Nerd talk: The magic of torque vectoring
 

The S-AWC is a unique but highly effective system when it comes to improving evo's track and everyday performance. The torque vectoring(TV) on our cars is simply brilliant. I have always wondered how it stacks up against quattro, honda's TV, suburu's awd.
Finally i found this. Its an interesting read, goes over your head at times. Check it out

Very interesting... Thx

Thank you for that I feel smarter now

Neither Audi nor Subaru have torque vectoring that I know of. The second generation of Honda's SH-AWD does have torque vectoring, but it's completely different from from our AYC and is really a component of the Honda's (gas/electric) hybrid driveline. In a nutshell, on the latest Acuras with SH-AWD, the separate electric motors on the rear wheels are not powered equally when turning, producing the desired yaw. It's not clear to me whether this really is better than the first generation of SH-AWD, which was a Haldex center.

My understanding is the SH-AWD (non-hybrid) is capable of splitting power front to rear as well as left to right. The F-R split varies by model but the L-R split can be up to 100% in either direction.

That matches my understanding. The first version of SH-AWD (which is on the non-hybrids) had a Haldex center, so it can control the torque distribution in detail. But those cars didn't have torque vectoring (that I know of); that is: they couldn't do anything left/right.

But, to be honest, the only stuff that I really know about Hondas is what I can see in a rear-view mirror. :)

but they do

I wish I could say the same but all of my hondas are much quicker/faster than the evo.

Ummm stop being such a mitsubishi homer. Honda was the 1st to come out with rear torque vectoring.

My wife has an Acura MDX with SH-AWD and it distributes up to 70% troque to the rear and up to 100% of that to either rear wheel when needed. Oh and the AWD graph in the dash is a hell of a lot nicer and responsive than the evo's.

This thread makes me want to build another boosted honda for cheap and pick on some evo's on the freeway

If one or both of you are saying that the first generation of SH-AWD - i.e., the one with a Haldex center - had some kind of torque vectoring, that's not only news to me, but I don't see how it can do it. In contrast, if you're talking about the second generation - i.e., that which comes on a hybrid - then we agree, because that's what I said. In the second-gen cars, the torque vectoring is achieved by differences in power to the two, separate electric motors in the rear.

With regard to claims about X% of the torque being sent to one end of the car or Y% being sent to a given wheel, I've given up on arguing about this. Very few people seem to understand the distinction between torque split and torque distribution for a conventional AWD. When we're talking about a Haldex....

The torque split is variable front to rear and side to side. The first sh-awd could go from 70 percent front/30 percent rear to 30F/70R in the rl, 90F/10R to 50/50 in the mdx, and 90/10 to ,I believe, 60/40 in the rdx. The torque sent to the front or rear is also variable from side to side, up to 100 percent. I don't understand why that wouldn't be considered to be torque vectoring.

With regard to the haldex you keep referring to. Apparently between the transmission and rear differential there is another component which over drives the rear and that is how they accomplish the adjustable f/r split.

Edited for correctness: no center differential or haldex

There is no center differential in a car with a Haldex.

Honestly, I don't know what youre talking about
There is no haldex there is no hybrid
There is a transfer case and a mechanical rear dif
Its always had torque vectoring front to rear (unlike the evo) and left to right the day it came out in the early 2000's and if you want to get nitpicky honda also had torque vectoring in a fwd configuration in the late 90's in the prelude

You're right there. But as someone else also pointed out, Honda doesn't use a center differential or a haldex.

It seems I missed one generation. Sorry about that. More accurately, what I was calling the first generation was not considered to be SH-AWD. I learned a lot this morning. Thanks.

List of systems capable of active left-right torque vectoring

• Audi's quattro with Sport Differential
• ...
• Subaru's AWD on 2015 WRX

http://en.wikipedia.org/wiki/Torque_vectoring

Haldex also makes center differentials for vw's system. I'm learning a lot as well :-)

What I mean by a "Haldex" is a device that connects one axle to the transmission via a clutch, instead of a differential. They are a huge step above the old method of using a viscous coupling for the same purpose because they don't wait for slip and react to it; they can lock before slip occurs. I'm tempted to add that I believe that VW is the maker who has made the most of these devices, but I need to stop talking about cars other than Mitsus (for obvious reasons).

I was embarrassed enough to spend/waste some time learning how the rear diff in an Acura's SH-AWD system works. It's pretty much the same as our AYC with one difference: while our system either speeds up or slows down the right rear wheel and lets the diff, itself, cause the opposite change to the left rear wheel, the SH-AWD rear either speeds up the right rear wheel or speeds up the left rear wheel, letting the diff slow down the opposite wheel. In other words, instead of having a faster-than-input and slower-than-input shaft both going to the right side of the rear end with both sets of clutches on the right, as we have, their rear is symmetrical, with one faster-than-input going to each side and one set of clutches on each side.

If you're hung-up on symmetry, I suppose you might like Honda's version better. Otherwise, it's six of one vs half-dozen of another.

Okay. But Haldex is a brand name, not a technology.

Aye. But so is "Frito," while no-one (that I know) says "corn chips." Likewise, people say "Quaife" for "helical," etc. As long as we both know what's being said....

The specificity of calling something a haldex would be like saying that a car has a Delphi.

Maybe a better analogy would be to say that Mitsubishi uses vtec.

I have also never, ever heard anyone use "Quaife" to refer to a diff.

Same with "Frito."

Should we just start calling SH-AWD (there was never a SH-AWD branded system without F-R and (rear) L-R torque vectoring), "dual Haldex," since apparently, Haldex invented clutch control AWD? Even though Honda's similar RT-AWD predates Haldex by nearly a decade?

The L/R torque split in the rear of the latest SH-AWD system is accomplished by a combination of a conventional diff and two speed-up clutches, one on each output. It has almost nothing in common with a Haldex center. You can, of course, call it whatever you wish, but if you're looking for a label that will help people understand how it works, then Haldex should be pretty far down the list.

As to the Frito analogy: I withdraw it. The parallel would be calling corn chips "Lays" so it fails.

The Audi S4 with sport diff has L/R torque vectoring. I believe it also came out in the RS5 first?

http://www.audi.com.au/au/brand/en/a...vectoring.html

- Additionally distributes drive torque in variable proportions between the wheels at the rear.
- If required, full propulsive power at the rear axle is applied to only one of the two rear wheels.
- Instead of braking the inside wheel, more power is directed to the outside wheel when steering or accelerating into a bend.

- Basic distribution of drive torque: 60% to the rear axle, 40% to the front – which permits high levels of traction and good handling characteristics.
- If one axle loses grip, up to 85% of the tractive power can be diverted to the rear axle and up to 70% to the front.
- Torque vectoring enables propulsive power to be distributed to each individual wheel.
- Power and torque are redistributed without any delay, even before a wheel starts to spin.
- Power is distributed according to the driving situation and driving style.

http://en.wikipedia.org/wiki/Quattro...quattro_system

Vectoring quattro system

Audi's new sport differential, debuted 'torque vectoring' to quattro generation V. The Audi sport differential allowed the dynamic allocation of torque across the rear axle of the debut vehicle: the B8 (2008) S4, and is now an optional addition to all quattro vehicles, which continue to use the 40:60 asymmetric Torsen (Type "C") centre differential. The sport differential replaces the normal open rear differential while the front axle still rely on an open differential with EDL.[4]

The torque vectoring rear axle differential is designed and manufactured by Magna Powertrain,[5] and is being offered on Audi A4, A5, A6 and their derivatives (including RS models). The Sport Differential selectively distributes torque to the rear axle wheels thereby generating a yaw moment, which improves handling and also stabilizes the vehicle when it oversteers or understeers, thereby increasing safety.

The sport differential operates by using two superposition ("step up") gears at the differential, which are operated via multi-plate clutches each side of the differential crown wheel. When required by the software (using lateral and longitudinal yaw sensors, the ABS wheel sensors, and a steering wheel sensor), the control software (located in a control unit close to the rear differential), actuates the relevant clutch pack. This has the effect of taking the output shaft drive through the step-up gear to the attached wheel, while the other shaft continues to drive its wheel directly (i.e., the clutch pack not actuated). The higher speed output shaft produces increased torque to the wheel, producing a yaw (turning) moment. In normal operation increased torque is delivered to the wheel on the outside of the turn thereby increasing the vehicles turning moment, in other words, its willingness to turn in the direction pointed by the steering wheel.

I try to avoid reading descriptions of the effects unless, at some point, they get around to saying how it works. Thus, this is the key section:

At first, this was sounding like an AYC (or the Honda version thereof). But then it starts taking about one output going through a step-up while the other is being driven directly off the diff, which is quite different. Do you know which reading is correct?

This might be helpful?

http://www.pistonheads.com/pics/news/19868/audi2-L.jpg

http://www.audiworld.com/wp-content/.../header220.jpg

That active suspension is such a tease....

I am 100% sure the audi quattro with a sports differential has torque vectoring. The sports differential is an optional package( i remember seeing their brochure).
The new WRX STI has 100%. That's something Subaru is bragging about.

<= starting to regret correcting himself in separate posts, rather than deleting the original error....

Is 100% of that regret directed towards the post in which you corrected yourself or is there a 50/50 split between that and the original post? How would regret vectoring distribute the regret in a situation like this?

Rather than having a differential with a meaningful native regret split, my retrospection system using a Haldex, such that sometimes my regret has no meaningful split, only a moment-to-moment distribution, and sometimes - e.g., when I yank the mental equivalent of the hand-brake - my regret snaps wide open and I no longer care.

I'm in the process right now of retuning my regret-distributing Haldex's ECU, because I've opted to cease being a Mod. For a while, I'll probably limit the clutch to a 25% duty cycle, at most.

When I had a 08 rdx sh-awd it did handle quite well. However I did notice under heavy throttle, it would put most of the power to the front wheels, unless in snow.

Nowhere near the handling of a evo, apples & oranges being one is a SUV & one is rally car.

Btw that was a solid motor, just the factory turbo was a little on the weak side. No power from a dig til about 20 mph. Then again, it weighed 4400lbs.