| Archive for The Motor Forum talking cars since 2006 |
| Gurney |
Diffs and traction controlOne for the Techies, and of course ALF who has first hand experience.My GTA has the Q2 diff but judging from a recent post in AlfaOwner it seems I may (or may not - this is the query) be making full use of it's talents. The GTA saloon has ASR as opposed to ASR and VDC which the 147 GTA has. Besides prooving the Italians are as fond of acronyms as the Brits are of Hawaian Pizzas it does show the engineers had mild concern about channeling 250bhp through the front wheels. The ASR on mine has remained firmly on, it seems to have a very deft touch - except for full bore starts in anything above damp conditions, in which case the little yellow skidding icon on the dash flashes prettily. I have now been informed that as Q2 is fitted it should remain firmly OFF - except perhaps in 'anything above damp conditions' - yes, living in Manchester you could argue it should stay on but every now and then we do have a dry spell. The ASR works as follows:- The antilock braking and anti-slip regulation systems (BOSCH 5.7 ABS with ASR) modulate brake pressure sent to the wheels to prevent loss of grip under all tyre and road surface conditions by cutting in automatically whenever one or both drive wheels begin to slip. The ASR system increases vehicle stability and active safety by controlling drive wheel slip. If slip is caused by excessive power transmission, it cuts in to reduce engine power through communication with the engine management control unit. if slip is detected at a single wheel, the system cuts in to brake the slipping wheel by acting on the modulation solenoid. ASR comes on automatically whenever the engine is started. The system can be deactivated by operating a button on the central console. When the system is off, a led on the button comes on at the same time as a warning light on the control panel. The warning light flashes when the system cuts in to notifiy the driver that the ASR system has cut in due to road surface grip conditions. The warning light comes in in fixed mode when the control unit detects an error in the ASR function. It therefore uses both braking AND throttle to modulate slippage. Am I negating some/all the benefits of a torsen diff by having it on? should I only switch ASR on in the wet? Yours Confusedly Gurns 
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| Turbonutter |
Gurney, is the Q2 diff an ATB/Quaife type rather than a proper limited slip diff?
i.e. by that I mean do you lose drive if one wheel is airborne/off the ground? |
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| "him" |
Yes it is (in that situation it works like an "open" diff), and that would be the case in my car (though there is some pre-load), but with a TCS the car should be able to brake the spinning wheel slightly and the LSD should then be able to maintain drive to both wheels at 'all' times. Does your Mini have a Torsen type diff.? |
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| Gurney |
It's a Torsen type rather than a conventional LSD.
Transfers drive to the one with most grip, yes? Autodelta fit the Quaife to the 3.7Am conversions, presume the Quaife is a torsen? http://www.autodeltashop.com/prod...p?cPath=28_61&products_id=269 Noticed that one IS compatible with ASR. |
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| "him" |
The Quaife diff is a torsen yes... http://www.quaife.co.uk/What-is-a-Quaife-ATB-differential |
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| Gurney |
So if both the Quaife and the Q2 are Torsen why is one 'compatible' with TC and one - albeit allegedly - not?
I suspect there is more than a tad of 'are you a man or a mouse' attitude amongst the vast majority on AO who have said the ASR should remain OFF. Prefer the reasoned, balanced, argument myself before switching to DefCon 1. |
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| "him" |
Why are you thinking that leaving TC on is somehow negating the use of the Q2?
Surely the TCS detects wheel 'overspeed', and reacts accordingly? The Q2 will give the car more traction so the TCS will need to intervene less? I can't imagine for a moment that the Q2 is "incompatible" with the TCS, but that is based on nothing more than my gut feeling. I have a Quaife ATB in my car, but no TCS... and I am still a mouse! 
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| Gurney |
Card carrying Mouse here to 
Several posts on AlfaOwner say (not even suggest) I am negating the ability of the Diff to do it's job by leaving the ASR on. Have to admit I haven't noticed any particular problem, the car seems to cope with 250 rampant Italian stallions rather well which suggests to me it's working fine, BUT, I have never driven with it switched off so hardly have evidence to suggest I am a buffoon. |
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| Turbonutter |
Hi, yes 'him', the Cooper S has the standard option GKN 'Super LSD' which is a Torsen type diff. I do know that on the Mini they program the traction/stability control slightly differently if you take up the 'diff' option......however, having said that Gurney, I can't see why it would make any difference whether you have the Quaife or Q2 diff in conjunction with your traction system unless the settings are markedly different on the Quaife. I've only ever driven the Mini hard once with the traction/stability systems switched off. You can 'feel' the diff working maybe a bit more but I was properly going at the time. I've never bothered switching it off again as there was little if any perceptible difference under normal driving. I did notice a difference driving a Cooper S that didn't have any LSD though. For £110 it was a no-brainer to spec it really ( we didn't choose the Chilli Pack which the majority of R53 MCS owners did and which gives you the LSD option as part of the pack ) |
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| Turbonutter |
What he said ^ 
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| Gurney |
Well tomorrow night I will be heading back over the Woodhead from Penistone at late o-clock. I shall give it a blast minus ASR - providing it isn't chucking it down of course.
Tending to lean towards Turbonutter on this one. |
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| SpecB |
I would agree with that. The only way I could see the TC interfering would be on the limit on a track. | ||||
| DaveGibson |
Forecast for Thursday is that it will be persisting down. Better luck next time. |
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| JohnC |
I have never had experience of a Torsen diff but the fwd Fiesta and Nova I used to race had LSD's with the Nova having a plate diff which could be cranked up to almost solid.
Tha advantage of an LSD without TC is that you can balance the car with both wheels spinning, applying a bit more or less lock in conjunction with more or less power. On the track this adjustability is essential to get the right line and maximum grip through and out of a corner. I would imagine that if TC cuts in just when you feel like (or need to) applying maximum throttle, extra lock and plenty of wheelspin then it is going to compromise what the driver is trying to do. On the road though, switching off TC in normal driving is probably best left to those looking to lose their licences or end up in a field. For a maximum attack drive though I could see advantages in turning off TC provided there is the room to play with. |
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| JohnC |
I'd have to say that those are the conditions in which you would notice the biggest differences. In the dry with a modern car the speeds would have to be very high and margin of error very small. |
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| Gurney |
Thanks John, interesting. Of course in the wet everything happens sooner, should've thought of that.
Someone on AlfaOwner has now commented that with Q2 and ASR off - in wet conditions - they booted it on the inside lane of a deserted M-way and ended up in the outside lane, all with no steering input. Backing off and it returned to the inside lane - again without the assistance of the steering wheel. Think I will keep it on. |
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| ALF |
Plate and Torsen diffs are very different in operation. My understanding is that Torsen diffs are compatible with ESP/TC systems , and my friend at Quaife (who is the person there who deals with all customer enquiries) tells people to leave the TC on, but that the diff ought to make it redundant.
I always switched the TC on the GTA off prior to getting the LSD fitted, and almost always left it on afterwards - only if absolutely on it did I switch it off, because in some circumstances it prevented a little slip that I wanted. But 99% of the time I left it on, and it proved very compatible with the diff, every now and then the light blinked slightly but it rarely or never went to "cut power" mode, which it is too keen to do on the standard car. A Torsen diff shunts the torque from side to side well before a wheel spins - if a wheel does spin up, then the diff has been been overwhelmed and can do no more, and the TC is probably beneficial. And I'd suggest I probably drove my GTA as rapidly as the keyboard warriors on AO... Edited to add: there are no "settings" and there is no "tuning" of a Torsen diff. A Torsen diff is a Torsen diff. It funnels torque to the wheel with the most available grip. End of. The stuff in the press about the "new" Quaife in the new FRS being different to the last one, is bollocks. Advice for the Q2 and Quaife should therefore be the same. |
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| Turbonutter |
You are right in a sense Alf - what I should have said was the gear angles on the worm gears. They all act in the same way but I wasn't sure whether the Q2 has quite the same angles as the Quaife one and whether it had the same bias ratio. I suspect the Q2 and Quaife ones are the same though |
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| Gurney |
I wonder who actually makes the Q2 diff? doesn't seem to be Quaife or indeed Alfa.
They are still supplying & fitting for around £600 at all the Alfa specialists and so far I haven't heard of a single one going pop. Unlike the standard diff... |
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| Turbonutter |
Don't know Gurney - it seems to be Alfa's preferred supplier like Quaife for the Focus. My friend had one on his 147 GTA and liked it Hope you have a good drive tonight! |
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| Mark |
I'm struggling to believe that anybody (if they are telling the truth - which I seriously doubt) could be quite so stupid to let that scenario play out on a public, open motorway - even if it was deserted. So, from next to the hard shoulder out to the central reservation and back in to the hard shoulder again just using varying degrees of throttle and no steering input? Without bottling it/shitting yourself and still holding your nerve as you approach the barrier? And, that's an awful lot of ground to cover too if you think about it - regardless of how quickly it might happen. Yeah, right. Fantasy, I think. |
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| Turbonutter |
I suspect hyperbole is involved ...although i wasn't there. The 220 turbo coupe was supposed to be a bit wayward but never that bad - I drove K456 VUT, a nightfire red one, a few times and it did used to pull this way and that to an extent......but nowhere near crossing 2 lanes of motorway bad! |
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| Gurney |
ALF mentioned 'keyboard warrior' a term that probably sums up a lot of forum posters though strangely not this forum - well not much
Still not raining here so possible fun over the tops tonight but after the opinions here the ASR button will only be experimentally off, I think it's prudent to keep it on for everyday use. If I ever track the GTA I would of course probably switch it off. Wouldn't want my godlike driving skills retarded by electrickery. That's a joke btw... |
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| Turbonutter |
I'm sure you'll be fine - quite a few powerful fwders use Torsen-type diffs and have no traction control at all other than the driver's right foot ...as mentioned before, the Rover turbo Coupe had a Torsen diff and quite a few of those survive even today |
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| Blarno |
Mmmmm, Rover Tomcat Turbo Coupe...
*heads to Autotrader. |
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| Turbonutter |
The one I mentioned earlier Blarno, was bought by a friend ( he now has a WRX ) about the same time I got my Sierra. They were very fast in a straight line - both our cars were standard back when we got them at the end of last century and I could only watch it pull away slightly on a rolling start on the bypass. The Sierra was faster round and out the big roundabouts. We swapped cars a couple of times and I think mine scared him more than vice versa, not through anything happening but just that he thought he would instantly spin as soon as he pressed the throttle on any hint of a bend. I found you could really 'feel' the torsen working out the bends in that car. They changed the diffs for the later 600/800s I think the Autocar car timed under 6 seconds in their test and about 15 to the ton with a genuine 150 top end. He ran it for about 3 or 4 years on a 40 mile commute - the only problems he had was paint flaking off the rear spoiler and the head gasket failing ( not a compression blow but a severe oil leak from one corner of the block ). Best moment in it was when he gave me a lift one night from a work do - one of the early Dakar Yellow E36 M3s came past and we followed him in a spirited driving fashion |
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| ALF |
I would leave it on, Gurney - when you do exceed the limits of traction/grip when cornering in a FWD with LSD, what happens next can be quite savage. Both fronts spin up at the same instant and you just spear straight on. And if you back off too suddenly, then (bearing in mind the GTA has a fairly neutral balance and no ESP) the chances of losing the back are quite high. I found it a more brutal an experience than exceeding grip with an open diff and either FWD or RWD.
Do switch it off on track - that's the last place you want your brakes fighting the torque, they'll be hot enough already... A lot of powerful cars without switchable TC/ESP grind to a halt on track with overheating brakes and ESP errors after a while. Edited to add: Quaife don't make the Q2. My mate knows who do - he suggested Quaife's quality would be much higher, but as you say the Q2 does incredibly well even with the 3.7 litre and supercharged cars. Interesting that Autodelta quote quaife now - they used to use a plate-type diff that was very expensive and apparently superb in use, but they started breaking... |
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| Turbonutter |
They're pretty good quality, all the Quaife stuff. Interesting about the plated diff - not commonly used on fwd road stuff. |
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| ALF |
Apparently it was amazing on track or road when driving hard, very effective yet very benign, with barely any torque steer even on a 3.7. This was the diff in the Autodelta 147 GTA 3.7 that Clarkson tested an TG and raved about - and he hated the mk FRS, if you recall, so he's clearly a one-hand on the wheel numpty who doesn't like steering interaction
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| Turbonutter |
I do remember that car - it set a faster time than the E46 M3 on their track I think. I didn't realise it was a plated diff though - just presumed it was a Quaife or Q2 type. Did many cars get them fitted? |
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| ALF |
I know one guy on the AO forum who had a hugely modded 156GTA saloon (AD 3.7 plus supercharger, shocks, brakes, and a lot more!). He has tried all sorts of diffs, and he loved this one. Until it broke. Now he uses a basic Q2 and while he doesn't like it quite as much, the fact it is still in one piece speaks volumes - especially as he tracks it a lot! | ||||
| Turbonutter |
Hmm, I was wrong 0-60 in 6.3 in Autocar, 30-70 in 5.4, 15.6 to 100 and 149 on the Millbrook bowl so add a few onto that for a straight bit of road with no tyre scrub. I know in one of the mags of the time it definitely broke the 6-second barrier - not bad for a fwd scrabbler anyway. One of the first fwd cars I remember with a Torsen diff Tiff Needell found them a bit of a handful...
When Torsen diffs go wrong! Top Gear test Dave Gibson might find these interesting Part 1 Part 2 |
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| DaveGibson |
I never had a coupe, just a 220SLi hatchback which followed a 420GSi saloon. I don't have any speakers on this PC so the videos lose something in the translation (so to speak). | ||||
| Turbonutter |
Ah, I didn't know you'd owned a 200 , just meant you seem to have an interest in AR stuff 
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| DaveGibson |
When you work for them (or associated an company) and have a company car, you tend to drive the product. | ||||
| Mark |
But, if he was (supposedly) to do that in his BMW/Audi, he would simply be called a stupid wanker. |
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| Turbonutter |
Anyway Gurney, did you have a good drive last night? |
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| GonnaBreakABuggy |
I'd always take a lightly set plate over a torsen myself, more consistant. |