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Thread: Rev-matching vs not matching downshifts?

  1. #21
    Nickname: "Rally" MirageRally's Avatar
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    Quote Originally Posted by MirageRally View Post
    Sooo after watching the video. lt seems to me that he uses the same amount of throttle blip for each gear when downshifting correct? Also l love watching this guys youtube videos on car reviews.
    He'll also hold down the accelerator pedal a rad longer when going down gears.


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    Quote Originally Posted by MirageRally View Post
    He'll also hold down the accelerator pedal a rad longer when going down gears.
    Not sure which clip you are referring to?

    If it is the smart drive test guy from Canada, he doesn't downshift. He has a clip on downshifting that basically tells you to not do it.

    I have been driving manuals for over 40 years. I don't downshift through the gears EVER. When I slow down, I simply to go next gear that I want for the next maneuver that I need to make with the car. I may downshift from 5th to 4th when climbing a hill, but I am never rowing through the gears to come to stop. That's way more wear & tear on your engine/clutch that isn't necessary. I would rather replace brakes. Having said that, I had the same vehicle the smart drive test guy uses in the video. When I had to replace the vehicle, my 2000 Honda CR-V was still on its original brakes at 154,000 miles. I never downshift. I use brakes to stop after I coast down in whatever gear I was in at the time. If I am coming to stop, I don't need to make the engine work that much any more unless it may be a steep downhill stop.

    Driving a large semi (non synchronized transmission) is different. You will use the torque of the engine (downshifting) more to bring the large vehicle to stop.
    Downshifting a large semi one gear involves -
    lower to 1000 RPM
    push in the clutch (half way)
    shift to neutral
    let out the clutch
    hit the throttle & get your RPMs back up to 1500
    push the clutch in again (half way)
    now you can shift down to the next lower gear before your RPMs drop to low again
    let out the clutch the second time & let it coast back down to 1000 for the next downshift & do all the above steps again for the next lower gear.

    All these steps are necessary to make a single downshift of one gear on a non synchronized manual transmission. This is double clutching a semi.

    If you miss the shift (gear), let up the clutch again, hit the throttle to 1500 RPM, push in the clutch (half way), and try to make the shift again. If you don't shift at the right RPMs, the truck will not shift into gear.

    Every one of those steps must happen with downshifting a large semi by double clutching a non synchronized transmission. You must do all of those steps for every gear you downshift into & most semi trucks have 10 or more gears. The clutch on a large semi has a clutch brake. You only fully push down the clutch when stopped (engaging the clutch brake) and shifting into your first gear. The first gear you select, however, may be something like 3rd or 4th.

    I would enjoy your synchronized transmission. When you shift a synchronized transmission, your foot should be off the gas when you push in the clutch & shift. That's all you really need to do.

    On a non synchronized transmission, you have to get my RPMs up to a certain range to upshift. This is called the "sweet spot" for trucks. Then you need to clutch half way, shift to neutral, let out the clutch, push in the clutch a second time half way, select the next gear up. All that needs to happen before losing 400 RPMs during that double clutch shift. If you miss the gear, you will have to let up the clutch again, rev the engine again, push in the clutch again, & try to make the shift. It will not go into gear otherwise. Thus, be thankful that cars have synchronized transmissions.

    With a typical 10-speed semi, you are shifting around 1100 RPMs for gears 1-5. Gears 6-10 are done around 1500 RPMs. Lower range gears have a lower "sweet spot" to shift at. If you are climbing a hill, you may have to shift at a slightly higher RPM. That's because your RPMs may drop on your faster when going up a small slope. A large semi engine has so much lower torque that you don't even put your foot on gas when letting out the clutch. That even applies to starting out in a higher gear like 3rd.
    Last edited by Mark; 09-05-2020 at 02:28 PM.

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    Nickname: "Rally" MirageRally's Avatar
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    Quote Originally Posted by Mark View Post
    Not sure which clip you are referring to?
    One that Loren posted Youtuber: The Topher. He seems to blip the throttle for every downshift 3k rpm instead of what l was doing...holding in clutch, rev to 5k rpm, then let out clutch...it would take too long to rev the engine and let out the clutch unless like l said "l'm doing it wrong"...either way, l'm going to continue practicing today, l'm driving out to Jefferson bc l want to just drive and hate being stuck at home.
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    Senior Member dspace9's Avatar
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    Quote Originally Posted by MirageRally View Post
    One that Loren posted Youtuber: The Topher. He seems to blip the throttle for every downshift 3k rpm instead of what l was doing...holding in clutch, rev to 5k rpm, then let out clutch...it would take too long to rev the engine and let out the clutch unless like l said "l'm doing it wrong"...either way, l'm going to continue practicing today, l'm driving out to Jefferson bc l want to just drive and hate being stuck at home.
    The guy in the Subaru video doesn't know how to steer. Watch him at an intersection with a green making a left in second gear. What the heck is that?! He doesn't use his palm at all, and his turns end up terrible and in the other lane. He would fail a driver's exam driving like that. His shifting is o.k., mine is no worse.

    I drive a forklift truck, so I have that palm ball on the steering wheel, giving me a double whopper of 360 degrees turning.
    Last edited by dspace9; 09-05-2020 at 04:34 PM.

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    Quote Originally Posted by dspace9 View Post
    The guy in the Subaru video doesn't know how to steer. Watch him at an intersection with a green making a left in second gear. What the heck is that?! He doesn't use his palm at all, and his turns end up terrible and in the other lane. He would fail a driver's exam driving like that. His shifting is o.k., mine is no worse.

    I drive a forklift truck, so I have that palm ball on the steering wheel, giving me a double whopper of 360 degrees turning.
    Sadly those are illegal in the U.S. bc l know my uncle got into trouble with one...but yeah they offer a lot of turning plus it's nice shifting with one hand and turning with the other...l have extremely sticky driving gloves that l use (sometimes) and they help with keeping one hand on the wheel and offer the same degrees of turning.
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    Quote Originally Posted by MirageRally View Post
    Sadly those are illegal in the U.S. bc l know my uncle got into trouble with one...but yeah they offer a lot of turning plus it's nice shifting with one hand and turning with the other...l have extremely sticky driving gloves that l use (sometimes) and they help with keeping one hand on the wheel and offer the same degrees of turning.
    The ball things are still on new forklift trucks. I drive a 2018 etruck, and it came from the factory with the ball thing. I put the first 10 hours on the etruck eh. For specialty heavy equipment, you need the ball thing.

    A driving glove: that is the smartest idea I have heard all week.
    I know the old school race car drivers even wear special suede shoes. Light desert suede style, light so you get better feeling with your feet. I have a pair of dress shoes that are light suede, and it does make the clutch feel better.

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    Quote Originally Posted by MirageRally View Post
    One that Loren posted Youtuber: The Topher. He seems to blip the throttle for every downshift 3k rpm instead of what l was doing...holding in clutch, rev to 5k rpm, then let out clutch...it would take too long to rev the engine and let out the clutch unless like l said "l'm doing it wrong"...either way, l'm going to continue practicing today, l'm driving out to Jefferson bc l want to just drive and hate being stuck at home.
    This is why I like buying discounted new cars like a Mirage. I don't want a car that's been driven that way.

    Good luck practicing!

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    Quote Originally Posted by Mark View Post
    This is why I like buying discounted new cars like a Mirage. I don't want a car that's been driven that way.

    Good luck practicing!
    Thanks, l'll do my best Sometimes l miss the "shifting mode" in my Subaru Outback...that thing was a POS but the automatic would let you shift up and down and was a hoot to drive since l didn't need a clutch...plus the automatic had safeties built in so you couldn't "wear" the engine by downshifting and it wouldn't let you downshift if the trans or engine would be hurt...that's why l'm driving this car for 3 years then going back to automatic...l do love this little car, but sometimes l'd like to not shift as much...l'd also never buy a New Toyota Camry...have you seen how big those are?? Dang, l test drove one and it was sooo long l didn't like it...plus the new ones have an 8speed whereas the 2010-2016 had the old school 6speed...plus V6...l'll want more power later on
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    Quote Originally Posted by MirageRally View Post
    Thanks, l'll do my best Sometimes l miss the "shifting mode" in my Subaru Outback...that thing was a POS but the automatic would let you shift up and down and was a hoot to drive since l didn't need a clutch...plus the automatic had safeties built in so you couldn't "wear" the engine by downshifting and it wouldn't let you downshift if the trans or engine would be hurt...that's why l'm driving this car for 3 years then going back to automatic...l do love this little car, but sometimes l'd like to not shift as much...l'd also never buy a New Toyota Camry...have you seen how big those are?? Dang, l test drove one and it was sooo long l didn't like it...plus the new ones have an 8speed whereas the 2010-2016 had the old school 6speed...plus V6...l'll want more power later on
    You don't have to shift as much, & that may be the point that I am making (& you're missing).

    My Mirage will never see one hard downshift in the 10-15 years that I hope to own it, nor will my 5-speed manual Forester. That doesn't mean I don't have to creep down snow covered hill roads in a low gear. I find myself in about 3rd gear by time I reach the top of the ridge road leading to my home. Today I need to use my trailer, the same will happen with my Forester. I will be in third gear by time I reach the top, but the downshifts are super gentle & easy. If I am pulling my 4WD compact tractor on the trailer, I will be climbing in 2nd gear before I reach the top. I use downshifting to gain power to make climbs. I never use downshifting to stop my car. There's nothing wrong with going from 5th (or 4th) to 1st gear once stopped.

    I don't do much big city driving. If I did, I may feel differently about manuals.

    Sadly, 4 cylinder turbo engines are making more & more V6 engines without turbos disappear.

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    Still Plays With Cars Loren's Avatar
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    Quote Originally Posted by MirageRally View Post
    instead of what l was doing...holding in clutch, rev to 5k rpm, then let out clutch...it would take too long to rev the engine and let out the clutch unless like l said "l'm doing it wrong"...
    Yes, that would be totally wrong. The whole point of rev-matched downshifting is to be quicker and smoother. There's no "holding in" of the clutch at all. Just blipping the throttle at the same time as you're pushing in the clutch to bring the revs up by 1500-2000 rpm (don't target 5,000 rpm, don't even look at the tach... just bring the revs up enough that they fall into the right place in the targeted gear), and then let the clutch out and continue.

    Something needs to be pointed out here, just in case it's not obvious.

    Mark's approach to driving is purely as a "conservative street driver". And that's fine. That's the way most people drive, and it's perfectly appropriate. And nothing he's telling you is wrong.

    When you're talking about rev-matching, and heel-toe downshifts and that sort of thing, the intent is "performance driving". It might not be as efficient. It "shouldn't" cause any more wear if you're doing it properly, but done wrong, it certainly can. (always keep "mechanical empathy" in mind)

    So, Mark's telling you that when he approaches a curve, he'll slow to an appropriate speed, and only downshift if he NEEDS too to be in a gear that will let him accelerate out of the curve. And that's fine.

    But, a performance driver wants to be in a gear that gives them maximum throttle control in the curve. We're talking "race track" here. Where we're driving the curve at 10/10ths, and if the car starts to lose traction, having the revs in the right place allows us to more readily shift the weight of the car with the throttle. A tiny bit less throttle will shift weight forward to help reduce understeer. A tiny bit more throttle will help catch oversteer. If I'm in a turn at high speed and really low RPM (especially in an underpowered car like a Mirage), my throttle inputs don't do as much as they would if I were somewhere in the 3-5k range. Throttle response can be important.

    We're also trying to get out of the corner quicker, so we want a gear that's going to give us maximum acceleration out of a turn... in the performance environment. So, whereas on the street we could take a 35 mph posted curve in 5th at 40 without missing a beat... and no problem getting back to a 45 mph speed limit without shifting... on a race track, we'd be going 70-80 approaching that curve, we'd brake, rev-match a downshift to 3rd (and if we knew how, we'd do it with heel-toe so that we can brake later and be braking WHILE we downshift), take the curve at 65 mph and rocket out of it because we'd be right at around 4,000 rpm ready to rip to the redline.

    Different techniques for different reasons. But, with your stated intent of learning to be a rally driver... I'm assuming that you're trying to learn some performance driving techniques.

    But, once you learn to be a performance driver, those habits stick with you. So, while I'm not taking the curves around here anywhere near as fast as I could, even if I'm only slowing from 45 to 35, I still might blip a downshift from 5th to 4th just out of habit... and also to keep in practice.

    You'll likely develop your own driving style that's a mix of a lot of things. I know I have. My mix includes performance driving and hypermiling! Seemingly two polar opposites. But, if I'm trying to employ the "driving without brakes" method along with using "DFCO" when coming to a stop, while also trying to not be an impediment to traffic flow... things get interesting.

    And there's a lot of "hypermiling" stuff that I sometimes do that are completely against things that I learned over the years. Like, when you're driving in traffic, always be IN A GEAR ready to move if you need to. Coasting up to a traffic light in neutral is "bad" because if somebody compromises your space in a bad way, and you suddenly need to speed up to get in front of the guy in the lane next to you... you need to be in a gear that will allow you to do that. Hence, nicely rev-matched downshifts as I come to a traffic light. (In the Mirage, I usually only downshift to 3rd, sometimes 2nd, never bother with 1st) But, if I'm all-out hypermiling, those super-long neutral coasts are nirvana! You don't want to be in gear when you're trying to coast as far as possible, so neutral-coasting is the best. Now, if you're coming to a stop, then you want to be in a gear that keeps your revs above 1200 so that you stay in DCFO. But, otherwise... for hypermiling, neutral coasting can be good.

    Different techniques for different reasons.

    And if I'm hypermiling, "throttle blipping" in any form is wasting fuel! Not a lot, but some. I usually do it, anyway unless I'm really hardcore hypermiling because I like the feel of a properly rev-matched downshift.

    So, ultimately, you have to do what works for you. But, if you're LOOKING at the tach and trying to rev to some mystical magical number between shifts... that just tells me you didn't do your homework. It's 2020. There are TONS of videos out there that can show you how to do this kind of stuff. Not a single one of them is going to tell you to try to do what you're trying to do.

    You just might do yourself a service by taping a piece of paper over your tach and start learning to do things by sound and feel for a while. I run into the same sort of thing with new drivers just teaching them to make basic residential turns. "How fast should I drive this corner?" You'd be the student trying to watch the speedometer to keep the speed at exactly 15 mph rather than just learning what an appropriate pace "looks and feels" like while keeping your eyes on the road and thinking about where your lane is going.

    How far should I rev the engine on a shift? "To where it feels right." How much do I need to blip the throttle for a perfectly rev-matched downshift? "Just enough, and no more." Quit trying to think in concrete terms, that's not how this works!


    Simplify and add lightness.

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