CVT pros and cons

Discussion in 'General Motoring' started by Agent Smith, Dec 18, 2003.

  1. Agent Smith

    Agent Smith Guest

    I've been doing my share of research about CTV (Continuously Variable
    Transmission) for some time now. From what I've read so far the idea
    and technology behind it is pretty fascinating. I also noticed in
    Honda's lineup of Civics that only Civic HX comes with CVT.

    Reading marketing slicks is nice and educational, but I'm very
    interested in hearing opinions about the pros and cons of CVT, and
    being a Civic HX owner in particular. Don't mean this to become a
    flame along the lines of Windows vs xNIX so please be patient with me
    and other posters.


    Thanks in advance!
    Agent Smith
     
    Agent Smith, Dec 18, 2003
    #1
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  2. .......

    I have never driven a CVT, but I spent quite a few miles as a passenger
    in a Civic gas/electric hybrid with a CVT. It is very smooth, and obviously
    you feel no shifts whatever. Still, it feels a bit odd, because the engine
    will rev to about 3000 rpm under light acceleration, and then gradually ease
    back at modest cruising speeds. In that model, you get quite a bit of what
    feels like engine braking from the electric motor running in reverse thrust
    mode, so it is hard to tell what a CVT might feel like under deceleration.
    Pros would be:
    - better gas mileage than a conventional torque converter automatic;
    essentially the same as manual tranny
    - better performance than conventional automatic; essentially the same
    as manual tranny
    - In theory, the result to be at the optimal rpm point on the power
    curve for a given vehicle speed and accelerator position. Newer issue CVT's
    are apparently much better than the designs of several years ago, which
    would go into a 'rev and roar' mode if you stepped down on the gas. This is
    to be expected with more and better microprocessor control.
    Con would be:
    - CVT's do not yet have the degree of development and refinement of
    torque converter automatics; this is mostly a matter of time. Some of the
    automatic transmissions of the 50's and 60's, which I have had the dubious
    pleasure of driving, were just plain terrible by today's standards.
     
    Joe and Ruth Levy, Dec 19, 2003
    #2
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  3. Agent Smith

    Randolph Guest

    The only con that I know of is that they feel a little "nervous" as the
    ratio changes freely and frequently. Not much of a real concern, just
    takes getting used to.

    The technology is fairly old by automotive standards. The Dutch auto
    maker DAF (bought by Volvo in the 70's) pioneered the CVT in the late
    50's and several other auto makers have used them off and on since the
    mid 80's. It is sometimes also called a Van Doorne transmission after
    the Dutch inventor.
     
    Randolph, Dec 19, 2003
    #3
  4. Agent Smith

    dold Guest

    I have about 17,000 miles on a 2003 Honda Civic Hybrid CVT.
    The first time I let my son drive it, he said "this is creepy" as he pulled
    away from a stop. As opposed to the 'rev and roar' that is noted below, I
    find that casual acceleration from a stop is at about 1500 RPM, just barely
    fast idle, and you either "glide" or "ooze" away from a stop.

    On open road, I typically step on the gas until I get to about 3000 RPM at
    20mph, and then stay at 3000 RPM until the speed gets up to where I want it
    to be... 3000RPM can be well over 70mph. Then I back off the gas, and find
    myself crusing at 2000RPM at 60mph, the same RPM as my Dodge Durango with
    4.7l v8 and four speed auto with overdrive.
    My Hybrid is noticeably quieter, smoother and quicker than a Civic LX with
    4 speed auto. Some of that is Hybrid, some is CVT.

    Two odd things about the "rev control". Sometimes, romping on the gas will
    max out at 4000-4500rpm. Sometimes it will go to just a needle's width
    below red line (6000rpm). I haven't quite figured out which is which yet.

    Heavily loaded, uphill away from a stop, it climbs up to around 5000, at
    which point it is fairly buzzy. Then the speed climbs, but that isn't
    readily noticeable to a passenger not watching the speedo. My wife would
    say "shift!", thinking that the car was just out of power and going
    nowhere.

    In hilly country, slipping the stick to "S" raises the RPM and give more
    engine braking. This was something that concerned me before I bought the
    car, because I live in hilly country, and wanted to be able to use that.

    In the Hybrid, at least, I'm sure I get better mileage with the CVT than I
    would with a 5 speed, because it runs such low RPMs. I would never hold a
    shift that low with a 5 speed.

    http://www.fueleconomy.gov lists the the 2004
    Civic VTEC-E (I think HX)
    City/Hwy
    Manual 36/44
    CVT 35/40

    Civic Hybrid
    CVT 47/48
    Man(5) 45/51
     
    dold, Dec 19, 2003
    #4
  5. Agent Smith

    Mustangbrad Guest

    I drove a Nissan Primera in Trinidad about 2 months ago. It was weird to
    drive, you mat it and it just pins itself at 6000RPM and doesn't shift. It
    takes some getting used to as you are used to an acceleration with a shift
    ..... it's like driving a golf cart, you push the pedal and it drives.
     
    Mustangbrad, Dec 19, 2003
    #5
  6. Agent Smith

    dold Guest

    I don't notice anything resembling this "nervousness". I don't think the
    ratio changes all that frequently. At freeway cruising speeds, it seems
    quite normal.

    If I have the cruise control set, on downhill grades there is some surging
    as the regenerative braking on my Civic Hybrid changes rate. You can see
    the charging display hunt a bit. This is kind of queasy, and I haven't
    really gotten used to it, I just put up with it or cancel cruise control.
     
    dold, Dec 19, 2003
    #6
  7. the only negative I have ever heard is that they cannot handle high torque
    applications. That will probably be fixed with more R&D. Otherwise, they are
    a great idea.
     
    Alex Rodriguez, Dec 23, 2003
    #7
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