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Rev matching

Discussion in 'Off Topic' started by Apex000, May 22, 2010.

    • Member

    Apex000

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    Okay , so i will admit that i am an amateur in the world of manual transmissions. The 3er i own is my first car with a manual transmission and i execute all basic techniques very well (get the car moving with out jerking, properly shifting , proper clutch usage).

    But i have not a clue of to properly rev match . although this morning on my way to work i go lucky and had a perfect rev match , i tried it again and failed :mad:

    anyway, can someone please give me some advice ?

    thanks
    • Member

    CRKrieger

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    There is no advice to give. Practice is what does it. You need to get used to your gearbox (each one is different) and your throttle response and practice, practice, practice. It will come to you.
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    Apex000

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    hmm Thanks :)
    • Member

    steven s

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    Some is going to depend on your throttle cable too.
    My cable was so worn and dirty that it was difficult to blip the throttle.
    Replacing the cable was like night and day.
    • Member

    MGarrison

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    Well - there's rev matching on UP-shifting, & then there's matching revs when DOWN-shifting...

    As CR says, it is a matter of practice, and gaining familiarity with your car.

    Rev matching on up-shifts is fairly straightforward - depress clutch, change gears, revs fall (which you can control through throttle modulation), release clutch in time to where the rpms in the next gear will match the speed you'll be going. Feedback: instant; mis-time it, and you'll get a lurch as the engine is either sped up to match the drivetrain, or the drivetrain is shocked by the rpms being too high for whatever speed you're going. You have to factor in how quickly you're accelerating and how quickly engine revs fall and how quickly you're. shifting, but, yes, that all should come with practice.

    Rev matching on downshifts can get a bit more involved. First, you'll want to practice blipping the throttle a bit to bring the revs up to where they should be for the lower gear . You may find the timing a bit easier if your 'blip' takes rpm's slightly higher than the perfect match and time your clutch release as revs are falling. Eventually, with enough experience, you'll gain the feel for exactly what you need to do for a good rev-match (what rpm's you need for any given gear/speed). Note that you want to match revs without having to slip the clutch, whether for upshifts or downshifts.

    Also, time to fold in practicing your "heel and toe" technique, which will allow you to get your downshift done when braking. Heel & Toe is a bit of a misnomer, as seating positions in modern cars usually preclude one having their leg absolutely straight, (which would enable one to keep their toes on the brake pedal while blipping the throttle with the heel).

    So, heel and toe is really more like 'left ball of foot and right side of foot', in as much as you tend to move your foot slightly to the right on the brake pedal and roll your foot over to the right a bit (possibly even the ankle a bit) to 'blip' the throttle, while still keeping the bulk of your foot on the brake pedal. That's the right foot mechanics of it - the rest is getting the amount and timing of your 'blip' right, along with the gear change and timing of the clutch release. Blow it one way or the other and you'll either be thrown forward in the seat, or back - get it perfect, and you'll be in the next gear, lurchless.

    Since you want to rev match, I would assume you are aware of the reasons to do so, but just to reiterate: less wear & tear on drivetrain and clutch components, and a much improved, far smoother driving technique. Proper shifting and clutch useage would consist of executing things smoothly, quickly, and completely, without excess force or abuse. No need to slam-shift or jam the shifter into gear with anything more than the light amount of force it takes, and make sure to fully depress the clutch pedal. Make sure to keep your left foot on the 'dead pedal' except when shifting, to do otherwise is not only a bad habit, but could also lead to unconsciously riding the clutch and leading to premature clutch wear.

    This is pretty much a 'get a feel for it' thing, based on the audible cues you'll learn from the engine sound throughout the rpm/speed ranges, and learning your car. If you find yourself staring at the tach or trying to figure out the exact rpm's, that's going to be overthinking it, as far as basic learning goes. You'll want to get it down pat based on sound, feel, and increasing experience. Once it's instinctive and second nature, then you can hit the spreadsheets and figure the optimal rpms, shift points, etc - but that's only of particular relevance if you're trying to figure out how to absolutely accelerate as fast as possible - I'm assuming you're not hitting the dragstrip tomorrow. ;)

    Have patience, particularly w/ the heel/toe routine - I recall it taking me about a year of doing it in daily street driving for it to get pretty seamless; it takes time to build new habits and change old ones. Street driving is optimal for building your heel/toe downshift rev-matching skills - lots of 3rd gear driving on city streets with slowing down and downshifting to 2nd for 90-degree turns. You'll want to get your downshift completed (clutch pedal released, left foot back on dead pedal) immediately before initiating your turn. If it's a struggle at first, be selective when trying it; you wouldn't want to find yourself lurching or over-slowing unexpectedly in rush hour traffic with cars or trucks close on your rear bumper, for instance.

    Also relevant: http://bmwcca.org/forum/showthread.php?t=4559
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    Brian A

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    Garrison and Krieger are the HPDE Driving Instructor Demi-Gods, but I will throw in my amateur 2 cents. At first you don't have to do it fast. One second to neutral, rev, lower gear, clutch back out, two seconds. With practice you will get a lot faster, but first and foremost it is rhythm thing not a speed thing. FWIW, if I mess up a downshift, it's because I didn't rev enough; your results may vary.

    You missed one: the ecstasy of perfectly executing two consecutive heel-and-toe downshifts while braking hard. Indescribable.
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    CRKrieger

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    Oh, PUH-LEEZE! We're just a couple of guys who have done this stuff for awhile. I mean, who's got THREE 'Rep' points and who has only TWO? :cool:
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    az3579

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    +1 to the "it's a rhythm thing". You cannot "tell" someone how to do it, you have to get a feel for it.

    After a couple of years, I'm still learning how to do it. I finally almost master it, then bam, new engine, transmission, and lightweight flywheel, and now I have to start all over again!


    And CR, guess who has FIVE rep points and who only has THREE! :D
    • Member

    lcjhnsn

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    I initially taught myself rev matching on downshifts on motorcycles. It's kinda important for aggressive corner entries on a 4-stroke bike to keep from swapping ends on the entrance.

    Then I just ported the concept and rhythm over to cars. My problem wasn't so much a smooth downshift, but was avoiding stabbing the brake pedal while heel-toeing the downshift.
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    Brian A

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    I just gave Krieger and Garrison an extra point each out of sympathy. No reppie point for Botond!!


    Our little brains have all jumped to the ragged edge of high performance heel-and-toe downshifting. Instead, a good first step is to practice while motoring along some smooth-flowing boulevard in 4th gear at 2000 rpm. No need to touch the brake pedal. Just clutch in, neutral, rev, third, clutch out. A few seconds later, shift back to 4th gear. Repeat shifting back and forth from 3rd and 4th until the people traveling in the lane next to you start giving you nervous side glances.
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    az3579

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    I've always found 3rd-4th and 4th-3rd shift the easiest to master. 1-2, 2-3, and 3-2 are always a lot harder for me. I'd say if he can master those shifts, then he'll have no problem with the rest of them.
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    CRKrieger

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    ... and then ignore them. They're as clueless as a 3-year-old watching you texting. This is good advice. I remember Charlie Goodman recommending it for the long straights at Watkins Glen in my first driver school. While I don't recommend learning to rev match shift for corners at a driver school, practicing on straights is just fine. Practicing on the streets is just fine, too. Learn to do the shifting first before attempting to add braking (heel and toe shifts). Doing it while the car is maintaining a steady speed gives you a 'feel' for that gearbox.
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    CSBM5

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    Wow, nice to hear Charlie's name here. I first met him at the Walter Mitty at Road Atlanta back in 1981. We both had E3's and exchanged lots of notes and all over the following few years we met there and at O'fest in '82. We used to have some awesome "battle of the E3s" at Road Atlanta as the open track sessions were timed at the Mitty back then. Great times on the "old", i.e. original, Road Atlanta circuit. Charlie passed away a couple of years ago now. Great fellow. My wife and I always enjoyed his company. :)
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    CRKrieger

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    You were fortunate to know him that well. I only met him the one time, but he was an instantly unforgettable character. Sad to hear he's gone.
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    CSBM5

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    Apex000

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    Great advice , thanks for the responses.
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    Apex000

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    Update

    After some patience i finally have rev matching down, it is second nature to me now. it's weird because i really didn't "practice" , I just caught myself doing it when i had to to quickly shift into a lower gear to merge onto Mopac and from that moment on rev matching has been a joy.

    heel toeing is coming along nicely as well.

    * i really need to post on this forum more often.
    • Member

    az3579

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    I just started venturing into double clutching. What a job that is... the sound of a perfectly executed 3-2 double clutch downshift is pure joy. :D
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    Apex000

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    awesome! hopefully i will get that down sooner or later.
    • Member

    CRKrieger

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    I only double clutch on my tractor. There's a reason God gave you synchros ... :D

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