lotus and LSDs

[istoo]

I have done a search and not found and answer that sums it up.. but often wondered this, why have lotus never fitted / installed LSDs to cars until very recently?

[robin]

I think in the days of the K it really wasn't worth it. With sticky tyres and little to no torque there wasn't really a need for LSD - there wasn't much S to L

With big superchargers and engine capacity the torque has become more problematic to deal with ... diesel, anybody? ... and so an LSD perhaps makes more sense to get mechanical drive out of the corners? But I must confess I have no idea!

[mckeann]

Simon Scuffham will tell you that it causes understeer, and it only tries to mask the problem of too much roll, so better to just fix the problem of roll rather than try to mask it with an LSD.

I don't know myself, but I'd be inclined to agree with him.

[Dominic]

On older elises I don't think they are needed,
https://youtu.be/PlMc-EKZvyw

On newer lotuses I think IIRC that the traction control acts like a virtual lsd.

[pete]

I think in the days of the K it really wasn't worth it. With sticky tyres and little to no torque there wasn't really a need for LSD - there wasn't much S to L

What do you mean "in the days of the K". That's today!

[Rosssco]

Are LSD's essentially a sop to optimal suspension design though? With the suspension correct set up on a road car, the suspension should keep the inside wheel in contact with the ground sufficient to prevent it spinning up.

On the road, with 220lb/ft but decent road suspension (Exige Bilsteins) I've never really found the need for an LSD, except perhaps trying to gun it out a really tight bend. At which point an LSD would probably spit me off the road!

[Victor Meldrew]

When I drove Mikes S1 at Boyndie I said to him at the time that I thought his car was reluctant to turn in off the throttle. It was totally different to mine. Could have been a number of things but the only fundamental difference between both our cars other than power was Mike's had an LSD fitted.

[robin]

Nobody should need LSD on the road.

The question is whether it is needed on track.

Traction control can produce a virtual LSD only if it is the kind that can apply brakes independently per wheel as opposed to limiting engine output.

The Elise has no rear anti roll bar (unless really new ones do?). So you can only really prevent traction loss due to roll using the front arb and strong springs and lots of droop travel at the rear.

You would need to ask someone who has experience of racing modern Elises with lots of power whether the LSD would help.

Cheers,
Robin

[Shug]

I had an interesting experiment with my old Elise. Fitted a torsen diff when I built up a gearbox out of a few different ones. I had an open diff ready to go back in if I didn't like it, but actually for the track driving I was doing, it was better fun.

My Elise always needed more roll control - had uprated suspension, but road/track rates, and no uprated anti roll bar. Photos showed it rolled too much on track. So, for mine, it was great - actually helped turn in (I think largely by over-rotating the rear) and made it much more throttle adjustable on corner exit - could hold better slides more easily. Now, would it be faster? That, I don't know as I never timed laps or videoed many to compare. But in my case, a combination of factors made a torsen a positive addition to the car.

On road, it was a different story - with the Elise being more traction limited at the front (pretty rearward biased weight), it would dart about on power if the rears were on different surfaces or different cambers - in other words, pretty much all the time on the patchwork quilt that is the Scottish road network Made it less composed on the road - combined of course with the fact that I was running reasonably pointy geo at that stage.

Interesting that McLaren's P1 - which chucks an awful lot of torque and horsepower through the rear tyres - doesn't have a mechanical LSD. It does work the rear brakes, as Robin talks about, though.

I think the view is probably right, that if the car is set up well, there's no need for an LSD on the Elise unless you're chucking out an awful lot of torque and using it as a track car -mostly because of that light front end and the diff dominating proceedings on the road if you're not careful.

[istoo]

now that does have some explainable logic, combination of CoG, lightweight and low torque does make sense. On that basis do Caterfields use LSDs?

Mine doesnt have enough torque (VVC) to set it alight at KH, unless i really force it out of shape at the hairpin it will step off the AD07s, otherwise only trail braking seems to let the back step out... the M3 was so playable on throttle. The elise, not that turn in was ever bad in the first place... just curious!

Does weight have anything to do with it?

[Shug]

Caterfields have all their weight over the front axle (yeah, I know it's a bit more balanced than that) where the Elise has the engine sitting pretty much directly over the rear wheels. So yeah, quick Caterfields do tend to use LSDs as their weight isn't over the driven wheels so the dynamics are different.

[van cleef]

Isn't the gearbox from a BRM rover be a straight swop with a Torsen LSD as standard? I was searching for one to try out on my vvc but, never could find one when I was looking.

[Mike Scib]

Is the issue with fitting a LSD to the Elise not that it can cause understeer in slower speed corners as the front end is pretty light?

I have never felt my car requires a LSD even with 260bhp

https://www.youtube.com/watch?v=jDf9YEnIUFQ

Jump to 8.20.

[j2 lot]

My only experience of an LSD was many years ago in a rally mini - it was a nightmare to drive as it seemed to randomly leap about the road - think bucking bronco. I couldn't drive it to save my life, the owner who was used to it could make it perform seemingly impossible turns with almost no loss of speed. You needed muscles like Popeye and an understanding of what it was trying to do to make it work - I had neither

[Shug]

Isn't the gearbox from a BRM rover be a straight swop with a Torsen LSD as standard? I was searching for one to try out on my vvc but, never could find one when I was looking.

Yup - but the final drive was wrong. I built up a BRM box with the standard final drive, giving a decent close ratio box. Can't remember the ratios off the top of my head, but just chucking the BRM box in would have given funky results - either far too high or low overall. Ideal with the CR gear cluster in it and the standard final drive.