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This is a discussion on downshifting is bad for tranny? within the Transmission & AWD forums, part of the Tech & Modifying & General Repairs category; Hey does the turbo on the WRX help with back pressure I had a NA impreza and around 3k rpms ...

  1. #31
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    Hey does the turbo on the WRX help with back pressure

    I had a NA impreza and around 3k rpms the WRX feels like its produssing a significant amount of back pressure.

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  3. #32
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    Heel-toe is way easier when you are barefoot. Better feel to not over brake too.

  4. #33
    Registered User jomotopia's Avatar
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    the purpose of downshifting is not to slow down or stop. it is to get into the correct gear to accelerate from the speed you are going. slowing down for a turn, downshift. slowing down for a red light, no point. slowing down for a red light that then turns green, downshift and go.

    and there are situations, such as going down a long hill, where it's beneficial to downshift and use engine braking to maintain your speed down the hill and not over-work your brakes.

    double clutch downshifting can actually be faster than single clutch downshifting (rev match in both cases) once you get used to it, because you don't have to wait on the synchros to speed up the input shaft and let you into gear. rev to the right point in neutral and the stick will practically get sucked into gear. practice enough and it's very fast. i double clutch all my downshifts except 6-5 b/c the gap is so small on that one.

    double clutching saves your synchros, but that's not a good enough reason to do it as the synchros should last plenty of time anyway if you don't abuse them. the main "reason" for double clutching in modern synchromesh cars is pretty much just driver preference. i prefer double clutching because, aside from being a bit faster, it feels like a more natural motion to me. the feet are always going in opposite directions, one up one down, as opposed to a single clutch rev mathced downshift where you're holding the left foot down while you blip with the right.

    and no, downshifting and engine braking will not hurt your engine or transmission as long as you do it right and it's smooth. and it will not cause any excess wear to your clutch if you rev-match properly.

  5. #34
    Registered User turbo_bxr's Avatar
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    so i guess this is why my old 02's trans lasted me over 60k miles of hard, unforegiving, no care in the world abuse. i downshifted at highspeeds....

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    Besides the fact that I would expect to get 200k miles out of a decently cared for tranny, did you have a point?

  7. #36
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    Quote Originally Posted by Rocker View Post
    Besides the fact that I would expect to get 200k miles out of a decently cared for tranny, did you have a point?
    His point seemed clear enough to me. Why the hostility?
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  8. #37
    Moderator YBNormal07's Avatar
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    Quote Originally Posted by jomotopia View Post
    the purpose of downshifting is not to slow down or stop. it is to get into the correct gear to accelerate from the speed you are going. slowing down for a turn, downshift. slowing down for a red light, no point. slowing down for a red light that then turns green, downshift and go.

    and there are situations, such as going down a long hill, where it's beneficial to downshift and use engine braking to maintain your speed down the hill and not over-work your brakes.

    double clutch downshifting can actually be faster than single clutch downshifting (rev match in both cases) once you get used to it, because you don't have to wait on the synchros to speed up the input shaft and let you into gear. rev to the right point in neutral and the stick will practically get sucked into gear. practice enough and it's very fast. i double clutch all my downshifts except 6-5 b/c the gap is so small on that one.

    double clutching saves your synchros, but that's not a good enough reason to do it as the synchros should last plenty of time anyway if you don't abuse them. the main "reason" for double clutching in modern synchromesh cars is pretty much just driver preference. i prefer double clutching because, aside from being a bit faster, it feels like a more natural motion to me. the feet are always going in opposite directions, one up one down, as opposed to a single clutch rev mathced downshift where you're holding the left foot down while you blip with the right.

    and no, downshifting and engine braking will not hurt your engine or transmission as long as you do it right and it's smooth. and it will not cause any excess wear to your clutch if you rev-match properly.
    Although I agree with many of your points and examples, I really can't understand how double clutching can possibly be faster than a single clutch down shift. Double clutching only even exists due to poor or no synchros in a manual trans. I would dare say that if todays modern synchros had been developed at the advent of manual transmission introduction (what...+100 years or so ago???) no one would have ever even tried double clutching. I might say it can be just as fast if you are coming to a hairpin from a long straing at high speeds and is someone who prefers to downshift say from 6th all the way to first. But for someone who prefers to row through the gears, I just can't see it. It's also well know that skip downshifting is not recommended anyway, so this application is not the best example. It just makes sense that a single action of the clutch will be faster than a double action of the clutch. Of course, this is all being said from the perspective of modern cars. All bets are off for older cars with poor synchros or something modern with straight cut gears.
    All I can say is you must be the god of shifting if you can truly shift faster pumping the clutch twice vs once.
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  9. #38
    Registered User jomotopia's Avatar
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    Quote Originally Posted by YBNormal07 View Post
    Although I agree with many of your points and examples, I really can't understand how double clutching can possibly be faster than a single clutch down shift. Double clutching only even exists due to poor or no synchros in a manual trans. I would dare say that if todays modern synchros had been developed at the advent of manual transmission introduction (what...+100 years or so ago???) no one would have ever even tried double clutching. I might say it can be just as fast if you are coming to a hairpin from a long straing at high speeds and is someone who prefers to downshift say from 6th all the way to first. But for someone who prefers to row through the gears, I just can't see it. It's also well know that skip downshifting is not recommended anyway, so this application is not the best example. It just makes sense that a single action of the clutch will be faster than a double action of the clutch. Of course, this is all being said from the perspective of modern cars. All bets are off for older cars with poor synchros or something modern with straight cut gears.
    All I can say is you must be the god of shifting if you can truly shift faster pumping the clutch twice vs once.
    well, if i didn't have a problem slamming my shifter then it might not be faster, and it's only marginally faster at best anyway. but when doing a single clutch downshift, there's a slight pause when putting the stick into gear as the synchro speeds up the input shaft. the more the input shaft needs to be sped up, the longer this pause will be while the synchro does its work. so you either wait that split second, or you force through the synchro.

    but when you double clutch you don't have to wait for the synchro. so if you can blip accurately and quickly, you can probably get the gear engaged a split second quicker. especially if you're skipping gears as you said.

    though i guess i should qualify it by saying that it's more effective the higher in the revs you are downshifting (the more work for the synchro to do). i guess i should also further qualify it by saying that i started learning rev-matched downshifts with double clutching, so i basically became proficient in double clutching before i really ever single clutch rev-matched much.

    also, you don't have to clutch all the way out in neutral on the double clutch, just enough to catch. there's not much mass in just the clutch and input shaft so it will synch up and speed up quickly without having to clutch all the way out. i think that may be part of why some people find double clutching slow, because they are coming all the way out on the clutch in neutral.

  10. #39
    Registered User RedWRXwagoN's Avatar
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    i actually was having a debate with my brother about this matter that soon turned into an argument and then a lets find out scenario! aha but i feel that rev matching is absolutely necessary....its just as simple as when you dont match the rpms to where the lower gears rps will end up, the car bucks a lot, but when you get those rpm's matched to the exact rev speed of the next lowest gear, its so smooth you cant even feel the down shift....

    Our only disagreement was that if your coming to a sudden stop and dont have time to get the rpm's up, can you just press the clutch, switch to the next lowest gear, and just let the tranny take the entire load, without rev matching??....that was my brothers philosphy on a sudden stop....mine was, just go to neutral and rely on your breaks, rather than put such a heavy load on your tranny...

    so the question is, put a ton of stress on your tranny for that dog in the middle of the road, or go neutral(or just press down clutch) and use your breaks?....seemed easy to me...the cheaper part to fix is my choice!

  11. #40
    Moderator YBNormal07's Avatar
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    In an emergency situation like you are describing, where a split second decision is needed, there won't be time to even use the trans along with the brakes to slow down. It'll be a "slam the binders to the floor and try to steer around it", situation. Trans braking will not help at all in this situation as 1) your speed is decreasing very fast already with the brakes fully engaged and 2) not enough time to allow trans braking to be effective.

    In an all out race situation, you can definitely use trans braking in conjunction with your brakes to provide additional stopping power, but I've found this to be too rough on the power train in general, and prefer to nail the brakes at my braking point and while coming down to my desired speed, putting the trans in the gear needed for exiting the corner, generally performed using heal and toe and rowing down, or sometimes just keeping the clutch in and going skip shifting down to the correct gear, with a throttle blip to match revs prior to releasing the clutch. This can be deadly with a car with close gearing (re: STi) as it is sometimes hard to tell what gear you are in without rowing down through them.
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  12. #41
    Registered User gimme_cat's Avatar
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    Quote Originally Posted by RedWRXwagoN View Post
    i actually was having a debate with my brother about this matter that soon turned into an argument and then a lets find out scenario! aha but i feel that rev matching is absolutely necessary....its just as simple as when you dont match the rpms to where the lower gears rps will end up, the car bucks a lot, but when you get those rpm's matched to the exact rev speed of the next lowest gear, its so smooth you cant even feel the down shift....

    Our only disagreement was that if your coming to a sudden stop and dont have time to get the rpm's up, can you just press the clutch, switch to the next lowest gear, and just let the tranny take the entire load, without rev matching??....that was my brothers philosphy on a sudden stop....mine was, just go to neutral and rely on your breaks, rather than put such a heavy load on your tranny...

    so the question is, put a ton of stress on your tranny for that dog in the middle of the road, or go neutral(or just press down clutch) and use your breaks?....seemed easy to me...the cheaper part to fix is my choice!

    No. Don't even try it. I had an idiot kid drive my car once. He made a U-turn at like 10mph, shifted to first gear, didn't rev match, sidestepped the clutch, and my car made a thud so hard I wanted to smash his freakin face in.
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  13. #42
    Registered User RedWRXwagoN's Avatar
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    I agree YBN...also, whats a throttle blip?

  14. #43
    Registered User gimme_cat's Avatar
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    Throttle blip is applying a quick and appropriate application of the acceleratrix while clutched in (or in neutral if you're double clutching) to match the speed of the crankshaft to the transmission.
    Last edited by gimme_cat; 09-24-2008 at 01:41 PM.
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  15. #44
    Registered User RedWRXwagoN's Avatar
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    Quote Originally Posted by gimme_cat View Post
    Throttle blip is applying a quick and appropriate application of the acceleratrix while clutched in (or in neutral if you're double clutching) to match the speed of the crankshaft to the transmission.
    isnt that just rev matching?

  16. #45
    Moderator YBNormal07's Avatar
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    Quote Originally Posted by RedWRXwagoN View Post
    isnt that just rev matching?
    Yes.
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