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  1. #221
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    Quit interesting that Hyundai has opted for next to driveshaft mounting on R5 but WRC 17 still has on top of driveshafts mounting (at least based on the pictures I`ve seen)
    I think Hyundai now are the only ones with on top mounting of all the WRC manufactorers.

  2. #222
    Member NickRally's Avatar
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    Image of the Yaris from Rally Mexico reveals (possibly) yet another small Venturi tunnel - the design team appear to have come with a very interesting from aero point of view car.

    Yaris Aero 9.JPG

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  4. #223
    Member NickRally's Avatar
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    3. Hyundai i20

    Finally time for the Hyundai i20 – the car seems very fast and no doubt this is because the complete package is fast rather than one particular thing being exceptionally outstanding. On the floor aero side, it appears less aggressive overall than the Yaris, sitting somewhere between it and the Fiesta, though some features are possibly closer to the Yaris than the Fiesta.

    i20 aero 1.JPG

    i20 aero 2.JPG

    i20 aero 3.JPG

    i20 aero 4.JPG

    i20 aero 5.JPG

    To be continued in the next post...

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  6. #224
    Member NickRally's Avatar
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    i20 aero 6.JPG

    i20 aero 7.JPG

    At 1 we can see the diffuser transition point with maybe touch more gentle curvature than the Yaris (could be optical illusion though), which would suggests touch less pressure suction peak, but more forgiving and stable one, though once again this is more applicable to a circuit racer with very low ride height than a rally car. The diffuser appears less steeply inclined (2) than the Yaris, once again suggesting the design team has been after a bit more forgiving downforce, albeit potentially sacrificing some headline numbers. The quantity of strakes (3) is similar to the Fiesta.
    An interesting feature of this car’s diffuser is the second curvature region (4) past the mostly planar middle part of the diffuser, which is unique to the i20. In my experience this hasn’t been very effective on a circuit racer, but maybe they tried to regain some of the headline numbers without causing too much peaky-ness. Or the whole diffuser arrangement could be a result of what they can package given road car components in this area (i.e. curved transition from floor, followed by flat-ish region followed by another curved section) in order to have a longer diffuser for the same exit height, see image below:

    Diffusers 1.JPG

    At 5, as already pointed out on this forum by Ctesibios, is the small but very aggressive Venturi channel ahead of the rear wheels – it is very steeply raked and I wonder if the air stays attached there, though ahead of the wheels, all sorts of amazing things happen. Nevertheless it is smaller than the one on the Yaris and its suction peak will be further rearwards.
    The floor of the i20 appears relatively rough (6) to what I am used to, but maybe certain features can be used to benefit the aerodynamics, like the longitudinal railings. Either that, or the design team did not consider these components to be too penalising or of sufficient importance, to change the design direction from the traditional rally floors.
    The offset exhaust (7) is embedded in the diffuser, once again feature unique to the i20 with all the other cars opting for central exhaust above the diffuser. I suspect they have done this for packaging, but I could be wrong. Nevertheless, the fact that the exhaust is embedded in the diffuser closer to its transition point from the floor, means its effect might be more powerful. Or, once again, it might just be a packaging exercise.
    At 8 is a good view of the complete diffuser and its more square appearance relative to the Yaris with its gradual sides.
    9 shows a mismatch between the two suspension guards in their sitting relative to the rest of the floor with the wheels in fool droop, presumably caused by road damage. Or, if the design was too optimistic, it might be that the actual suspension travel have distorted one of them. On another note, I wonder how much the curvature (10) of these guards helps aero downforce creation – I know they are not very rigid, but even so.
    11 shows the lack of front Venturi channels, while 12 represents an interesting idea about potential duct, channelling air from underneath the car to the top surface.

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  8. #225
    Senior Member itix's Avatar
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    Very nice read as usual

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  10. #226
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    Educative

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  12. #227
    Member NickRally's Avatar
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    I am sure you have been wondering how long before I use the upside down image of the Yaris from Corsica (Hanninen’s unfortunate off), so here it is with few notes.



    Attached Images Attached Images
    Last edited by NickRally; 15th April 2017 at 11:46.

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  14. #228
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    I have a question about center differentials on the new 2017 spec cars. How do they work exactly. The way I understand it the active center differential can be either open or locked and the state is hydraulically controlled with help of electronics. While locked, front and rear axles act as if there was no differential (like in previous models) and when it's open it acts like a front open differential on a regular road car, when one side loses grip then it spins out robbing the torque from other side. The active part lets it go between both states depending on the data from a number of sensors. The power split between the axles is 50/50 on WRC cars as far as I know (correct me if I'm wrong). Now what confuses me are the problems Ogier had faced in Rally Corsica. His hydraulics had failed and he ended up with a rear wheel drive vehicle. Shouldn't he had ended up with an open differential instead, since the hydraulics would be responsible for locking the center differential?
    Last edited by Kris82; 20th April 2017 at 08:06.

  15. #229
    Member NickRally's Avatar
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    Hi Kris82, very valid point and one that has puzzled me too. Assuming what was said about ending with rear wheel drive only as a result of the problem is correct (which is by no means certain), then maybe the centre diff on the Fiesta is not of the usual epicyclic gear type with clutch pack to vary the degree of locking, but maybe it uses two clutch packs each controlling the flow of torque to the front and rear axles. This would permit infinite degree of variability in the proportion of torque send to the front and rear axles. I am not sure how reliable such device on a current WRC car will be, but to the best of my knowledge it is used on the current Focus RS to distribute the torque between the two rear wheels in place of the usual epicyclic type rear differential.
    I need to watch the footage from the first Sunday stage (only seen the power stage so far) and see if Ogier’s car really behaves like a rear wheel drive one and if the statement to that effect is likely to be correct or just an expression by a frustrated driver (if of course my memory is correct and it came from Ogier).
    Regards,
    Nick

  16. #230
    Senior Member Fast Eddie WRC's Avatar
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    Interesting interview with Mads Ostberg including quite a bit about the 2017 car's active centre diff, plus the info from M-Sport not being shared with Mads team...

    https://www.podbean.com/media/share/pb-qu8kn-69e93e

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