Here's how the Focus RS awd system works

"Textured Soy Protein" (texturedsoyprotein) 02/03/2015 at 12:49 • Filed to: None

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Having owned a few awd/4wd vehicles, I have learned that not all awd/4wd is created equal. Some gadgety kinds of awd are fine, while others...not as much. Most of the articles on the new Focus RS say it has some kind of torque-vectoring awd system but don’t go into details. Luckily, Ford has !!!error: Indecipherable SUB-paragraph formatting!!! .

UPDATE 11/30/2015: this post is kind of old. But it keeps getting linked back to, and there’s more recent information, including !!!error: Indecipherable SUB-paragraph formatting!!! . You can see more details about the system in that press release. My speculation about it being a Haldex system, well, it was just speculation. The rest of the original post and my initial update a couple of days later is as follows...

The Ford Performance All-Wheel-Drive system is based on twin electronically controlled clutch packs on each side of the rear drive unit. These manage the car’s front/rear torque split, and can control the side-to-side torque distribution on the rear axle – delivering the “torque vectoring” capability that has a dramatic impact on handling and cornering stability.

The control unit in the rear drive unit continuously varies the front/rear and side-to-side torque distribution to suit the current driving situation, monitoring inputs from multiple vehicle sensors 100 times per second. A maximum of 70 percent of the drive torque can be diverted to the rear axle. Up to 100 percent of available torque at the rear axle can be sent to each rear wheel.

During cornering, the rear drive unit pre-emptively diverts torque to the outer rear wheel immediately based on inputs such as steering wheel angle, lateral acceleration, yaw and speed. This torque transfer has the effect of “driving” the car into the bend, achieving improved turn-in and stability, and virtually eliminating understeer.

Translation: There isn’t a center differential, but the rear diff has an electronically-controlled clutch pack that can send up to 70% of the power to the rear axle. It has another clutch pack that acts as an electronic LSD for the rear axle. The rear diff does active (i.e. not brake-based) torque vectoring.

To deliver optimum driving dynamics, the Ford Performance All-Wheel-Drive system was calibrated alongside the car’s advanced Electronic Stability Control, in particular the brake-based Torque Vectoring Control system that works in parallel with the torque-vectoring AWD.

Translation: The front differential is an open differential with brake-based torque vectoring.

The big question this press release doesn’t address is the default front-rear torque split. Ford doesn’t mention the word Haldex anywhere in their press release, but it’s sounding pretty Haldex-y to me. At least that’s my guess. The overall description seems very similar to Saab’s XWD system, which was a Haldex Gen IV awd system combined with a rear eLSD. Here’s a !!!error: Indecipherable SUB-paragraph formatting!!! :

!!! UNKNOWN CONTENT TYPE !!!

The hardware consists of a Power Take-off Unit (PTU) in the front final-drive that transmits engine torque through a prop-shaft to the Rear Drive Module (RDM). This incorporates a Torque Transfer Device (TTD) and an electronically-controlled Limited Slip Differential (eLSD). Both are wet, multi-plate clutch units from Haldex .

Also, both the Ford press release and !!!error: Indecipherable SUB-paragraph formatting!!! talk about preemptively sending torque to the rear wheels, and Ford has used Haldex awd in other transverse-engined cars with similar platforms to the Focus.

Haldex is sometimes a bit of a dirty word. Many people have the partly-mistaken impression that Haldex awd doesn’t send power to the rear wheels until the fronts slip. “Oh your car doesn’t have real awd, it’s just Haldex .” But remember, Haldex and Ford talk about preemptively sending torque to the rear wheels.

Haldex can actually work pretty damn well for sporty handling, especially combined with a rear LSD of some sort. I used to have a Mazdaspeed 6, which had Haldex awd and a Torsen mechanical rear LSD. It was stupid easy to take turns way too fast, and rocket out of them. It was basically just an exercise in braking late, turning in, and then stomping on the gas. Based on the steering & throttle inputs, the Haldex awd would preemptively send power to the rear wheels before the fronts would spin, and that plus the Torsen rear diff gave plenty of rotation through the turn.

Really, the only major downside of a properly-tuned Haldex awd + rear LSD system is deep snow. Because there’s no fixed resting torque split, Haldex tends not to keep all the wheels churning, and then you’re more like in a fwd car. My MS6 with Blizzaks on it was a very capable winter car, but I got stuck a couple times in the deep stuff precisely for this reason. Even with the traction & stability control fully disabled, I couldn’t get all 4 wheels to spin together. The computer couldn’t quite make up its mind. Luckily that car had a handy-dandy tow hook that screwed into a mount behind a plug in the rear bumper.

So, for sporty driving and 90% of most winter driving situations, I’ll bet the Focus RS is great. But if you’re planning to drive through foot-deep snow drifts on a regular basis, well, can I perhaps interest you in something with a real center differential?

UPDATE: There’s a slide from Ford that goes into more detail on the actual mechanical layout than the wording of their press release. Turns out the system is somewhat different mechanically than the Haldex/XWD although likely achieves a similar function.

(H/t to !!!error: Indecipherable SUB-paragraph formatting!!! and !!!error: Indecipherable SUB-paragraph formatting!!! .)

Will with a W8 races an E30 > Textured Soy Protein 02/03/2015 at 13:01

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Note that the press release says "twin clutches" not "two clutches." Maybe this refers to the Twinster system used in the Range Rover Evoque?

http://www.gkn.com/media/News/Pag…

RamblinRover Luxury-Yacht > Textured Soy Protein 02/03/2015 at 13:04

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Sounds about right. I also agree with your judgment on suitability.

Opposite Locksmith > Textured Soy Protein 02/03/2015 at 13:05

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thanks!

Hermann > Textured Soy Protein 02/03/2015 at 13:06

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Awesome article! Nice to cut the bullcrap and distill the content of the press release.

Isn't this the same system they use on the AWD Fusion?

Textured Soy Protein > Will with a W8 races an E30 02/03/2015 at 13:15

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Hmm interesting. Here's why I think it's not the GKN Twinster though. From your link:

The GKN PTU synchronizer and GKN TWINSTER ® are controlled by a dedicated driveline control unit designed to constantly monitor vehicle dynamics, disconnecting during steady-state driving speeds above 22mph and automatically reconnecting (within 300 milliseconds) when required .

In addition to the disconnect function the GKN TWINSTER ® also acts as an electronic differential combining drive vectoring and limited slip differential technology for active torque biasing.

Ford doesn't say anything about disconnecting the rear wheels. Only that up to 70% of the power can be sent to them.

nermal > Textured Soy Protein 02/03/2015 at 13:17

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This is excellent info!

When I hear "clutch" associated with a sporty-ish car, I begin to think about wear. What's the expected lifespan of these?

Textured Soy Protein > RamblinRover Luxury-Yacht 02/03/2015 at 13:17

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I definitely learned the hard way that Haldex just isn't so great in deep snow. ;) That rear bumper tow hook mount saved my bacon more than once.

Textured Soy Protein > Hermann 02/03/2015 at 13:18

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The awd Fusion has Haldex awd but I don't think it has a rear eLSD. Not sure if it has any sort of brake-based torque vectoring either.

Will with a W8 races an E30 > Textured Soy Protein 02/03/2015 at 13:18

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Twinster is only the RDM. The disconnect is in the PTU, and used for fuel economy - a traditional PTU is just a ring and pinion. Using just the twinster RDM with a traditional PTU would give the car "twin cluch" torque vectoring.

Textured Soy Protein > Will with a W8 races an E30 02/03/2015 at 13:28

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Valid point. I'm trying to find more information on how exactly the Haldex eLSD works, but so far the most I've found is this old press release which states:

Haldex will supply SAAB Automobile with an electronic AWD-system, based on the fourth generation of its established Haldex Limited Slip Coupling and the all new, evolutionary Haldex electronic Limited Slip Differential (Haldex XWD) developed from the Haldex product platform of limited slip differentials.

Employed in conjunction with the Haldex coupling, the electronically controlled add-on module integrates in the power and control systems of the longitudinal device thus offering a flexible and cost effective solution for further enhanced vehicle dynamics. It can be optionally used in the vehicle product lines to control the side-to-side torque distribution and constitutes an efficient alternative relative brake based systems which dissipate power for control. The limited weight and size maximizes performance with minimal impact on fuel economy. For more detailed information regarding Haldex XWD, www.haldex-traction.com/xwd

Haldex currently supply three of the major OEM groups , VW AG, Ford Motor Company and General Motors with proprietary and advanced systems and solutions for AWD.

Only problem is, that second link no longer works, and this press release doesn't say if the eLSD uses a clutch or what. The main Haldex rear drive unit does have a clutch . So if the eLSD also has a clutch, that could make for the twin clutches Ford is talking about.

Edit: Oh yeah, the Jalopnik post quoting a Saab press release that I included orginally, says the eLSD is a clutch. So yeah, two clutches.

Not saying it couldn't also be GKN, as they also supply Ford . Overall the systems seem to operate on the same basic idea of a front power takeoff unit and rear drive module that does most of the power distribution.

Textured Soy Protein > nermal 02/03/2015 at 13:30

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Honestly, I have no idea on the lifespan.

Will with a W8 races an E30 > Textured Soy Protein 02/03/2015 at 13:37

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The issue with eLSD is it is just that, eLSD - not torque vectoring. eLSD is only capable of locking the two wheels together, not driving just one wheel. That ability to pick between wheels is critical to achieving this effect:

During cornering, the rear drive unit pre-emptively diverts torque to the outer rear wheel immediately based on inputs such as steering wheel angle, lateral acceleration, yaw and speed. This torque transfer has the effect of "driving" the car into the bend, achieving improved turn-in and stability, and virtually eliminating understeer.

Although, to be true torque vectoring, the RDM must be capable of overdriving one wheel, similar to this behemoth from Audi (also relying on twin clutches, but with a step up gear on each halfshaft):

Hermann > Textured Soy Protein 02/03/2015 at 13:47

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Got it.

Let's hope this system works well. I'd love to see someone kick the Golf R's ass (both performance and sales) so VW has to come up with something even better, and Ford, too.

Textured Soy Protein > Will with a W8 races an E30 02/03/2015 at 13:48

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LSDs—mechanical or electrical—don't "only lock the rear wheels together." They continuously vary torque, whether by means of a clutch pack that has varying degrees of slip, a helical gearset that biases torque, a viscous coupling, hydraulic gerotor pumps, whatever.

From the same link as before:

This is the first application of an electronically-controlled, rear limited slip differential in this segment of the market. The eLSD is installed alongside the RDM and operates via pressurized clutch plates on a principle similar to the larger TTD. In icy or wet split-friction conditions, for example, it uses inputs from the rear wheel speed sensors and can transfer up to 40% of torque between the drive shafts, to whichever wheel has more grip.

The eLSD also gives the driver enhanced control when cornering hard or completing a high speed maneuver, such as a lane change, by momentarily applying more or less torque to either of the wheels to help the rear of the car more closely follow the direction of the front wheels. This yaw damping effect can keep the car better balanced and more tightly controlled, without requiring 'outside' intervention from electronic stability aides.

I believe, by saying it can transfer 40% of the torque between the drive shafts, that means up to 90% of the torque to one rear wheel. (50/50 normal L/R split +/- 40% = 90% total) And that's talking about the eLSD in the now-old Haldex Gen 4/Saab XWD system. So it could stand to reason that in the 7 years since that press release came out, Haldex has developed an updated rear eLSD that can send 100% of the power to one rear wheel as Ford describes.

As I've said before, I'm not ruling out the possibility of this system being supplied by GKN rather than Haldex. Ford in their press release doesn't mention the supplier. This is just my guess.

But in the end, both the GKN and Haldex operate on similar principles of a power takeoff unit and rear drive module, rather than a true center differential.

Textured Soy Protein > Hermann 02/03/2015 at 13:52

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Golf R uses Haldex, but with open front & rear diffs with brake-based torque vectoring. Since the Focus RS has a Haldex-like awd system with rear eLSD and front brake-based torque vectoring, that's theoretically better.

Will with a W8 races an E30 > Textured Soy Protein 02/03/2015 at 14:13

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Yes, it's certainly a PTU and and 2 clutches, the question is just how are the clutches arranged. I guess we'll have to wait to find out for sure.

In the mean time, this XWD system is interesting. It seems a bit excessively complicated, but I think this is a cutaway of it:

It looks like it works by connecting the left side halfshaft to the diff carrier through a wet clutch. This would allow it to effectively limit the relative speed between the two wheels, and I suppose even wheels locked together could result in whatever torque split you want depending on surface. But, given a smooth, consistent surface, there is no way to apply torque to only the outside wheel - the inside would be driven simultaneously and with the same torque, until one wheel breaks traction.

Hermann > Textured Soy Protein 02/03/2015 at 14:21

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Yeah. Exactly.

Ford's system looks more complex, yet more clever to be able to deliver more power and handling. And as it seems they're not recycling the system from another project like the S3 and the Golf R using the same drivetrain, sharing most components with more cars from both brands, for example the Haldex system is also on the Q3, A4, etc (basically all cars with with transverse engines).

So, there's another reason why this should work well. Ford could use this much cleverer new system do deliver AWD on more models. Perhaps a Fusion ST someday.

Textured Soy Protein > Hermann 02/03/2015 at 14:34

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I dunno if I'd say Ford's is much cleverer. It's still a Haldex-type system for the front/rear split, but adds the rear eLSD. Kinda like Saab XWD.

Textured Soy Protein > Will with a W8 races an E30 02/03/2015 at 14:43

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So, the way I understand a mechanical clutch-type LSD works in a turn, is that typically if you don't have wheel spin, the outside wheel is going faster because it's covering a larger distance. If the inside wheel spins, its speed starts catching up to the outside wheel, which causes the springs in the diff to start progressively engaging the clutch. The clutch slip starts transferring power that is being sent to the spinning inside wheel, back to the outside wheel. Effectively slowing down the inside wheel, and speeding up the outside wheel. If the clutch locks then both wheels spin at the same speed.

In an eLSD where the clutch is controlled by a computer rather than a mechanical reaction to wheelspin, wouldn't it stand to reason that the computer can use things like wheel speed, steering angle, and yaw sensors to say, "oh hey we're turning, let's engage the clutch now" and speed up the outside wheel?

racingmaniac > Textured Soy Protein 02/03/2015 at 14:48

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Haldex also supplies the eLSD(VAQ) on the VW GTI/Seat Cupra 280. Which is able to vector torque 100% to either front wheel. It sounds like if Ford got the normal Golf R style Haldex and added a GTI like eLSD to the back it is basically what they got. Which I guess is the XWD from Saab...

420SX > Hermann 02/03/2015 at 14:54

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Correction: Only A3s come with the Haldex system.

A4s are the "Quattro" drivetrains.

HammerheadFistpunch > Textured Soy Protein 02/03/2015 at 14:56

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great work, i think you nailed it

Gary Yogurt > Textured Soy Protein 02/03/2015 at 14:57

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Excellent write-up! Thanks for the lesson.

MoogleMD > Hermann 02/03/2015 at 14:58

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Pretty sure the A4 is longitudinal and torsen based awd.

A3, Q3, S3 are all transverse. PQ35 and MQB based.

Ratchet when he's all hopped up on synthetic energon > Textured Soy Protein 02/03/2015 at 15:00

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Isn't this how the rear axle works in the AWD Juke, too?

jlnbos > Textured Soy Protein 02/03/2015 at 15:01

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The only way you can get all 4 wheels to turn together is with front and rear locking diffs and either a part-time 4WD system (transfer case with no diff) or a locking center diff. There are few vehicles with this type of system — Mercedes G-class, Wrangler Rubicon.

Any word on maintenance for these type of clutch pack systems? Do they wear out and what is the cost to replace them? One advantage of Torsen limited slip, locking diffs is that other than a fluid change now and then they will last the life of the vehicle. I've put 150k on my '03 4Runner and haven't done anything to the Torsen center diff other than fluid changes.

CBus660R > nermal 02/03/2015 at 15:02

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The clutch based LSD in my '98 2wd F150 was working flawlessly when I sold it with 160k miles on it. My '06 Mustang GT with 106k when I sold it was working flawlessly too. Rebuild kits are about $100 (of course labor could add up).

natrat > Textured Soy Protein 02/03/2015 at 15:02

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re the deeper snow, the low clearance means high centering gonna probably get you first anyway

ProjectVroom.com > Textured Soy Protein 02/03/2015 at 15:03

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The Ford Performance All-Wheel-Drive system is based on twin electronically controlled clutch packs on each side of the rear drive unit .

To me this sounds like there is always power being sent to the rear drive unit, and then there's a clutch on each side that engages the drive shaft to the left and right rear wheels. So that drive shaft from the front to back is always getting power, whether those rear clutch packs are engaged without slippage is the question. Sounds like an open diff up front with brake based vectoring.

Will with a W8 races an E30 > Textured Soy Protein 02/03/2015 at 15:04

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Close - the clutch doesn't really transfer power from inside to outside so much as progressively lock the two together. This obviously slows the inside wheel, as well as the engine (the outside wheel remains at road speed, and does not slip unless its traction is overcome as well). At full lock, the wheels will spin together at the same speed, regardless of the torque on them. At lower clutch pressures, they can still spin at different speeds, but this differentiation is resisted by the clutch pack.

Think of it this way - in an open differential, carrier torque is the sum of the wheel torques. The torque on each wheel is equal - if the inside wheel looses traction, the other looses torque. Now imagine if you could take that inside wheel, and slowly apply the brake. Force to the road on that wheel stays the same, but the torque on that wheel that the differential sees increases by the amount of braking. The two wheels have to have the same torque, so now the torque to the outside wheel is the same as the torque applied to the inside wheel by the brake. This is how brake torque vectoring works.

Now take that brake, and instead of applying it to one wheel, have it attempt to hold the two wheels at the same speed. Now there is still little torque on the inside wheel when it spins, but the torque on the outside wheel is still the amount applied by the brake (plus what little the inside wheel can muster). This is how a clutch type LSD works - it ties the two wheels together such that the outside wheel can get inside wheel torque PLUS clutch torque, instead of just what the inside wheel gets.

Finally, the only difference between eLSD and clutch LSD is that the clutch is controlled by a computer instead of some mechanical mechanism.

Justin Hughes > Textured Soy Protein 02/03/2015 at 15:04

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A maximum of 70 percent of the drive torque can be diverted to the rear axle. Up to 100 percent of available torque at the rear axle can be sent to each rear wheel.

That explains those shots from the teaser video that clearly showed the RS going three wheeling. The Focus is designed to be a FWD car, so it's going to have FWD handling characteristics, and this is one of them. This was one of the strong arguments used to predict that the RS would be FWD rather than AWD. As it turns out, the system is able to send all of the power to the rear wheel remaining on the ground, which means none of it goes literally into thin air.

natrat > Textured Soy Protein 02/03/2015 at 15:05

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much much cheaper to fix than an automated clutch

Hooneriphic > Will with a W8 races an E30 02/03/2015 at 15:06

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So here's my question: How does this setup perform on a track with some super stickies? I regularly track my MS3 and although I bought the car as a utility with a side of fun type vehicle, I've been really happy with it's track performance. Keep in mind I'm a weekend warrior at best. No competition track time and I have very real expectations about what a 370 hp fwd vehicle can/will do.

With that said, I recently moved to PA and I'm fairly sure I've found a secret society of Subby owners. They'er everywhere. Mostly because we get some snow/ice and we have hilly roads. Maybe a few of them like to rally but I'll wager that's a severe minority. If the new STi hadn't been so disappointing in the looks department I would have already bought one. The new RS looks great (IMO) and if it's truly priced in the STi category, I may very well get in line. To me, it seems like the perfect car for me. Great utilitarian function (4 door hatch) with AWD (great for bad weather) and a platform that can easily be coaxed to make more HP. I love tracking my car and if I could solve some of the issues I (expectedly) encounter with my MS3 at the track, I'd be pretty well sold.

Textured Soy Protein > Ratchet when he's all hopped up on synthetic energon 02/03/2015 at 15:08

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In a quick search I'm not finding too much detail on the exact mechanism by which the Juke's rear axle accomplishes torque vectoring, beyond the fact that it is in fact a real torque vectoring differential and not an open diff with brake-based torque vectoring.

So the answer to your question is likely yes, at least in concept, if not necessarily in having the same mechanism.

BC1BC2BC3 > Textured Soy Protein 02/03/2015 at 15:09

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Ford Focus RS day is my favorite.

typhoon5000 > Textured Soy Protein 02/03/2015 at 15:09

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The Fusion or any current Ford product does not use a Haldex AWD system. They stopped using them after the Fivehundred/Freestyle/Montego went to the Taurus/Taurus X. Since then, they've used JTEKT (who own Torsen) as their sole supplier of AWD systems.

Cheapo > Will with a W8 races an E30 02/03/2015 at 15:10

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After hearing the Focus would be AWD I was curious how it would actually stack up. Im cross shopping this with a WRX/STi to be used in Denver, guess that gives the edge to the Subaru pair.

Treemendous > Textured Soy Protein 02/03/2015 at 15:10

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!!! UNKNOWN CONTENT TYPE !!!

Will with a W8 races an E30 > Hooneriphic 02/03/2015 at 15:10

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I would assume well. The EVO video posted earlier said it comes with Pilot Sport Cup 2s as an option, which is pretty damn close to a sticky. Given all the language about track focus this and that and the tires, my feeling is that Ford put a lot of thought into making this car handle track days well.

AdamKing > Textured Soy Protein 02/03/2015 at 15:11

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Is it just me, or did Ford miss a big opportunity to go after the STI with this AWD system? The numbers all scream STI competitor, but yet again we're looking at an AWD system that won't hold a candle to Subaru's system.

typhoon5000 > Textured Soy Protein 02/03/2015 at 15:11

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So the rear diff on the RS probably works like this:

LongbowMk2 > nermal 02/03/2015 at 15:11

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standard clutch LSD'S seem to last for a while (100+k), but I've never cracked open the diff on my high mileage cars to actually see the wear. i imagine these would last long enough that future replacement wouldn't be a deal breaker.

Textured Soy Protein > natrat 02/03/2015 at 15:12

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High centering definitely caught me out in my MS6. Having a real center diff that keeps the front & rear wheels churning helps to break free of high centering.

Hooneriphic > Will with a W8 races an E30 02/03/2015 at 15:13

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Just realized I replied to the wrong thread. I'd love to blame Kinja, but that was just me being a bonehead. Didn't mean to jump into your thread.

BTW, thanks for the reply

Hooneriphic > Textured Soy Protein 02/03/2015 at 15:13

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So here's my question: How does this setup perform on a track with some super stickies? I regularly track my MS3 and although I bought the car as a utility with a side of fun type vehicle, I've been really happy with it's track performance. Keep in mind I'm a weekend warrior at best. No competition track time and I have very real expectations about what a 370 hp fwd vehicle can/will do.

With that said, I recently moved to PA and I'm fairly sure I've found a secret society of Subby owners. They'er everywhere. Mostly because we get some snow/ice and we have hilly roads. Maybe a few of them like to rally but I'll wager that's a severe minority. If the new STi hadn't been so disappointing in the looks department I would have already bought one. The new RS looks great (IMO) and if it's truly priced in the STi category, I may very well get in line. To me, it seems like the perfect car for me. Great utilitarian function (4 door hatch) with AWD (great for bad weather) and a platform that can easily be coaxed to make more HP. I love tracking my car and if I could solve some of the issues I (expectedly) encounter with my MS3 at the track, I'd be pretty well sold.

edit: posted a second time because I'm a bonehead

Textured Soy Protein > jlnbos 02/03/2015 at 15:15

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Well, short of having 3 lockers, at least having 3 LSDs (like a Mitsubishi Evo, Subaru STi, or WJ/WK Grand Cherokee Quadra-Drive I/II) is going to do a lot better than open front & rear diffs.

I now have an '05 Grand with QDII. It's pretty impressive in deep snow.

Textured Soy Protein > Hooneriphic 02/03/2015 at 15:18

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My MS6 had a similar way of transferring torque front to rear, and a mechanical rear LSD instead of electronic. So the driving style isn't quite the same as if you have a center diff that starts out with always having some power going to the rear, but you can definitely turn in then jump on the throttle to get the car to rotate. At least in the MS6. Focus RS may behave similarly.

Textured Soy Protein > AdamKing 02/03/2015 at 15:18

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In terms of dry-road performance I don't think there's going to be as much of a disadvantage for the Ford as you think. But the Subaru would definitely be better in deep snow.

Xkjacob > Textured Soy Protein 02/03/2015 at 15:19

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so.. Is there already a post that explains all this AWD gibberish?

I'm FE RWD Torsen diff. General rule, turn off TCS and any auto braking "stability management", unless you enjoy wearing brake pads out and creating unanticipated body roll.

With my limited AWD knowledge I'd feel comfy with any type of LSD on front and back. Sounds like they use brakes for front wheels though. So I'm skeptical there.

Having an electronic clutch like system for front to back power seems fine.

Anyone want to tell me these systems are awesome for autocross?

I don't honestly understand the hoonfest over AWD. Well, unless you aren't comfortable with the cars power or live in Antarctica.

Sheriff Of American Douchetown > Textured Soy Protein 02/03/2015 at 15:19

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Hi,

Just out of curiosity, and I know they are completely different types of vehicles, can you please explain the differences between the Jeep Renegade AWD system and the one in this Focus RS? Sure, you won't be doing any track time with a Renegade. But what about how each vehicle would cooperate with the snow? Would you trust the Renegade TrailHawk in foot-deep snow drifts over this Focus RS?

Yes, I like Jukes > Textured Soy Protein 02/03/2015 at 15:19

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So in other words, this is the same TVAWD that is in the Nissan Juke AWD

Textured Soy Protein > Yes, I like Jukes 02/03/2015 at 15:22

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Conceptually yes, mechanically, who knows?

WaxhawBrad > Will with a W8 races an E30 02/03/2015 at 15:23

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Semi-relevant question for the gang; my car is small (2200lb), front-engine, RWD, and I've installed a Torsen. I still overcome the bias ratio and spin the inside tires. Is there an OE electronic torque vectoring rear differential that I can rob/install to electronically improve upon the Torsen? I loose sleep over the blissfull idea of being able to send all the torques to the outside wheel, there's got to be a way. Even if I have to make my own microcontroller to control the switching, no prob (raspberry pi maybe), I just need to source the O.E. hardware.

Thanks for the thread-jack (blog-jack, that sounds weird)

Yes, I like Jukes > Textured Soy Protein 02/03/2015 at 15:23

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I just like being able to say Juke came first. :)

schwartz > nermal 02/03/2015 at 15:31

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Well if earlier Haldex systems are to judge about 150k miles before you start to run into issues.

Will with a W8 races an E30 > Textured Soy Protein 02/03/2015 at 15:34

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And here is your Answer, courtesy of Burglar Can'r Heart Click Anything - no eLSD, and no rear diff.

http://oppositelock.jalopnik.com/focus-rs-has-d…

Waynemar66 > Textured Soy Protein 02/03/2015 at 15:50

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so this awd system is almost identical to sh-awd by honda? like how the 70% to rear wheel can be sent to one side of the rear wheel? and being a fwd biased car what are the usual distribution of power for this car? like my old tl shawdy :P it was mostly 70-80% front wheel when I'm just driving but heavy acceleration goes from 50/50 to 70/30 i see this by using the fancy display they had on the tl :P I drive an sti now and hell its two different drives but tbh I like the SH-AWD when I'm doing hard turns and somewhat high speed lol

foxbody > Textured Soy Protein 02/03/2015 at 15:54

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fuck all that

gimme a regular-ass LSD

MazdaMonkey > Textured Soy Protein 02/03/2015 at 15:54

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Great write-up. I love the MS6. Very unappreciated car for its time.

lddk > Will with a W8 races an E30 02/03/2015 at 16:01

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Great thread! Interesting discussion.

lddk > Textured Soy Protein 02/03/2015 at 16:06

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Thanks for this info! I need to see more of these technical, engineering-related posts on Jalopnik.

Separate topic - the Haldex as found in the MS6: I'm not familiar with these in practice, but if spinning the front in the snow, and the computer gets confused and won't spin the rears, does dragging the brake help to trick the computer into transferring torque to the rear based on wheel speed vs throttle input, vehicle speed, etc? I imagine this being a smarter version of dragging the brakes on an open diff to transfer torque to the non-spinning wheel (or in my case, my front diff on my Jeep, when one wheel is in the air while off-roading or rock-crawling, gets you a poor-man's limited slip action).

WaxhawBrad > Will with a W8 races an E30 02/03/2015 at 16:09

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Semi-relevant question for the gang; my car is small (2200lb), front-engine, RWD, and I've installed a Torsen. I still overcome the bias ratio and spin the inside tires. Is there an OE electronic torque vectoring rear differential that I can rob/install to electronically improve upon the Torsen? I loose sleep over the blissfull idea of being able to send all the torques to the outside wheel, there's got to be a way. Even if I have to make my own microcontroller to control the switching, no prob (raspberry pi maybe), I just need to source the O.E. hardware.

Thanks for the thread-jack (blog-jack, that sounds weird)

Scooby921 > Will with a W8 races an E30 02/03/2015 at 16:14

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This is the correct answer.

Scooby921 > Textured Soy Protein 02/03/2015 at 16:16

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Twinster and Disconnect are technically two different things. The "Twinster" simply refers to the twin clutch rear drive module. "Disconnect" is the addition of a disconnecting power transfer unit, which you correctly point out that the RS does not have.

Scooby921 > Textured Soy Protein 02/03/2015 at 16:34

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You are correct that it is similar to the sh-awd, but not all of them. These days a manufacturer's name for its AWD system is just a name and not descriptive of the system. For Honda the sh-awd in the MDX is different from what is in the TL or new TLX. What Audi puts in the S6 (RWD based) is different from what they put in the S3 (FWD based), but both are quattro. What is in the S3 should be exactly what is in the Golf R, but in the VW it's called 4motion. The BWM X6M AWD system is different from every other AWD vehicle in their catalog.

Names are great, but it'll take a lot more research and understanding of who supplies the active hardware and how their software works before anyone can fully understand how something works and what it is capable of. I'm probably going to forget a few of the global AWD suppliers, but you have GKN, Borg-Warner (Haldex), JTekt, American Axle, Magna, Linamar, and (insert forgotten suppliers here). But the rabbit hole just starts here.

Dave on bass > Textured Soy Protein 02/03/2015 at 16:41

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"Golf R uses Haldex" - it's super effective!

I have never even played Pokemon, but I couldn't resist.

jisok > Textured Soy Protein 02/03/2015 at 16:57

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Well it may not be that much more clever, BUT if it sends power to the rear during most all demanding situations, then IT IS going to be much better at delivering AWD power much more often than Haldex on a Golf R does. In the Golf R you will need to get the front wheels slipping or moving side to side before you can get power to the back- that is the biggest part of the argument for full time AWD! This Ford will therefore likely handle much more like a Subaru or a Torsen quattro than a golf r. j

Textured Soy Protein > Xkjacob 02/03/2015 at 17:45

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In order of importance of which differentials on an awd car should be limited slip, it's center, rear, then front. The Focus RS has a limited slip "center" diff but not really a center diff, limited slip rear, and open front with brake-based torque vectoring.

Textured Soy Protein > jisok 02/03/2015 at 17:48

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The Golf R does not need to slide the front wheels to transfer power to the rear. Like all Haldex systems, it transfers power to the rear based on things like steering angle, throttle input, yaw sensors, and wheel speed sensors. I have owned a Haldex-equipped Mazdaspeed 6 and it was very easy to predict when the car would transfer power rearward in a turn, and it was definitely proactive in that transfer of power.

The main difference between the Focus RS and most Haldex systems, is that it also has a rear LSD. But that transfers power side-to-side across the rear axle, and has nothing to do with the front/rear torque split.

Xkjacob > Textured Soy Protein 02/03/2015 at 18:01

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I wonder if TV has gotten better since 2012 or if just running it on front wheels reduces the issue.

http://www.motorauthority.com/news/1052953_2…

That makes sense,center, rear then front for priorities thanks for the info!

ClassicDatsunDebate > Textured Soy Protein 02/03/2015 at 18:28

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Could this be using the ZF Torque Vectoring Diff? Sounds very similar.

Textured Soy Protein > Will with a W8 races an E30 02/03/2015 at 19:32

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Updated with this slide and h/t to you and burglar.

Textured Soy Protein > Waynemar66 02/03/2015 at 19:33

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The torque vectoring effect on the rear axle is similar. The rest of the system is mechanically not quite the same as SH-AWD.

Textured Soy Protein > lddk 02/03/2015 at 19:34

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On the couple occasions I got high-centered in the MS6, best I could manage is it would spin the fronts for a while, then spin the rears for a while, and kinda scrabble around trying to get some grip without much success. Tapping the brakes didn't really free things up.

jisok > Textured Soy Protein 02/03/2015 at 21:28

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Thanks for letting me know more about the new generation Haldex... Onto this point you make about your Mazda and presumably the Golf R and maybe the new RS; it seems as if it is precisely what you write here, that is major issue for most when comparing reactive systems to full time systems. It is a detriment to the handling when a car must shuffle around power when you are entering a curve and there is a surprise situation/condition that comes up before the torque is applied- especially if that situation is a wet or slick patch. It is always better to have the ability to find grip before you might need it. What Ford may have done is made the AWD system more full time than your Mazda or the Golf r. They may have the default setting at a certain split (they do say they have an oversteer setting) with the rears getting power, and/or they may have designed their system to kick in with far less provocation than the other haldex systems- say kicking in just because the car hits a certain speed or any time the steering is moved more than would be normal for highway driving. This ford may be much more rear driven than any part-timers we have seen before. j

Textured Soy Protein > jisok 02/03/2015 at 22:09

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I can tell you that in my experience with the MS6, the transfer of torque rearward was pretty spot-on with when you would need it. A couple examples:

In abrupt turning situations, like say trying to sail through an about-to-change green light at the bottom of a highway off ramp, I'd carry a bunch of speed down the ramp, jump on the brakes at the last second, heel-toe downshift, turn in, then stomp on the gas. The car would send power to the rears, and it would shoot itself through the turn. Having power going to the rears while braking or turning in wouldn't really make much of a difference.

There was another road I had on my commute that was a 2-lane highway with a sequence of a couple high-speed sweepers and a 55 mph speed limit. These were gradual enough turns that you wouldn't be braking heading into them unless you were doing well over the limit. But if I'd want to accelerate in the turn, and roll on the gas, the power would go rearward and help rotate the car through.

Basically, any time the steering wheel was turned and I gave it some gas, power went to the rear wheels in a proportional way. Even though the default was to send all the power to the front wheels. And if you think about it, having power go to the rear wheels while you're braking or turning in doesn't really matter, because your foot's not on the gas anyway.

To put it another way, before I bought my MS6, I tried out an '05 Audi S4 V8. It had a torsen center LSD that always had some power going to the rear, but an open rear diff. The feel of the power shuffling front-to-rear in a turn was a bit more progressive on the S4, but the overall handling balance of the MS6 was much better. I think the rear LSD on the MS6 had a lot to do with that.

DavidHH > Textured Soy Protein 02/03/2015 at 22:56

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This reminds me of the Camero that used to win the slalom events. It was an almost stock 350 automatic camero, except the owner had a suspension shop, and it had turn brakes. So rather than steer the car with the front wheels, he steered it with the rear, via powering one wheel or the other.

4 cam torino > Textured Soy Protein 02/04/2015 at 14:35

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I'm not sure if this is established later in this conversation, but this is not Haldex on the RS. The Haldex has a clutch for the AWD at the front of the pinion and then the eLSD clutch on the differential. The Haldex eLSD function just controls how much the two sides are locked together.

The RS system I assume is the GKN twinster, although Borg Warner has a similar system that Honda has used (under utilized the capability of). The twin clutch systems of this type control the AWD and individual side to side wheel control using a clutch at each halfshaft.

4 cam torino > Will with a W8 races an E30 02/04/2015 at 14:36

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I really wish the SAE would come out and define the overspeed capability as torque vectoring and stop the other marketing speak nonsense that calls anything else torque vectoring.

Will with a W8 races an E30 > 4 cam torino 02/04/2015 at 14:40

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Part of the issue is that there are just so many different ways to drive 4 wheels, and so many ways to achieve a torque vectoring effect. Does something like the twinster with mismatched final drives count as torque vectoring? If the entire rear axle is overdriven, does that count as as overspeed capability?

4 cam torino > WaxhawBrad 02/04/2015 at 14:41

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The problem with robbing a unit out of something else is that the controls are quite complex. It is taking in signals from the car's accelerometer for lateral acceleration, the steering angle, vehicle speed, wheel speeds, throttle pedal, brake pedal and ABS state, etc. It utilizes these signals to determine the state of yaw of the vehicle, it monitors for counter steer in order to properly react to a counter steer situation. It watches for ABS in order to decouple the system during an ABS event to keep the ABS from destabilizing the vehicle. It uses the speed, steering angle and throttle position to prevent binding and crow hop in tight turns as you would see with an old school 4WD truck. There is a lot to the calibrations of the systems.

Textured Soy Protein > 4 cam torino 02/04/2015 at 14:44

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I think it was a separate comment thread, but if you go to the update section of my post and click the link on the h/t to Will with a W8's post, it shows where the part about it not actually being Haldex was originally brought up.

4 cam torino > Textured Soy Protein 02/04/2015 at 14:47

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On the eLSD you have an open differential and then a clutch to control lock up. You are literally just locking the two sides together by applying the clutch. So, with the open differential you are sending ~50% (approximate because even an open diff does some biasing just due to friction) of the torque to each wheel, no traction on one side means the other side just doesn't spin. The clutch of an eLSD, including the eLSD function of the Haldex is just progressively locking the two sides together to stop the low traction wheel from spinning and allow torque to be biased to the high traction wheel. So at full lock up you could lift one wheel off the ground and the other wheel would still move the vehicle. In this theoretical situation you could measure the torque at each wheel and the one in the air would have no torque meanging in a way 100% of the torque is going to the other wheel, although the wheel in the air would still be spinning.

4 cam torino > Will with a W8 races an E30 02/04/2015 at 14:51

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I agree that it is a complex issue. I wouldn't consider a ratio mismatch between the PTU and the RDU alone to be torque vectoring. An overspeeding of the rear axle in addition to the overspeeding of each rear wheel was part of the original application of the Acura SH-AWD though.

d1ck > Textured Soy Protein 02/05/2015 at 07:30

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One of my favourite features of the e46 AWD system is the torque split: 62% Rear / 38% Front. It's such a predicatable system that lends itself to snow hooning very well, and I was very impressed that BMW did it so right considering the AWD system in general feels like an afterthought on those cars.

Textured Soy Protein > d1ck 02/05/2015 at 10:12

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BMW's center diff is pretty solid. It'd be nice if they included at least a rear LSD as well, but they decided to stick with open front & rear diffs + traction control.

d1ck > Textured Soy Protein 02/05/2015 at 10:35

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Yeah, the brake system is adequate for snow hooning, but ultimately it's still too slow for any real "performance" driving. Works okay for ensuring you don't get stuck in deep snow as easily as well.
A buddy of mine has a 135i with bolts ons and it's actually scary. When you put your foot in it while turning you feel the inside tire start to spin up and then BAM, the brakes activate and kick the rear end around.

rcasi > Will with a W8 races an E30 02/05/2015 at 16:49

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Yeah, but what about OPP?

STRumpetrider > nermal 02/05/2015 at 17:15

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I'm making 1060 lb/ft at the wheels and I stomp on my Lsd all the time, it blew up

at 215k miles. In a car? Probably be on your second engine.

AntiLag > Textured Soy Protein 02/05/2015 at 17:15

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Can an AWD system effectively deliver no less than 30% of the power to the front wheels (which means 40-70% are a more likely estimate for a constant average) at all times, and still not have crazy understeer? Is the problem with Haldex due to the horrendously idiotic placement of the engines in Haldex vehicles, being mounted in front of or above the front axle? Can anyone even answer these questions definitively??

TahoeSTi > Textured Soy Protein 02/05/2015 at 17:16

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Guess I'll be sticking to the STi for winter driving for a while longer, it's 3 LSDs have put many other awd systems and 4x4s to shame in the deep stuff. I was really hoping the Focus RS would be something that could also make it out of my driveway.

Textured Soy Protein > AntiLag 02/05/2015 at 17:23

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I think most people associate Haldex with VW transverse-engined cars. Which, yeah, they've got their engines way out front, and they have open rear diffs.

I can tell you that in my old MS6, the engine wasn't quite so far forward, and it had a rear Torsen LSD. It had a little understeer in stock form because of its suspension setup, but it was still reasonably easy to get it to rotate in turns.

The big thing it needed was more negative camber in front and more roll stiffness in the rear, but front camber isn't adjustable from the factory. Once I lowered it and added front camber kits, the handling was pretty incredible.

AntiLag > Textured Soy Protein 02/05/2015 at 17:37

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Thanks for the input! What was the torque split on your Mazda?

44444444444 > Textured Soy Protein 02/05/2015 at 17:37

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Haldex preemptiveness means the coupling is precharged at startup and proactively adding power rear. It'll send power rear within 1/17 wheel revolution if it detects slippage. It's probably 90/10 in city driving with more when accelerating. I wonder if Fords haldex decouples when you decelerate like Volvos does. The Focus ST is just an S60R with smaller brakes and actual torque vectoring and a 4 cylinder engine.

I want a pair of torsen LSDs for my R. Haldex is great, seriously. And with torque vectoring it is even better. The R has brake based torque vectoring and it works ok... Real torque vectoring would be nicer.

Textured Soy Protein > TahoeSTi 02/05/2015 at 17:50

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I agree with you on 3 LSDs in deep snow. Since I got rid of my MS6, I now have a '13 BMW 135is which I store in the winter, and an '05 Grand Cherokee with 3 LSDs and General Grabber AT2 all-terrains with the severe snow duty rating. The Jeep is silly good in deep snow.

As far as I know, the only brand new vehicles you can buy with 3 LSDs are the STi, Evo, and manual transmission FJ Cruiser. The center and rear diffs on the FJ are lockable.

The WJ ('99-'04) and WK ('05-'10) Grand Cherokees had 3 LSDs with as part of the optional Quadra-Drive 4wd system, and you can lock the center diff. Quadra-Drive on the current WK2 ('11-up) Grand Cherokee has an open front diff.

In a truck or SUV with a locking center diff, a front LSD is nice but not quite as big of an issue if it's not there, and you still at least have a rear LSD (or locker).

Textured Soy Protein > 44444444444 02/05/2015 at 17:52

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I had no complaints with my MS6's handling in sporty driving situations, especially since it had the rear Torsen LSD. Only time it ever let me down was in deep snow.

44444444444 > Textured Soy Protein 02/05/2015 at 17:54

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I really wish the R had come with Torsen LSDs stock... Adding them is pricey at 1k each.

Textured Soy Protein > AntiLag 02/05/2015 at 17:56

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It progressively varied the torque split from 100/0 F/R to 50/50 depending on the situation. It had no problem sending power to the rears based on detecting I was in a turn and stepping on the gas, rather than say, waiting for the fronts to spin.

Textured Soy Protein > 44444444444 02/05/2015 at 18:07

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Who makes a rear LSD for the Golf R? I've seen Quaife and Wavetrac LSDs for the front of the Golf R, but not the rear...granted that's just on a quick search.

44444444444 > Textured Soy Protein 02/05/2015 at 18:30

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This isn't a Golf R, it's a Volvo V70R... probably should have mentioned that. Quaife makes them front and rear.