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This is a discussion on Rev Matching within the Transmission & AWD forums, part of the Tech & Modifying & General Repairs category; Originally Posted by speedDman1 double clutching is so worthless...I mean I can do it, but heel toe-ing is much faster. ...

  1. #31
    Moderator schischwein's Avatar
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    Quote Originally Posted by speedDman1
    double clutching is so worthless...I mean I can do it, but heel toe-ing is much faster. They made synchromesh for a reason, use it! There is no sense in not using at all, when you can heel-toe and relieve a lot of the stress on the synchros and shift faster.
    No, you are wrong. Syncromesh was indeed made for a reason. The reason being that it is easier for most average drivers to shift. Heel toe is part of the technique involved in double clutching. Straight rev matching(or heel toe if you prefer) is not faster than properly conducted double clutching. Surely if one reads on paper the steps involved, it seems longer, but rev matching without double clutching involves waiting for the syncros to realign, to mesh...it may sound insignificant to you, but there is time there. This is also why dogboxes are still used in various racing...the instant response from the lack of syncros....every little bit counts.

    Furthermore, heel toe doesn't relieve stress from the syncros but rather on the contrary in fact. Smooth downchange it may seem, but this is where one is really working the syncros.

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  3. #32
    Registered User blahblah's Avatar
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    double clutching is not the same as heel-toeing. Back in the good ol days of no synchros, you had to rev up once to get the engine speed equal to the tranny so u could get it in gear without grinding ur gears, and then again when u need to get the wheel speed equal to the engine speed. with synchros all u have to do is rev for the engine to be the same speed as the tranny. Synchro's or the lack of them are the difference between heel-toeing and double clutching. of course u could double clutch with synchros to slow down the wear on em, but i think that if they are there i might as well use em
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  4. #33
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    I double declutch when I down shift. More out of habbit than anything else (plus it makes me look like I know how to drive).

    Someone said earlier that they had problems timing the rev matching. Durring my years driving I've found out the imput shaft decelerates at about the same rate as the engine RPMs. When you double declutch they spin at the same speed. If you apply light (very light) pressure on the shifter it will *fall* into gear at the same time you need to let the clutch up.

    Using this method I can pop the clutch with no jerk because the revs are nearly idential.

    FYI, if your know your not going to match the revs correctly it's better to blip it at a higher RPM (and have the engine not under load slow down to match the car) than have the revs too low (and put all that stress on the clutch and engine as the 3,000 lb car forces to revs to jump higher without throttle imput).

  5. #34
    Registered User cavallino333's Avatar
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    I double clutch my down shifts. It feels much smoother. I know its not necessary but it can't hurt.
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  6. #35
    Moderator schischwein's Avatar
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    Quote Originally Posted by matt30
    I double declutch when I down shift. More out of habbit than anything else (plus it makes me look like I know how to drive).

    Someone said earlier that they had problems timing the rev matching. Durring my years driving I've found out the imput shaft decelerates at about the same rate as the engine RPMs. When you double declutch they spin at the same speed. If you apply light (very light) pressure on the shifter it will *fall* into gear at the same time you need to let the clutch up.

    Using this method I can pop the clutch with no jerk because the revs are nearly idential.

    FYI, if your know your not going to match the revs correctly it's better to blip it at a higher RPM (and have the engine not under load slow down to match the car) than have the revs too low (and put all that stress on the clutch and engine as the 3,000 lb car forces to revs to jump higher without throttle imput).
    I reckon you must be from the UK.... ''double declutch''....

  7. #36
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    why double clutch

    im a truck driver who drives a 10 speed mack with no syncros and i double clutch all day long. what i was taught is that double clutching "in a cmv" is clutching once to neutral allowing revs to fall then clutching again to selected gear. same thing when down shifting but adding revs before selecting the next lower gear. we "rev match" to avoid having to double clutch = faster. i rev match in my wrx but cant at all see why you would want or ever need to do both. btw...my first post. love the forum

  8. #37
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    Quote Originally Posted by ScrappyDoo555
    im a truck driver who drives a 10 speed mack with no syncros and i double clutch all day long. what i was taught is that double clutching "in a cmv" is clutching once to neutral allowing revs to fall then clutching again to selected gear. same thing when down shifting but adding revs before selecting the next lower gear. we "rev match" to avoid having to double clutch = faster. i rev match in my wrx but cant at all see why you would want or ever need to do both. btw...my first post. love the forum
    welcome.

    we understand that synchronizers match the shaft speeds for you, so you don't have to.

    the problem is that Subaru synchronizers suck big time. in any of the manuals, including the beefed up STi manual, people will complain that their transmissions grind. to make matters worse, up until 2006, there was only one synchro in each gear. they *finally* put dual cone synchros in the 06 transmission, but that's early 90's technology. my economy car, and my girlfriend's economy car, have triple cone synchro's.

    in order to preserve synchro life, we double clutch. it also makes us feel like race car drivers
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  9. #38
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    why double clutch

    oh ok... point taken. you dont double on an up shift do you?

  10. #39
    Moderator schischwein's Avatar
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    I don't think anyone here double clutches on upshifts...there isn't much of a point to since the revs fall and one is selecting a higher gear.

    Double clutching done right is just as fast as simply revmatching without double clutching.

    Smoother syncros also means slower response btw...eg in gear response to throttle input while say modulating the throttle.
    Last edited by schischwein; 11-28-2007 at 05:02 PM.

  11. #40
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    now that my car is stabe 2 with a protune from pre i really try and rev match as much as possible. Gotta admit thought subarus have to be the hardest cars i have driven to shift smoothly. You guys are right about it needing to be second nature and something you just do and don't think about. If you think about it, odds are the rpms have dropped and you have missed your chance tap the gas and then let the cluth out.
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  12. #41
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    almost always, i try to anyways... I would like to learn heel toe downshifting, instead of just rev matching but my pedals need to be replaced before that

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