when all-wheel drive is not needed

In order to be as efficient as possible, the xDrive system deactivates the pump that controls the multiple disk clutch when all-wheel drive is not needed, turning the car into a front-wheel drive vehicle. Thanks to a spring-loaded valve, the oil level in the clutch is lowered, reducing friction losses, making the car run even more efficiently.

This answers the question I had earlier. I suspected that BMW would make FWD xDrive platforms with a FWD bias since it's a, well, FWD platform. :/

[neilr_]

Originally Posted by BMW335iOn18s

I would get a 3 or 4 series and continue driving rwd sporty BMWs with manuals. Or, I'd get a BRZ or STI. Maybe Audi? Who knows. Nothing FWD for sure.

I expected to keep my FR-S for longer, but the mutterings of a FWD 2er in the immediate future spurred me to swap for my 228i.

Because my preference is for a small, fixed-roof vehicle (and I'm not in a position to install charging hardware), the 2er is the only BMW that I could consider. If the equivalent model is FWD when I'm ready to look for a replacement, I'll likely end up looking elsewhere (assuming there's still somewhere else to look).

[BMW335iOn18s]

Originally Posted by neilr_

I expected to keep my FR-S for longer, but the mutterings of a FWD 2er in the immediate future spurred me to swap for my 228i.

Because my preference is for a small, fixed-roof vehicle (and I'm not in a position to install charging hardware), the 2er is the only BMW that I could consider. If the equivalent model is FWD when I'm ready to look for a replacement, I'll likely end up looking elsewhere (assuming there's still somewhere else to look).

I believe they'll continue to make a rwd coupe/convertible 2 series based on the 3/4 as they do now. If not, they'll make the 4 series steer and handle like the 2 series should. BMW won't abandon their enthusiasts completely, at least I don't believe so.

[neilr_]

Originally Posted by BMW335iOn18s

BMW won't abandon their enthusiasts completely, at least I don't believe so.

My concern, if that's really the way to phrase it, is that someone will decide that M cars (i.e. M2, not M235) are for enthusiasts, and anything less is not.

I don't track my car, so I want to have fun driving my usual routes. My 228i is a good fit for this (as was my FR-S), but I'm not convinced that an M235i would be better (an M2 definitely wouldn't be). I just don't drive anywhere exciting enough to benefit from it.

Not that this has anything to do with the original question. :-)

[BMW335iOn18s]

Originally Posted by neilr_

My concern, if that's really the way to phrase it, is that someone will decide that M cars (i.e. M2, not M235) are for enthusiasts, and anything less is not.

I don't track my car, so I want to have fun driving my usual routes. My 228i is a good fit for this (as was my FR-S), but I'm not convinced that an M235i would be better (an M2 definitely wouldn't be). I just don't drive anywhere exciting enough to benefit from it.

Not that this has anything to do with the original question. :-)

I get it. An M2 might be out of budget, and the lesser BMW ms are still enthusiasts cars. But I think BMW knows this. Notice how they still bring the 6MT 2/328i to the US, presumably because they do sell in significant numbers, even compared to their larger capacity brethren.

[uberspeed]

Originally Posted by neilr_

I expected to keep my FR-S for longer, but the mutterings of a FWD 2er in the immediate future spurred me to swap for my 228i.

Because my preference is for a small, fixed-roof vehicle (and I'm not in a position to install charging hardware), the 2er is the only BMW that I could consider. If the equivalent model is FWD when I'm ready to look for a replacement, I'll likely end up looking elsewhere (assuming there's still somewhere else to look).

Yesterday for grins and giggles I started pricing out a few quasi-competitors (Toyobaru twins, WRX, etc. ) to the 228i and kept going back to it thinking it just hits a great balance for me. Here's to hoping they don't ruin it as RWD is a huge checkmark for me.