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I'd really like to see an independent tester like Road and Track or Automobile do the test, not Subaru's (or Audi's or Volvo's, or Honda's) marketing department. What the heck did you expect the video to show?
Sir Mix-a-Lot, the rapper who famously praised big butts, must have been reading Porsche's mind. The new 911 Carrera 4 with all-wheel drive sports an extra 1.7 inches of rump. It's a fashion statement, an engineering solution, and an anticipation of customer enthusiasm for the wide-body look wrapped into two curvaceous Carreras. The fat rear fenders are standard on the C4, whether you opt for the 325-hp edition or the 355-hp S we had the joy of flinging down Monte Carlo Rally roads in the French Alps.
The meat accompanying these potatoes includes at least 5 percent but not more than 40 percent of the available torque sent to the front wheels via a viscous coupling, major structural changes, revised brakes, a 1.3-inch-greater rear track, and fatter rubber. The C4S's rear tires grow from 295/30YR-19s to 305/30YR-19s, and curb weight is greater by 122 pounds. Dual-mode dampers with new suspension calibrations are standard on the C4S. Adding the 4 insignia to the deck lid costs $7970 in a Carrera S and $7770 in the regular 911.
The engineering changes yield what feels like a whole new 911. The C2's bobble-head front-end motion is gone; the handling dynamics reek of confidence. The steering is more communicative, with the front axle carrying an additional 75 pounds. Yank the wheel, and the nose dives aggressively for the apex while the tail hangs tight. Hammer the gas early to exit, and the front tires haul you forward instead of wide of the desired arc. No matter how you play the right pedal, the C4S drives where it's pointed.
But the extra traction and poise don't improve straight-line acceleration or top speed. That will change next year, when Porsche boosts the 911's wide booty with a turbo.
Now that's what i'm talkin' about!
Regards,
OW
Now as a 2007 911 Turbo owner, you would think I would be a fan of AWD. True enough, in the Turbo, it is almost a necessity in order to put all of that power to the pavement without stripping all the rubber off your tires.
...But, I drove a RWD GT3 last week in Germany and fell in love. Probably not enough to ditch my blisteringly fast 911 Turbo and it's more civilized interior / ride. But there is no 911 that handles like the GT3. And with it's non-turbo 8,400 rpm redline, it is an absolute hoot to drive.
Forget the "wide booty" thing. The difference is not that noticable. Get a C2S or C4S - or a GT3 or Turbo - based upon what you will enjoy driving for the conditions you will be driving in. As much as I like my Turbo and the PASM button that switches the suspension between normal and sport settings, it would be sheer nirvana if I had a button that could toggle between AWD and RWD, with a way to ditch 300-400 lbs for the latter.
Subaru's system is not the most advanced, but it is simple, strong and effective. It's not intended to be used off-road (or on the beach). It's on gravel roads and snow it really works well. Unlike reactive systems most Subaru's send power to all wheels all the time. This means that you can take advantage of the AWD at higher speeds, which is why so many rally people use Subaru's. And I'm not just talking about high-dollar performance rallying; I'm talking about the grassroots navigational rallies and rallyX events that people enter with their daily drivers. Check out the entry list of any of your local rally events and you'll find probably half the cars entered are Subaru's. I've yet to see a SH-AWD Acura signed up (perhaps they're too new).
The Audi torsen system and the Mitsubishi Evo system are probably the only systems that work as well or (arguably) better in a reasonably priced car, but then Subaru's also have other advantages like better balance, lower center-of-gravity, interchangable parts and overall price.
If you want an AWD luxury car get an Audi or BWM. If you want to go off-roading get a Jeep. If you enjoy driving on twisty backroads get a Subaru.
http://www.canadiandriver.com/articles/pw/acura_awd.htm
Other systems can route power from left to right, but they do so "reactively" and accomplish the task by braking the wheels. To date, Acura's AWD is the only one steering the car by overdriving the outside wheel. Audi and others have openly admired the torque vectoring properties of SH-AWD and are actively developing their own systems.
Somewhere in earlier posts, I read a few remarking that SH-AWD doesn't distribute all that much power to the rear. We might as well correct that.
Depending on the vehicle, the default torque split for SH-AWD is either 70/30 (RL) or 90/10 (MDX and RDX). That is how power is split when cruising.
When you stomp on the gas from a standing start, power is split between 60/40 and 50/50. It varies from vehicle to vehicle and seems to match up with the vehicle's weight distribution. The RL, which is the most nose-heavy, get the most power to the front wheels. So, each wheel gets as much power as it needs to move the weight it bears.
In corners, upwards of 70% of the power is routed to the rear, and may be sent to the outside rear wheel. That wheel is also overdriven by either 1.7 or 5%, depending on the vehicle. This is accomplished without braking. The front wheels retain 30% to pull the vehicle out at the end of the corner. (The last is similar to the way Nissan's ATTESA works.)
Of the 3 vehicles currently using SH-AWD, only the MDX has programming which automatically routes power to the rear for hill-climbing. It also has algorithm's for towing.
But it's kinda hard to divorce the AWD system from the car. For example, while SH-AWD is a better system than your basic torsen Quattro, I might take an A6 over an RL because the RL's chassis isn't up to par.
FWIW, a Honda Ridgeline passed many Fords, Hummers, and other 7S class competitors in the 2005 Baja 1000.
So my idiot brother buys himself a new Subaru wagon (and thinking he has a REAL 4WD) drives it out to the beach and promptly buries his "grocery getter" in the sand...
So he calls me on his cel phone and after I laugh for several minutes (he hates that), I drove out to the beach in my Land Rover LR3, wrapped a tow strap around his chassis (had to dig down almost two feet to get there), and pulled him out pronto...
http://www.worldcarfans.com/rsslink.cfm/article/2070329.002/bmw/bmw-dynamic-pefo- rmance-control-in-detail
http://motoring.iafrica.com/newsbriefs/653507.htm
Here's another AWD system with lateral torque vectoring not unlike Acura's SH-AWD. Couple of observations...
BMW's rear diff routes power even during lift-throttle situations (SH-AWD does not). The X-drive AWD system can send up to 100% of the engine's torque to the rear drive shafts (SH-AWD will not).
On the other hand, SH-AWD will route 100% of the rear axle's torque to an outside wheel (it appears DPC will not). Acura's SH-AWD will not only route power, it will also over-drive the rear axles (it appears DPC will not).
everyday on-road or light off-road driving. Put another way, the differences are rather marginal, while the tradeoffs between AWD/4WD and 2WD are more significant. Every AWD/4WD system requires negative tradeoffs in terms of initial cost, fuel economy, handling (except at or near the limits), and complexity. It seems to me that for the vast majority of driving situations, in most of the country, FWD, with winter tires, when required, is a better compromise than AWD/4WD. For those willing to trade traction in slippery comditions for better weight ditribution, RWD, and winter tires for the months when it's helpful, may be the best compromise. In a minority of cases, AWD/4WD offers the best solution. In extreme cases, it's the only solution.
It seems to me that AWD systems that employ braking are wasteful, in terms of fuel and brake wear. I'm just not
sure how significant these losses are.
In my opinion, clever marketing has oversold the real world benefits of AWD/4WD, and conveniently neglected to mention the tradeoffs, for most driving requirements. It's what politicians tend to do when they try to sell a program.
I'm not sure it's accurate to say AWD/4WD has been oversold because it really wasn't heavily promoted until carmakers noticed that people were buying SUVs and 4WD P'ups in part because of their all-weather abilities. Truth be told those all-weather on-road capabilities of Explorers, Grand Cherokees and the like were a bigger factor in the rapid acceptance of those vehicles than their little-utilized (by the majority of owners) off-road abilities.
In other words it was more something people convinced themselves of. The first time I accelerated up a slushy hill in an AWD A4, I was sold.
Ironically I traded the A4 Quattro in on a RWD BMW 528 despite the fact that I live on a steep hill in NH.
I found out that in more than a few inches of snow it's all about the tires, no matter which wheels are driven. I decided that if it was going to be neccessary to go with dedicated snows there wasn't any point in putting up with the inherent front heaviness of either a FWD or AWD system.
2001 BMW 330ci/E46, 2008 BMW 335i conv/E93
To me Audi would have to be in contention for AWD as would Subaru. I prefer 4wd if I have a choice but AWD works pretty well in street applications. Living is Southern California AWD is simply another way to decrease my fuel mileage because I might need AWD two or three days a year. And then it would be simple preference rather than need.
It’s still a car that appeals to drivers who favour unruffled progress and appreciates the unmatched comfort of Saab seats. The 9-3, like its forebears, is not intended as a car for hardcore drivers.
But that could all change next spring when Saab introduces the 9-3 XWD (Cross Wheel Drive) as the ultimate expression of a facelifted range.
The XWD transmission is based around the new, fourth-generation, Haldex clutch, mounted ahead of the rear differential.
The really good news is that the unit is now ‘predictive’ so you don't have to wait for front wheel slip before torque is fed rearwards.
But Saab engineers have fitted another Haldex clutch – dubbed the eLSD - to the output side of the differential so torque can also be divided between the rear wheels.
For example, if the XWD hits standing water with its right front wheel, 85 per cent of the engine’s torque would be directed instantly to the rear wheels.
That 85 per cent would then be split by the eLSD 80 per cent to the left-hand rear wheel and just 20 per cent to the water-bound right-hand wheel.
We drove a late XWD prototype on a circuit of gravel, water spray and extreme lane-change manoeuvres and there’s only one conclusion. The XWD works, and brilliantly.
You can see how much difference it makes by checking out our videos section, or clicking here. No matter how extreme the steering action in the simulated lane-chances, the XWD remained neutral and extremely stable. Nose-led lurching and weight transfer were virtually absent.
And with the tail drifting on gravel, the eLSD would tweak it back into line with uncanny accuracy.
On a section of conventional tarmac, the XWD behaved remarkably like a car with 50/50 weight distribution. It cornered hard and flat, gripped like a limpet and could easily deploy all its 280bhp and 295lb ft. We look forward to getting XWD on the open road.
-Rocky
(1) A viscous coupling system used on manual models; it's reactive, but is 50-50 when not locking up.
(2) Clutch packs on automatic models; it's pro-active, but is 90-10 divide on most models when no wheel is about to slip.
Actually Subaru has a few more AWD systems that are completely different from each other:
3) The system in the 6-speed equipped Subaru WRX STI has a planetary gear center differential and electronic transfer clutch packs, in addition to mechanical differentials in the front and the rear. The default torque split was 35/65 front/rear in the past, which was readjusted to 40/60 front/rear in the 06/07 model years. Due to the mechanical nature of the differentials, the power/torque re-apportioning to the front/rear/side-to-side as conditions require, is instantaneous, as different from the cheaper visous-coupling employing but several thousand dollars cheaper, manual-WRX.
4) Variable-Torque Distribution or VTD-AWD system: The system in the Automatic Impreza WRX, which too has an STI-Type planetary gear center differential and electronically controlled transfer clutch packs, in addition to an LSD in the rear. The default torque split is a rear-wheel biased 45/55 front/rear. This type of AWD is also found in a few other VTD equipped Subarus like the Automatic Legacy GT and the LL Bean Outback. Please note that the manual WRX gets the cheaper Viscous-fluid/coupling based center differential like the lesser Manual Imprezas and not this planetary gear-based system (as present within the WRX STI and Automatic WRX). Please also note that all other Automatic Imprezas and other non-VTD Automatic Subarus, are left with the cheaper center-differential lacking "Haldex" type system, which is the 90/10 front/rear power distributing system you referenced above.
5) The system in VDC Outback (Automatic) and Tribeca etc., that is fundamentally similar to the above VTD system and sharing the same center differential and the electronically controlled transfer clutch packs but which lacks the rear-LSD of the above but in turn has a stability-control system, which they call as the VDC. It uses throttle-sensors etc to brake individual wheels to re-apportion power as needed, even though the default torque split is still 45/55 front/rear.
I think your brother did make a mistake of taking his Subaru to the beach thinking that he wouldn't get stuck, but I don't think that's what make the LR 4WD better.
You have the advantage of
- Better/Bigger Tires
- Locking the Center Diff. 50/50 on your T-Case at low range
- Probably some form of LSD front and rear
But in real 4 wheeling condition, it probably isn't as good as my Grand Cherokee that has the QuadraDrive to transfer torque up to 100% to any wheel.
The real question should have been what is the best AWD/4WD system for some specific driving condition.
Say: High Performance Driving with skilled drivers: The STI & EVO AWD are probably at top of the list
For Non-High performance daily drive, regular drivers: AWD systems that limit the torque output or brake at slip maybe better.
All it comes down to are preferences and compromises.
I seriously doubt the CV Joints and/or U-Joints can actually handle 100 percent of the torque from your engine.
The LR3 has a center locking diff that can be locked in high or low range depending on the terrain response system setting. Also a locking rear diff is optional and the ABS, Stability and Traction control systems can be adjusted using terrain response.
Terrain response
Video
Also the LR3 has a lot more axle articulation, 13 inches for the rear axle, then your Jeep which is just as important as the 4wd system. The LR3 can keep all four wheels on the ground longer then the Jeep can.
Well, I guess the wheels must be "spinning" to some degree. No AWD is going to work if the wheels are stopped. :P
Here's a snippet from Acura's description of the RL:
The logic and control of SH-AWD™ is integrated with the RL engine's Electronic Control Unit (ECU) and Vehicle Stability Assist™ (VSA®) ECU. The Engine ECU provides engine rpm, throttle position, intake manifold pressure, and transmission gear ratio data. The VSA® ECU provides data on lateral g, yaw rate, wheel rotation speed and steering angle. The SH-AWD™ ECU monitors the status of the acceleration device and the distribution of right and left Direct Electromagnetic Clutch torque. Traction is calculated based on the information from the engine ECU. During a hard acceleration situation, lateral g and steering angle are used to calculate the torque split between the right and left rear wheels. At the same time, this data is used to control the total amount (ranging between 0.6- and 5.7-percent) of rear wheel acceleration.
However, IIRC, the new Xdrive doesn't overdrive the outside wheel (change it's speed) it just supplies more torque. My memory is also fuzzy on the details.
He liked the styling of the Matrix while I liked what I had read about the ride/handling/traction of the Subaru. We were about to get the Matrix when the Subaru sales lady suggested that my son drive them back to back and push them hard. I suggested that we also find a slippery area to test the AWD systems. Besides the better on center tracking and cornering testing of the Subaru, we found a muddy road behind the dealership. The Subaru went up the hill. The Matrix couldn't.
I'm running all-seasons on my Outback and if I wasn't paying attention, I could lose it on the snowy road going up to my local ski hill.
My $0.02 would be that the Impreza has stability and traction control and the Matrix probably doesn't - I don't think it's standard on Matrix and is in fact a fairly hard-to-find option.
Which for the money definitely swings the advantage in favor of the Subaru, IMO.
2014 Mini Cooper (stick shift of course), 2016 Camry hybrid, 2009 Outback Sport 5-spd (keeping the stick alive)
That doesn't even begin to describe the (lack of) snow capabilities of the Bridgestones on my Impreza...
I understand why they put cheap tires that wear out fast on new cars... but, putting these tires on a full-time AWD car is criminal..
Given similar tires, I'd have to agree that the Subaru has it all over the Matrix in the AWD department, though.
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I hope they don't still use those, but I fear they just might.....not on STIs though, thank goodness!
2014 Mini Cooper (stick shift of course), 2016 Camry hybrid, 2009 Outback Sport 5-spd (keeping the stick alive)
The Impreza did have the above mentioned RE92's (described as awful) but did make it up the hill anyway. Just for the fun of it, I tried the hill today with my 2002 A4 Quattro with Michelin Exalto Sport A/S tires. It rained last night so it was even muddier than it was yesterday To my surprise, the A4 did NOT make it up the hill either. It does have ASC which I left turned on. It does not have a differential lock like my 1990 Audi 200 Quattro did.
BTW, both the Subaru WRX and WRX STI come standard with high performance SUMMER tires. I think you'll see that everyone agrees that if you these tires in snow country, you MUST switch to either Snow or All Season tires in winter.
I do have to wonder why an AWD "rally" style car would come with summer tires.
With 260 treadwear rating, I expect to be replacing these tires soon (my trade-in had Bridgestone Dueler Revos rated at 520). I haven't driven the Potenzas in any demanding conditions yet but the comments are not encouraging. Recommendations for replacements?
Owners are kicking tires around over in the Subaru Outback/Legacy Tires and Wheels discussion.
http://www.youtube.com/watch?v=ooQRxlChvMw
You would expect any AWD car to be able to move up the ramp if remove traction from the front wheels while the rear wheels have full traction, right? Well, in this test the Honda CR-V and Toyota Highlander were unable to do this. I thought that was a little shocking; if a CRV or Highlander is AWD, I would expect it to climb that wimpy incline if the rear wheels had 100% full traction.
This video was obviously put together by Subaru so they mainly tested manufactures that had inferior systems. I belive that Audi has really good AWD systems, and I think that they would be able to match what Subaru does in a test like this.
In any case, I certainly think that Subaru's AWD system is one of the best.
http://www.edmunds.com/insideline/do/Drives/Comparos/articleId=135807
I wish they had compared the TL SH-AWD to the G37x, the more logical comparison.
So does anyone have any opinions on the Infiniti AWD system?
2014 Mini Cooper (stick shift of course), 2016 Camry hybrid, 2009 Outback Sport 5-spd (keeping the stick alive)
I have an older forester without any traction aides and I can tell you that it is still a great system, and consistently keeps the car pointed where you want it too!
http://www.youtube.com/watch?v=0_MXK2nzt2Y&feature=related
http://www.youtube.com/watch?v=kRniF4JQN2U&feature=related
But I feel this discussion has taken many bad turns, like sport fans arguing about their teams, or soccer moms about their kids...
There is no such thing as the best AWD system. A farmer in Idaho most likely needs a different type of AWD than a NewYorker in a rain, or a motorhead on a dry race cource.
Many posters here have erroneously linked performance of an AWD system with the behavior of their vehicle during sharp turns. That is plain wrong. I know physics. The forces acting during a turn have nothing to do with the performance of an AWD system in the sense of preventing the car from skidding. Adding a tangential force to the centrifugal one most likely will decrease your chances of survival.
AWD is all about movind a car FORWARD (or where you turn the wheels).
I've had three Subaru Imprezas in the last 14 years. The best one was the oldest one, with viscous locking center differential. I could not stop myself from plain having fun with it in Lake Placid on all kinds of snow! Deep snow on grass, and downhill? You got it! Going back uphill? You bet! Compressed snow/ice on a parking lot in front of a restaurant? I put it into spins yet being sure it would not park itself inside that restaurant! And all that with just stock tires. If it had some Blizzaks on it, "it would probably be able to climb trees" - as one guy put it once.
Later I had a WRX with electronically-controlled CD. It was OK but very hard to control on some 6" snow. My latest WRX got me home safely when I got stuck in traffic on a 4" snow and just EASILY crossed the boggy-ditchy median to get to the opposite (but free!) lane, leaving hundreds of cars behind. I had my evil laugh at all those Beemers, Merces and Lexuses I'd left behind... sorry!
This year I quietly drove my wife's Honda CRV on 1" snow over asphalt, and had a feeling that the car was struggling to keep a straight line while wiggling side-to-side a few inches all the way. That CRV was OK in a pooring rain, though...
ALL I AM TRYING TO SAY: You guys - just go and test-drive all those different AWD systems, right where you live and the way you usually drive, and one of those systems shall be the best for you.
Only don't do that on a sunny Summer day going 'round the block -- if you want to test an AWD
Regards:
Oldengineer
There is but two correct answers to this question. Subaru and Audi. The difference? I don't know about Audi, but Subaru's starts as an AWD and remains that way all the time. Both Audi and Subaru have been hard at work for more years than I've been alive perfecting and advancing their AWD system. Acura's just came out, what, 5-10 years ago? Yeah...they've got some catching up to do.