David_Wallis

as above

sammyh

iTrader: (1)

Something to do with rallying? as in a diff guard sort of thing?

I'm probably wrong though

mutant_matt

I don't know the answer but it seems to be that there are two main types, the Viscous like the rear diff's on the UK cars and the Plated like on *some* STi/Rs'/RA's (this still seems to be a matter of debate). (Having said that, there are probably loads of other types).

I suspect a Plated diff is like a multiplate clutch, as used on motorbikes with a progressive degree of lock up, but presumably, the lock up is faster and perhaps can take more loading than the Viscous type?

Time for someone who knows to tell us?

Also, can anyone tells us what type of diff the front Suretrac diffs as used on the STi 7 are? (and I don't mean LSD, I mean which type Viscous/Plated/xyz?)

Matt

Pavlo

Yes a plated diff has a clutch pack in it, it's also ramped, so the friction when the 2 sides are spinning different will further load up the diff. Different ramp angles and preloading can set the diff to behave differently.

ATB diffs are based on the Torsen design, using the fact that you can only drive a worm gear in one direction.

Viscous Diff is hydraulic based, but uses a thixotropic gel that resists sheer, loads up based on speed.

Dave R

When I think of a plated diff (Kazz/Type R/RA) i think of the classic Salisbury/ZF LSD.

Each side of the diff has a set of plates that are compressed and therefore grip each other when there is a differential speed between the axles. The force on the plates is generated in the centre of the diff by a set of cross pins rising up rmps on a plate that sits against the friction plates...

Best look at www.howitworks.co.uk etc...

Vicous diffs and the STI Electric diff also have plates but in the viscous diff the locking is generated by a 'stiffening' of the silicon fluid and in the STI unit, it's generated by the electro magnet, clamping all the plates together, and resisting any differential in speed between the front and rear axles...

Daver

David_Wallis

but what I dont understand is the transmission losses...
say we loose 70bhp in the transmission..

1.341 bhp = 1 kW

then that = 52.19Kw Loss ???

could also convert it to btu if you want..

thats a lot of heat to loose in a gearbox?? if its a loss then it goes somewhere... or am I missing some point??

http://www.coxhardware.com/usefulinf.../3a_engtbl.htm

David

Adam M

I was under the impression that in the manual centre diff, the viscosity of the fluid drags the plates relative to each other.

The degree of separation dictates the amount of relative slip permitted, but ultimately both input and output shafts always reach the same speed.

David_Wallis

top

dowser

Umm - the centre diff is different, I guess you'd always want a viscous diff here. It resists difference of speed between front and rear axles more, the more difference in speed there is.

For front and rear, left and right differences, you'd want something more 'immediate' than a viscous coupling....

Or am I talking out of my bottom.....again? :-)

Richard

Pavlo

you are correct david.

But much of the power loss measured on a rolling road is in the tyres. That said, Andy F's gearbox is too hot to touch after a long blast.

Paul

David_Wallis

what are the actual transmission losses then...

just wondering if a gearbox oil cooler would be a worthwhile addition...

David