Rev matching
+ Reply to Thread
Results 1 to 14 of 14

This is a discussion on Rev matching within the Everyday Impreza Talk forums, part of the Community - Meet other Enthusiasts category; I googled it, and i can't see the difference between Rev matching and double clutching.. From my understanding, its only ...

  1. #1
    Registered User P8baller07's Avatar
    Join Date
    May 2006
    Posts
    179

    Rev matching

    I googled it, and i can't see the difference between Rev matching and double clutching..

    From my understanding, its only to get the syncros spinning when you're downshifting.... But is there any way to shift up safely/smoothly without that jolt in between gears, i have a RA gearset with JDM STI tranny in my 02, should i not even worry?

    I did search and google this topic a lot, so any pointers to good reads would be nice. Thank you.

  2. Remove Advertisements
    ClubWRX.net
    Advertisements
     

  3. #2
    Registered User LRPct's Avatar
    Join Date
    Jan 2006
    Location
    Lime Rock Park Ct...
    Posts
    264
    sounds like you need to release the clutch with a lil slower motion on your UPSHIFTS with either no gas or jus a lil bit that will match the revs in your next higher gears.. Alot of this depends on how long it takes you to do your upshift, and how far the revs drop in between. Keep in mind you don't want to rush the shifter and the syncros...esp in our cars... Thats one of the keys to longevity..
    Rev matching on downshift would jus be the "blip" of throttle that will raise the revs to matching the RPMs of your next LOWER gear with a normal single clutch. Double clutching is the same except letting the clutch out on your way thru nutreal while you do the blip, basically treating nutreal as as a seperate gear....
    I've been driving manual street cars for over 25 years, racing manual (of course) motorcycles for 20, and cars for5+ years ( NOT streetracing, thats NOT racing thank you..) and have NEVER had to replace a clutch or tranny part. I usually put between 150K - 250K miles on my streeet cars B4 I retire them...So you CAN drive a REX for that long, even an 02, hard without hurting a tranny if you just know what you are doing and use alil mechanical sympathy..

  4. #3
    Registered User subaru_crazy's Avatar
    Join Date
    May 2004
    Location
    NYC
    Posts
    878
    rev matching means blipping the throttle when downshifting so that there is a smooth transition into the lower gear. If you don't do it you will get a big jerk becasue the tranny will do the matching for you, and will wear on your synchros. I always rev match when getting a lower gear especially when doing that at higher speed when I need fast acceleration, ususally going from 5th to 3rd. Double cluthing is for upshifts and it was done becasue older cars had no synchros or very poor sychro design I am talking about 20 -30 years ago cars. I remember my dad had to double clutch his truck becasue he had to match the revs for the gears to go into the gear. I have played with the rev matching to the point that I can go into gears without pressing the clutch in, but only do it at lower speeds and very rarely.
    Last edited by subaru_crazy; 11-04-2006 at 09:56 PM.
    MY LUG NUTS NEED MORE TORQUE THAN YOUR HONDA MAKES!!!!

    Cobb Stg 2 helix up/dp combo
    Kartboy short shifter

  5. #4
    Registered User
    Join Date
    Oct 2006
    Posts
    642
    wouldnt giving the car rev when downshifting cause the RPMS to go higher (because downshifting causes RPMS to spike up) when you want to lower the RPMS to slow down?

  6. #5
    Registered User rr1911's Avatar
    Join Date
    Nov 2005
    Location
    Central Florida
    Posts
    0
    Army Ranger For Life ! Thin Blue Line
    Military Militia # 1911/ Blobeye Syndicate # 1911/ Modifier's Anonymous # 1911/ Hawk-Eye Alliance # 1911
    All We'll Drive
    DIFFERENT STROKES
    EVEN MY DENTIST TOLD ME FLOSS 7 DAYS A WEEK
    POST WH0RE KING

  7. #6
    Registered User subaru_crazy's Avatar
    Join Date
    May 2004
    Location
    NYC
    Posts
    878
    Quote Originally Posted by momolicious View Post
    wouldnt giving the car rev when downshifting cause the RPMS to go higher (because downshifting causes RPMS to spike up) when you want to lower the RPMS to slow down?
    yes what you are saying is correct but when you going down a gear let say you are in 5th at 2k rpm, and when you go to 4th you will need more revs to stay at the same speed so your rev will jump approx 500rpm. Now if you are trying to slow down, you can just go down the gear and dump the clutch, but that will put all of the force on the transmission and the synchros and your car will dip downwards becasue off the braking effect. Now to avoid the jerk and all of the stress on the gears and the motor you can press the clutch in, blip the throttle till rpms jump to 2.5k and dump the clutch. This way you avoid the jerk and all of the stress that will be transfered to the drivetrain when you are not using rev matching. At slower speeds down shifting without rev matching, will not be as dramattic but try to go down 2 gears from 5th to 3rd at 60 mph and you can cause the car to jerk so much that you can hit your head on the steering wheel, or break your gear. Also if you are trying to accelerate quickly, not rev matching will hurt your reaction time becasue the car will need to recover the momentum that it lost while trying to synch the engine speed to the transmission speed.
    Last edited by subaru_crazy; 11-04-2006 at 10:24 PM.
    MY LUG NUTS NEED MORE TORQUE THAN YOUR HONDA MAKES!!!!

    Cobb Stg 2 helix up/dp combo
    Kartboy short shifter

  8. #7
    Registered User scubynubie's Avatar
    Join Date
    Jun 2003
    Location
    Taunting Happy-Fun Ball
    Posts
    846
    A synchro's job is to help the gears match speeds to allow you to shift, so once you are in gear, their job is done. Rev-matching is to help the synchro's out, and smooths out down shifts.

    My experience has been that jerkieness on up-shifts is usually do to letting the clutch out too quickly, or getting on the gas too soon... Try letting the clutch out a little slower, and wait a split second longer before getting back on the gas.
    "I never drive faster than I can see."
    - Jack Burton

  9. #8
    Registered User
    Join Date
    Oct 2006
    Posts
    642
    wouldnt you car be going too slow if you gotta wait till you slowly release the clutch to put in gas? ive tried doing those slow motions and cars behind me from a stop try to pass because the car is not accelerating fast enough to get up to speed

  10. #9
    Registered User subaru_crazy's Avatar
    Join Date
    May 2004
    Location
    NYC
    Posts
    878
    Quote Originally Posted by momolicious View Post
    wouldnt you car be going too slow if you gotta wait till you slowly release the clutch to put in gas? ive tried doing those slow motions and cars behind me from a stop try to pass because the car is not accelerating fast enough to get up to speed
    Are you new to driving stick, well if you are then don't worry keep trying and wit practice you will get it so its sikly smooth. The WRX is has a very jerky transmission and i think its due to the AWD since in any car that is FWD and RWD if you shift too fast you will just chirp the tires since there is a lot less grip. There is a definite balance between shifting too slow or too fast, in up shifts if you release the clutch too fast you will jerk the car , if you release too slow when the rpms drop too much, again you will jerk the car. So practice is where its at and learning what is the speed to rpms ratio of each particular car that you drive which has a manual tranny. Unfortunately no one can really tell you what that ratio is becasue its learned instinct, that again you will gain after driving a car with a manual transmission.
    MY LUG NUTS NEED MORE TORQUE THAN YOUR HONDA MAKES!!!!

    Cobb Stg 2 helix up/dp combo
    Kartboy short shifter

  11. #10
    Registered User scubynubie's Avatar
    Join Date
    Jun 2003
    Location
    Taunting Happy-Fun Ball
    Posts
    846
    Quote Originally Posted by momolicious View Post
    wouldnt you car be going too slow if you gotta wait till you slowly release the clutch to put in gas? ive tried doing those slow motions and cars behind me from a stop try to pass because the car is not accelerating fast enough to get up to speed

    No, not really. I mean slower than you are currently releasing the clutch, not turtle slow. If you are shifting up, and imediately release the clutch (read side-stepping), that will cause a jerkyness.
    "I never drive faster than I can see."
    - Jack Burton

  12. #11
    Registered User subaru_crazy's Avatar
    Join Date
    May 2004
    Location
    NYC
    Posts
    878
    The natural tendency of the engine is to drop rpms, to make rpms you need to supply gas the faster you make the engine spin the faster it will drop rpms. So if you are not accelerating fast then going into another gear will require you to let the clutch out more slowly, however you are redlining it then you need to shift and release the clutch much faster. Again in a FWD car if you just dump the clutch when shifting fast it will just chirp, in a WRX all of that instantenous accleration will be contained in the drivetrain and make the car jerk instead.
    MY LUG NUTS NEED MORE TORQUE THAN YOUR HONDA MAKES!!!!

    Cobb Stg 2 helix up/dp combo
    Kartboy short shifter

  13. #12
    Registered User WRXED06's Avatar
    Join Date
    Oct 2006
    Posts
    506
    great advice on that. At first i was having trouble with the rev matching, but like they said every car is different. AWD is not a car that i would want to learn how to use a clutch on...way to hard on the tranny

  14. #13
    Registered User
    Join Date
    Oct 2005
    Location
    California
    Posts
    848
    The only time I personally do rev matching is when I'm decelerating quickly or when approaching a corner faster than I normally would (you get that need of speed sometime, you know).

    But when I drive at normal steady pace, I downshift but I release the clutch enough to catch in order to get the speed of the tranny and engine speed to gradually match. Therefore, when I completely release, it would be a smooth transition from a higher gear to lower gear. I'm used to it that it does not abrupt my flow in traffic or put the car on a jerk. It's smooth and steady. Practice is the key!

    Although, this practice might be a little slower when comparing it to rev-matching, but it still does the trick and easier (IMO) to do when cruising around local streets.
    Last edited by Me&05WRX; 11-05-2006 at 02:20 AM.
    I might be back in the market for the new STI sedan!

  15. #14
    Registered User Racenut's Avatar
    Join Date
    Dec 2002
    Location
    California
    Posts
    0
    Don't feel bad... even when they taught drivers ed in high school, they didn't teach this stuff.

    But it's hard to learn how to drive on the internet too. Get out there and practice.

+ Reply to Thread

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.
If you do not want to register, fill this field only and the name will be used as user name for your post.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself. We strongly suggest that you stay away from using aol, yahoo, msn, and hotmail accounts. Sometimes the mail server blocks the emails from our server. As a result you will not receive any notifications including the confirmation email.

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Posting Permissions

  • You may post new threads
  • You may post replies
  • You may not post attachments
  • You may not edit your posts
  •