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Synchros

Discussion in 'General Tech and Maintenance' started by JDMSpecAccordSir-T, May 14, 2003.

  1. JDMSpecAccordSir-T

    JDMSpecAccordSir-T Member

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    I read Calesta's post on double clutching and i think i may have found a error in the explanation of the role of synchros. My arguement is this: when the car is in motion and you sink the clutch, the tranny remains at the same constant speed being that it is connected to the road via the wheels and driveshafts, just the engine speed decreases because it is no longer connected to the tranny.

    The two halves of the tranny are still connected to each other at this point and only when you shift the lever into neutral are they then separated which is why you can only let the clutch out if stopped in neutral or either you just sink the clutch (the tranny is stopped so if it is in gear with clutch in the engine will also stop) and why every manual tranny has to pass though neutral to change gears. This is not the case in F1 trannys, WRC car trannys or high end machines such as Ferraris and why we cant buy one for a Honda (we could but who has $85K :blink: to spend on a tranny?)

    This is where the synchros come in, they allow the two halves of the tranny's gears to mesh together, remember that one half is connected to the wheels and the other half is connected to the engine. Therefore when the clutch is sunk and you move the lever through neutral the two halves separate very briefly but this is necessary because the next ratio will be different from the last and the half that is connected to the wheels is still spinning as is the other half that was connected to the engine. So the synchros job is to slow the engine half and allow the two halves with different gear ratios to mesh and join then their job is over and you can then release the clutch and allow power to pass through the tranny again from the engine.

    Synchros are only in use for a very short period of time during shifts and are not very strong. This is why you can damage them if you try to shift at WOT and do not sink the clutch fully allowing the engine half to slow enough to mesh with the wheel half. Power will then try to pass through them and the other halfs gears will shear off the teeth on them (not good) :unsure:

    As to why cars without synchros had to put the gear in neutral to change gears? The answer will now be very clear. That was the only way to allow the engine half of the tranny to slow enough to mesh with the wheel half of the tranny. This is also why you guys with bad synchros have to put the car in neutral before trying to put it gear.

    Older Hondas come with synchros on all forward gears and the new K series trannys as well as the S2000's have more than one on the first three gears (i think or at least they are reinforced or something) because they are the most abused gears as you would agree ;) .

    In regards to bliping the throttle to save syncros during downshifts i would disagree. Although it does save wear on the engine and tranny because of the smoother transition, i dont think it is directly related to synchro life nor do you have to put the car i neutral to blip the throttle. Just sink the clutch, move to a lower gear, blip the throttle and release the clutch matching the revs (can anyone say :worthy: Heel and Toe).
     
  2. CRX-YEM

    CRX-YEM Super Moderator Moderator VIP

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    OK can we re-phase that in english please.
    very hard to follow your argument.
     
  3. Jay_256

    Jay_256 Junior Member

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    go to www.howstuffworks.com to learn how a manual transmission works, that website explains how everything you can ever think of works.
     
  4. phunky.buddha

    phunky.buddha Admin with a big stick Admin VIP

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    You just explained yourself why double clutching helps to save synchronizers. My explanation is correct- your understanding of it is not.

    You double clutch more to smooth transitions during road racing and turns- the better all your revs are matched when you engage gears, the smoother your downshift is, and the less you'll tend to break the car loose by having an abrupt change of speed at the wheels. When you're at the limit of adhesion (as you should be on a race track) during a turn, the last thing you want is to upset the delicate balance between your tires and the road surface.

    As for saving the synchros by double clutching- it's true that the synchros are only engaged for short periods of time, but if that's your argument- why do they wear out in cars at all? They still do wear, and not only in cars that have been beat on quite a bit. If your synchros have to do less work to match the internal speeds of your transmission, the incur less wear than they would if you did not double clutch. You also lower the stress on the rest of your transmission parts, because you're not "jerking" the two "halves" of it back and forth with the synchros. You're matching the revs of the two "halves" of the transmission before any additional stresses are placed on them by the synchros, so that when you do get into gear, everything slides into place.

    Double clutching isn't necessary with today's transmissions in normal driving, but it does help to reduce wear on the transmission, and it definitely helps to smooth out your line at the race track.
     
  5. CRX-YEM

    CRX-YEM Super Moderator Moderator VIP

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