Tigmd99

Hey all,

Just today, i was reading Edmunds preview of the new MB S550. It now comes with "Torque Vectoring Brake." TVB is very simple...and you kinda wonder why no one thought of this much earlier. TVB lightly brakes the inside rear wheel in a corner to decrease understeer.

So, Acura SH-AWD has an extra gearset to "overdrive" the outside wheel in a corner to overcome understeer. Mercedes' TVB brakes the inside wheel to accomplish the same.

What do you guys think?? Which system is better?? For me, without knowing much about Mercedes system, i prefer the Acura's overdriving of the outside wheel, BUT prefers the Mercedes simplicity of the system (no extra gearset needed). The rear brakes on the MB would die sooner i would assume, while Acura system needs a bit more maintenance of the rear differential (fluid changes). I just don't buy into the idea of BRAKING something (MB TVB) to make you go faster...it just sounds weird.

BTW, i believe that Audi has a similar system to Mercedes??

PsychDoc

I don't believe that the quatro system does anything but vary the power fore and aft, pretty much like every other AWD setup prior to the Acura design. I also agree that this new M-B system sounds weird and pretty clearly counterintuitive. But it's nice to see others embracing the inherent logic behind the Acura system.

What was that about "imitation being the sincerest form of flattery?"

Tigmd99

On the newest Audis, there is a differential torque vectoring system on the rear diff...to accomplish the same thing.

JD23

I thought the newer Audi's only vary torque from front to back, but not side to side. The 2010 S4, however, will have an optional rear differential that can distribute torque from side to side, like the SH-AWD system.

Tigmd99

Right...but i am not sure how that system works. From Audi's description, it sounds like a brake related system, not an overdrive system like SH-AWD. I could be wrong....

Colin

I believe the Audi system will be optional, and does not include an acceleration device to overspeed the outside wheel.

winstrolvtec

Sounds like really advanced stability control, probably not that great for handling performance but a little more useful than just for safety.

Colin

The MDX has used cooperation between the VSA and the AWD system since 2007. Kinda sounds similar.

Tigmd99

Well, VSA corrects the understeer and oversteer to keep the vehicle on course. The Mercedes system, on the other hand, is actually designed to induce slight oversteer by braking the inside wheel in a corner. Therefore, it is more than just a regular stability control.

For me, i think that the end result is probably the same as the SH-AWD. The reason is that by braking the inside wheel, you are forcing more power to flow to the outside wheel (on the same axle), thus, "technically" overdriving that outside wheel...inducing slight oversteer. So, if you look at it from a theoretical point of view, it performs the same function around a corner as SH-AWD. How it performs in the real world is yet to be seen.

Ken1997TL

I wonder how much extra wear this is upon the brakes..

Tigmd99

Yup, i agree...i wonder the same. However, this is on the rear brakes, which tend to wear less than the front brakes anyways.

cp3117

It sounds like a interesting system.
I can see where it would be a lot less weight but IMO i think i would prefer the mechanical system.

It seems to be hard finding any info on the system but here is a link to Daimler Global Media site that gives a very brief look at it but not much more than what you have already stated.

http://www.daimler-financialservices...0-0-0-0-0.html

As far as the other companies systems are concerned here is another link explaining them.

http://www.popularmechanics.com/blog...s/4225886.html

Colin

The SH-AWD with cooperative VSA combines the advantages of both, ie. braking if necessary and overdriving as needed. IMO, the difference if that braking a wheel isn't going to make you faster around a track compared to accelerating a wheel.

I forget which race driver said this but it went something like this: "My advice to young drivers who want to go fast: don't use the brakes. They slow you down" (of course he was joking a bit).

The Mercedes system is interesting, but is seems like a slight modification to any 4 channel ABS system's programing. Considering how expensive a Merc brake job is, any extra wear is not a good thing for consumers. I will also concede that there probably that many Merc buyers that would drive a car that hard to induce this system.

cp3117

Thats what all the Mitsubishi owners say, now that torque vectoring is becoming so popular being they where really the first to develop it.

Over the years other manufactures have improved on it and developed improvements such as Acura, Audi etc to this system. Apparently BMW now has the most advanced system (developed by ZF) and is currently used on the X6 as it does the transfer of power even on deceleration.

cyberbro

Acura wins, to apply break to a wheel can only do so much. It's like the break systems used in SUV's that try to replace a rear differential it is OK but can not replace actual gears.

iforyou

iTrader: (1)

It's sort of like the Mechanical LSD vs the electronic LSD, I think most of us, if not all, agree that mechanical LSD is better.

Most stability control systems can also brake individual wheels to correct understeer and oversteer. It seems to me that in system from MB, it's been programmed so that the system purposely brakes the inside rear wheel when you are turning and on the gas. If that's the case, then you are wasting some of the energy through the braking system (mechanical energy is converted to heat energy). The net effect is similar, to induce some moment to turn the car.

I don't think we can argue which one is better. Some might say, simpler + cheaper = better. Some will say the mechanical system is more effective is making the car faster and thus it's better.

winstrolvtec

Provided that you want an AWD to begin with than SH is better, but if you want a RWD than TVB gives that a new twist, but if it was applied to standard AWD vs. SH-AWD, I don't think it's even a contest. Mercedes describes it as an additional safety feature within the ESP system at the physical limits, sounds like a refined ESP function, not something that's going to improve handling, but we will have to wait and see.

Tigmd99

Actually, i would think that TVB could easily be adapted to 2wd or AWD, with no additional hardware needed. 4Matic AWD system on MB (also Infiniti and BMW) have a rear-bias programming, which is more favorable than front-bias programming on the Acura's SH-AWD system.

While you have to wait for SH-AWD to divert power to the rear axle around a corner (since most power normally goes to the front axle), Mercedes 4Matic + 4ETS already have most of the power going to the rear axle all the time. And if you then add in this TVB function on the rear axle, then the rear axle should have a very good response time (in theory) around a corner. The mechanical systems like SH-AWD (or Mitsu EVO) have had unfavorable reviews in the slalom where quick transitions often show that these systems response time is a bit slow.

In addition, with less hardware (thus, less weight & less drag on the powertrain), i wonder if fuel economy of the MB's 4Matic + 4ETS + TVB system would be more economical than Acura's SH-AWD's???

winstrolvtec

What I know of SH AWD makes me think that if you are merely coasting or cruising with very light throttle application than it is mostly operating FWD, the more throttle and the severity it is applied in will result in how much power is transferred to the back wheels and if you are then turning, it will transfer left or right. If you are floored going into the turn than most of the power is at the rear anyway. I don't think SH adds that much more weight when you are already going for an AWD system, and the front drive bias helps the gas mileage as long as you drive moderately. Most AWD dynos show no more power loss by average % compared to standard AWD. I see what you are saying about the slalom, I am just not sure if that's an SH characteristic or just the TL being heavy with light steering nor do we know if the TVB is going to be effective prior to ESP engagement.

Tigmd99

I don't think that the front bias of the SHAWD adds any gas mileage since European AWD systems have rear bias...so, i don't think that the bias has anything to do with fuel economy...it is just that each system has a different philosophy on where most power goes most of the time. Personally, i think that the rear bias is more effective in a sports car.

The SHAWD system adds complexity and weight to the rear differential. Remember, the rear differential on MB AWD system is an open differential...the power distribution left and right is being managed by 4-ETS and/or TVB. The SHAWD rear differential is much more complex and involves more gears and clutch-packs.

In most reviews that i have read, the TL SHAWD and Mitsu EVO systems are slow to react to quick transitions when doing slalom testing. This has NOTHING to do with steering or weight of the car. This slow reaction has been mentioned specifically in all the reviews that i have read. The good news is that, in REAL LIFE, these super AWD systems work as advertised.

From my understanding, TVB will work with ESP (stability control) just like SHAWD and VSA interaction. So, TVB is the "European answer" to Acura's system. I would like to read more on what BMW is offering...i hear that BMW system is quite impressive.

cyberbro

"Wait" for SH-AWD, You don't drive one do you?

blakura

Do any of these rear wheel gizmos work as well as the Nissan/Infiniti system that turns the rear wheels slightly to help the vehicle's turn in? I would think that its pretty instantaneous and doesn't add weight to the car.

winstrolvtec

From my understanding in rear bias awd they have to power the driveshaft and rear differential no matter what, in SH that isn't always the case. Up to 90-percent of available torque can be transferred to the front wheels during cruising to help maximize fuel efficiency. Rear bias is likely more suitable for sport driving but it has no bearing on how it will handle, that will be up to the suspension and it's components, but when accelerating on slippery surfaces, cooperation between SH-AWD and VSA greatly enhances stability and control. The SH version adds more weight to the TL, by spec it's 250 lbs, but keep in mind it also adds a larger displacement engine amongst everything that goes along with that so it is very hard to determine just how much the SH adds alone. The E compared to it's 4 matic adds about 200 lbs, the 5's xi adds 250 lbs, base weight vs base weight on both. With that, I have no reason to believe it is actually a heavier system. On the MDX, SH-AWD allows for a 7-percent reduction in weight compared to the previous VTM-4 system, and again, dynos do not suggest that the SH shows more drivetrain lose than conventional awd setups. If the SH doesn't help the slalom then I would imagine the steering and weight of the vehicle, along with how the suspension is set up to respond to light intermittent compression, might have a lot to do with it, not really sure if the TVB will help out the slalom either, but it also serves a real life purpose regardless, good to see more innovation, it will only lead to better cars for everyone.

Tigmd99

Remember, even with front bias on the SHAWD, the driveshaft is still spinning because that 10% of power is still going rearward. Either method of power delivery will equal to gas useage.

Hmmm, i think that you're contradicting yourself here.... Remember, there is more to "handling" than just ultimate grip...i know that you don't believe that but it is true.


As for the weight issue, you bring up a good point. SHAWD will nonetheless add complexity to the rear differential where TVB does not. As stated by me above, i still prefer SHAWD's way of minimizing understeer. And i don't really care about slalom performance as long as, in real life, it works as advertised. (Thus, i am also a big fan of EVO's AWD system!)

TL|GTX

The wrx sti, has something like this and its really really good.

winstrolvtec

Naturally, I don't exactly expect the other 10% to disappear. I find that 90% front, under normal driving conditions would allow for more efficiency than most European makes which are now all about 40/60, some variations 50/50 and 30/70, all under normal driving. Regardless, it will be nearly impossible to determine the mileage effects individualy and so many other elements go into making the car effecient, so no point in debate. The SH is actively variable, front to rear and rear side to side, under all driving conditions, all the time, the Germans power transfer occurs only under slippage or wheel lose to maintain traction, with no additional benefits to handling before the occurance. In other words no traction needs to be lost for the SH-AWD do its job, this is something all the other AWD systems need. They can try to modulate the SH with braking in the TVB systems but there is no acceleration of the wheel taking place, so it will never acheive what SH does by this method because these systems are already not as fluid to begin with. That still doesn't mean it can't outhandle the SH system, it will still depend on the suspension setup and it's components. Some other systems might actually be more of benefit in the snow and weather, they can transfer side to side on the front and rear axles, just not actively like the SH can, but most feel with the 90% front drive capabilities, it's not needed. In a lot of ways it is viewed as a simpler, smarter system, only utilizing a front open, and rear "active" differential, most other systems use a center differential and front & rear open.


I am not contradicting myself I was suggesting the same thing only in different words. You are correct in saying that, dynamic feel, steering feel, neutrality, and balance are very important elements to handling in a conventional nature, but the most important one is grip, which comes in the form of tires but more importantly in the form of the suspension and it's reaction to compression. What makes SH-AWD non conventional is that it delivers those same great characteristics but can give up some grip and still outhandle a car with more. SH can actively transfer up to 70% the power to the rear wheels, and 100% of that power to either rear wheel, whitout the need of wheel spin or slippage. The other AWD systems that can transfer 100% to the rear, acting like RWD, cant actively do so, nor left and right. SH allows you to push the limits, all other drivetrains, at best, bring you back in once you have stepped outside the limit.

I see no reason why SH would not act fast enough to benefit the slalom, it's more active than standard AWD and the only reason RWD or FWD would do better in this test is mostly due to the suspension setup for that type of movement, weight and steering to greater influence the driver, but as you said, at least in everyday turns and corners it works and well.

Tigmd99

Remember, SHAWD shifts power "proactively" because it is a FWD bias system...and shifts power proactively to the rear axle to achieve RWD balance. With European AWD system, the balance is ALREADY RWD...therefore, there is no "need" to shift power at all. Again, this is where a FWD bias system has to make up for its handling deficiency by having to do an "extra" step to catch up to the competition. So, no, the European AWD systems do not need to be as active as Acura's SHAWD system to achieve the same (if not better) handling balance.

Braking an inside wheel is probably as smooth as accelerating the outside wheel around a corner IMHO. Either method is not "natural." And since European AWD system is already RWD bias, i would even argue that SHAWD "frequent active shifting of power all of the place" is more disruptive around a handling course.

Can SHAWD move a vehicle with only one wheel having traction?? I always wondered this. Is there traction control over the front axle?? VSA does not actually help you move forward...so, if Acura's both rear wheels are stuck in deep snow and one of the front tires is in deep snow, then can the Acura move forward?? If you say that the front diff on the acura is OPEN, then i would imagine that the European AWD is far better in bad weather (and in off-roading, if MDX owners ever take it that far!).

As for the European AWD system transferring power rearward, i don't know enough to argue with you. But, i doubt that it is as "dumb" as you say it is. Since most of these systems ALREADY have at least 60% of power going to the rear (withOUT the need for any slippage), these systems are equivalent to SHAWD (when working at its best!) in terms of rear power distribution. And NOW, with TVB, these systems can brake the inside wheel and force more power flow to the outside wheel around a corner, thus emulating exactly what SHAWD is trying to do.

As for the speed of which SHAWD acts, i can only refer you to the several magazine and Edmunds tests that stated that SHAWD was slow to react around the slalom course. Again, this is expected because mechanical overdrive systems like SHAWD are known to be slow around a slalom...again, please refer to Mitsu EVO X system and slalom testing results.

I think that you are confused between being active and being already RWD bias. The Acura system HAS TO BE ACTIVE because it is FWD bias...and thus, has to frequently shift power rearward to make the car more natural in handling. The European (mainly BMW and MB) systems are already RWD bias (thus, have good handling feel ALL THE TIME) and has NO NEED to be as active as the Acura system. At the same time, the European systems have 4-wheel traction control for bad weather driving. And now, with TVB, it can also compete with Acura by saying that they have a technology that is nearly (if not equal) as good around a corner.

iforyou

iTrader: (1)

With the TVB, it's essentially a derivative of a vehicle stability system. I highly doubt that will increase cornering speed as much as the SH-AWD. As I have mentioned before, there are stability systems out there that can brake individual wheel already. With the TVB, it will work specifically when you are taking a corner hard too. And I'd imagine it would work all the time, doesn't matter if you are on the gas or brake. However, that system works by dissipating energy through heat. That's wasting energy. Some of the power might get directed to the outside wheel because the inside wheel becomes hard to spin (due to the brake). But instead of purely feeling the car is being "pushed" around the turn, it would feel like the inside of the car is being "dragged" from behind. In that sense, I think that would make the car slower, even though it might feel more neutral.

But before I say/assume too much, I think it's a good idea to wait and see more test results first.

Tigmd99

Yeah, it is a derivative of stability control/traction control systems.

ALL stability control systems should be able to brake ANY individual wheel because if it cannot, then you cannot have stability control. Stability control, by definition of how it works, must be able to control all 4 brakes individually. This is why ALL vehicles with stability control MUST have 4-channel ABS.

winstrolvtec

Obviously it is front bias but that is what makes it more efficient, it is not as balanced but it is allowed to behave like it is. I wouldn't necessarily call it an extra step, they could have easily made it a rear bias system instead, but for many reasons they chose not to, not to mention it can be modified as it has been already. I think we are putting too much faith in the system that drives the car and not enough on how the car is actually setup to handle.

Yes I agree, with todays technologies braking the inside wheel should be just as smooth, but there is energy wasted there and to a degree it will slow down the car to get it around the turn instead of accelerating it around. It is behaving just like pre stability control and it's foundational purposes are to slow the car to get it back on track. SH may still need to distribute to the rear but the left to right rear transfer is also active and does not need to detect slippage or lose for it to work, before the other AWD systems transfer power to the other wheel it is already somewhat pointless for handling, it's primarily a safety measure first.

VSA incorporates 4 wheel traction control, and acts on the SH similar to TVB, in a situation where one of the front wheels has traction and no other, the system will brake that wheel engaging the opposite (as well as the others), back and forth until traction can be granted enough to then fully engage the rear. Acura may even form their own version of TVB in the front, which they sort of already have, but hopefully in an active way to mimic a fully variable front and rear AWD system.

SH-AWD acts fairly instaneously, as the throttle goes down and you turn, power is already transferring to the rear and outside rear, with still enough up front to keep it from oversteering, it mimics the opposite of what you put in, hard to explain, if it is of any interest there is an SH demo on Acura's website with a meter that even comes on the car, it will display how it is actually working as you drive variously.

The other systems are not dumb, they obviously work vey well and sell. These new TVB sytems will be very good, I just don't believe that they are at an active phase, they must still be triggered by traction lose or slip to engage. SH does not need slippage to defer any portion of power anywhere.

I will have to look into the Evo X system, I may be wrong but as far as I know SH is the only one to be able to transfer side to side actively to actually prevent the slippage or lose in the first place and assist handling. Again, I really feel as good as these systems are if the car is not set up right to handle in the first place then there is only so much that they can do. There were better handling cars before and there still will be after.

Tigmd99

winstrolvtec, i was going to write a long post, but then i realize that i did that already in the previous post...and yet, you simply refuse to understand! I am simply dealing with someone who has blind enthusiasm for a brand...i am not gonna convince you otherwise because Acura can do no wrong and everything Acura is top-notch. I should have figured this out long ago when you stated how high quality Acura leather was!

Have a good day...i sure hate to be around you when you finally open your eyes...your world will come crashing down!

Tigmd99

For more info on the various "torque vectoring" technologies, here is a good link: http://www.popularmechanics.com/blog...s/4225886.html

As for Mitsubishi AYC (active yaw control), here are several links:
http://www.lancerregister.com/faq/G04/g04.html (excellent explanation!)

http://www.mitsubishi-motors.com/cor...003/15E_11.pdf

http://www.lancerevoclub.com/evoclub-ayc-e.htm

Seemingly, Acura system is not a breakthrough as i once thought! Mitsubishi is apparently a leader (creator??) in torque vectoring differentials. It is probably that Acura is better at advertising it than Mitsu! Mitsubishi has been installing torque vectoring differentials since 1996...way before Acura came out with AWD system in their MDX in 2001! Thus, there have been torque vectoring differentials long before Acura came up with the idea.

Tigmd99

BTW, the main difference between EVO X "S-AYC" (super-active-yaw-control) and the previous versions is that the trick rear differential is now also working together with the new stability control...so, in essence, it works like SHAWD + VSA. (Prior EVOs did not have stability control.)

winstrolvtec

Mitsubishi does not offer a product that would interest most people anyway, S-AYC or not. Acura put it in a premium luxury sports cars and utility vehicles. Biased has nothing to do with it, therefore I dont own an AWD vehicle but intend to do so, I do know that when it comes to "handling" there is no other AWD system, hence the name. You are just going to have to get used to the idea that Japs, in particular Honda, are much more innovative considering their target markets and price point. I already talked about the shortcomings of the SH system and I can even elaborate, there is a difference in blind enthusiasm vs knowing what you are talking about. You made several comments about needing to be active because of front bias and rear transfer, but it seems to me you failed to realize that this front to rear active nature has never been done before, and no other AWD system (besides the Mitsubishi) "proactively" distributes left and right, only "reactively", even if they can transfer rear to front and front side to side, unlike the SH. It truly is a breakthrough when considering FWD effeciency, RWD handling, AWD versitility, in this regard nothing comes close. I also have reading material.

http://www.edmunds.com/insideline/do...ticleId=132226

Tigmd99

Yes, the front to rear has never been done before...because it did not need to with a RWD bias vehicle! Acura is fixated on the Honda platform...and thus, needed this extra step to keep up. Why is this so hard for you to understand??

TVB will "proactively" do the same thing (in theory) as SHAWD rear differential clutch plates. Why is this so hard for you to understand??

Sorry if the Mitsu EVO X does not have FWD bias...it is afterall, a "proper" sports car with 50/50 weight distribution and an amazing AWD system that surpasses everything else (bar none) except the Nissan GT-R system.

What does "interest most people" have to do with anything?? Are you being arrogant again?? Are you being "aristocratic" again by saying that only the rich can afford the TL?? Did you know that the EVO X MR costs only a few thousand dollars less than your TL SHAWD?? Did you know that, on a technological AWD basis, the EVO X is a lot more advanced than the TL SHAWD?? READ those links above and you will be wowed by EVO X's powertrain! And lets not even get into the heritage between the two vehicle...not even close!

But, we digress. It is clear that the trick rear differential on the SHAWD Acura is NOT a first in the auto industry. And now, more and more brands are coming out with near equivalent (or equivalent) technology to compete with Acura's system.

Tigmd99

See, i have indeed educated a person who claims to "know what he is talking about."

Hint: blind enthusiam.

winstrolvtec

SH AWD can overcome limiting vehicle dimension, does not need a near perfect weight distribution, is less intrusive, simpler overall system with less drag and drivetrain lose, improved efficiency and performance, by allowing to drive mostly on the front wheels when needed then driving the rear as needed. Aside from all this and the point of the thread, VSA already acts on the SH-AWD system better than these new TVB systems do, and modulate the SH for improved safety function and can help to further enhance the dynamics in any situation WITHOUT having to apply any brakes, they only come on as a last resort in severe situations.

winstrolvtec

Correct, it is not, but the overall function of the system has never been done before, that's all Im saying.

And thank you for that, afterall you do owe me I have been educating you all along.

Tigmd99

Oh boy, here you go again showing your total lack of knowledge on driving...have you ever taken your car to the track or drive a RWD car on a track?? Nevermind, don't answer that because i am sure you are a professional track driver in disguise!

BINGO...you have no idea what you're talking about!! Thanks for making it crystal clear for everyone. You don't even understand how VSA (stability control) works!! By definition, VSA works by modulating the BRAKES on individual wheels to avoid excess oversteer and understeer. It will also dethrottle the engine to kill momentum.

Ok, i am done with arguing with you...it is like talking to a freaking wall. GET A CLUE!

Tigmd99

*COUGH* bullshit *COUGH*