CVT pros and cons

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

 

.......

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.

 

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.

 

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

 

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.

 

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.

 

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.