RE: Ask the expert: All you want to know about differentials

[Dagnut]

BarnatosGhost said:

To be level with the 2nd to last opposition player is to be onside.

it used to be 2 players now you only need 1 to play you onside

[angusc43]

My S14 200SX had an oil cooler on the LSD.

I always thought it looked fantastic.

On the other hand the oil cooler might actually been there because the LSD was inherently inefficient.

So was the oil cooler a neat bit of motorsport-influenced over-engineering? Or was it covering up some shortcomings of the diff?

[AliMc99]

I'm potentially in the market for a new Mercedes C63 AMG. I can potentially see the benefit of an LSD for circuit use but would a LSD make any real difference in road driving (it is a £1750 factory fit option)

[Alicatt1]

doogz said:

Only as long as you reverse with your left arm around the back of the passenger seat.

Ooo err missus thats a bit difficult in LHD car

Does a partialy inflated tyre cause transmission wind up in LSD/ locked diff vehicles?

[frisbeerhero]

There's a lot of 'horsepower' going through those rear legs

[Marf]

Kozy said:

For a FWD racing car, is a helical or plate diff a better option?

Do Quaifes/Torsens/helicals work under braking?

Helicals require both wheels to be loaded in order to work, i.e. if one wheel is in the air, then no power is being transmitted to either.

Plate type diffs do not have this little foible.

[GFWilliams]

Our Caterham doesn't have an LSD but I can still drift it and hold a drift. So what benefit would an LSD have?

[BarnatosGhost]

Dagnut said:

BarnatosGhost said:

To be level with the 2nd to last opposition player is to be onside.

it used to be 2 players now you only need 1 to play you onside

You're assuming the keeper is on his line, but he doesn't have to be. It is any two opposition players who count.

[BarnatosGhost]

GFWilliams said:

Our Caterham doesn't have an LSD but I can still drift it and hold a drift. So what benefit would an LSD have?

Your caterham is probably relatively stiff, so doesn't have a great deal of lateral weight transfer, and relatively powerful, in combination enabling it to still light-up both wheels even when cornering.

Most cars in the same condition will only light up the inside wheel, as the outside wheel has more traction from the weight-transfer, and so before the engine can overcome that grip, the power is spun away by the inside wheel.

[OperationAlfa]

Ediffs or Electronic diffs are not really differentials at all are they?

I have fitted mechanical diffs to most of my cars but it annoys me when people tell me their car has an LSD when it really doesnt.

[Marf]

OperationAlfa said:

Ediffs or Electronic diffs are not really differentials at all are they?

Depends, some real differentials are electronically controlled(assume the ramp angle is able to be altered) but most common or garden e-diffs are just an electronic system which brakes a wheel to simulate the effect of an LSD.

[Dagnut]

BarnatosGhost said:

You're assuming the keeper is on his line, but he doesn't have to be. It is any two opposition players who count.

You are correct sir , apologies.

[s m]

angusc43 said:

My S14 200SX had an oil cooler on the LSD.

I always thought it looked fantastic.

On the other hand the oil cooler might actually been there because the LSD was inherently inefficient.

So was the oil cooler a neat bit of motorsport-influenced over-engineering? Or was it covering up some shortcomings of the diff?

Did you ever see the light on the dash for it come on Angus?

To get the pump to run you need to trigger 2 switches.

The first one is dependent on the diff oil being approx 130 deg C and over.
The second one is speed sensitive and the car must be registering over 75mph.

When both these conditions are met, the dash light should illuminate in conjunction with the pump.

In reality, most people never ever see it used.

I think the S13 was dependent on a speed of 6mph plus ( and temp )

The S13 and S14 LSD was a VC type - over time the constant heat cycling means the slicone fluid degrades and loses some of its properties. They can be re-rated/uprated though, much like a plate diff

[BarnatosGhost]

Dagnut said:

BarnatosGhost said:

You're assuming the keeper is on his line, but he doesn't have to be. It is any two opposition players who count.

You are correct sir , apologies.

[jatinder]

I've heard you can knacker your diff, if just messing about in the snow?

Is this true or rubbish? I heard it the Integra forums.

I think rubbish, but still just wondering….

Edited by jatinder on Thursday 23 February 15:11

[sparkyhx]

s m said:

Did you ever see the light on the dash for it come on Angus?

To get the pump to run you need to trigger 2 switches.

The first one is dependent on the diff oil being approx 130 deg C and over.
The second one is speed sensitive and the car must be registering over 75mph.

When both these conditions are met, the dash light should illuminate in conjunction with the pump.

In reality, most people never ever see it used.

I think the S13 was dependent on a speed of 6mph plus ( and temp )

The S13 and S14 LSD was a VC type - over time the constant heat cycling means the slicone fluid degrades and loses some of its properties. They can be re-rated/uprated though, much like a plate diff

What he said, I didn't know the exact figures but I knew the combination for when it came on was beyond when normal mortals would see. I knew someone who wired it to a switch so he could do it himself.

So probably over engineered unless Datsun were pre empting the drifting craze

Edited by sparkyhx on Thursday 23 February 14:19

[_g_]

GFWilliams said:

Our Caterham doesn't have an LSD but I can still drift it and hold a drift. So what benefit would an LSD have?

I could do tight drifts/dougnuts in both my old TD Transit and a friend's non-LSD MX5.
Yet when we took the MX5 to a proper drift-day it entirely refused to let go of both wheels at once.

I'm presuming that it's merely a case of provoking both wheels to let go at the same time means they're still at a state where both are in similar conditions, so no reason for one to grip and the other to spin up.

[s m]

sparkyhx said:

s m said:

Did you ever see the light on the dash for it come on Angus?

To get the pump to run you need to trigger 2 switches.

The first one is dependent on the diff oil being approx 130 deg C and over.
The second one is speed sensitive and the car must be registering over 75mph.

When both these conditions are met, the dash light should illuminate in conjunction with the pump.

In reality, most people never ever see it used.

I think the S13 was dependent on a speed of 6mph plus ( and temp )

The S13 and S14 LSD was a VC type - over time the constant heat cycling means the slicone fluid degrades and loses some of its properties. They can be re-rated/uprated though, much like a plate diff

What he said, I didn't know the exact figures but I knew the combination for when it came on was beyond when normal mortals would see. I knew someone who wired it to a switch so he could do it himself.

So probably over engineered unless Datsun were pre empting the drifting craze

Ideally, you need a press demo

[kedaha]

This might make me sound stupid, but for a long time I found it hard to actually fully grasp how and diffs do.

A 1930's video helped me figure it out
http://www.youtube.com/watch?v=K4JhruinbWc&lis...

[300bhp/ton]

PH said:

If you've any questions for Jorg let us know below and we'll get them across to him before we meet up with him later on today.

Q. What is his opinion on fully mechanical limited slip differentials vs the trend of modern computer controlled ones from a drivers point of view?