AWD systems not created equal video

[boost4life]

[ame=http://www.youtube.com/watch?v=t09ExAUgtyE&feature=player_embedded]YouTube- All ALL WHEEL DRIVES are NOT created equal. (Subaru Vs Other[/ame]

 

Watch the end when they test the legacy.

[Drift Motion]

very interesting video

 

Suby FTW

[ehsnils]

It was posted a year or two ago too...

[Platinum_Racing]

I think this video is cool, but it is biased towards Subaru because it is a SOA video. If you can find the video in its entirety, they actually say at one point during a hill climb test that "The Subaru driver is really trying to get the Volvo up the hill." Or something along those lines.

 

 

Also notice that they said the car was full throttle, well when the tested the LGT the wheels sure didn't look like the throttle was pinned. Don't get me wrong, I hate transverse engine layouts as much as any of you guys, but I think this test is somewhat biased. The fact that a Subaru dealership edited about 2/3 of the video away and uses it as advertising on YouTube proves my point.

[underground000]

repost...

[ehsnils]

In any case - the main difference is that many AWD systems are actually FWD systems and only engages the rear end when there is a detected slippage and releases as soon as there is no slippage at all. This results in a case where only a limited amount of torque is transferred to the rear end.

 

Works fine for dry roads and medium hard terrain where it isn't too bad but when it gets really bad it just can't cope and loses it. Same if you have a trailer because then you offset the weight distribution.

 

A bit old video, but makes the point (screw the sound - it sucks):

[ame=http://www.youtube.com/watch?v=XyLgYskj-oc]YouTube- Subaru Legacy Outback vs Volvo V70 Cross Country[/ame]

 

Both cars have AT gearboxes and I suspect that the Outback has the EAT4 gearbox.

Trailer with 200kg load.

 

But I sure hope that Volvo have made a better AWD since that video was made.

[LosAngelesLGT]

ANCIENT NEWS. This has got to be a repost. I saw this YEARS ago on youtube

[Platinum_Racing]

In short, transverse AWD engine layouts are for sissy's, soccer moms, and uneducated people looking to buy a car that says AWD on the back. These people are more concerned with how many cupholders their car has rather than actual performance/safety features.

 

This is why Honda, Toyota, and Mitsubishi AWD vehicles are a joke.

 

I mean, even the Chrysler 300C AWD has a longitudinally mounted engine with a transfer case. Its not the same as a Subaru with the front diff built into the transmission, but it's built more like a truck than any other AWD system you're going to find unless you start looking at midsize SUV's and pickup trucks. I bet money that if you put a Dodge Magnum AWD and a Chrysler 300C AWD in that first video along with the other cars, it would perform similar to the Subaru.

 

What other companies are doing is basically taking a FWD car and adding RWD to it, which is not the way to go. I think these designs are cheap, ineffective, and should've never been made. As a former off-road truck enthusiast, I despise the transverse AWD layout with every fiber of my being. Everyone who thinks this system is best should go buy a Grande Iced Nonfat Caramel Latte at Starbucks and stay the F*** home when it snows.

[rao]

So the Subaru system is the best?

[LosAngelesLGT]

The Subaru system is the best!

 

Fixored

[EvoFire]

I currently drive a Highlander, while I won't say its a good system, it definitely doesn't do that. They make it seem like the Highlander is actually a FWD car, I won't say its exceptional in bad weather, but I haven't gotten stuck before in the snow.

 

On top of that, on ice, traction control is actually detrimental to driving the car safely. I would say heavily biased video. As much as I think Subaru has a good system, its really not that different than any system out there, its just a bunch of diffs in all the connecting points.

[Platinum_Racing]

It is different though.

 

The transverse layout with the tranny next to the engine is just a bad design IMO. The whole design makes it look like the RWD was a complete afterthought, which in most cases it was. It allows manufacturers to reuse components from their AWD and 2WD platforms without redesigning critical components (Chassis, engine bay, front drivetrain, front suspension, steering, and half the transmission).

 

The longitudinally mounted system with a transfer case and separate front/rear driveshafts is great for trucks because it gives you great suspension articulation without bottoming the chassis. It also allows a sufficient ride height without extreme driveshaft angles you get should you happen to try and lift a Subaru. The downside is the amount of rotating mass, and usually the center driveshaft is offset from the centerline of the vehicle. In addition to all this, the front half shafts are unequal length. Its also expensive to make because of all the extra parts and metal it takes to make one. All this contributes to why you only see these on slow, lumbering off-roaders/pickups/some SUV's. Usually these designs lack a center diff as well.

 

The Subaru design has all critical bits inside the transmission except the rear diff. The front diff, center diff, and transmission are all one unit. The longitudinal layout balances the car, and most of the rotating parts are on the centerline of the car. All CV shafts are equal length at each end of the car, and you don't have much rotating mass to soak up all your power. The Subaru design is the best of both worlds with several added benefits. It just costs more to produce than a transverse layout, which other companies have screwed themselves into sticking with ever since small engines and FWD became the norm.

 

They all have their uses though. The transverse layout design is for cheap afterthought cars that shouldn't have AWD to begin with, driven by people who don't know how to use AWD in the first place. The longitudinal design with a transfer case is good for heavy 4WD vehicles with plenty of chassis room where speed, acceleration, and handling aren't of much concern. The Subaru design is best for cars that need to retain speed, accelleration and handling while maintaining a small driveline "Footprint". They are cheaper to make than the transfer case design, have lower rotating mass, and are provide superior on-road driving performance. When compared to a transverse design, the Subaru design is more efficient and more durable.

 

 

 

 

[/thread]

[ShrinerMonkey]

This past winter I gave a neighbor a ride home and she has an extremely steep icy driveway. She said that I could drop her off at the curb and I said I can take you up to your door. She was pretty sure I wouldn't be able to make it up. She was amazed that my car was able to scale her driveway without any drama, slipping or anything. She asked, "How come my Ford Escape can't make it up my driveway but your car can?" I just said I had no idea.

[F-WDC Spec B]

^ post that in the funny phrases/questions thread.

[Beanboy]

Don't care about layout/how power is transferred, as long as it is done well. Some clutch-based systems are better than Subaru in certain situations.

 

What I really like about Subaru is that on most models, a good percentage of power is being send to the rear all of the time. Keeping momentum going from high to low traction situations.

 

With the amount of electronics nowadays though, many things can be programmed out.

 

But just like mechanical bits, there's good traction/stability programming, and bad.

[jfg22557]

She asked, "How come my Ford Escape can't make it up my driveway but your car can?" I just said I had no idea.

^

instant classic.

[ehsnils]

Just be aware that if you want to compare systems you can see the difference between the Mitsubishi Evo and the Subaru Impreza. Both are doing well in most conditions so the layout isn't really critical.

 

What's critical is how the power is distributed and the weight distribution. The point is as long as the design provides matching traction to all wheels you have a good solution. If the design also can handle a surface that's different between the wheels it's an even better solution.

[EvoFire]

Maybe I'm missing something, but either way I look at it, some forms of Subaru's Symmetrical AWD is just a crude system of diffs at the right places. The crudest system is also the most popular system amongst enthusiasts barring the STi and its DCCD.

 

All the manual versions of Subarus come with diff in the middle and diff on the rear. Simple and really not much more than most systems out there. Its the same on most of these so called cobbled together systems from other manufacturers. Its just that some of the other implementations have limitations (ahem Honda's CR-V, slip too much, over heat the diff, 4WD stops working until it cools down).

If the system on the other cars, say the Highlander(what I have), I wouldn't have the nice experience of kicking the tail end out on corners in the snow(or even rain with bad tires, yep done that before).

 

While I agree most systems are just FWD drivetrains with a driveshaft stuck to the rear wheels, they do have limited slip diffs in between. Its a crappy system, but it works, and in places with a FWD would have gotten stuck, the cobbled-together AWD system will keep going.

[ehsnils]

^ Nice avatar! Full size can be found here: http://www.bedug.com/?q=gallery&g2_itemId=22879 (I took that pic)

 

Anyway - A system with a center diff is simple, but reliable and has few quirks. And with an automatic LSD coupling it solves the problems in most cases. The DCCD is essentially the same, but there the driver has the option to adjust the slip of the LSD, which is a blessing and a curse.

 

A pure clutch pack isn't as good as a center diff since it only enables drive on the secondary pair "when needed", but that specification "when needed" will depend on what the manufacturer thinks is appropriate - and that's often too little in some conditions (as with the Volvo in the YouTube video). Same thing with the early VW Synchro. A true AWD will place equal amount of torque to all wheels when driving straight on a consistent surface which will keep down the tire wear.

 

But since manufacturers often place AWD in FWD cars they don't want too much on the rear wheels since that will cause the car to behave in a different way from the FWD models. And it will also add strain to the driveline. This means that some cars actually can have an inferior AWD system.

[boost4life]

here is a test between the sti and evo this was done up here in the U.P. as well:)

[ame=http://www.youtube.com/watch?v=uHKjXfbqc90]YouTube- Ice Bowl! - EVO Vs STI Snow Challenge[/ame]

[Platinum_Racing]

That video kinda sucks.

 

They didn't give you any specs related to their testing. No times, no statistical data, and only about 45 seconds worth of personal opinions.

 

I understand the conditions were bad and they weren't going fast, but I bet if Top Gear ran that test their camera angles and editing would've made it look like those cars were doing 500 MPH.

 

Top Gear FTW.

[EvoFire]

^ Nice avatar! Full size can be found here: http://www.bedug.com/?q=gallery&g2_itemId=22879 (I took that pic)

 

Anyway - A system with a center diff is simple, but reliable and has few quirks. And with an automatic LSD coupling it solves the problems in most cases. The DCCD is essentially the same, but there the driver has the option to adjust the slip of the LSD, which is a blessing and a curse.

 

A pure clutch pack isn't as good as a center diff since it only enables drive on the secondary pair "when needed", but that specification "when needed" will depend on what the manufacturer thinks is appropriate - and that's often too little in some conditions (as with the Volvo in the YouTube video). Same thing with the early VW Synchro. A true AWD will place equal amount of torque to all wheels when driving straight on a consistent surface which will keep down the tire wear.

 

But since manufacturers often place AWD in FWD cars they don't want too much on the rear wheels since that will cause the car to behave in a different way from the FWD models. And it will also add strain to the driveline. This means that some cars actually can have an inferior AWD system.

 

Definitely agree about the car handling a different way. For people that have never driven a AWD car, the attributes on a AWD car can be a bit unnerving, especially in bad weather conditions. Probably why most cars in the ditch when it snows are the AWD SUVs and CUVs.

 

And lol, didn't expect to run into the maker of that picture here.

[Penguin]

Meh. A real all wheel drive or four wheel dive system has a low range transfer case. Even better if it also has mechanically locking front and rear differentials.

[Gire]

True, but we all can't drive Land Rovers.

[Platinum_Racing]

Thank God for that.