Block heater usage

1 to 2 hours (more toward the 1 in your mild case). Grill blocking helps retain the heat, too.

 

We asked about them. The dealership here has them, but they have never installed one.

So far we are 3 years into driving a Prius, and we love it. But have never used a block heater. It normally dips to -20F for a couple weeks every year, but most of our winters it stays mostly between 10F and -10F.

We park outside.

 

I found it useless in Pearl, a GII Prius. So, when I ordered Pearl S (GIII) in the colour I wanted, and they found the only one in Western Canada on Vancouver Island with no block heater, I told them to not bother installing one (and charging me the ridiculous price they wanted). I think I have the only Prius purchased in Alberta -without- the useless block heater.

In our climate it takes at least a 1000W block heater to make a difference. My old Subaru had a 1700W immersion one (the type you pop out a "frost plug" and install). Now THAT was an impressive block heater. Parked overnight one cold winter night outside a motel in Blue River at -50C it was plugged in. When I started the car the heater was blowing warm air! Car didn't want to move though because both differentials and the transmission were too stiff! Had to rev. the engine to get it moving and drive -real slowly- for a mile or two to get it moving properly.

 

Is that really your question ? If so, you are asking at what temperature the black body radiation of an engine is 400 watts.

Look here, and note Stefan's law

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I would be more inclined to estimate the engine's heat capacity (in joules/C) based on weight and ALU construction, and shoot for ~ 20C increase.

Googling says
Engine weighs 100 kg
Specific heat of ALu is 900 J/Kg*k

So ignoring losses to the environment since you are going to heat the engine and go, supply
900*100*20 joules. At 400 watts, that would be (9*100*20)/4 seconds, or 75 minutes. I'm not sure how easily heat moves to the transmission. If practical heat mass is doubled then 150 minutes.

 

Do note that because "modern" block heaters are no longer immersion types (they are smeared with heat conductive grease and inserted into a dry hole in the block), they tend to run a little hotter than they used to. This is also why they are limited to around 400W. I've seen reports on this forum of failures after a few years. I can't add any input on that as my GII (Pearl) block heater was used only once, to see what it did (not much). I couldn't be bothered to plug it in.

Now, around here, block heaters aren't used to increase efficiency, they are used to make sure the car will actually -start-. The Prius uses a 200V battery, boosted to 560V in a 20+ HP three phase starter motor, and is turned at about 1000 RPM, not 300-400. It starts no matter what! Pearl had no problems at -30C, the one time she was not parked in the garage.

The Subaru block was also aluminum, and about half the size of the Prius one.

 

You are not really in the target market for a block heater.

These conditions are closer and it will be more advantageous.

But almost 100% of the advantage is to personal comfort; that is, how quickly you are able to get heat to the cabin.
The engine uses a tiny bit more gas when it's colder but your heater will only help for the first few miles.

The engine really doesn't care much if it is +50 or -20 F but there is a cutoff there somewhere that being extremely cold is hard on the engine too.
My guess is somewhere around -20.

Cost wise, you will never recover the initial cost plus the electricity, most likely.

Block heaters are necessary for diesel engines which sometimes won't fire if it is TOO cold, even with glo plugs in place.

 

These two reasons cover a lot of Prius owner purchases. And 'tiny' bit more is very much in the eye of the car owner, particularly an owner that tends to drive short routes and likes to glide in the first ~ 3 miles.

An EBH can just about wipe out the winter MPG penalty in NM.

 

What difference did you note from no_EBH ?

Errr... $375 ? I thought the EBH was ~ $80 US

 

That would convince me to heat at least that long then. Your use of the cabin heater is preventing the car from reaching its optimal engine operating temperature.

I know from monitoring engine temp with a SG that once the engine reaches ~ 160F - 180F, it will stay there even if I P&G and/or use cabin heat; but if I turn on cabin heat while the engine is heating up I delay S4 for a *long* time. So I suggest you hold off on the cabin heat for a couple minutes into driving, and continue using the EBH for 2+ hours.

 

They stick a cylinder into a hole for heaven's sake. DIY is a pain because of access, but this job takes all of 87 seconds on a lift.

Done is done, but your mechanic/dealership does not deserve its customers.

 

By the way, some interesting EBH reports courtesy of Google:

Block heater installs - Milwaukee in September - CleanMPG Forums
Engine (preheating) block heater | PriusChat

 

On a new car in Alberta it's listed as a "$350 required option". Every dealer charges that when I checked. They wouldn't let me "delete" it. But because Pearl S came from Vancouver Island and didn't have it, I was able to persuade the dealer to leave it off. They probably didn't know how to install it anyway.

 

I have a diesel tractor with a pto-driven snow-blower, that I use for clearing snow. Older diesels need it more than newer ones.

When I bought this tractor [Massey-Ferguson] I asked about block heaters. The dealer said that only about 10% of the tractors around here use a block heater, but for an extra $50 he could install one. I held off on doing it, and so far [4 years later] I have not needed one.

 

Even though I live in one of the most extreme climates in North America, I haven't used block-heaters in over 20 years; since I started using zero-grade synthetic engine oils. I've become convinced that there's no compelling reason for doing so.

The most significant reason why gasoline engines have trouble starting in cold weather, is because the engine oil becomes stiff, and the starter can't turn the engine over fast enough to start the engine. The gasoline itself is volatile enough, even in extreme cold conditions to ignite and combust in the cylinders. Cranking speed is usually the issue, not combustibility of the gasoline.

Most of the engine oil sits in the oil pan. The block-heater and the coolant are usually above it. Since heat rises, it usually takes many hours for the heat generated by the block-heater to work it's way down to the oil. It makes far more sense to me to burn a few ounces of fuel to warm up the engine instead of using many kilowatt-hours of electricity to do so.

I only time I encountered a problem starting my car (a '93 Taurus with 0W-30 synthetic) was back in 2005, when the thermometer was registering -42C, and the car failed to start after 3 tries. I gave up and caught a ride to work that day, and when I returned around 4pm, it fired up right away without a problem, and the temperature was -36C.

The Prius engine is much less likely to have a problem starting up in cold weather, because it uses a powerful motor-generator to turn the Atkinson-cycle engine. I've seen reports that the Prius is very popular in Central Asia because of it's cold-weather startability.

The hassle and extra expense of plugging in a block-heater makes no sense to me for all the above reasons, but most importantly of all, the expense of consuming electricity for several hours in comparison to running the engine for 5-8 minutes for warm-up is a no-brainer to me. I'll continue to hit the remote-start button while I'm getting ready to go somewhere, and when I get in the car, it's nicely warmed-up and ready to drive.

 

There seems to be an inverse relation between winter extremes and block heater adoption, funny. Anyway:

I'd say a couple of hours is sufficient runtime, three if it's extremely cold. Two hours is my usual target, anything more and the temp raise mostly holds steady.

It'll typically raise coolant about 20C above ambient.

Be sure to insure for the time you FORGET TO UNPLUG. It will happen. Make sure your extension cord from the wall is easy pull-out, and secure. Ditto for the BH cord: securely double zip-tie it along a lower grill slat, with just enough hanging out. Not enough that it'll drag on the road.