Spools or welded diffs on track cars

[Russ Noble]

Jac Mac,

As always, I defer to your superior knowledge.

In the meantime an 80/80 Porsche set up will do me fine.

It would be nice to be running a 9'' like JO's TVR where you could relatively easily and cheaply fit and compare spool, locker, and maybe various LSD's. oke:

Cheers

 

[Sandy]

Jac Mac,

As always, I defer to your superior knowledge.

In the meantime an 80/80 Porsche set up will do me fine.

It would be nice to be running a 9'' like JO's TVR where you could relatively easily and cheaply fit and compare spool, locker, and maybe various LSD's. oke:

Cheers

Nothing like a 9 inch and leaf springs, dependable, cheep, loads of options. I didn't jump in earlier as I was busy in Detroit , but I would never run a spool unless a dirt or drag car. No reason for beating the drive line up. Ton's of good diffs from the Torsen to the detroit locker and many variants in between. I think you can get a Torsen (might be the 2R model for the 9") that has clutch packs to preload the diff which sounds like the best of all worlds (except the price). I talked to a few folks that road raced older front engine cars and not were keen on the lockers, most said more violent driving with them then clutch types (Like Russ said). They said the tighter the course the worse they are. All recommend clutch style or Torsen style. My cousin has a detroit locker in his early bronco that replaced an open diff. The car drives completely different in a bad kind'a way. Very throttle sensitive steering and not in a good way.

For the GT40's I asked around and some said the clutch pack is a better way to go then the Torsen (quaif/guard/etc), but didnt get enough concensus as I only had a few folks that I could pester for the info. Some of the porsche guys seem to not like the Torsens, but for mid engine car might be better. One interesting comment was that the Torsen's have no decel bias might be the reason, don't know. Also not sure what it will do vs. a clutch pack with some split bias which I guess is more what the discussion is about. I have 3 boxes with the Quaife version of a Torsen and will see how they work when the car gets on the road.

Sandy

 

[Russ Noble]

Dalton,



Interestingly, if you achieve fitment to a mid engined setup by flipping the crownwheel (as opposed to inverting the box) you then get the ratio split reversed 40 front/80 rear then becomes 80front/40rear. Because the direction of rotation of the diff is reversed. Much more desirable but the additional motor height involved is not.

Before some eagle-eye says "not strictly correct" ...... oke:

40front/80rear should of course read 40power/80overrun etc.

Thanks for the input Sandy re spools.

The Mark Donohue aspect still intrigues me though............

Cheers

 

[Jac Mac]

Sandy,
The TVR 9" is IRS, previous diff was late Vette all alloy posi which we now know was inferior to current Trutrac torsen type. Owner had raced with Lockers before and was not keen to use one in TVR. Car in question appears to have the 911's beat in most areas except exit from slow corners.

Russ,
If you continue to behave you may just get the opportunity to try all three types, but given this afternoons news I imagine you are looking at LPG tanks of suitable size for the car.
My old OSCA Imp( Rear engine/Transaxle) had an NZIG spool and was called a "brave mans" car (stupid might be more appropriate) . It had a narrow sweet spot between terminal understeer & out of control oversteer that it had to be driven in, as Randy pointed out in an earlier post this had a useful effect on fellow competitors who were reluctant to get involved in the impending accident.

Jac Mac

 

[Russ Noble]

Jac Mac, I'm keeping my fingers crossed!

I used to have a (std) Imp once but it kept running into ditches so I sold it! Also I'm well aware of the racing advantages of an unstable car. There's always a silver lining......

This afternoons news that Jac Mac is referring to, is a move by MSNZ (motorsports rule makers here) to ban AvGas. Shall start a new thread in the Racetrack Forum.

Cheers

 

[Lynn Larsen]

Sandy,

From what I have read, you are spot on re: Porsche drivers liking the clutch type LSD for the braking bias they give vs a Torsen type. If they could get the overrun number (as Russ calls it, translating for us 'mericans ;-) up on a Torsen, it would actually be preferred. So, maybe you're rigth about the preloaded Torsen as well.

Lynn

 

[Keith]

Well I reckon y'all in OZ and NZ should run those "free wheeling hubs" now they've been banned by Supercar V8 Series

Whaddya mean "they weren't running them?"

 

[Ron Earp]

For the GT40's I asked around and some said the clutch pack is a better way to go then the Torsen (quaif/guard/etc), but didnt get enough concensus as I only had a few folks that I could pester for the info. Some of the porsche guys seem to not like the Torsens,

Sandy

This is the concensus with the SCCA crowd I race with as well. The Quaife is a good setup I think but isn't adjustable and if you get one wheel unloaded it'll transfer power to the unloaded wheel. On the other hand, it is bullet proof, doesn't require rebuilding, and works on smooth tracks. There is a Quaife in my partner's TR8 and it is good 85-90% of the time, but occassionly in a race at a rough track it'll not be stellar. However, this is what I'd pick for my street/track car due to low maintenence. If flat out track car I'd still might pick it since I've seen that they work pretty well most of the time.

R

 

[Jac Mac]

Well I reckon y'all in OZ and NZ should run those "free wheeling hubs" now they've been banned by Supercar V8 Series

Whaddya mean "they weren't running them?"

Could not resist mentioning that the influx of team owners/managers etc from your region might have some level of responsibility for the introduction of these questionable modifications that have appeared on the scene over the last few years. You know the type-broke one week,millionaires the next.

Jac Mac

 

[wanni]

The welded diff is for sure beter than the open diff in terms of traction.
You must be able to go through the corners always in oversteering but this kind of driving does not pay really on the lap time.
Anyway there is a possibility, already used to drive in a profittable way a welded diff, without getting a drive shaft in your head, is to create a torque fuse somewhere.
The most common system used in Europe is to let slip the tyre on the rim.
This technique was used on the Dauer Porsches 962 in 1994 at Le Mans.
Any differential was capable to take all the torque for 24H in such a small place. In order to give an help to the drive shafts, one rear tyre was fitted with lubricant and the other with a normal soap anaerobic, converting to a glue in an ambience without oxigène.
The tyre was slipping when the drive shafts were completely preloaded and this was happening in the long fast corners. The natural oversteering was doing the job in the slow corners.
Not bad as a system. Who said that Germans are stupid?
Ciao

 

[Keith]

Could not resist mentioning that the influx of team owners/managers etc from your region might have some level of responsibility for the introduction of these questionable modifications that have appeared on the scene over the last few years. You know the type-broke one week,millionaires the next.

Jac Mac

Teeeee Dubble-Yer?

Had to be a man with a bow tie anyway....they know how to cheat