Extreme cold

JonB505 – Thanks much for the personal data point of 6.1 l/100km (38.5598 MPG) Fuel Economy when operating in Extreme -25°C (-13°F) to -28°C (-18°F) Cold Temps. It is informative to see excellent MPG- l/100km numbers that reflect only a 3.6% “Hit” to the US EPA 40 MPG Rating Estimate in Far North Temperate Zone Fall-Winter operating conditions.

Fuel Economies of 40-ish MPG (6-ish l/100km) delivered when operating out of the 60°F (16°C) to 80°F (27°C) “$weet $pot” Ambient Outside Air Temperature (O.A.T.) range that makes the Prius Hybrid Synergy Drive the happiest, is great performance. It is an especially impressive number after a 5 hour “Cold Soak” in -25°C(-13°F) to -28°C(-18°F)’temperatures, with no Grill Blocking or Block Heater Plug-In, and running the HVAC to keep the cabin at a toasty “Room Temperature” during the short 35-minute trip.

I see that your tires were Up-Pressured by 5 PSI above Toyota Door Post PSI. I am just curious. What Drive-Operating Mode were you in --- Normal, ECO, or PWR, and did you use the EV Mode at all during the 35-minute trip? Additionally, what was the nominal travel speed during the trip, and is your normal driving technique “Hybrid $mart” or “Just Drive It”?

As far as responding to your, “Anyone else have any cold weather experience to share?” question. No can do…. Not from down here in “Hybrid Friendly” balmy Florida, where our O.A.T. temperatures currently are running in the high 60°Fs (Mid Teens °C) overnight to low 80°Fs (Mid 20s °C) for daytime highs with no HVAC A/C or Heater use required or desired.

FWIW FYI: The running MPG for my current tank full of gasoline, as displayed on the MID, is 65.7 MPG (3.58 l/100km). Across multiple tank-full refills during this “Idyllic” time of Florida’s weather season, I generally average in the mid-to-high 50s MPGs (4-ish l/100kms).

Yes, I do drive “Hybrid $mart.”
Yes, I do operate in the ECO Mode 99.99% of the time.
Yes, my tires are Up-Pressured to MAX SIDEWALL PSI.

 

According to cbc news our Prius is good down to -40C ( -40F) without plugging it.
Yellowknife's winter cold tests hybrid vehicles - North - CBC News

 

Judging from the picture, not only was it extremely cold, you were also driving at a 90° angle. Well done you, I couldn't drive in those conditions.

You should start grill blocking. Based in the Gen III that would be 100% lower and perhaps leave the upper grill open.
From my observations, when the engine is stopped the coolant temperature will drop about 1c° every 5s or so at 0°c (32F). If I remember my thermodynamics, a hot object will transfer heat to a cold object or system quicker proportional to the difference in temperatures. So your block is losing at least 1c° per 5s. (If I've got that right.)
When you're stationary, grill blocking helps keep some of that heat in and slows the rate that the coolant will cool and keeps the car in a higher Stage.
If you've got heated seats, you might be able to switch off the cabin heater at long stops... but would the windscreen freeze?
I'd go with grill blocking.

BTW, it just topped 39.5°c (103F) in Canberra.

 

Yep. OP should definitely grille block w/temps that cold.

 

Yes, it will help at low speed driving. Even 10mph is enough to push air through the grille. I find grille blocking to be beneficial even at temps approaching 55F. Anything over that I wouldn't bother with unless you are only doing low speed city driving and/or short trips.

 

I think our high today is supposed to be +6C, and low tonight +5C. Hoh hum, LOL. And of course I've had our snows on since the start of November.

Have you got the blockheater? You really could use it with that clime.

Really cheap-and-easy is grill block: a couple of 4'x3/4" foam tube from Rona or Home Depot will cover the lower grill, which is warranted any time the temps are staying below +7C or so. (from 7 to 15 I'd just block 50%, and nothing above 15, just my preference). Just push the tube's slits onto the grill slats, and secure with zip ties or velcro strips (my preference). With the upper grill, you can block, but leave at least 50% open, for the inverter radiator.

You can also put short pieces of the tube insulation on the flanges on either side of the engine bay, just under the hood. This helps to hold the heat in.

Something to consider: set your cabin temperature to 19C, instead of 23C. Actually, it might not make a tick of difference with those temperatures, but try it. It will not be that much less comfortable, might drop your cabin fan speed, and improve your engine warm up time.

I've found when stopped I can sometimes get the engine to to turn/off by raising/lowering the ventilation system temperature. You might be locking out auto-stop, on some occasions, with high cabin temperature set.

Similar ploy works with AC in the summer. When you first turn it on, set desired temp high, say 27~28C, at a point where the fan stops running at extremes. Then gradually back the temp down as cabin temp stabilizes.

 

How much does the engine block heater raise you engine temp at initial startup? I'm curious about its capabilities. For example; if your engine temp is 55F sitting in the garage what would the engine block heater bring it up to?

 

I should have been a bit clearer... when the engine is stopped and the car is stationary, I've observed a drop about 1c° every 5-10s at 0°c (32F). Before I had an EBH and blocked my grill the coolant could go from 50°c to 40°c after about 1 minute stationary, causing the engine to start. Blocking the lower grill does seem to help contain the warmth and prevent the coolth from getting in. So at the same point in that journey my coolant would be 65°c (because of the EBH) and only drop to 60°c (because of the grill block) after 1 minute. Very different situations for economy and drive-ability.
FWIW I put 5mm draft-excluder foam on the inner wings (fenders) so that when the bonnet (hood) is closed there's an air seal either side so the heat can only escape under the car or near the wipers. In extreme cold, that might actually make a difference.
When moving with the engine stopped (gliding) the drop would be greater, however that is balanced because at some point you're regularly using the engine to drive along. A long downhill at a moderate speed where the engine isn't turning might result in enough cooling to drop. But if you've already at 90°c, you can afford to lose a lot.

I have a single row of lower grill blocked and it's over 30°c here. My lower grill was fully blocked until daytime temperatures were regularly over 25°c in early December. Note: I have a Garmin ecorouteHD and a Scangauge-e that both show coolant temperature (and other gauges) that you won't find on the Prius dash. Handy for showing you when the car is warm.

 

A lot of people who live in cold climates install their own block heater. The PC Shop sells them.

 

Yeah, our block heater was extra, and pricey. Frustrating: put in at the factory, for all, would likely be much cheaper for consumer. And with a lot of cars the block heater is immersed in coolant (but not Prius), necessitating coolant replacement, for post-factory install.

And, besides driving around in +6 on our snow tires, we're using our block heater year 'round, LOL.

 

If ambient temp's at say 5 deg C, if I don't use the block heater that what the coolant temp is going to be, and it hurts.

Same ambient temp, if I've plugged it in 2 hours in advance, coolant temp (as displayed by ScanGuage) will initially read around 35 deg C. And by the time I've gone a block it will have quickly climbed to around 40 deg C, as the coolant circulates and the temp homogenizes more.

In those conditions it'll auto-stop within a block or two at the most, especially if you have cabin temp set not too high.

 

The block heater draws ~400 watts. I plugged one in on the bench and it was too hot to touch within seconds.
So I suppose one could figure the cost of 400W per hour vs the fuel saved in the first 5 miles and come up with some reasonable formula for deciding how long to run it before starting out. But in really cold temps it takes more than 5 miles to bring the ICE up to max temp. You could easily run A-B tests on the same commute with no heating vs 3 hr heating and compare the MPG on the commute.

Back in the day, using old style block heaters in the water jacket on a cast iron block, we used to plug then in while the engine was still warm and leave them on all night. In sub-zero temps that was the only way to have heat when you came out in the morning - and in many cases the only way to have a car that starts.

With a small aluminum block, that 400W heater could easily bring the block up to max temp in a few hours - depending on the ambient temp in the car. I'd say that if your heater blower runs in auto mode when you first start the car, you've been able to warm it enough for most purposes.

 

Two hours seems good for all but extreme cold. I've read some research, and consensus is you're reaching the top of "curve" somewhere around 1.5 hours. After 2 hours it's pretty much levelled.

 

Hey!

Funny you should mention - 28 as this is exactly what my Prius displayed this morning.

I use an 800 watt electric heater between the front seats 3-4 hours before leaving so the cabine wasn't too bad... and no scrapping required!

No block heater, started just fine, should be just as cold tonight, will take a picture if I beat you

 

It's been below -20℃ here. Last night on a 35 min drive my SGII showed that I never reached 90℃ and this is not the only time I've had this happen. Time to look into grill blocking. At one point I was at 81℃ and went into EV mode, temp immediately dropped to 78℃.

Also managed to discharge the 12-volt battery. We were on vacation so it was about 5 weeks between using the v. After reading forum threads on the subject I concluded that I'd use my roadside assistance and the problem was resolved in ~30 mins. Once my Eliminator Power Box shows up I'm hoping to be able to start the v without outside assistance in such circumstances.