84 replies to this topic

[damontite]

ive got a LSD from courtenays, dont know which make it is tho. i will have to ask! i noticed quite a big difference, i used to get rear end wiggle under braking and accelerating, now its almost completely gone. i can corner under accelerating and feel the car controllably drift out with a sudden snap of oversteer. i know some of this maybe suspension but the lsd does make a big difference. cheers damon

[Ricky2772]

i noticed quite a big difference, i used to get rear end wiggle under braking and accelerating, now its almost completely gone.

that is the second reason why I decided to install the LSD.... I hope it will partly/fully cure the tendency to lock-up the rears FIRST, when at the limit or trail-braking....

[Thorney]

i noticed quite a big difference, i used to get rear end wiggle under braking and accelerating, now its almost completely gone.

that is the second reason why I decided to install the LSD.... I hope it will partly/fully cure the tendency to lock-up the rears FIRST, when at the limit or trail-braking....

The wing did this for me

[barrybethel]

Thanks for that Ian. All my questions answeres and then some! It definetly seems the thing to have. I was discussing slippy diffs with Mike at Tollbar the other day - I asked him if he thought one would make a lot of difference to lap times and his reply was "yeah loads". He did mean reducing them, before any of you smart-arses pounce. BTW my front spoiler is fibreglass. The guy that made it still has the mould and could make you one in carbon fibre if you wanted but it would be quite a bit more money. I thought it was unecessary as mine weighs very little and is very strong. The rest of the body is fibreglass after all! Pm me if you want his number. Dean

[Crabash]

I got a ATB diff for my westy and a quaife SC HD syncro type 9, it was the stuff I wanted (reccomended to me by SBD who I bought all my engine part's, dry sump, TB's, clutch etc etc off) so I kept at em but my god it was a nightmare getting it, I 1st ordered it in january, then after many month's of being fobbed off they stopped responding and played dumb as if I hadn't ordered it, so I phoned demon tweak's for a quote who did the stuff for the same price as quaife would direct, so I handed it over to them, finaly got my stuff in the november, look's good in the garage next to my engine and box of electric's I must get the rest of the car moved in and finished this year.

[Thorney]

Well as soon as I pick mine up it'll be going in with the hardended driveshafts along with an adjustable ARB and a re-set up from Plans Will post up details of what they all do to the handling

[the gits]

Advert mode on.. Plans Motorsport have a lot of experience with Quaife and the ATB diiferentail. We do a very special tweak with our Elises/ Exiges fitted with this diff. We have found that this diff, being designed for Front Wheel Drive applications, needs a different helix angle when in RWD applications. The standard ATB slipper usually causes "push-on" understeer mid/exit corner.. our version solves this. We have a special batch of PG1 diffs made at Quaife. We are getting one prototype one made soon for a VXR customer, and if it better than the FWD version, we'll get a batch made. It'll be the same price £495.00 plus VAT. And of course we can fit and set up the rest of the car to get the most from the better grip that the ATB diff gives.

[s1oww]

I would love a ride in someones vxt with an lsd. I would like one for mine, but want to see how it handles being mid engine. They've made a big difference in my other cars. I had a Quaife ATB LSD fitted in my old Westfield. The car slid about a little bit more on bends, but was more controlable. ATB's are more realiable and modern than clutch style ones, atb's work much better. I find the vxt can be twitchy in a straight line under full power, i know it would cure that. The best bit is it makes roundabouts even more fun, i would spend lots of time going round them looking out the passenger side . It makes you want to drive your car more when its wet. Word of warning tho, make sure you put the correct oil in it. I had mine filled up twice by idiots that put the wrong oil in it and nearly fried it. Once was on my way to le man and it had to be trailered back from france by the AA.

[cyberman]

The standard ATB slipper usually causes "push-on" understeer mid/exit corner.. our version solves this. We are getting one prototype one made soon for a VXR customer, and if it better than the FWD version, we'll get a batch made.

Dear "the gits"

This sounds interesting but being a bear of very little brain I don't think I understand. This is probably compounded by the fact that although I understood various types of simple minded LSD (which mostly do nothing or lock up) I have no idea how the ATB actually does its stuff.

Do you think you could explain in a bit more detail what the characteristic of the FWD ATB is that you suggest causes it to provoke understeer and why your differently made unit won't? You don't need to tell me (unless you want to) how yours works inside but I should like to know how the transfer function differs (i.e. the mapping of drive distribution under different conditions of load, power and wheel speed differential).

Unless the thing is very sophisticated and can alter drive distribution to accord with the dynamic toe-in / toe-out at the rear end I have a bit of trouble seeing how it can yield a very different handling result. I don't say it doesn't - its just that I have trouble seeing it.

Kind regards - Ian

[dude]

to make this a little more understandable. 1. a plate-type lsd without ramps will increase understeer both on fwd and rwd. 2. a plate-type lsd with ramps (angle depending on vehicle type) will increase understeer on exit of turn(under acceleration). 3. a torsen-type differential will not add any understeer regardless of fwd or rwd. i has a little problem(i never noticed it). if we loose traction(100%) on one wheel,all acceleration will be lost. but only after a period of time depending of the mass/speed of the wheel that has lost all traction(in the air for example).

[the gits]

Dude/ Cyberman Have a look at the Quafe brochure. It has an excellent cut-away diagram of the ATB diff. Note that the ATB works if a differnt way to both Torsen or plate diffs. The Limited Slip functionality is governed by the six helical gears. The helix angle of these gears is very critical, and Quaife will confirm that he diff design does affect understeer characteristcs. Plans ran these diffs in 36 races last season. We have done about a zillion miles of testing. So please don't confuse with the usual internet "this must be right because I read it in a forum" answers It's simple physics. If you have weight transfer from the front to the rear under acceleration, and you have more grip at the rear than the front, your going to get understeer.

[dude]

Dude/ Cyberman

Have a look at the Quafe brochure. It has an excellent cut-away diagram of the ATB diff. Note that the ATB works if a differnt way to both Torsen or plate diffs.

The Limited Slip functionality is governed by the six helical gears. The helix angle of these gears is very critical, and Quaife will confirm that he diff design does affect understeer characteristcs.

Plans ran these diffs in 36 races last season. We have done about a zillion miles of testing. So please don't confuse with the usual internet "this must be right because I read it in a forum" answers

It's simple physics. If you have weight transfer from the front to the rear under acceleration, and you have more grip at the rear than the front, your going to get understeer.

don´t get me wrong either, but i have raced with a quaife atb the last 5 years on my endurance-car(started 1992).

a lsd gives understeer i every configuration(in theori) but if you put a driver in the car, he will probably say that the atb gives no(or minimal) understeer in comparisation with a plate-type(whatever configuration) on at least exit turn.

before i changed to a atb i had a traditional preload plate-lsd, and the differens was like night and day.

[cyberman]

It's simple physics. If you have weight transfer from the front to the rear under acceleration, and you have more grip at the rear than the front, your going to get understeer.

As it happens I am a simple physicist so I ought to understand.... I do not dispute your remarks that if you get more power down you will generate weight transfer and lift the front and this will lead to reduced front end grip. No problem at all.

However, either you were talking about another effect when suggesting that your LSD didn't cause understeer or by your definition your LSD inhibits power transfer (and therefore weight transfer etc etc). I am sure you didn't mean us to infer the latter.

So, what exactly is it that differentiates your device from the Quaife? I will go and read the Quaife stuff and see if I can work it out. However, all I really want to know is something that is "black box" measurable. I don't need to understand how it arises. If it really works it should be possible to say through what mechanism (e.g. when approaching wheel slip we transfer power earlier to the non-slipping wheel - or whatever).

Kind regards - Ian Douglass

[cyberman]

Sadly the Quaife website seems to be in a state of flux and the technical drawings are "coming soon". I didn't find anything else except their overview of the ATB which is rather a summary. They do very carefully say that the ATB does not affect the handling of FWD cars. Trying to be analytical about this, the VX220T with regular set-up does (AIUI) toe out at the rear when compressed. Presumably when extended the reverse is true (or relatively so). If cornering at high g there is roll and the outside rear squashes down and the inside lifts - maybe more than the outside squashes. So there is a change in rear end steer characteristic as cornering force builds and as duration of time in the corner increases. Putting more power down and generating weight transfer should lead to greater common compression of the rear suspension and presumably less overall roll. One would expect this to lead to the variation in steer characteristic being reduced as both wheels move towards complementary alignment. Putting power through the outer wheel which is toed out should lead to a more over-steering characteristic as a consequence of the power vector angled out from the line of motion. As power builds up and common compression sets in this effect should be reduced. Couple that with the reduced front end load and yes I suppose one would expect less oversteer / more understeer to be induced as a consequence of getting more power down. However, I still don't quite see how you get a very different effect - and I would like to. Kind regards - Ian

[the gits]

A litttle bit of cross-purposes here. I was not refering to the difference between different types of diff, or that our diff isn't any different in basic design to the Quaife diff... it is the Quaife diff, but we have modified it based purely on race experience. And Quaife do the work - not us. If you stick the ATB diff in a FWD gearbox put it in a RWD, mid engined car you get a lot more grip at the rear than the standard car. This causes the front to push away when you get on the power. You can drive round it (like everything) but ultimately you get a slower lap time. Or, if you not timing, it's just a pain. So, we experimented with a different configuation inside the ATB diff to reduce this understeer effect. I don't really want to go into the technical details because of course we would like people to buy the diffs from us . And, I can say, it works. It works in the Elise.. and although we haven't tried it yet in a VX (we will very soon) I will gaurentee it'lll be better. That's because the problem will be exacerbated in a VX as you have even more weight over the rear. We will have a demo car, so you can come down to us and we'll show you out on the circuit. Not many people can do that.

[dude]

this sounds very interesting. what company are you from?. website?.

[cyberman]

If you stick the ATB diff in ... a RWD, mid engined car you get a lot more grip at the rear than the standard car. This causes the front to push away when you get on the power.

You can drive round it (like everything) but ultimately you get a slower lap time. Or, if you not timing, it's just a pain.

I don't have any problem with your first statement as discussed and agreed earlier.

However, I don't agree that fitting the ATB leads to slower lap times than without the ATB. One may not be able to put full power down in some circumstances but thats always the case even though the reasons may vary. The question is: is more power being applied and is acceleration faster than without the ATB? I think it is so in all circumstances WRT my car.

[cicastol]

this sounds very interesting.
what company are you from?.

website?.

www.plansmotorsport.com

[Thorney]

Just to give those who don't know a heads up, Graham (the gits) runs Plans and has many a year in racing Elises. He set up plans to essentially set up and tune Elises and VX220's. To his mind (and I agreed) there wasn't anyone with lots of racing history in these cars around to help set them up. I've been helping Nitron set up the 3 way system (I'm erring to harder springs on the front but that might be me) and asked Guy (Nitron) who to go to for help, he suggested Plans so I met up to see what they were about. I came away thinking they had a nice set up, Graham was a nice bloke and the fact you get to use the circuit to set the car up (on the road isn't any good IMO) was a nice touch. I put the Plans banner up on the site primarily to let people see what they were doing with the promise that if I'm came away unimpressed I'd take it down again, its still there. I've asked Graham for more info on this Quaife set up as I have a stock LSD wating to go in the car so need convincing this ATB version is worth the extra so I'll share what I find out when I know. I'm also interested in thier ARB as the Elise one will only fit if you hack out some of the undertray and I didn't want to do that. Bottom line, there aren't that many people who tune/mod the VX220 so long as the service is good and they know what they're doing then more the merrier IMO.

[the gits]

Thorney - Thanks for your kind comments. cyberman - I haven't poted on here much (i) because I think it is advertising and hence feel it is not in the true spirit of these forums (fora?); and (ii) because it is so easy to be misunderstood. I am not saying a VX will be slower with a Quaife ATB LSD - far from it! What I am saying is that a VX will be slower (I'm not just saying it I'm gaurenteeing it) with the Quaife FWD ATB LSD as opposed to our alternative version of the Quaife ATB LSD thats made for us at Quaife with different helix angles. And, if this doesn't clear things up, I'll give up this whole game and resort to selling them on small pieces of rice paper with tattoos on. That'll stop your understeer!

Edited by the gits, 28 January 2005 - 05:21 PM.