AWD and LSD or spools - discuss !

So I want to setup my car to be the most fun (that an AWD car can be)

which is probably to make it behave more like a RWD car .

what changes would best accomplish that ?


right now my car is Torsen - 4kg Center viscous - rear viscous .

I want it to behave a lot more like my STI (torsen - computerized center - Clutch)

not planning on buying a fancy center .

Lets say we are in a typical R3

In my STI on the dirt if you just turn in more and go WOT the back steps out and you drift (weeeeee)

in my RS 2.5 on the dirt if you Only turn in more and go WOT the car drives through the corner, maybe after 1-2 seconds the rear "locks up" enough it starts to step out a little, but that's usually after the apex. its not very helpful and its not Nearly as much fun.


should i just throw a rear clutch LSD (maybe up the break away torque) and call it a day?

would a spool be a better idea ? would a spool in the back be a horrible idea for something i'm not thinking about ?


thanks

How spensive is the 20kg center?

Locking the center and rear (so two spools) makes my AWD car drive like a rear drive car, but not in a good way.

I don't see why you'd want to make an AWD car drive like a rear drive car. Make it drive like an AWD car, otherwise why bother?

IIRC, the Delta Integrale had some sort of center diff that biased heavily towards the front, theory being the car is nose heavy so the torque should be nose biased. Seemed to work just fine for them.

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Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.



Edited 1 time(s). Last edit at 07/28/2014 05:12PM by Pete.

I'm dealing with the same situation but with an even less desirable factory setup.

I have open front & rear diff with a viscous center, and it is very unpredictable on gravel and wet tarmac. Almost exactly the same driving situation as the OP described.

I'm interested in what others have done.

20 kg center and clutch type diffs front and rear then alignment settings and test test test.
Rear toe can have huge effects though you also have to balance things like straight line stability and low speed turn in and such.

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Grant Hughes

I found a guy in japan that will ship a 12kg or the 20kg for about 750$ us shipped ..

strangely i never really thought i should touch that diff.

hmmm ... so if the center is a bit more "locked" you are always getting more power to the rear so any positive handling changes on that diff, become more pronounced.

would that be part of the why ?



with a torsen in the front as long as your entry speed is reasonable you don't get throttle on under steer.

the very very little I've driven a car with a plated (clutch) Front diff i noticed that some really bad understeer was possible at a reasonable speed if you didn't lift a bit before your steering input.


do you feel the benefits of a plated front out weight a torsen (front axle only) I have definitely noticed that with the Torsen if your left tires go over some looser gravel and the right side is hard packed you get sort of a "push off" from the right side .

when my car was FWD the effect was much more notable. i found that my car was Much easier to drift and modulate the line when the front diff was open, versus the Torsen. i was much faster with the torsen, but i had to drive a more tidy style which in and of itself isn't as much fun (to me)


with the AWD setup and directional tires i don't notice the torsen jacking with my drift angle . it never requires a rebuild , and does not require friction modifier or frequent fluid changes either.


good info btw!

Torsen front is fine. Center first so that the ends have something to work with. Clutch rear if you must. Spend the front diff money on entry fees. At that point you have 3 tires trying real hard and the 4th doin whatever the torsen tells it to

Here's some previous discussion on this topic.
http://www.rallyanarchy.com/phorum/read.php?5,34956,35059#msg-35059

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Grant Hughes

Center diff first, weld it if you have to. Then rear diff. Front diff last, and really it's optional. A limited slip front diff is going to give you initial understeer. If you don't address the center diff first you're never going to have anything that behaves properly.

If you were going through all of this effort, I'd look at sourcing a DCCD 5 speed close ratio box. The price won't be much more than the 20kg center and the close ratios will really help you out.

I know that this doesn't answer the OP's question, but knowing that he is doing stage rally, that means he is racing. I'm recommending the best course to take for going faster.

Also, the 20kg will require a significant change in driving style. You REALLY have to be aggressive with the car or you will hate your life.

Read that entire other thread.

I think the reason i'm attacking from the wrong end is that my first 12 or so rallies my car was FWD. (4 of which i did with a Torsen front LSD)

the Torsen (OBX For $370) was really amazing in that it did not introduce any under-steer what so ever.


so center, center, center, center is what i'm reading.


If i was OPen - Stiff center - Rear clutch . am i going to get that "heavy" drive train feeling that burke's car has? cause i don't like that heavy , "hey you better THROW your car into every corner, every time" kind of feeling.

i like options . like the option to drive through some corners while keeping it very tidy (Ruts, Rocks, Extra Rough, hell maybe i see 2 rally guys at a triangle with an OK sign, the same 2 guys i saw last running of the stage and i can get by their car at speed, but i really don't want to spray their windshield with rocks )

and of course the option that yes i can throw it very sideways and steer around with the gas peddle.


So it sounds like i should Keep my best Clutch pack rear LSD. sell off a few of my extra LSD units and get an upgraded center? and do the front last (or get that cheapie obx that's been working for me)


I did break my front obx @ idaho in 2012, by sliding into a boulder with my front left tire .

Hey Jvab do you recall saying you know of 1 guy that can re-set a viscous ? happen to have his number.

think you said it was around 150 pounds or euros (maybe it was 250) i want to give him a call and figure out options

[this would be for my center diff]

was it these guys ?
http://www.baramotorsports.com/viscous_couplings.htm



Edited 1 time(s). Last edit at 07/29/2014 11:43AM by A1337STI.

Quote
A1337STI
Hey Jvab do you recall saying you know of 1 guy that can re-set a viscous ? happen to have his number.

think you said it was around 150 pounds or euros (maybe it was 250) i want to give him a call and figure out options

[this would be for my center diff]

was it these guys ?
http://www.baramotorsports.com/viscous_couplings.htm

Yeah, it's Bara. My memory says we had a talk about fuckin email. Like me most of those Pommie bastids hate email so yeah call him...

I think its +8 hours.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.



Edited 1 time(s). Last edit at 07/29/2014 11:56AM by john vanlandingham.

that will save me a few weeks of wondering why my email goes unanswered , thanks


funny that ralli-spec has anti marketing on their center diff page, but if you read carefuly they do agree with rally anarchy

http://www.rallispec.com/dif_gls_rst1215_t.html

Quote
.rallispec
What is the best upgrade path for differentials in an AWD application such as a Subaru? Usually we suggest upgrading the front differential first because it will greatly assist in allowing the driver to get on the power as early as possible out of the corner. The rear diff is generally the second to be upgraded and will allow for a stable and predictable rotation and straight line acceleration and braking on loose surfaces/wet pavement or with large power outputs. In cases where the car has large power output and is an open diff from the factory, it may be better to start by upgrading the rear diff first. The center diff is almost always the last upgrade although for loose surface applications it may be necessary to upgrade this first to ensure sufficient reliability.

$1200 .. ouch guess the viscous rebuild folks might be a cheaper option, even after shipping and converting my US GDP backed paper for UKs GDP backed paper

Quote
A1337STI
that will save me a few weeks of wondering why my email goes unanswered , thanks


funny that ralli-spec has anti marketing on their center diff page, but if you read carefuly they do agree with rally anarchy

http://www.rallispec.com/dif_gls_rst1215_t.html

Quote
.rallispec
What is the best upgrade path for differentials in an AWD application such as a Subaru? Usually we suggest upgrading the front differential first because it will greatly assist in allowing the driver to get on the power as early as possible out of the corner. The rear diff is generally the second to be upgraded and will allow for a stable and predictable rotation and straight line acceleration and braking on loose surfaces/wet pavement or with large power outputs. In cases where the car has large power output and is an open diff from the factory, it may be better to start by upgrading the rear diff first. The center diff is almost always the last upgrade although for loose surface applications it may be necessary to upgrade this first to ensure sufficient reliability.

$1200 .. ouch guess the viscous rebuild folks might be a cheaper option, even after shipping and converting my US GDP backed paper for UKs GDP backed paper

Well I have a "pumped up" center diff on my Frod Crossways thing and a ordinary VC rear..
Car works real good but Ford's center epicyclic power split sends 2/3s powerz rear, 1/3 powerz front..
It is loadsa fun... Like RWD+

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.