Prius Heater

Actually I'm pretty new here myself, this will be my first Prius winter, but I have been reading a lot of the old posts from some of the experts. From what I've read I would say you are not missing a thing. That is no doubt one of the reasons for reduced winter milage as well as keeping the cat. converter warm. Someone, can't remember who, said he had noticed some difference in milage by lowering the temprature from 72 to 70. Maybe the HVAC system operates a little differently below 72 but I can't remember exactly what it was. I'll try to find it again. Try a search for things like heater, temprature, winter driving, etc. and I bet you can find lots of stuff to help.

Hope you don't ahve to wait tolong for your new 06.

 

yes it does have an impact on fuel ecomomy in the winter. The heater core has two electic heater elements embedded in it to provide some warmth while the ICE is in pre heat mode with the thermous flush, as it does this there is a rotating valve in the heater hose circuit to block the thermous flush from going into the heater core. The best thing to do is on first start to set the fan speed to low to maximise the electric heater output. Then when the low coolant temp light goes out turn the fan speed up. But just like all automobiles the heat in the cabin comes from burning gasoline. Sorry life sucks and you burn more gas in the winter.

 

Indeed, the ICE will run to provide climate control for the cabin.

Try this as an experiment...
Turn on your Prius.
Set the Climate control to "off"
Let the car warm up; eventually it will shut off.
The instant the engine cuts off, turn on the HVAC control (you can shut off the AC while your at it)
If the cabin is cold, the ICE should crank up almost instantly to begin heating the cabin.
Keep turning the temperature down until the ICE cuts off.
Then turn the temperature back up

You should see that the ICE will start and stop when you adjust the temperature.

I sacrifice comfort for efficiency... Especially if that means I can still keep getting mileage in the 50s.

I notice that the ICE runs less frequently when I set the temperature between 65 and 70 and more frequently when set to 71 and 80 (duh).

 

Since the engine is already warm/hot it is just as easy to pull heat from it. It would also take a _lot_ of electric power to create heat.

A decent ammount of resistive electic heat would require 10 or more amps.
Most home in-wall or floor board heaters use 1200 Watts = 120V * 10 amps (not an inductive load so phase angle isn't an issue).
1200 Watts = 12V * 14.4kA
It would be easier to get the heat from the ICE.

 

Key things I do for winter

1 I use an electric Holmes heater in the cabin on grid power to pre warm the car interior. And now this winter a block heater too for the engine.

2 I run without heat on at all if I can without fogging windows, till car engine gets warm enough for economical operation.

3 Then use heater but with fan on a low speed.

4 I have to take faster routes to work because the slow ones don't keep the engine warm.

5 I put sound deadening and absorber layers in my doors, at least 50% to keep car warmer in winter.

6 I have carpets to block the radiator and cover front of engine so it can hold the heat better. You need to monitor temperatures and also let some radiator air flow over the hybrid inverter cooler part at the bottom of the radiator.

 

In Winnipeg city driving, my ICE runs constantly in temps much below -18 C. At -25 C or colder, the heater cannot keep up.

My worst fuel economy was a long stretch of -40 weather with a few blizzards in January. A lot of the side streets were closed due to snow routing, so my usual 12-15 minute commute became a 45-60 minute PITA with stop-n-inch traffic. Under those conditions my MFD claimed 9.8 l/100km, around 28 MPG Imperial or about 25 MPG U.S. gallon.

Ironically when the ICE has to run so much, my battery SOC is almost always green. Instead of a wimpy PTC ceramic 12 vdc heater Toyota could have used the NiMH battery to operate a decent 208 v 1 KW auxillary heater.

The variable speed A/C is 208 v, and it's probably 1.5 ton capacity. The A/C in my 2000 GMC Sierra was rated around 1.5 ton. For the same power consumption at least I'd be toasty warm at -25 or colder.

 

So if Toyota did not worry about winter weather in Winnipeg they could have put in an electrically driven heat pump instead of the AC and "cold" weather in Florida would have had no more impact on my mileage than hot weather.

george

 

One problem is that the efficiency (actually coefficent of performance) for heat pumps, AC's and refridgerators is inversely proportional to the difference in temperatures. If you want 70 degrees F in the car and its 90 degrees outside then temp diff is 20 degrees. If you want 70 degrees in car and its minus 40 degrees outside then temp diff is 110 degrees. It'll take about five times as much power to heat from minus 40 as it does to cool from 90! But if cold means 50 degrees F then the heat pump is a great idea.

george

 

The 2004 and later Prius has an electric heatpump that does not require the ICE. It both heats and cools the cabin. I do not know if ICE coolant is also pumped through a cabin coil. I cannot find any reference to that. There are several references to Gen2 heatpump heating and cooling the cabin. I saw a page on a Toyota website in December 2004, but I can't seem to find that page again.

Here is one

This morning was the chilliest yet this year. I checked the heat as soon as I turned on the car and I had nearly instant heat.

 

This explains how I get heat in my car before the engine is warmed up...and it doesn't change the fact that the ICE will still need to run more to keep the battery charge up, even though it isn't producing the heat directly.

-Roger

 

Your car interior gets heat before the ICE is warmed up because the Prius has supplemental electric heaters. It puts out about has much heat as a hair dryer and is there for your comfort and for clearing the windshield sooner, but not for efficiency. That is because the electric power that is used by the heaters could have been used to propel the car instead. The electric heat is pretty wimpy and I can't notice much effect from it when the temperature is below freezing. Once the ICE is warmed up it generates quite a bit of waste heat (that's why there's a radiator) which is used to heat the cabin because it's free.

The heat pump is just a fancy name for an electric pump that moves liquid between warm and cold places.

 

I don't think that URL is entirely accurate in that claim.

The air conditioner is a variable speed electric scroll compressor, run off nominal 208 volts. The coolant is R-134a, a common automotive non-Freon air conditioning coolant.

There are two coils inside the HVAC: an avaporator coil for cooling and a heater core for heating.

In temperatures -10 C and higher, the supplemental PTC ceramic 12 vdc heaters work great. Below -25 C in city traffic, the efficient 1.5 litre motor doesn't make much heat and you had better wear a wool cap and mitties. I speak from personal experience.

 

In addition to what gcoyne said, heat pumps also only work in areas of the country where there is humidity in the air...

 

Richard:

The ICE runs almost constantly in city driving at -25 C or colder. The battery SOC is almost always green too.

So I would have to suggest the former and not the latter.

Jay

 

Jayman,

Since this will be our first winter with the car in Winnipeg, I'm wondering if you block off the rad at all to help retain some of that engine heat (especially in January and February)? What's the car like at highway speeds during these months?

I'm a little disappointed to hear that the engine doesn't throw a lot of heat. Sounds like it's back to mid-80's Toyota heating performance (which wasn't very good). Perhaps an interior heater to go on when the block heater gets programmed will help.

shaun

P.S. I also thought the vacuum thermos was enough hot coolant to negate the use of a block heater at all. The disappointments in the car are starting to stack up <_<