johnfelstead

Yes, the RB5 did use the STi 4 door shell rear bulkhead setup. The only diference i can see between the two is a 1" square bar that braces the bottom of the shell behind the seat. Thats why you cant use fold down rear seats. That's not much in terms of technical changes in the context of what i am trying to express.

The UK spec STi Gearbox differs from a JDM VC spec STi gearbox in a couple of ways. Firstly they have diferent gear ratios in 5th and 6th, with the JDM being lower geared up top. They also have diferent drop gears, JDM being 1:1 and UK being 1.1:1. This is why the UK spec STi has a diferent rear diff ratio to the front diff and a JDM has the same front/rear diff ratio. The effect of this is to change the torque split from 50:50 on a JDM to 55:45 on a UK, making the UK STi more FWD biased and more prone to understeer. They are using the front/rear diff diferences in leverage to give this change in torque split. With the DCCD-A the 65:35 torque split is achieved via the design of the centre diff unit, the more locked the centre diff becomes, the more torque is transfered to the front, fully locked it gives a 50:50 torque split, so the same as a JDM spec VC STi, but with a much tigher clamping force.

It's taken me a while to get my head round the way the DCCD centre diff unit works, because its a combination of a plated LSD and sun/planet gears that gives both more LSD clamping force and a change in torque split at the same time.

p1doc

at least it explains why you cannot get hold of driving lights for sti8 unless your car is ice blue which looks better in flesh than on camera
the wr1 is pretty good value for money
sti £25000
ppp £2000
18" wheela and tyres £2000
driving lights (depending which version) £250-£750
dccd-a £450 from town end garage
interior trim,plaques etc £50 halfords
martin

johnfelstead

"dccd-a £450 from town end garage" That is just a GEMS centre diff ECU that allows you to program the diff setting of a manual DCCD such as fitted to the earlier STi TypeR/RA's, it is more limited in its inputs than the DCCD-A. You cant bolt the TEG setup onto a VC equipped Impreza, you have to have all the hardware such as centre and rear diff from an STi TypeR/RA already in place.

The DCCD-A comprises of a diferent centre diff assembly, diferent rear diff, a gearbox ECU that takes inputs from G sensors, Engine ECU, ABS etc to provide an active centre diff based transmition system that is fully integrated into the ABS system. If you were to buy all that kit individually it would cost quite a chunk of money. It wont cost Subaru much to install though because its being installed on the production line from their current parts bin.

greasemonkey

It's a tricky thing to work out in my head, but I don't think I agree with you there John.

You are right in saying that the 1.1:1 drop-gears create a difference in rotational speed and torque distribution across the shaft carrying the front front diff pinion and the propshaft.
However, this imbalance is mathematically corrected by the ratio of the rear diff crown-wheel and pinion, so, across the front and rear axles, the inherent torque split on a UK viscous coupled car is the same as a Japanese one.

In any case, if what you are saying is true, and the use of the unequal drop gears altered the effective torque distribution of the diff, the WR1 (assuming it keeps the CW-P and drop gear ratios of the normal UK STi) wouldn't be 65:35 like the Japanese cars, would it? If your theory is correct, the torque split would also be affected by the unequal front and rear shaft rotation ratios, just as the viscous cars are.

P1Doc: £450 from TEG doesn't buy you a complete DCCD-A system, all it gets you is a controller to add automatic mode to a car already equipped with the diff. When you also consider that the WR1 has a plated rear diff instead of the viscous one, it's even better value than you're giving it credit for, at least if you take the normal price of the UK STi as a base.

[Edited by greasemonkey - 1/13/2004 4:24:19 PM]

johnfelstead

They wont use the 1.1:1 drop gear in the WR1 IMHO. It would make zero sense because they would have to do a complete reprogram of the active control system to make it work. That would cost them thousands in aditional R&D work and would achieve nothing worthwhile. The DCCD-A used in the USDM STi retains the 1:1 drop gear ratio even though the majority of US spec Impreza's have a 1.1:1 drop ratio. We wont know for sure until the oficial (acurate) specs are released, but i am prety confident it will retain the normal drop gear spec.

With regards to the torque split on a UK car with VC, you will get the same efective gearing, but you will also get a diferent torque distribution due the diferences in leverage at the diffs. Thats the way i understand it and is also the view of Prodrive. I am no transmition expert by any means so you will have to take that as my opinion, i am happy to be proven wrong if that is the case.

AR

Trying to keep it simple - I know that no one will agree will me and I know why Subaru don't do it but I wish you could have it as a WAGON!!!

Gangsta Smurf

Don't know why there is a massive fuss being made about the looks of this absolutely amazing motor. If it looked rubbish Subaru wouldn't have sold pretty much their complete allocation at the AutoSport show over the weekend. I think that says it all. Well done I say - what a car!