MINI’s All4 System In-Depth
The addition of the ALL4 Countryman to the MotoringFile garage has led us to wanting to know more about the rather novel all-wheel drive system in the car. When we first drove the Countryman in May of 2010 we found that the system was purely a safety device and not intended to be a performance option. And all subsequent drives we’ve had with the car (including with our long-term test car) have reinforced that fact. But that doesn’t make All4 any less interesting from a technical perspective (or less relevant). So we wanted to get past the marketing and hype and understand the technical details of All4.
All4 is a product of GKN Driveline, a leading global producer of CVJ Systems, AWD Systems, Trans Axle Solutions and eDrive Systems. The heart of All4 is GKN Driveline’s Electro Magnetic Control Device (EMCD®). It’s an actively controlled coupling on-demand and full-time all-wheel-drive drivelines as well as in axle applications. And according to GKN, EMCD is a most compact and versatile electronically controlled driveline and axle coupling on the market.
The benefits of a system like this are:
– Improved vehicle traction and handling
– Compact design
– Low power consumption
– Lightweight and reliable (ie simple)
– In production in other uses since 2001
The system allows up to 50% of torque to go to the rear wheels when the system detects front wheel slip (any more wouldn’t make sense from a weight distribution prospective). However under cruising conditions (on a highway for instance) the ALL4 equipped Countryman is entirely front wheel drive.
The operating principles of the system are:
– Current supplied to an electro-magnet generates a magnetic field causing the armature to compress the pilot clutch
– The resulting pilot clutch drag generates a rotational torque across a bi-directional ball-ramp mechanism
– This rotational force causes the balls to roll up the opposing ramps which pushes the front cam forward
– The cam thrust is transmitted through the pressure plate compressing the main clutch
– The rotational torque from the outer plates (input) is then transferred to the inner plates (output) proportional to the electrical current
– An Electronic Control Unit (ECU) controls the clutch torque by adjusting the amount of current based on available vehicle inputs and control algorithm
As we mentioned last week, there are some notable differences between ALL4 and BMW’s xDrive. First ALL4?s control unit is fully integrated into the DSC unit and thus transfers data much faster than a typical set-up (thus reacting to conditions faster). As described above, it works by a small clutch in the front detecting wheel slip and engaging the rear driveshaft. Unlike xDrive, it’s a simple system that doesn’t use complex electronics. As you’d expect the system is highly patented by GKN as they consider it fairly unique and effective solution.
In its entirety ALL4 adds 70kg (154 pounds) to the Countryman’s weight.
Yes All4 (or EMCD) is simply a safety option. But what MINI has done in selecting it as the technology is to make sure that there isn’t a huge weight penalty and thus performance and efficiency hit by adding the system. At the same time All4 is so effective at doing it’s job seamlessly that it’s hard to ever detect it on. And for the average Countryman All4 buyer, that’s likely music to their ears.
<p>Interesting description for sure, but I keep wondering at the repeated description “that doesn’t use complex electronics” when it’s fully integrated into the DSC system and has it’s own ECU for control of the electro-mechanical bits. Can’t get more complex electronics than that!</p>
<p>It certainly can.</p>
<p>the mb 4matic is perhaps one of the most complex systems produced.</p>
<p>And the worst for performance.</p>
<p>But how good is the ALL4 if you want to drift alot in the snow? I had the BMW 320d xDrive last year and it was great, but will a Countryman S ALL4 be as fun in the snow?</p>
<p>if you take all the nannies off any vehicle is fun in the snow</p>
<p>Can this be disabled via a toggle switch like DSC? I don’t think so…this nanny might be a permanent babsitter.</p>
<p>If DSC is off and there is limited traction it doesn’t matter if you have AWD, wheels are still going to spin- As Gabe noted in his previous post about needing a slippery situation to make it drift. I have never heard of a vehicle that you could have fun in the snow with that allowed traction and stability control to switched off (AKA- the nannies). In all seriousness- I’ve drifted Range Rovers and Honda CRVs so I am not sure how a Countryman couldn’t be drifted in the snow. </p>
<p>If DSC is off and there is limited traction it doesn’t matter if you have AWD, wheels are still going to spin- As Gabe noted in his previous post about needing a slippery situation to make it drift. I have never heard of a vehicle that you could have fun in the snow with that allowed traction and stability control to switched off (AKA- the nannies). In all seriousness- I’ve drifted Range Rovers and Honda CRVs so I am not sure how a Countryman couldn’t be drifted in the snow. </p>
<p>How about a quattro option for the JCW hatch and Coupe?</p>
<p>“quattro” is exclusive proprietary state-of-the-art “vag” technology therefore it ain’t never gonna be seen in a bmw/mini product, unfortunately.</p>
<p>I used it as a generic term for AWD, something to set the JCW line apart from the regular models.</p>
<p>a non-haldex, torsen diff as used by vw/audi w/ quattro is superior unless off-road is priority, then go w/ borg-warner. interesting that getrag is now a gkn holding. for performance quattro is the finest available, proven system now in it’s 6th generation.</p>
<p>That is a bit of propaganda there, as Quattro has its drawbacks and continues to evolve because of those drawbacks- weight and the fact that it can’t distribute full power just to name a few. The latest gen relies heavily on electronics and ABS braking system to allow for a more balanced transmission of torque and takes cues from other manufacturers as while Audi markets the system well it really doesn’t provide a performance increase in most applications (RS models not withstanding). So in reality Quattro and the torsen diff (even with the “crown” ring giving 70% to the rear) is nothing more than electronics and at that point xDrive can shift more power quicker with less weight- but is neutered by BMW’s inability to realize people want a real sports suspension with AWD. </p>
<p>The best system on the market in a non-super car is the xDrive system in the X5/X6 ///M models as well as the OPTIONAL “Sport Vectoring” Quattro system- which just happens to be a product of ZF/GKN and was debuted in the X6 and later used in the RS4. </p>
<p>By no means am I a Quattro hater or an xDrive proponent- they both have ups and downs and I have had both in my garage many times now. </p>
<p>-M </p>
<p>“So in reality Quattro and the torsen diff (even with the “crown” ring giving 70% to the rear) is nothing more than electronics and at that point xDrive can shift more power quicker with less weight- but is neutered by BMW’s inability to realize people want a real sports suspension with AWD.”</p>
<p>Michael thanks for writing this so succinctly. Agreed 100%. If BMW changed their strategy on xDrive and offered it with a sport suspension (at very least as an option) they would heavily blunt any real AND perceived advantage Audi has with quattro.</p>
<p>Very detailed report, but as in the initial assessment i wonder how Gabe does not detect significant differences in handling compared to the standard CM? From my experience since last winter, not only in snow but in wet conditions as well as on dry surfaces, All4 has a significant impact when the car is been driven hard: you can enter fast in corners, accelerate on the apex and the rear wheel torque throws you around perfectly with a lot of confidence. Can only compare with my former Clubman S, but it’s definitely more than just added security. It’s amazing and very predictable…. just my 2 cents</p>
<p>The differences are there. We reported in them in our three way CM test last year that the FWD Countryman won.</p>
<p>Sorry, didnt express myself precisely causing misunderstanding: my impression was that All4 has significant advantages over the FWD regarding traction with positive impact on handling. Can not imagine the FWD CM has better traction e.g. in uphill curves than a Clubman. Where the All4 delivers the power to the rear and supports a narrower line by “oversteering”, the FWD may only use the ESD to distribute more power to the outer wheel, but with less positive effect on power distribution.</p>
<p>Are you sure you drove All4 vs FWD with same specs (sum of extras, suspension & wheels?)</p>
<p>Yes the wheel/tire/suspensions were the same… you can look the comparison. It’s on the right side of this page under reviews.</p>
<p>Thanks i read it at the time of publication;-) that’s the reason for my post: I tend to stick to my statement that it’s definitely a handling improvement in certain situations (as described earlier) of the CM ALL4 over the Clubman S!</p>
<p>But will try to arrange a back to back comparo & open to be proven wrong;-)</p>
<p>Anyway, the CM provides an astounding quality level of handling especially when compared with it’s classmates</p>
<p>Same question again. Why didn’t it work while I was with my front wheels in mud (front of the car a little lower than the back)? It does not work while standing? The front wheels were slipping, the back wheels were dead…</p>
<p>All4 seems to be working just fine, just under those circumstances it didn’t… I’d really like to know why…</p>
<p>Thanks</p>
<p>Regarding snow drifting, here’s a short video I did last winter: http://youtu.be/JNeLrr89LcM</p>
<p>I feels great :-)</p>
<p>Was DSC on? If it was off that makes sense as there is no way to brake the spinning wheels and thus there is no torque to go to the back- this is why Audi had to add electronics to Quattro as well. Basically it is an open diff without DSC on so the spinning wheels keep spinning. I may be wrong in my analysis with All4 as aside from the engineering info I have, I have no hands on with it.</p>
<p>On, off and traction on….nothing…</p>
<p>On, off and traction on….nothing…</p>
<p>Was DSC on? If it was off that makes sense as there is no way to brake the spinning wheels and thus there is no torque to go to the back- this is why Audi had to add electronics to Quattro as well. Basically it is an open diff without DSC on so the spinning wheels keep spinning. I may be wrong in my analysis with All4 as aside from the engineering info I have, I have no hands on with it.</p>
<p>I have to take issue with 2 claims made in the article. Also, I’m curious about the rear differential as it appears the countryman will drift a bit, hard on the gas in slippery surface conditions. It’s not mentioned in the article. GKN makes some wicked limited-slip diffs so I think there’s a good chance the rear end is limited-slip.
My first issue is the claim that this AWD is mainly a safety feature. From videos I’ve seen, it looks like if you drive it hard enough, the substantial rear-end torque does improve handling and provide some throttle steer. If it’s an all -electronic system, the control system can probably be hacked and modified.
The other issue I have is with the statement, “any more wouldn’t make sense from a weight distribution” with regard to torque split. I say, “nonsense”. Plenty of cars use rear-wheel-drive and rear-biased AWD systems to improve handling and reduce understeer. I’m not saying there aren’t reasons for having the driveline directly attached to the front (other transverse AWDs require an additional differential to send a majority of the power rearward), but to say sending more torque rearward doesn’t make sense, simply isn’t true. I’d be shoocked if the WRC version doesn’t include the ability to send more torque rearward.</p>
<p>Thanks for the write-up!</p>