Block heater revisited

[Frank Hudon]

Back in May of this year I did some experimenting with the block heater in my 2003 Prius and found some interesting results. See posts
http://priuschat.com/forums/just-as-a-test...ht=block+heater
with the onset of fall/winter here on the coast I decided to get a timer and do some more testing. The use of winter gas and the lower normal mileage that it produces also has had an effect. The OAT has been running around 3-6 degrees C and the normal first 5 minute block has been around 8.5-9 Liters per hundred km. 26.1 to 27.6 US mpg. I initially set the timer to give me 6 hours of preheat starting 12:30AM and shutting off at 6:25AM as I usually leave for work at about 6:30 and on the mini scanner the temp was usually about 35C-96F and it took the first 5 minute block down to 7-7.5 L per hundred 33.6-31.3 US mpg. Then one morning I left at 6:40AM and the temp was 27C-81F and I thought that was a bit of a hit so the next morning I left at 6:20AM and the temp was 43C-110F so pulled the timer and reset the shut off to 6:40AM and the temps were at 42-43C when I left at my usual 6:30AM so thought what about shortening the on time so started resetting the start time down an hour a day and see where the temp started to drop. Well it turns out that 2 1/2 hours keeps the temp at 43C so that's where the timer is set. 2.5x400watts=1kw which costs me just over 6 cents. Now that its colder outside from when I first did the test, I have to drive almost 1.3 km further to get the car in S4. Gas costs, currently 88.2 cents a liter so it looks like I'm plugging her in. The worst hit has been winter gas followed by the colder temps followed by the rain/water on the road(increase in rolling resistance) For you people in the cold climates this might help with your mileage

[jayman]

I've used block timers for years, and they save you tons of money over not plugging in a motor. Unless it's -30 or colder, you don't need to plug in 24x7. I suppose folks in warm climates can only shrug at what we're talking about.

Before I moved into a condo with heated underground parking - and stopped worrying about it - I had a home with an attached insulated garage.

I would set the timer to click on about an hour before I left if the garage temp would be at 40 F or colder (Around 0 F or colder outside). Since the garage was heavily insulated, even at -40 outside, it never got colder than +15 F in the garage.

Driving a 2000 GMC Sierra pickup, not plugging in the motor cost almost an extra $2/day in gas. Remember, this was from an insulated attached garage. Plugging in cost around 4-8 cent depending on how long with the GMC 600w heater. By my math, I'm $1.92 ahead, per day. A high quality block timer costs around $35, so it pays for itself after 18 days of use.

Once at work, I'd leave it plugged in all the time if the temps were below freezing. So did everybody else, that's what plug ins are for.

When I drive out to my hobby farm, I have an insulated but detached garage for the Prius. So the winter temps are a good 10-30 degrees F colder inside than with an attached garage. At the hobby farm I'm not really on a schedule, so I just walk out to the garage and plug it in around 2-3 hours before I have to drive somewhere.

The small diesel tractor I use for snowplowing and the old Ford pickup are in the old barn, which is enclosed but minimally insulated. The tractor I like to plug in for at least 4-6 hours before use, it starts instantly and warms up within 5 minutes.

If you have to park outside all the time, then PLUG IT IN!

I'm still amazed in a cold winter climate like Minnesota, NW Ontario, Manitoba, etc, folks will refuse to plug in their cars even at -10 F, thinking it "costs too much." In the worst driving cycle of pure city stop-n-go, they will easily use 2-3x the fuel with an ice-cold motor.

Sort of like how a sad poor person tries to save a nickle, but it costs him a dollar every time?

[bruceha_2000]

I'm trying to get this straight in my head.
Assumptions ($ and gallons are U.S.)[list]
Calculations[list]

[jayman]

Good Lord your power is expensive!

Here in Manitoba, Manitoba Hydro charges around 5.8 cents per KWH for the first 175 KWH consumed, then around 5.4 cents for the remainder.

I've noticed the biggest difference in city-cycle driving. When I used to have a house in the city with an attached and insulated garage, and my 2000 GMC Sierra, I would average 4-6 MPG without plugging in during cold Manitoba winters.

Setting the timer to turn the block heater on around 1 hour before I had to leave, I would get at least 10 MPG. The biggest difference was hitting all those red lights with the motor cold. Parked outside, it would make an even bigger difference.

Sure my Prius took a big hit in MPG thanks to the cold and the reformulated gasoline, but I'm still getting at least 4x the fuel economy my truck ever did in the same driving cycle.

If the temps are hovering around -40, especially with a nasty wind, you had better plug it in. A friend of mine spent some time mining in the Arctic and even the oil pans and transmission pans have heaters.

All I can suggest in your scenario is to try the plug-in for a couple of weeks and see if it makes any difference. If at best you only break even, then ask if the quicker warmup is better for the motor.

If it ends up costing you more money to plug-in, and the motor doesn't seem to mind, then carry on as usual.

[bruceha_2000]

<div class='quotetop'>QUOTE(jayman\";p=\"54348)</div>

Good Lord your power is expensive![/b]

Yes it is!

All I can suggest in your scenario is to try the plug-in for a couple of weeks and see if it makes any difference. If at best you only break even, then ask if the quicker warmup is better for the motor.  

If it ends up costing you more money to plug-in, and the motor doesn't seem to mind, then carry on as usual.

Ah, but you see I would have to BUY and INSTALL a block heater to try it. I don't know what they cost but the ROI may not be there. I need a guinea pig to try it first and post the actual tank MPG difference. :-)

[jayman]

Oh right, you don't have a block heater already. My Prius came with one, as here in Manitoba it's a "mandatory option."

Well, I'm heading to the hobby farm this weekend, so I'll try leaving the Prius outside and see how it likes being lonely in the snowdrifts for awhile. At the very least, I want to see how the HSD reacts to weather below 0 F, if it gets that cold.

[Frank Hudon]

<div class='quotetop'>QUOTE(bruceha_2000\";p=\"54307)</div>

I'm trying to get this straight in my head.
Assumptions ($ and gallons are U.S.)[list]
Calculations[list]
[/b]

yes the calc is for the first 5 minute block of time. I'll check where the car would nomally go into S4 tomorrow and where it goes into it and tell you the difference. I only plug it in over night and not at work so it's only one partial warm start per day.
Were on winter gas here now and I filled up tonight and I've gone from a 5.85 (40.2 USG) liter per hundred kilometer average to a 5.62 (41.85 USG) average. A very slight decrease and probably not statistical enough to say it's a resounding success, but what would it be with out heat? I don't want to try and find out,I'll continue to plug it in.
It's nice to have heat almost instantly and the first few minutes see's the engine temp go from 42-43C to 37-38C and then start to climb. That is problably the water pump circulating coolant in the block and taking it from hotter areas to cooler areas inside the motor.
If you don't have a block heater, at about $125 you problaby won't recover your expense, not in one or two winters, longer term and will gas keep going up or have we seen the total spike in price? I dont' know.

[bruceha_2000]

Thanks, Frank. I'll watch my MPG numbers through the winter to see how low they go. Right now, my 1st 5 minute block hovers around 25 MPG.

If the only gain is the first 5 minutes or so, the "miles to ROI", even if I already had a block heater, would be much, much higher.

I wonder if someone who drives only a few miles/minutes to work in the morning would make out though. The people in my neighborhood that got theirs last Feb fit that driving pattern.

The engine probably never gets fully warmed. Even if it didn't get to stealth, would their MPG be significantly higher? You calc suggests a 4 MPG gain in the first 5 minute block. hmmm.

[Frank Hudon]

short trips are limited by the O2 sensors in the exhaust system. They control the length of time the engine runs to get the catylatic converts up to a stable temp. The ceramic matrix of the cat's take a long time to get warm and in turn the O2 senders get to a temp where they provide a signal to the computer to allow the car to go into S4. I left the block heater unplugged last night to be able to tell you how far I went before the ICE temp got to 70C but the bad traffic (abnormal) prevented me from getting an accurate reading. Just as a guess I'd say about another 4KM's, probably about 2.5 miles.

[Lectricar]

All this talk about block heaters...well, the good news is that there is a block heater that will fit the 2004-2005 Prius, but, the bad news is (according to my dealer and Toyota) that you have to remove the engine or transmission to install it. Yes, that's right, after having the dealer order it and then waiting for two hours to have it installed, the tech told me that it's too long and it can't be installed without removing the tranny...not a good idea.

The smartypants folks at Toyota Central initially balked at the dealer's conclusion, but they came around and offered me $150 credit for service (I accepted).

So, if it ain't there to begin with, just forget it.