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Double Clutch?

Discussion in 'Members' Lounge' started by Skenehc, Aug 9, 2007.

  1. Skenehc

    Skenehc New Member

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    i dont get it...
    double clutch when downshifting

    1. apply brake
    2. (Still braking) depress clutch-> shift to neutral -> (may release brake if appropriate) -> engage clutch -> heel(foot) hits gas
    3. depress clutch -> lower gear engage -> engage clutch

    why....? Is the heel toe the fast version of double clutch? (am aware of double clutch heel toe too)
    double clutch is slower, no?

    single clutch:

    1, apply break
    2, (still braking ) depress Clutch -> shift to and engage lower gear -> heel hits gas -> engage clutch
    3, release brake if appropriate

    whhyy?
     
  2. nootrac22

    nootrac22 Well-Known Member VIP

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  3. Skenehc

    Skenehc New Member

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    i can only read the content, but not allowed to reply, anyway, i've read it.

    it still doesn't help me solve why using double clutch over a simply single clutch heel toe.

    However, I learnt that the purpose of double clutching is to higher the revolution of the "engine half" of the transmission.

    As for "single clutch" heel toe, it's really to match revolution of the engine of the entire "transmission", and it doesn't have the pause of having to shift to neutral. I think it achieve engine brake more efficiently as well <-- oh well wut do i know.

    anyway, i still need to find out clearly how is double clutching different than single clutch heel toe downshift...
     
  4. reckedracing

    reckedracing TTIWWOP VIP

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    lets say you're in 4th gear and want to shift to 3rd
    normally you would press the clutch, change gears, then rev the engine a touch before releasing the clutch so the motors revs match what the transmission will be doing in 3rd gear

    when you rev with the clutch held in you're not bringing the disc/input etc up to speed, but if you shift into neutral, release the clutch and rev the motor then you are bringing the "engine half" into synch for an easier mesh

    syncros in the transmission do this for you now so its really just a waste of time
     
  5. Skenehc

    Skenehc New Member

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    does it mean it lowers chance of shiftlock?
     
  6. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    First off, double clutching and heel/toe have nothing to do with each other. You can do one without doing the other.

    Double clutching basically just reduces the amount of work your synchronizers have to do. You can use it to slow down more smoothly, coax an ailing transmission to downshift if its synchros are dying, or use it when you're driving an older car that doesn't have any synchros at all.
     
  7. Skenehc

    Skenehc New Member

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    sry for misleading...ur 200% right, heel toe has nothing to do with all these...what i meant to ask was "ultimately what is the difference between "single clutch(dont know what it's called, basically downshift without the hassle of shifting to neutral and clutch twice)" and the double clutch...ULTIMATELY..." im trying to get some reference in terms of results and effects regarding the question. These two techniques do have simliar outcomes and for the purpose of rev matching, no?
     
  8. Celerity

    Celerity Well-Known Member

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    Before the advent of "Synchro Technology" (Circa 1952) You "had" to clutch in to remove it from gear, then clutch in to engage the next. When I say "had to" I really meant "May have to". It's just a method of rev-matching an old vehicle.

    Today, old trucks and large vehicles (Like MACK trucks and the like) MAY need the method.

    Since Fast and Furious "double clutching" is the unicorn of the ricer groups. Like "Granny shifting".
     
  9. reckedracing

    reckedracing TTIWWOP VIP

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    yes, same purpose
    rev match

    except one method doesn't match the insides of the transmission
     
  10. Skenehc

    Skenehc New Member

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    good! now i get one thing cleared, that is they have the same purpose.

    Yet, regarding "shifting smoothness" or driving stability, doesn't make a difference using one or the other?

    i really dont care about fast and furious lol
    i am just a newly-become Touring Car and GT fan.
    I saw a lot of their onboard vids, it's like the european racers use double clutching, when japanese racers seem to be all for "single clutch". And, i might be wrong, I saw a few vids that the same racer using both techniques in the same car on the same track. That's where i got my question from: r these technique different?
    And the GT racings just require super fast shifting, almost all the GT level racers seem to use the single clutch method. and that's where i got the idea that one method might be faster than the other. Lower lv of GT racing like GT3 seem to use double clutch as well. again, i still notice the same racer using both techniques in the same car on the same track.

    I really think there's a different in terms of affects to performance...hope I can get more detailed answer somewhere. I assume that double clutch rev match the inside of the transmission, thus it has more stability...but what do i know...
     
    Last edited: Aug 10, 2007
  11. Celerity

    Celerity Well-Known Member

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    ALL modern race cars do NOT require or even suggest double-clutching. Even australian V8 Supercar, as you're interested in.

    ALL modern race cars (say from the 80s on) have synchros that can be modified (Ground) to make the shift easier (And the synchro more delicate and prone to breakage). Racers make fast shifts as a result of a few technologies:

    As was discussed earlier: A long shifter
    Only in an engineered fashioned manner: "Short Shifter" (Not a replacement stick, but a shimmed transmission)
    Sequential shifting transmissions (High dollar, but it shifts like an F1 / Motorcycle)
    Multi-disc clutch. Multi-disc clutches have been around since the 50s. They mash together with multiple pressure plates. The end result is that you can't use a friction zone on the clutching, the clutch is simply "On or off".

    High powered drag cars use hydraulic or pneumatic shifting mechanisms to get the shift to within .00 seconds. You won't find that tech in a GT car. (Ferrari tried it with the 348GTS, before moving to a simple sequential paddle-shifter)

    VW Tried, with their semi-automatic, to engage an electric clutch that was triggered by the movement of the stick. Some early porsche efforts had this before abandoning it (Because it never worked right)

    Youtube has plenty of driving vids from real track pros. You can see how they shift smoothly not because of technology, but because of experience. THAT is the winning trait, not the gear.
     
  12. reckedracing

    reckedracing TTIWWOP VIP

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    i'd like to see the videos you speak of
     
  13. Skenehc

    Skenehc New Member

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    sweet infos!!

    YouTube - Double clutch and heel toe


    YouTube - Double Clutch Downshifts

    i think it is a modern car on infineon...if i didn't remember wrong, it's an alfa

    and one thing i need to get cleared...sequential means +/- gear with clutch right? different than than the so-called semi-automatic transmission (which is actually an automatic that let u choose when to shift, fully computer operated), correct?
    I know bikes use manual sequential, but doesn't F1 use the semi-automatic using super fast comperter operated transmission?
     
    Last edited: Aug 10, 2007
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