Cold Weather and CVT

Since you have been here for a year, remember that the 'CVT' does not shift like a normal car would. The 'transmission' is a power split device, transferring power between both the wheels, and the MG1 (motor generator). The ICE will operate at a constant speed for the power requested, and as the car moves faster and faster, more power will shift from MG1 to the wheels. What MG1 generates from the 'excess' energy will either be directed to MG2, or the battery.

When the car is cold, HV will run ICE to warm it and the Catalytic up, even with no power demand. Some energy from this may be stored in the battery, but it is speculated the Hv may be limiting the load on ICE during warmup.

Good links:
http://home.earthlink.net/~graham1/MyToyot...PriusFrames.htm
and John's website, which I can't find right now.

 

I've noticed too that it acts like a reg. automatic is slipping, but I've never had to pull off the road and stop cause the eICE was racing so much and this am it was 5 F

 

I wonder if you are having the same problem as Fixitmhn in thread: http://priuschat.com/forums/04-prius-with-...lem-vt6589.html

 

We too had a cold snap and another factor is the defroster. For the first time I had the ICE coming back on at a stop light. The ICE was running more and at higher RPMs. I also saw more green battery than I have had in a long time. I think the care was doing it's job, keeping the engine at optimal temp for effency, keeping me warm though the thermostat was set on 68 most of the time, and keeping the windows defrosted. I have since learned to turn the defroster off when I don't really need it, the ICE runs a bit less and maybe a bit slower.

 

There simply is no way to properly prepare yourself for the difference in sound & feel that the CVT provides, especially in the dead of winter.

Trust me, it's totally normal. This is my 5th winter in Minnesota with Prius. The CVT works just fine, even at -18F degrees. The behavior will not resemble an automatic in any respect, especially when emissions are purged during the warmup portion of your drive (the engine will momentarily surge, even though the MPH doesn't change).

In a way, it is rather amusing... since it gives you the impression the vehicle is struggling. But really, it isn't. You've just been trained to expect an engine to respond in a very specific way. Prius doesn't. Still to this day, I get a kick out of accelerating rapidly onto a highway. The brain still sometimes expects to feel the soft thump of a gear changing. But instead, you get absolutely nothing... just a smooooooth acceleration.

 

And that improved things.. how? Did the engine stop racing when you stopped moving?

 

Acceleration during hill climbing gives the impression of a surge too.

Rather than the engine slowly increasing RPM, the motor does that instead. Then RPM will plateau and the engine will quickly change to the next higher efficient RPM for those particular conditions.

So if you're paying attention to sound, your brain will automatically try to counter that by making your foot compensate for the change in sound. The result is you fighting the CVT, rather than just letting it respond to road conditions the way it was designed to.

In other words: JUST DRIVE IT

 

We've already been down to -40 and I haven't noticed behavior like THAT. It's true the motor does seem to rev a bit faster, perhaps to assist in warmup.

 

<hehehe> Winter isn't all that bad here.

Though today's experience was a little odd. It has been around 0F degrees all of last week. That pushed my MPG dangerously close to the 40 mark. (Dipping into the 30's is not something I'd like to ever have to endure!) Well wouldn't you know it, the "warm" weather finally kicked in this evening. So when I filled up the tank, I was scared that reverse bladder-effect would cause the more gas to fit in the tank than last time... artificially deflated the MPG calculated. Phew! It was close. The value calculated to 40.1 MPG.

Anywho, it sure was nice driving in a temperature 50 degrees warmer than it was just a few days ago. Boy, does that ever change the behavior of the hybrid system. I can't wait until it warms up another 50 degrees... in June.

 

Also, at a stop, if engine resists turning off, and you feel it should be adequately warm, try turning off the AC and see if the engine shuts down then. If it does, you now know why the engine is running even at a stop.
Also, the ICE idle is a bit higher than a conventional car.

 

Hmmm, maybe if the Prius were loaded with gauges, this confusion wouldn't have happened? ;-)

 

What I have been noticing that bothers me is as follows, I don't know if it has less to do with the temperature, though I have only noticed it in the past week and it has been very cold. I have experienced this even when the engine is sufficiently warmed up.

I get to a cruising speed: A steady speed between 40MPH to 65MPH. Using my foot on the accelerator (Not cruise), I keep a steady pressure. The terrain is flat. I will feel what has been described above. The ICE RPM is really not changing, but I feel a "surge", then a retreat. A cyclical behavior where it surges almost once a second. I do not feel a steady flow of power to the drive train. One might say it feels like a slippage of an automatic transmission, but it is different. It feels like CVT slippage.

The MFD usually is showing power coming out of the ICE, and alternating display of power coming out of the motor to the wheels, or to generating electricity for the battery.

To be clear, this is a feeling of power to the drive train, nothing to do with engine sound.

- When I accelerate, it is as smooth as can be.
- If I decelerate and am just in regenerative state, it is again smooth.
- If I have to apply more power to maintain speed, when climbing a hill, it is also smooth.

It is just when cruising on relatively flat terrain, mostly going highway speed where constant power to the wheels from the ICE is necessary, that i feel this surge situation.

Help? Am I going crazy, or is this Normal. I don't remember feeling this behavior a two weeks ago.

 

mss, I've never experienced that type of sensation. Do you really have to pay close attention to feel it or not? If it's really noticable I'd take it to the dealer and let them figure it out. Hey can you feel it with the cruise control on? I wonder if that would eliminate the throttle sensor as the culprit????

 

I've had my Prius since Dec 03 and I haven't ever felt "surging" like you (and others) have described. The temp here in DC has been teens to twenty's. You might want to have it checked.

(P.S. 1st somewhat significant snow of the season today and the Prius handled it like a champ!! Of course, everyone else forgot how to drive!!!!!)

 

Definitely normal. Seems to be how it keeps the charge constant.