COLD! C.V.T. Analysis.
 

For those in the Northern Plains of the U.S. and in middle-Canada, I sympathize.

RH77 reporting on-location in Sioux City, Iowa. :p

Tonight, the low is expected to dip to -15F, which makes vehicle operation, "interesting" -- and definitely not efficient. The vehicle I was assigned is equipped with a Continuously Variable Transmission. When it warmed-up to +10F today, it was able to operate efficiently, but from a cold soak at 0-deg F, it has a tough time. Better gloves were required.

From a cold-start and go, the CVT keeps revs high, and makes it very inefficient; however, once warmed, driving at a variety of speeds from 30-70 MPH, RPMS are 1300-2000. This is the key to it's efficiency. When it was first started, I thought the parking brake was stuck, but that's the nature of the super-cold CVT. Driving slowly to warm-up didn't translate into low RPMs.

More on the vehicle later, the Nissan Rogue 2.5 S AWD is CVT only and is the more-efficient contender in this small-SUV/Crossover class (based on the Sentra). SG results will be inaccurate due to temps and shorter distances, but an idea can be gained.

I'm told that this cold-snap has been consistent and relentless up North. Has this effected your FE?

RH77

The FE of my TDI during winter is really bad. On the highway at 70 mph there is a 10 mpg difference between summer and winter (50 down to 40).

I can't say for the elantra yet, but one thing I already hate when then engine is cold is that it will idle at 1500 rpm. I know how to fix that however and will mod it to rev at a more acceptable 1000 rpm when cold.

With the TDI, what do you think causes the drop? I see you have a grille-block. Is it cold start situations or the weather dyanmic (snow, higher rolling resistance, etc.)? I'm curious about IATs as well as coolant temps...

RH77

There are multiple factors.

- Winterizing diesel additives lead to less mpg.
- Even with the block it takes some time for the engine to warm up.
- Rolling resistance is indeed higher as winter tires are only rated at 32 psi. Snow can add to that friction when present on the road.
- Coolant temp is a big factor in the determination of timing in the TDI so that might play significant role too.

Even just the wheel bearings themselves create a large difference in drag in the winter and take miles and miles to warm up.

I used to live in Sioux City when I first started driving. It's not as bad down there as it is further north in MN now.

The impact is far less now that I have my block heater installed and used every weekday (about the only days I drive my VX). I picked up ~5mpg the first tank, not to mention the savings on the wear and tear of the motor.

I've never been a big fan of CVTs. Mainly due to the cost of maintenance, in the form of them wearing out just about as fast as an automatic trans. My basis for this observation is based mainly on the Civic HX though.

Block heater anyone? It should definitly help offset some of these problems.

I did notice that my block heater is close to the trans and some of the heat is transfered to the transmission lubricant making for easier shifting and less friction than without the block heater.

I would think that engine temperature has the most to do with high engine rpms during a cold startup. Its programmed to get the engine up to temp quickly. I wouldn't think there are temp sensors in the CVT tranny, but I could be wrong?

Definitely warmer.

Although last night, the temp dropped to around -10F. When I started the Rogue this morning, it just barely cranked (155 miles, so essentially brand new).

Then the CVT made a horrible noise! It sounded like a belt slipping, but of a more metallic screeching. I don't "warm up" vehicles, so I just drove slowly until the noise went away. I'm confident it wasn't a belt since the transmission made the noise under load, and not in Neutral.

That can't be good for longevity. I like that it nearly lugs the engine when driving around town -- but it seems like a new technology that has to evolve a bit. Arguments can be made whether they're more efficient than standard autos...

RH77