Extreme Cold Weather Performance

Snow?

Bob Wilson

 

Snow. You know the white poly stuff you put around the tree. Snow.

or was it "Did you mean the grill was 100% blocked by snow"

 

Living in a fairly northern climate, where we actually experienced -46°C in the last few days outside the city at the international airport.I have to say I'm a little bit disappointed with the results. My 1994 Honda Civic is by no means new with 440,000 km on it and a small 1.5 L engine. It's got a huge windshield and it is able to keep the frosted as well as blow warm air into the passenger compartment. It's not able to defrosted side windows completely, but it's definitely enough to drive. Consumption in this weather increased from 6 L per hundred kilometers to 9 L per hundred kilometers. Increased consumption in such extreme weather is actually normal. I was really hoping that the heat exchanger in the exhaust pipe of the Prius would make a lot of difference. From what I'm reading, it seems to be not much more effective than without it and I am getting hints that it may in fact be less effective than the thermos that is in the second-generation.

I'm curious that you said that the engine never really warmed up. More disturbing is the fact that your windows fogged up and you were not getting a lot of heat in the car. I think the increased fuel consumption is actually very reasonable as it has to burn the fuel in order to propel the car and heat the car.

Would you say there was enough heat on the highway to keep at least the front windshield defrosted and the side window to defrosted enough to be able to drive?
Would you say you were still fairly comfortable in the car even though it was not blowing really hot air it should have still been blowing warm air?

If think the heated windshield seems like a good idea, but you have to realize that the heated windshield for the Lincoln navigator cost $9000 to replace in Canadian dollars.

It's interesting that this car is able to go electric mode in such extreme temperatures, I am actually very curious why there is a lot more heat generated when using the defroster. From what I understand, the outside areas actually cooled by the air-conditioning system when the defroster button is pressed in order to dehumidifier the air which is then heated again but is now a lot drier. I wonder if anybody has an explanation for this?

 

Living in North Alabama, I don't have a lot of experience with snow. I am under the impression it has structural properties:


Once warm weather returns, like my last snowman, the storage problem is solved.

Bob Wilson

 

There appears to be a misconception regarding the heater/cooling. Putting them to "max heat" or "max cool" won't make -any- difference until the cabin temp gets within about 10 deg of what you want. In other words the A/C system uses maximum heating to get the temp up to 22C in Pearl until the actual temp gets close. Then it "throttles back". Ditto for cooling. So setting the control to "max" is really unnecessary.

But if it makes you feel warmer, be my guest.

As far as the "defrost" setting, the reason it appears to cause faster heating is:
1. Dry air will feel warmer at the same temp as humid air (when it's cold).
2. The fan is run at max. which -should- extract more heat from the heater core.

Note that because it gets "windy" in the car, it can actually feel colder at first. Also, the A/C system will exhibit less control over the temp, so it will get hotter than what you set.

 

No automotive A/C will run in temps much colder than +3 C. The compressor oil will thicken and settle out, which will destroy the compressor

Whether my '04 Prius or my '07 FJ, the A/C is locked out in cold temps. One thing I don't like about my FJ is that when you set it for Defrost, the A/C mode is automatically selected.

Driving out of the heated garage, my compressor runs until it senses the bitter cold temps, then it locks out the compressor. You cannot defeat the A/C on Defrost mode.

I solve this problem by yanking out the A/C compressor relay

 

You must have had a "better" 10W-30. Most 10W-30 conventional oils have a rated pour point of -30 C.

I used to store motor oil in an uninsulated, unheated shed at my hobby farm. At -40 or colder, I grab the bottle of 10W-30 and try to squeeze it: hard as a rock.

Unscrew the lid, upend .... nothing. A 15W-40 is even worse

Note that some motor oils use "pour point depressants" to give an edge in cold weather. The PPD has nucleation sites in the molecule very similar to the wax crystals that start to gel in a conventional motor oil.

These PPD nucleation sites interfere with widespread gel/matrix formation by "robbing" the wax crystals. However, the PPD's are easily used up due to normal byproducts of combustion

Eg: a virgin 15W-40 that may be "good" to -25 C (Although most HD engine makers have a cutoff of -15 C for that viscosity) will, once loaded up with soot and other combustion byproducts, turn solid at -10 C

In the end, you must use the appropriate viscosity for the expected ambient temperature. You will ALWAYS do less harm by running too "thin" a motor oil, than too thick a motor oil

A viscosity too "thin" may result in increased long term wear, but even that is debatable. Consider all those Ford V-8's and V-10's in heavy duty applications, lasting at least 160,000 miles

A viscosity that is too thick can cause immediate and catastrophic engine damage. Eg, shear the oil pump drive, not notice, and walk inside to stay warm. The motor seizes up. Or, the front main seal blows out, and the oil sprays out - same result.