WRC Testing

[seb_sh]

Another point on aerodynamics:
Citroën C3 seams to have clearly the biggest frontal area (see it on the "small" fender flarings). Will be intersting to see if this potentially higher drag/or sacrifice in downforce will be noticable?

This is a more complex subject as far as I know. Look at LMP1 cars in recent times, there was a shift to more vertical front edges while also trying to control how air moves through and around the car. It's true this was also cause by regulations (the open slits on top or on the side of the wheel well) but it showed that having a more "blunt" attack angle is not necessarily worse, especially if you can control how the air moves around or over the surfaces. The dive planes (the small wings on the front bumper) play a big role here as well.

Overall I guess it's more about the shape of the whole package and low pressure areas behind the car, not just surface area.

There is a lot of analysis on this subject on http://mulsannescorner.com/ website and facebook group.

[Toyoda]

Very good explanation, but I disagree with you on one thing, and thats regarding the number of ratios.

Theoretically - yes, the "wide" power band of the 2.0 WRC cars would allow for fewer ratios.
The thinking behind this was that they would change gear more seldom (gaining time), and that a lower number of ratios would decrease number of parts, and therefore number of parts that brake.

When Porsche went serious about using turbochargers in racing the 930 turbo was one of the first cars. On this car (even on the road model) they used only four ratios so they could make each gear strong enough to handle the torque and power.

But we know how the story went. The Peugeot-drivers struggled to find the right ratio, and was caught in either a gear to low, or a gear to high. This resulted in them not having a decrese in number of gear changes on a stage/on a rally, but a big increase.
I think it was as bad a 25% increase, or something in that region.
I was lucky enough to test a Citroën Xsara WRC (something I will bring into each discussion when I have the opertunity, hehe) and found the power band to be very much like a turbo diesel. Actually a lot like a VW pumpe duse Yes it had a lot of torque, but it definetly had a peak, which in reality was quite a narrow power band (as all highly tuned engines tend to have in some form or another.)

So your theory in regards to smaller shocks pr shifting isnt totally alligned with turbo/gearbox-history.
This is because a gear box has a certain physical size, and if you cram a lot of gears in there, the gears them selves will be smaller, thus more fragile.
With Porsche at Le Mans it was not that big a deal to have only four gears, because even tough the engine had a very strong ketchup effect/turbo lag, and that you went in and out of boost, the power advantage was so huge that you made up for it anyway. In rallying it was a different story.

But regarding the torque, the teams with a good torque curve (in combination with good top end power) will off cource have an advantage. And sensitive drivers - like Ogier - will know how to take advantage of that.

Ratio wise it seems the i20 has a very short change between 2&3 or 1&2, as Sordo boosts straight on the rev limiter out of the hair pin corners, seems bang, instant whack of power in the videos.

[RS]

Different sound of the Fabia, anyone?

It perhaps sounds a bit louder and raspier but it could just be the atmospheric conditions.

Unless you know they've changed the exhaust system?

[J_n_z]

Torque can't be compenstated by higher revolution speed because of air restrictor, boost limitation, rpm limitation and fixed gear ratios. The general shape of the power curve is basically given by the rules. We are not here in the ideal world where You can do whatever You want.
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You miss my point, or (more likely) my english is the problem...

I wanted to comment your thought, that low torque is the thing that prevents car going sideways... tires slide.
But it is not, power is the thing that makes tires slide, because at same wheel rev. speed and increased power the torque on the wheel is bigger ie. more force to transfer to the ground...

I agree with your writing, but things like piston friction loses, torque curve shape, driveability of engine and transmition... all are caracteristics of power genereting and power transfer, that needs to be optimised as you said.

Still power is the thing that moves things and torque is just a component of it.

[Mirek]

You are right with that, sorry for misunderstanding.

Still while what You say it's true it doesn't mean that the car will go sideways because of the peak power. I take a slighly extreme example of S2000 car with atmospheric engine. They had enouh power for sliding at the top rpm. Sliding-wise S2000 cars had a typical behavior - nearly no drifting in lower speeds but sometimes violent slides at the exits of the corners even in very high speeds (for example when some dirt was present). In the end this fraction of a second long power slides can't by called driving sideways (my opinion) even though it was spectacular in the fast sections.

The new WRC are slightly similar even though they have double the torque to S2000. I can see similar pattern especially with the i20 on the videos but only in low speeds (presumably because S2000 has very low aerodynamic downforce). Very calm and clean with just a short powerslide at the peak power (Monte Carlo sessions).

Anyway for me the main reason why not to drift through the hairpins and sharp corners is the center active differential. The 16 cars with no center diff suffered from massive natural understeering and the drivers had to throw them around in drifts to turn. Sometimes it went to near ridiculously spectacular back-first driving. I remember very well the first impressions from Sweden 2011 and the discussion here on the forum.

[EstWRC]

Neuville https://www.youtube.com/watch?v=HJaGCeytqk8
Sordo https://www.youtube.com/watch?v=pW1n...ure=youtu.be&a

[A FONDO]

Anyway for me the main reason why not to drift through the hairpins and sharp corners is the center active differential. The 16 cars with no center diff suffered from massive natural understeering and the drivers had to throw them around in drifts to turn. Sometimes it went to near ridiculously spectacular back-first driving. I remember very well the first impressions from Sweden 2011 and the discussion here on the forum.

Here it is, at 0:45, 1:17 etc. you could never do that with 2011-2016 cars. I was so devastated in 2011 watching their lines. Finally we retrned to what the top rally category should be.

https://www.youtube.com/watch?v=kgyIdtO2Ass

[Rally Power]

Has it? I don't see that. I can see big difference in cornering speed but not more sliding. From Monte Carlo testing the by far most sideways-style video was the one of Tidemand with R5...

Even on tarmac '17 cars will go more sideways than current ones. In case you've miss them, he're some nice samples of the big slides ahead of us!

https://www.youtube.com/watch?v=dMJhwbQCy78
https://www.youtube.com/watch?v=lAeAe3yg6-k
https://www.youtube.com/watch?v=TqItOuzIElE
https://www.youtube.com/watch?v=lkVFd9RQnO0

[Mirek]

Slowson gave a good example with the hairpin @ 1:16 of his video link. This is what is hardly possible with 2016 car. Similar situation with Citroën here at 0:45: https://youtu.be/RumejYWCldc?t=45

By the way I have never said that 2017 can't go more sideways. Of course they can but why? The point is that while 2016 cars had to go sideways in certain situations the 2017 cars don't need so. That's the sole reason of active center diff and new aero package existence and I really don't see why do You argue about that.

[dimviii]

Latvala
https://youtu.be/BPJ_RXiSzhU