S2000 technical thread

[dimviii]

Why is the Skoda so much better than the rest these days?

What are the main areas it is best?

suspension
factory entry
drivers.

[Jacek]

Hello, I wanted to ask you where is it mentioned that S2000/WRC/R5 can't use center differential? Since when S2000 doesn't use center diff?
I was looking at FIA site and found this regulations:
fia.com/sites/default/files/regulation/file/255A%20%2813-14%29_08.03.2013.pdf - Article 255A – 2013, Specific Regulations for Super 2000 (Rallies) / WRC
this part even mentions central diff but without any specific information

Front/central/rear differentials Only the housings and mechanical limited slip differentials
homologated in the Super 2000 Rally extension may be used (without any modification).

fia.com/sites/default/files/regulation/file/261%20%2813-14%29_08.03.2013.pdf - ARTICLE 261 - 2013, SPECIFIC REGULATIONS FOR CARS IN GROUP R5
This parts mentions only front and rear. Nothing mentioned about center diff -> center diff is forbidden, it works like this ?

605-d0 Differential (front and rear)
The mechanical type limited slip differential must be homologated in VR5.

Does anyone know how this 4WD with just 2 diff works? How is power transferred to rear differential?
For example in productions cars with transverse engine and Haldex coupling (or other like All4 in Mini, or 4Matic in Mercedes A or CLA), power is transmitted directly from transmission to
front wheels: normally through front diff
rear wheels: through angle gear or spur gear to the rear coupling and diff, is it similiar in here ? (picture in attachment)
original picture: bimmertoday.de/wp-content/uploads/MINI-All4-Funktionsweise-02-655x491.jpg
ps. this is my first post here, great forum, tons of interesting information

[Mirek]

There are also homologation regulations which are not available for public on FIA website and I guess it's written there (for example specific regulations say that part A may be be homologated but it doesn't say conditions for it, those are in homologation regulations). I have them but only from 2007 when central differential was allowed and used by some teams. Or maybe it's not forbidden to use but no teams actually do...

Anyway I believe the main reason why it was abandoned was that it consumes power but being a mechanical plated type it doesn't bring enough advantage to the handling. For relatively underpowered S2000 it was vital to save every Hp. Also the gearbox without central differential is some 10 kg lighter. In those days the weight limit was lower and no team was able to reach it (in Barum rally 2007 all S2000 cars were 20-30 kg over limit).

First cars Toyota Corolla, Abarth Punto and VW Polo used central differential (homologated 2006). Peugeot was first to choose different (already the first homologation in 2007 was without it). Škoda tested both solutions and decided to take Peugeot way however with different supplier - X-Trac instead of Sadev. Abarth later abandoned the central differential too and also changed supplier to X-Trac. All later cars use only two.

Here X-Trac 633 from Fiesta S2000 specification sheet: http://www.xtrac.com/download.php?type=EVENTFILE&id=73

[br21]

I think in case of S2000 NA cars mechanical center diff is allowed, but currently nobody uses it. It's not worth using, as Mirek said - gives not enough advantages and some disadvantages - consumes power, weights some kgs and may become faulty.
So they use this special clutch in rear diff to disconnect it when handbrake is used.

I don't know how it exactly is homologated in R5, but it's possible that center diff is not allowed, as FIA saw nobody is using it and it surely adds cost.
Interesting is also that M-Sport uses Sadev in R5 instead of Xtrac, but it's subject for another topic .

[Jacek]

Thanks for the answer. I saw info on XTrac site, for 532 SUPER 2000 RALLY GEARBOX:

OPTIONS SUMMARY
..................
Centre differential (Regulations permitting)

So it might be present in older solution/gearbox, but not in the new one.

[Mirek]

Interesting is also that M-Sport uses Sadev in R5 instead of Xtrac, but it's subject for another topic .

Maybe Sadev is the only allowed supplier for R5? At the beginning of S2000 regulations it was also only Sadev...

Thanks for the answer. I saw info on XTrac site, for 532 SUPER 2000 RALLY GEARBOX:

So it might be present in older solution/gearbox, but not in the new one.

Yes, older 532 was used in Fabia S2000 at the beginning. I don't know if they later switched to 633 or not.

[br21]

Maybe Sadev is the only allowed supplier for R5? At the beginning of S2000 regulations it was also only Sadev...

Could be. Also I think Sadev might be cheaper than Xtrac.