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FWD, AWD, RWD and the Luxury Performance Sedans

tayl0rdtayl0rd Posts: 1,938
edited March 14 in Acura
So as not to get too far off topic in the LPS forum, let's discuss the virtues of these drivetrain layouts as they pertain to luxury performance sedans here.

I will start by saying that to be taken serious in the LPS market, you must at least offer a RWD platform. AWD is great, but a front-biased/primarily front drive AWD system (as in the Acura RL) is no substitute for good ol' RWD. A 50/50 split doesn't cut it either (as with Audi's new A6). For driving pleasure, it's got to be RWD or a minimum of rear-biased/primarily rear drive AWD.

Counter-points? Opinions? Insults?
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Comments

  • merc1merc1 Posts: 6,081
    I think AWD is ok, but FWD isn't - for this class. Audi does offer a V8 something Acura doesn't which I think makes all the difference in the world to some folks.

    Now when Audi updates the Quattro system in the A6 to that of the RS4 then they'll have that all-important 40/60 rwd bias.

    M
  • calidavecalidave Posts: 156
    I just asked a similar question in a more active thread:

    http://townhall-talk.edmunds.com/direct/view/.ef3fcce

    Maybe there will be more interest over there.
  • fedlawmanfedlawman Posts: 3,118
    I think that in this segment, the cars are predominantly too heavy, too long, too saddled by electronic nannies, typically equipped with automatic transmissions, and tuned from the factory to understeer at the limit.

    These aren't cars you take to the track, and where on public roads can you begin to approach the limits of a 300+ HP car wearing 10" wide performance tires?

    With a few exceptions, I think the majority of people buying these cars care about how fast they accelerate in a straight line, how comfortable/quiet/feature laden they are, and the perceived social status they represent.

    I really don't think it makes a difference what the drivetrain layout is.

    Just my $0.02
  • tayl0rdtayl0rd Posts: 1,938
    You might want to check out the Luxury Performance Sedans forum. Apparently it makes a HUGE difference in which wheels are driven. ;) Most of the folks there and in this class seem to prefer RWD.
  • mnrep2mnrep2 Posts: 200
    Ok I'll bite ;) One of the reasons I bought the G3x was because of the 100% rwd bias of it's awd. It handles like a rwd sports sedan until slip is detected. The BMW X series, Audi and, Volvo all split torque distribution by some ratio, front to back at all times. The Infiniti is unique with their application of AWD and I love the way it works!

    Fedlawman, before you start with the "its a overweight behemoth", yes the awd g is 180lbs heavier than the rwd only version. I do not track this car so I wasn't buying it to take to Road America or to AutoX meets.

    In my opinion and on the roads that I drive, the awd version of the G35 is the Best application of awd in a entry level performance sedan :D

    Flame suit ON
  • shiposhipo Posts: 9,152
    Flame suit ON

    Gee, what's worse?

    1) Donning your Nomex and weathering a bazillion flames.
    2) Donning your Nomex and sweating to death with nary a flame in sight.

    Sorry, couldn't resist. ;-)

    Best Regards,
    Shipo
  • patpat Posts: 10,421
    This discussion has no categories - that's why it's not attracting any attention. Tell me on which vehicle searches this discussion should appear and consider it done! I can go up to nine different ones.
  • tayl0rdtayl0rd Posts: 1,938
    Luxury Performance Sedans
    Entry-level Luxury Performance Sedans
    Performance Cars (if there is such a forum)
  • patpat Posts: 10,421
    Needs to be specific vehicles. I can list up to 9. Then this discussion will appear anytime someone searches for any of those specific vehicles.
  • tayl0rdtayl0rd Posts: 1,938
    Oh, I see.

    Acura RL (2005+)
    Audi A6 (2005+)
    BMW 5-series (530(x)i/550i)
    Cadillac STS/CTS
    Infiniti M35(x)/45
    Lexus GS/IS
  • patpat Posts: 10,421
    Okey-doke - you got it!

    I had to pick a specific model for each Lexus. I can change it if you want, but I can't add any more.

    Have at it!
  • jclumpnjclumpn Posts: 3
    Hey- have really appreciated the info on the forum.

    I am planning to purchase either a used Lexus IS-300 or a new IS-250 AWD soon. Live in Chicago, the windy and at times snowy city, and wondered how the old RWD models handle in snow/ slippery conditions vs the AWD now available. Anyone have experience with this, advice? Thx much!
  • tayl0rdtayl0rd Posts: 1,938
    I can't say if it's true across the board for the IS300, but I personally saw one dead in the "water" during a big ice storm a few years back. It was on a slight incline at a traffic light. When the light turned green, all it did was sit there spinning the wheels.

    Keep in mind any of a few things could have been true. The guy could've had traction control turned off, it could have had summer tires, the tires could've been nearly bald, etc.
  • wwestwwest Posts: 10,706
    With age comes accrual of knowledge, experience and wealth, generally.

    The wealth part allows us access to the Luxury vehicle market and our long driving history/experience has clearly taught us that RWDs are inherently safer than FWD and/or front bias AWD, or even symmetrical AWD.

    Knowledge comes into play when we read about things like the fact that Cadillac used an over-running clutch to prevent loss of control on their high torque Northstar equipped FWD luxury BOATS. And we cannot miss the fact that the Cadillac line is now predominantly RWD.

    Then there is the overall move to RWD and/or rear biased AWD throughout the industry to consider. And now there is these new AWD systems that dynamically allocate lead/lag engine torque away from the front when the circumstances dictate that the front tires' traction coefficient is best allocated to directional control.

    Speaking for myself, I grew up in an era before FWD was even available. That allowed me the experience, as FWD became available, of watching others of my age and era discover that "learned" RWD responses nor human instinctive responses did not work all that well with FWD.
  • wwestwwest Posts: 10,706
    On a RWD vehicle the only thing traction control is good for is to let you know just how slippery the roadbed is, might be. I don't know of any case wherein it wasn't necessary to turn off the traction control in my LS400 in order to get it moving in the circumstances you describe.

    Only the driver can develop the proper "feel" to interact with and feather the throttle at the proper time and level to apply just enough torque to the roadbed without wheelspin/slip.

    And then there are those admittedly rare times that a little wheelspin/slip can be of great help.
  • neil5neil5 Posts: 118
    Don't forget Avalon 2005+
  • carfastcarfast Posts: 1
    I have a related question, but with respect to older cars.

    Context: I already have a nice 'summer' car, a RWD convertible. However, I live in a hilly part of NJ where we do have ~15 days/year with snowy/icy conditions in the winter. I need a car to drive ~6k miles/year including through the winter, and am considering a used car from mid-1990's.

    Many cars of the vintage I am considering have ABS but are RWD. My question is, how much of a difference is exists between:
    (1) FWD sedan, e.g. 1996-97 Audi A4
    (2) RWD sedan (or coupe) WITH SNOW TIRES, e.g. MB 320E from 1994-95, BMW 6 series from 1985-1989
    (3) AWD sedan, e.g. 1996-97 Audi A4 Quatro, BMW 325 ix from 1988-91, MB 320E 4Matic from 1994-1995

    I'm hoping that the consensus is that while (3) and (1) are better than (2), the difference isn't large, and a careful driver of a RWD car with snow driver should be fine - but I'll wait for your expertise! Thanks,

    - carfast
  • wwestwwest Posts: 10,706
    3a: FWD "based" AWD are often front torque biased making then just as dangerous in/on adverse roadbed conditions as an actual FWD.

    3b: RWD "based" AWD which are often torque biased to the rear leaving the majority of the front tires' roadbed adhesion factor available for life-saving directional control.

    Look at the new Acura RDX SUV and RL sedan for a virtually perfect implementation of a modern day AWD system.

    Or the GS AWD that runs a close second.

    Subaru keeps advertising "Safety of AWD?...??

    I ask you ALL, what or when is AWD safer or a safety factor.

    Does FWD or even a 4X4 do anything more than get you up and going, moving, on a slippery surface, resulting in a false sense of security for many owners??

    Isn't stearing, the ability to maintain directional control of the vehicle and/or quickly coming to a stop a lot more important..??
  • "Does FWD or even a 4X4 do anything more than get you up and going, moving, on a slippery surface, resulting in a false sense of security for many owners??"

    I am sorry, but you seem to be stating your opinion rather than facts. The fact is that an AWD has engine power connected to all its wheels. Hence, it allows engineers to design additional features like anti-spin, anti-rollover etc. The BMW X_Drive is a perfect example. there is even a video on it on their website. In the context of a BMW, it is capable of rotating a single wheel more than the others when it encounters unequal spin in order to ensure proper steering. This has been designed to a point that the car does this until you are driving in the direction pointed by your steering column. The Acura RL has a similar patented system, as I am sure the GS-300 would too. These are FACTS !!!! I'm sorry, but I'd rather put my faith in the world's finest engineers than your opinion.
  • sfcharliesfcharlie Posts: 402
    "3a: FWD "based" AWD are often front torque biased making then just as dangerous in/on adverse roadbed conditions as an actual FWD."

    The language suggests that this is a quote from somewhere. Is it? Or are you an automotive engineer? I'm not being sarcastic, just wondering where the strong sense of conviction is coming from.

    What do you (or what does the author of the quote) mean by "adverse roadbed conditions"?

    Is the Audi Quattro in this category?
  • wwestwwest Posts: 10,706
    I am most knowledgeable about the Toyota/lexus AWD systems derived from a FWD series vehicle, and somewhat knowledgeable of the Chrysler T&C minivan AWD.

    Both of these are front torque biased ~95/5 but use different methods to get there.

    The T&C had direct drive to the rear driveline and uses a VC, viscous clutch/coupling, in line, "in series", with that rear driveline. As long as the rear tires are turning at an equal rate with the front the VC remains "flaccid" and very little engine torque is coupled to the rear tires.

    If the front, primary drive wheels, develop wheelspin/slip then the VC fluid "stiffens up" due to internal heating and begins to couple more of the engine torque to the rear.

    The RX300 also uses a VC but in a slightly different way. The RX300 uses a standard "open" center differential but with differing final drive ratios front and rear so the front receives the clear majority of engine torque "natively".

    In this case the VC is mounted across, between the two output shafts of the center differential. Here again a differing rotation rate at the front vs the rear results in the VC fluid stiffening up and increasingly "locking" the center differential depending on the duration and/or level of the disparate rotation.

    As of 2004 the VC aspect was dropped from the system leaving the RX330, Highlander, and Sienna using only the MB ML's brake proportioning concept to re-allocate engine torque to the rear if front wheelspin/slip developed.

    With the production of the RX350 the VC concept was re-introduced and I expect it will also be back in the Highlander and Sienna this fall.

    So be aware, all AWD systems are NOT created equal.

    FWD systems and front biased AWD can quickly become unsafe and even hazardous on an icy or snow packed, slippery, roadbed.
  • sfcharliesfcharlie Posts: 402
    Thanks for that information. I love cars and am always eager to udnerstand better what makes one or another function in ways I have liked or not.

    I ask about Audi because I imagine it (perhaps incorrectly) to be a FWD-based AWD system, but one which has seemed to me (a close friend had one when I lived in sn area with lots of snow and ice) amazingly able to keep traction, and also one which is described as able to keep traction in adverse conditions.

    Is Audi, so far as you understand it, doing somethign different than what you are critical/cautious about?

    Much has been made about the Infiniti M35's RWD-biased AWD system, but I've not read any comparative review suggest one should expect it to do better in ice/snow/rain than Audi.
  • wwestwwest Posts: 10,706
    Other than "blind" agreement with you about the Audi being derived from FWD I can't add anything. I certainly wouldn't go out and buy one until confirming that the AWD version is rear torque biased.

    If the Infiniti weren't so horribly ugly IMMHO (Bull-nosed...?) I would seriously consider it along with the RDX or X3.

    But I think, truly believe, that Honda/Acura's SH-AWD system is going to set the future standard for AWD.
  • james27james27 Posts: 433
    The AUdi QUatro all-wheel drive system is different than the others out there in that it is entirely mechanical. In normal mode, the drive is distributed (until this year) equally to each wheel (they've modified it slightly for this year to bias it to 40/60 F/R).

    It is a mechanical system thatuses a central TORSEN (torque sensing) differential - all mechanical, instantaeous reaction - not computer trying to catch up. It is capable of putting nearly all power to an individual wheel or axle.

    If it says Quatro, it is currently mechanical. If it says all-wheel, it may not be mechanical.

    If you do a search, there is a video clip done where they had 5 (I think) different all-wheel drive cars try to climb a ski slope. Only one car made it to the top - Audi. Neither the BMW, MB, nor the others tested made it all that way up. Quatro DOES work - Audi has "owned" the Mt Washington race and Pike's Peak race for most of the years for awhile.

    I replaced my last car, an Audi A6 Quatro with an M35x. It is basically a rear-wheel drive car that can (nearly) instantly apply up to about 50% of the power to the front wheels as well. So far (we didn't get much snow last year, nor was I home much to drive it) it has done a decent job, but I think the Quatro system was/is better. Still, the Infiniti seems pretty close.
  • markcincinnatimarkcincinnati Posts: 5,093
    Not too much current participation on this forum but your explanation is almost 100% correct.

    The Audi TT, alone, uses the Haldex AWD mechanicals -- it is NOT TorqueSensing.

    The TorSen system is entirely mechanical and it is able to act "instantaneously" -- it does not require slippage of any wheel to cause a shift of power. X-drive is "nearly instantaneous" and while I personally would not be troubled by X-drive's reactionary nature, it is NOT literally instantaneous. Some would argue but it is in the larger scheme of things little more than a nit. Given the choice, however, I'd take TorSen.

    TorSen as employed in almost all Audis remains to this day nominally a method of splitting torque 50 50 f/r. More and more of the Audi family is offering the newest iteration of quattro -- and it is RWD biased (40 60 f/r.) Frankly, I find this change, given the truly instantaneous capability to shift torque of the TorSen system, to be the result of Audi giving in to "marketing" pressure.

    It would be far more impressive if Audis were better balanced in terms of weight than RWD torque biased -- but it makes for less engaging ad copy.

    Audi has either "among" the best if not tied for best AWD implementation with Rear biased TorSen AWD these days.

    Yet, for years, Audi has offered AWD that was/is 50 50 biased and has time and again demonstrated its leadership in AWD systems.

    Now, in the real world of highway driving, I submit that -- in order -- the optimum drive layouts are: AWD, FWD and RWD. Now of course this statement is likely stir controversy and, for once, that is not my purpose.

    Under today's Urban and Sub-urban conditions and traffic, FWD is able to be driven without the concern of over-steer.

    RWD can become tail happy; and, for most folks understanding that the way to bring an understeering auto back under control requires "turning into the skid" is a concept that, these days, is unlikely to have been taught by dad, mom or the school driver's ed instructor.

    Understeer, on the other hand, can respond to increasing the turn of the wheel in the direction one wishes to go (which is the opposite of what will right an oversteering car -- and therefore counter intuitive.) Further, applying the brake during the onset of understeer serves the purposes of "shifting the load" to the wheels that are attempting to steer the car (assuming lock up does not occur, which with most cars ABS systems is increasingly unlikely) AND slowing the car enough to reduce the tendency of the car to continue understeering (2, 2, 2 benefits in one.)

    If one is driving a RWD car in such a fashion that it begins to oversteer, simply applying the brake may, as it reduces the load from the rear tires, increase the "tail wagging" (oversteering) behavior. Further the inherent reaction to a car that is oversteering left may actually be to turn the wheel to the right, thus exacerbating the skid. If the car is "apparently skidding left" many folks will not "naturally" turn the wheel left as they do not associate turning the wheel left with "making the car turn right" thus countering the apparent direction of the skid.

    FWD for the vast majority of drivers on the Interstates, primary and secondary ROADS and Highways is almost benign. RWD can be perceived as more difficult to control.

    AWD, even Volvo's and Acura's RL (95/5 f/r torque split) are capable, at least, of keeping the hapless driver from getting into trouble better than an RWD system alone.

    Traction control mitigates this, somewhat, of course.

    But, oddly, the main advantage that RWD has over FWD is the ability for the manufacturer to put ever higher HP and torque to the driven wheels. This higher HP and torque may tend to facilitate the car's rear end to break traction and induce tail wagging (a form of oversteer, more or less.)

    FWD seems to have come to the US in the fuel crisis of the 1980's as a way of packaging. As horsepower and torque increased over the years, the ability to put power through the front wheels alone became more and more problematic -- torque steer is not a problem in a relatively low HP and Torque environment, but with many of today's high output engines, FWD can be limiting.

    For years, Audi engineers believed 200HP to be the upper limit for a FWD chassis.

    The highest performing Audis and Porsches are AWD. Virtually every Mercedes is offered in AWD and the 7 series BMW will be joining the 3 and 5 series in its next generation due out soon.

    Lambos highest performing autos, too, are -- yep -- AWD.

    Today, AWD (and another old technology -- diesel) is seen as the high performance choice and several mfgrs, Audi notably, have made a career out of mastering it.

    If you must have 2WD, make it FWD -- especially if you live anywhere that has "weather." Otherwise, go for the highest performance and the extra measure of control and fun that is part and parcel of most of the AWD systems on the market today.

    Although NOT literally true, for many folks, RWD vehicles can require either skills or electronic assists (ESP for instance) that are NOT yet universal. FWD is both more pragmatic/prudent and safe than an otherwise identical RWD variant.

    Nothing of my remarks disputes some of the obvious RWD advantages when driven at over 9/10ths and/or by a skilled driver, used to "power steering" an oversteering (RWD or AWD) car. In most of the driving we mere mortals encounter, FWD is better suited to the job -- not a better drive system.

    AWD, on the other hand, is best suited to almost all jobs and is a better drive system.

    If you can, get at least a 50 50 system; yet, don't sweat if it is X-drive versus quattro unless you plan to compete and even if you end up with a Volvo S60 type R with its 95% front bias, you are very unlikely to ever suffer any issues due to the nominal torque split.

    Instant response is better than split second reaction, however, no matter what.

    TorSen is not as widely utilized due to its weight and extra cost -- many folks think it remains almost without peer and from a practical standpoint, without peer -- period.

    :surprise:
  • jimbresjimbres Posts: 2,025
    Odd remarks, yours, about RWD's purported "tail wagging" tendency. I've driven a BMW 330i (sport pkg & 5-speed manual) under all sorts of conditions & have never experienced this. (I do not, though, go out in this car when snow or ice is on the road; I have a 4WD vehicle for that sort of thing.) Moreover, I've been frequenting these boards since 1998 & can't recall anyone describing a "tail wagging" incident. Have you personally experienced this? If so, please post the details: make & model, road conditions, etc.
  • wwestwwest Posts: 10,706
    What's he's pointing out is that if you get heavy footed with a RWD on a low traction surface the rear end WILL try to LEAD. Generally a quick flick of the stearing wheel will prevent this, or bring the car back into line.

    ALL RWD vehicles have this unavoidable heavy throttle tendency, some more than others, the earlier 911's in particular.
  • jimbresjimbres Posts: 2,025
    Understood, but it seems to me that he's trying to say more than that RWD cars tend to oversteer. He describes "tail wagging" as a form of oversteer & hints that it's potentially lethal. This leaves me scratching my head, because I've never encountered this.

    Now I've read & enjoyed Mark's posts for years, & I know that he's an AWD evangelist. My own view is that AWD confers no significant benefit once the temperature is above freezing & the roads are clear of snow & ice. Under these conditions, I'd rather not carry AWD's extra weight around with me.

    That said, I think that the war is over & AWD is the winner. Not because it's better but because it's now so cheap that few buyers will decline it, given a choice. Back in late 80s, BMW offered an AWD variant of the E30 325 for an additional 20%. At that price, there were few takers, & BMW stopped offering AWD when it introduced the E36. Today, the AWD premium is less than 5%, based on MSRP for a 530xi. The result: in my neck of the woods (a NYC suburb), I see at least 4 530xi's for every 530i. Will BMW still offer the 530i 5 years from now? I wonder.
  • markcincinnatimarkcincinnati Posts: 5,093
    You've made my point.

    And you are, apparently, a prudent driver in that you recognize the issues that a low-er coefficient of friction causes in a RWD car. But before you say "yes but," read the next paragraph.

    The lower coefficient of friction that rain, snow or ice causes, merely brings out the inherent characteristics of the vehicle in question at a lower speed. I.E., if you can induce "tail wagging" at 30kph on packed snow with car "A" and it is 45kph on packed snow with car "B" this simply permits a slow-motion (relatively) demonstration of what would happen with car "A" at 120kph and with car "B" at 160kph, on dry pavement. Most of us would rather get the sense (the feel) of an out of control vehicle and the skill required to get it back into control at the lower speeds rather than the higher speeds (hence Audi's safety training is almost always conducted on a 1.5 mile square sheet of ice.)

    If you really want to demonstrate this and you have the facilities and the access to cars, try this:

    Get three cars of similar characteristics (size, weight & power) one RWD, one FWD and one AWD.

    Go to a snow covered or ice covered (snow would be prefereable and less frustrating) parking lot (empty)

    Drive each car in a circle -- pick a small enough circle so that you can avoid any light poles, buildings or other potential metal bending objects.

    Drive each car faster and faster and faster until it begins to "break away."

    The car that will lose control first is: RWD, then FWD, then AWD. When the RWD car breaks away, it will be "fish tailing" -- the FWD, by contrast, will simply begin to turn wider and wider and to a point will respond by applying further lock on the steering wheel, until it no longer can continue in a circle -- a let up on the gas or a poke at the brakes will immediately correct its "wide steering" behavior. Conversely a poke on the brake in the RWD car will almost immediately cause a "360" or what we love to call a "donut!"

    :blush:

    Please remember I am talking about the sub 9/10ths driving activities most of us undertake daily on Primary, Secondary and Tertiary roads -- not race courses. I am also talking about the skills that most folks might have learned in the "normal course" of high school driver's ed and a few years of driving in "weather" and with the common drive lines that have dominated our highways for some 20+ years.

    I am not here to argue against RWD in other conditions (although I might point to the success Audi -- but not just Audi -- have had w/AWD in competitions since a little race called Pike's Peak back in the 1980's.)

    The tail wagging in a "safe" set of circumstances -- circumstances that dramatically demonstrated what I am talking about -- was behind the wheel of a BMW 3 series (RWD.)

    Even the traction control and ASR and ESP electronics of modern RWD cars cannot completely eliminate the "fish tailing" behavior of a 2WD car (when those wheels driven are the rears.)

    If you want to put power down: AWD.

    If you want to increase control: AWD.

    Perhaps a controversial statement for some: if you want to win races -- also AWD.

    My comments, to repeat, however, are from a "real life" perspective -- on the highways and byways of our daily driving (which I submit are rarely, if ever at 8/10's, let alone 9/10's), most folks will find "nothing satisfies like beef," er, AWD. :surprise:
  • wwestwwest Posts: 10,706
    Sorry, you're dead wrong, DEAD wrong...!

    RWD offers the most "benign", "native to your basic instincts", driving experience of all.

    Having the front wheels/tires "contact patch" DEDICATED to lateral, directional control, and the rear to DRIVE, engine torque, leading or lagging (compression braking) is without any doubt the most optimal configuration overall.

    Yes, absolutely agree that as long as traction is good or at least reasonable FWD will be the WINNER.

    AWD, hmmmmm....

    Which version....?

    Front torque biased..... absolutely NOT!

    Rear torque biased...., fixed or dynamic (4runner, Acura RDX, Lexus AWD GS300), agreed.

    Front torque biased (RX300/330/350, Highlander) NOT!
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