1.6T wrc wheelbase/dimensions regs.

[Zico]

Im really looking forwards to see the new cars being thrown much more now the Electronic centre diff has gone. Im interested in comparing the new cars dimensions/wheelbases with each other and with the cars they are replacing, 34mm restrictor vs 33mm etc Hearing your views on how it should affect handling now that the centre diff has gone. There doesn't seem to be much info available on the net so I've had to use the S2000 dimensions for the Fiesta WRC (assuming they will be very similar).

Fiesta WRC (S2000)
Length: 3958mm. Width: 1820mm. Wheelbase: 2489mm. Weight: 1200kg minimum (inc drivers?)

Focus WRC 2009
Length: 4362mm. Width: 1800mm. Wheelbase: 2640mm. Weight: 1230kg minimum.

Citroen DS3 WRC
Length 3948mm. Width 1820mm. Wheelbase 2461mm. Track 1618mm (front and rear) Weight 1,200kg with driver pairing (regulations)

Citroen C4 WRC
Length 4274 mm Width 1800 mm Wheelbase 2608 mm Track 1598 mm Weight 1230kg

Mini countryman WRC
Length 4097mm (Width 1820mm-Guess) Wheelbase 2595mm

The cars have substancialy shorter wheelbases than the older format yet have no electronic centre diff which should make them very agile, maybe even nervous on the high speed. Should we expect to see the longer wheelbased cars perform better on high speed stages and vice versa on the tighter twisty stages?

Feel free to add the dimensions of the others if you wish..

[OldF]

Remembering one reason for Audi to develop the shorter Quattro S1, was the reason to get it more agile in turns. On the other hand it was more “nervous” on straights.

I’ve also have the feeling that the new WRCs without central diff are more prone to understeer so they’ve to be thrown into the turn.

They will also with the shorter wheelbase spin more rapidly.

[Mirek]

If minimal weight rule is same with S2000 (I believe so), 1200 kg is without crew. I haven't seen WRC regulations though...

[OldF]

By GP Week (Issue 105, page 46, http://mag.gpweek.com/?iid=41840) it’s 1200 kg.

Still no Appendix J for 2011. http://www.fia.com/en-GB/sport/regulations/Pages/InternationalSportingCodeA.aspx

[serial jeff]

Anyone know how much fuel is in the cars when they get weighed?

[OldF]

Anyone know how much fuel is in the cars when they get weighed?

"At no time during the event may a car weigh less than this minimum weight."

By this I understand that even with an empty tank the weight is min. 1230 kg (2010 WRC).


From “Article 255 (2010) Specific Regulations for Touring Cars (Group A)”

4.1 Cars are subject to the following scale of minimum weights in relation to their cubic capacity (see Article 4.2 for exception):

over 3000 cm3 and up to 3500 cm3: 1230 kg

4.2 In rallies, for 4-wheel drive cars with either a naturally aspirated engine with a cylinder capacity of between 1600 and 3000 cm3 or a turbocharged engine and a restrictor imposed by Article 5.1.8.3 and an equivalent cylinder capacity of less than or equal to 3000 cm3, the minimum weight is set at 1230 kg.

4.3 This is the real weight of the car, with neither driver nor codriver nor their equipment and with a maximum of one spare wheel. When two spare wheels are carried in the car, the second spare wheel must be removed before weighing. At no time during the event may a car weigh less than this minimum weight. In case of a dispute during weighing, the full equipment of the driver and co-driver will be removed; this includes the helmet, but the headphones external to the helmet may be left in the car. In case of doubt, and except in Rallies, the Scrutineers may drain the tanks containing consumable liquids to check the weight. The use of ballast is permitted in the conditions provided for under Article 252-2.2 of the "General Prescriptions".

[Zico]

Remembering one reason for Audi to develop the shorter Quattro S1, was the reason to get it more agile in turns. On the other hand it was more “nervous” on straights.

I’ve also have the feeling that the new WRCs without central diff are more prone to understeer so they’ve to be thrown into the turn.

They will also with the shorter wheelbase spin more rapidly.

Thats a better way of putting it.

The Mini Wrc may be the least aestheticaly pleasing of the bunch but I suspect its longer wheelbase may prove to offer advantages in other areas like the packaging & placement of components, the spare wheel etc for weight distribution, PMI and maybe even aero advantages.

I've read somewhere that they are allowed to disengage the 4wd transmission incorporated with the handbrake. How would they do this with no centre diff?

[OldF]

There’s a clutch in the rear differential, which is activated by the handbrake.

[Mirek]

Yes, it's already working for years in S2000 cars :)

[OldF]

Xtrac rear differential don’t even need an auxiliary hydraulic pump for handbrake operation.

Here is a brochure of the S2000 version.

http://www.xtrac.com/pdfs/532%20SUPER%202000%20RALLY%20REAR%20DIFFERENTIAL.p df

[Zico]

Xtrac rear differential don’t even need an auxiliary hydraulic pump for handbrake operation.

Here is a brochure of the S2000 version.

http://www.xtrac.com/pdfs/532%20SUPER%202000%20RALLY%20REAR%20DIFFERENTIAL.p df

Thanks OldF, I remember Mazda being the 1st to use it in the GrpA 323 ?. I'd always assumed it was a clutch within the centre diff.

[OldF]

Thanks OldF, I remember Mazda being the 1st to use it in the GrpA 323 ?. I'd always assumed it was a clutch within the centre diff.

I don’t know what systems earlier grp A cars used but if I’m remember correctly, by the end of 1995 all the grp A cars had an active centre differential, which could be controlled in such a way that when the hand brake is pulled, the centre differentials clutch was not activated.

Xtrac gearboxes used in S2000 have a centre differential as an option. The reason why it’s not used I think is weight saving. The lack of a centre differential doesn’t ruin the cars car's driveability that much that it would be worth using.

[Mirek]

I think it's not because of weight. In my opinion it's more likely because of power loses which are rather important with less powerful normally aspirated engines of S2000 cars. My estimation is that it can save 10-15 Hp.

The other thing is that mechanical center differential is not that useful for car handling as active one.

[OldF]

That must be the case.

In a Mitsubishi evo 9 dyno graph the max power from the engine was 202,7 kW (276 PS) and the max power from the wheels 170 kW (231 PS). The difference is 45 PS which 16 % of the power from the engine.

Assuming the losses in all three differentials are the same, with one differential less the power on the wheels would increase by 15 PS.

Maybe I know remember why they don’t use a centre differential. ;)