Slippy Diff Question

[5paul5]

Ok so on a RWD car fitted with a LSD on for example a wet roundabout is it easier or harder to get the back end out and promote oversteer ?

[thinfourth2]

Depends

They can also cause understeer

[StottyZr]

Generally easier as you'll spin both rear wheels instead of one

[Herman Toothrot]

Much easier as long as you have power.

[kambites]

An LSD makes it easier to generate over-steer under power (as long as the car has enough power to break traction) but will generally increase under-steer the rest of the time, depending on exactly what type of diff you're considering.

[5paul5]

Reason i ask is i have just bought a mx5 eunos 1.8 94 model and trying to determine if it has a LSD, on a recent wet trackday it wanted to swap end at the drop of a hat, i realise that tyres are also a big factor but i have done many a wet trackday in several of these cars but this one seems more tail happy than anything .

[kambites]

5paul5 said:

Reason i ask is i have just bought a mx5 eunos 1.8 94 model and trying to determine if it has a LSD, on a recent wet trackday it wanted to swap end at the drop of a hat, i realise that tyres are also a big factor but i have done many a wet trackday in several of these cars but this one seems more tail happy than anything .

It's easy enough to tell - jack up the back wheels, shove it in gear with the engine running and see if you can stop one of the wheels from turning (don't use your hand; that could hurt).

[Herman Toothrot]

Alignments probably all over the place.

A 1994 Eunos probably has a Torsen LSD so you can't test jacking it up it'll behave like an open diff.

My old 265bhp Eunos S had the type 2 Torsen and I'm the wet it was lairy.

[kambites]

Herman Toothrot said:

Alignments probably all over the place.

A 1994 Eunos probably has a Torsen LSD so you can't test jacking it up it'll behave like an open diff.

My old 265bhp Eunos S had the type 2 Torsen and I'm the wet it was lairy.

Ah OK, thought they were viscous.

[5paul5]

Sounds like having a LSD is not a good thing to have then especially on a trackcar, more fun perhaps but slower lap times surely ? not what i wanted to hear really.

[Captain Muppet]

kambites said:

5paul5 said:

Reason i ask is i have just bought a mx5 eunos 1.8 94 model and trying to determine if it has a LSD, on a recent wet trackday it wanted to swap end at the drop of a hat, i realise that tyres are also a big factor but i have done many a wet trackday in several of these cars but this one seems more tail happy than anything .

It's easy enough to tell - jack up the back wheels, shove it in gear with the engine running and see if you can stop one of the wheels from turning (don't use your hand; that could hurt).

Or try a massive burnout and count the number of black lines on the road.
More fun and less risk of Beullering a car.

[kambites]

5paul5 said:

Sounds like having a LSD is not a good thing to have then especially on a trackcar, more fun perhaps but slower lap times surely ? not what i wanted to hear really.

Depends on how good the driver is.

An LSD ultimately gives you more traction so you can get on the power harder, sooner on corner exit; however if you feed in too much power, an open diff will only spin the inside wheel so the car just wont accelerate, whereas with an LSD the outside wheel will spin up as well and the back end will step out.

[Kozy]

5paul5 said:

Reason i ask is i have just bought a mx5 eunos 1.8 94 model and trying to determine if it has a LSD, on a recent wet trackday it wanted to swap end at the drop of a hat, i realise that tyres are also a big factor but i have done many a wet trackday in several of these cars but this one seems more tail happy than anything .

Same here, the guys I bought it off were adamant that mine has a Torsen, even though they weren't fitted as standard to my model. Given how easily it slides I'm inclined to believe them however!

Without an LSD, or a worn out VLSD like some Eunos models, the inside wheel will spin all the power away and the outside wheel will grip, so they 'should' be a lot harder to slide purely on the throttle.

Chuck it in with enough vigor on a wet road though and either will probably scare you.

[kambites]

Captain Muppet said:

Or try a massive burnout and count the number of black lines on the road.
More fun and less risk of Beullering a car.

Or that.

[HustleRussell]

5paul5 said:

Sounds like having a LSD is not a good thing to have then especially on a trackcar, more fun perhaps but slower lap times surely ? not what i wanted to hear really.

With an open diff you'd probably just be spinning power away at the unloaded rear wheel. Make sure your tyres and suspension are up to it and with thoughtful driving an LSD shouldn't be any slower. I'm sure it'll be faster in the dry.

[Captain Muppet]

5paul5 said:

Sounds like having a LSD is not a good thing to have then especially on a trackcar, more fun perhaps but slower lap times surely ? not what i wanted to hear really.

It depends, are you doing the track days for fun or because you want to do more laps in less time? Sometimes having fun is more fun than timing yourself doing something.

Some old RWD touring cars used spool diffs (ie a sold "diff" which permenantly locked the rear wheels together) and they still set fast times. I'd be more concerned with tyres, pressures and geometry.

[5paul5]

Its an s special on factory bilsteins with just 60k so should be pretty tight.

[Captain Muppet]

kambites said:

Captain Muppet said:

Or try a massive burnout and count the number of black lines on the road.
More fun and less risk of Beullering a car.

Or that.

[Herman Toothrot]

5paul5 said:

Its an s special on factory bilsteins with just 60k so should be pretty tight.

Wheels could all still be pointing in different directions if it's not been setup recently.

[kambites]

Herman Toothrot said:

5paul5 said:

Its an s special on factory bilsteins with just 60k so should be pretty tight.

Wheels could all still be pointing in different directions if it's not been setup recently.

If it's that wayward, the geo being off is most likely, I'd imagine. Probably not enough negative camber at the back, but I suppose the rears being toed out would feels similar.