Mini experiments: 300w vs. 800w block heater warm up time
 

I thought I had done this already with my 300w external bolt-on block heater, but I couldn't find the data anywhere on my computer.

Moot point. I've since added an 800w inline coolant heater, and haven't collected any info from it yet.

So, what I'm going to do is plug the car in & check the temperature every 15 minutes for an hour or so.

The results will be skewed somewhat by the fact that the coolant is not heated uniformly, and I need to run the engine briefly to get an accurate temperature reading.

I know the coolant temp isn't uniform because when I read the temp on the ScanGauge before I start the engine, it gives me a value that's significantly lower than the value I see within a few seconds of starting the engine.

So the water pump has to circulate things briefly to mix it up and get an accurate (or "average") reading from the coolant temp sensor.

I can say with some confidence it's not the heat of combustion responsible for the temp jump, because it's quite large (say 50 degrees F) and shows up on the SG within 10 seconds.

The best way to run the test might be to take off the belt & spin the water pump manually/electrically, but I can't think of anything offhand that I can use to do that easily.

Anyway, I'll report back later with some DATA! ...

Oh, another fly in the ointment:

By circulating the coolant every 15 minutes to get a temperature reading, I'm probably distributing the heat differently than the convective currents would on their own.

Meaning, not counting the small amount of additional heat I'm adding from combustion, the final temp by this method will probably be different than if I just plug it in and leave it for the same amount of time.

Still, I'll carry on.

Looking forward to the results Darin. Could you please show a picture or a diagram of the placement of the heater as well for visual reference?

Results!

Darin,
Do you think there would be any hit in FE if you used the heater for 45 minutes instead of the 2 hours? I think the Prius holds the temp at 125 in the coolant reservoir and in 45 minutes you're sitting at 136. You might need to do a test on that:D Nice results by the way.

Yeah, talk about diminishing returns, eh?

Fact is, I never plug in for more than an hour anyway; I just did the 1:45 today for the purposes of the graph. 30-45 minutes is more typical.

Now that I've charted it, I can see that anything more than an hour and 15 minutes (#6) is probably not worthwhile in terms of return on time & energy invested.


Note that this probably isn't directly applicable to other cars. The 993 cc motor in the Firefly is a smaller heat sink. I'd guess that bigger motors may "level out" at a higher temperature (though they'll take longer to get there @ the same 800w).

I may do some other tests - like compare this to the performance of the 300w external heater (it's still bolted to the motor).

Also, I have plugged them both in at once a few times on really cold days.

It would be interesting to see the comparison of time compared to temperature.

How long would it take to get to 135 when it's -20 outside compare to 30?

I've read that block heaters are best when on consistently at a lower setting in terms of engine wear. This seems supported by intuition, in that the same amount of heat over a longer time will result in a better distribution of heat through the engine. The thermal conductivity of Fe also drops as the temperature increases, which could exacerbate this. Since automatics tend to rev higher when cold, presumably to heat up the rings and avoid excessive wear and oil contamination, I wonder how effective a block heater would be at reducing wear given the ECU would think the engine is warmer than it actually is and the warmup portion would be somewhat retarded. Manuals of course are in the hands of the driver at anything other than idle.

Also, I think a significant portion of fuel consumption at startup involves a rich mixture lighting off the catalytic converter/s, and I wonder how much fuel block heaters save compared to cold. I imagine a car with a single pre-cat oxygen sensor would likely realize a greater decrease in consumption compared to a car with a pre and post-cat oxygen sensor, so testing in that case would likely be fruitless, but testing the second system could provide useful info as to how much fuel consumption is associated with the higher idle, and how much is associated with lighting off the emissions system.

In any event, it seems that less over more is better than more over less for engine wear, but I imagine both are better than nothing in the cold.

I suspect the plot would just be shifted up or down relative to ambient temperature. IE - if it's 30 F degrees colder, things will level out @ about 131 F instead of 161.

I think the inline or frost plug installation is best for that reason - heating the water jacket is the best way to spread the energy throughout the block as evenly as possible. My external bolt-on heater is probably the worst, in terms of uneven heating & the stresses that result (not to mention far less efficient).

If heating up quickly is a bad thing in terms of wear, then this 800w unit pales in comparison to simply starting up a cold engine.

(I think you're saying the same thing there.)

Another point I often bring up: I don't use the block heater only for reasons of fuel / wear reduction. I really like being warm sooner.

This makes me rethink the amount of time I need the heater on for my VX.
Could you find the total amount of fluid in your cooling system? That would help to make a reference point for others to use in making a rough guesstimate of how long to run a heater in their car. You could also get the dimensions of the radiator and block in order to further the reference point.

Then Ben (SVOboy) could send me his SuperMID so I could do the same experiment in my VX and post results for the other VX owners. But now I might be going too far, lol. :D

Good info!

I've always shot for about an hour of plug-in time, based on not much more than an educated guess.

roflwofl: Don't overthink it! What difference does a/t vs m/t make? They both have ECUs to control idle... I use it only for wear reduction- if the cold bothered me, I wouldn't live here!

In an a/t the ECU/s prevent excessive load when cold by revving higher, which limits the peak force on the rings as well as heating them up faster via friction losses than if it shifted like normal with higher peak cylinder pressure and lower load. Seems to be significant compared to the m/t driver who short shifts IMO. Clearly not the be all end all, but something...

More data!

I repeated the test with the 300w external block heater. This is a bolt-on element style unit like this:


Results:

What's the wattage again? (Sorry, being lazy - I know you mentioned it in your installation thread.)

3.9 litres / 4.1 quarts.

I wonder if a better measure for comparison's sake might be the weight of the engine. The Suzuki 1.0L mill weighs about 135 lbs.

400Watts

This makes me think even more....does the firefly have an iron block and aluminum head? That 135 lbs. for a 1L 3 cylinder motor is really heavy! IIRC the 1.5L block in my VX weighs in at ~140 lbs. The block and head are aluminum with an iron sleeve pressed into the aluminum for the combustion chambers. Open block design as well.

It might not be a very measurable difference for the thermal conductance between iron and aluminum blocks especially when you have coolant in the mix as well.

Oh, Oh, just found some info:

Thermal conductivity of pure aluminum:

• Temp 68°F = 118 (Btu/(hr oF ft2/ft))
• Temp 200°F = 124 (Btu/(hr oF ft2/ft))
• Temp 400°F = 144 (Btu/(hr oF ft2/ft))

Thermal conductivity of Cast Iron, gray:

• Temp 70°F = 27-46 (Btu/(hr oF ft2/ft))

Thermal conductivity of Iron, nodular pearlitic:

• Temp 212°F = 18 (Btu/(hr oF ft2/ft))

Seems strange that they aren't really comparing the metals at the same temperature. I got the info from HERE.

"The block and head are aluminum with an iron sleeve pressed into the aluminum for the combustion chambers. Open block design as well."

That's some crazy schnizz.

Tom: I'm not sure if it's an Al or Fe block, but I suspect it's Fe.

More data!

This time I plugged in both heaters at once (1050w @ 120v, according to the kill-a-watt). And... blew the breaker! (I was also running a hair dryer at the time inside the ForkenSwift to defrost the windshield :o).

So I unplugged the hair dryer, and this is what I got:

(EDIT : note the ambient temp was highest for this test)



I find the plateau @ 172F interesting. I guess the engine/cooling system had reached equilibrium with energy in & heat loss. My other thought was perhaps the local temp @ the thermostat caused it to open and permit cold coolant in.

I like your tests.

Is it safe to say that, as a general rule, heaters should be plugged in from 45 min to 1 1/2 hours, regardless of ambient temp, no more and no less?

I think it's relatively safe to say that for an engine of approximately this size/mass.

I think a significantly larger engine would have a different warm-up profile.

Anyone? :)

Just some quick figuring based on standard energy conversion factors

If you run your 800 watt block heater smartly for an hour in the morning, that would be 0.022 gallons equivalent. If you are lazy and plug it in when you get home and run it for 10+ hours that would be a quarter of a gallon and a lot of electricity doing nothing for 9 hours.

edit: it *should* take more time (and energy) to warm up a larger engine. This is based on a motorcycle sized metro engine.

.022 gal to get near to operating temps... Any estimates on the fuel used to idle up to temp, or the fuel wasted by not being up to temp while beginning your drive? It seems moot to me.

is 0.022 gal equiv based on dollars, or energy conversion?

I just installed a soft plug block heater in my insight yesterday and used it last night for the first time. It uses 400 watts according to my kill-a-watt

I plug it in in the evening, but that is on a timer which turns on at about 6am and off at 8:30 or so. that gives me time on days where I'm a bit late or a bit early.

I don't have a thermometer at my house right now so ambient temps are from weather undergrounds history data.

At 6am it was approx 38f, I unplugged and started the car at 8am. The Scangauge said 112f and didn't drop.

I will change the start time to 7am tonight and see what its at tomorrow morning.

This general rule may work for most places, but not some the coldest of places on earth..like Winnipeg! I lived there for a year and a half and would leave the block heater plugged in alllll night and some mornings the Integra would still chug and scrape as it turned over. (it would send chills up my spine..along with the wind) Mind you, it was -40C or below when this happened..yea below..but out there I had my timer set for 4 hrs + before I had to drive it to work. Eventually, I just left it plugged in all the time, especially in January & February.

Those winters are so hard on cars, hard on all the rubbers, hard on everything. Thankfully I'm in Ontario now!:thumbup:

Very interesting read btw,

Ken

I'm not all that far from Winnipeg...

Since I ride my bike in the winter as much as possible, I have some of this: Gerbing's Heated Clothing, and I find it much more enjoyable for use in a car than waiting for the heat to come up in a car. (My parents fleet has no block heaters).

My jacket liner consumes 77w at full tilt, (which I can't operate at full tilt until it's in the teens or below, ON THE BIKE with windchill), and the gloves 22w, though they seem more susceptible to the windchill. I can't operate them at full blast inside a car, either.

My kit probably cost as much as your Forkenswift, but if you can find the stuff used, (it does last a long time), you might find it preferable... :thumbup:

I've heard about the cars left plugged in 24/7, as well as the ones left idling constantly, and the oil/batteries brought in the house at night!

I'd love to see someone repeat this test @ -40c.

Atomic: I prefer a hot engine AND warm air from the heater, and the coolant heater gets me both :P. But there are times I've been sailing where I would like 100w worth of heat in my clothes!

The best block heater I heard of was for the Ural, a Soviet military truck. Legend has it that on really cold days you could just build a fire under the engine to warm it up.

Has anybody tried a Thermos-style coolant storage arrangement ala Prius? I tried it a few years ago, but the Thermos only had about 1.5 litres capacity and the hoses were poorly insulated, so it barely worked. But I'm up for trying it again.

Where to buy Inline circulating tank heater
 

Any idea where to buy one of these inline circulating tank heaters for a 1990 Geo Metro? 5-speed 1.0l if it matters. thanks.

Try here, they ship to US and Canada via USPS:

http://http://www.warehouseautoparts...ank_heater.htm

There's 6.4 Qts of coolant according to my manual in a 1.0 Firefly/Metro/Swift so a 500W tank heater would do the trick. 850W is prob over kill..

Amazon also sells em. I went to Canadian tire and their cheapest Tank circulating heater was 75$ before tax. So I'm just going to order one too.

Engine block heater information
 

I have a Ford Escape Hybrid with an engine block heater. If the vehicle is left outdoors in the dead of winter-subzero temperatures, 75 mintues will not be long enough to raise the coolant/block to normal temperatures created by use of the engine block heater. My engine block heater uses around 430 watts and...I have a connection to the hybrid battery heater. Pre-heating this item prior to your AM start is extremely important and allows one to get into electric mode like one mile into their journey even when the outside air temperature is at or below zero. One also need to consider a front grille block to preserve the heat gain in the engine block area.

With my 550W coolant heater installed and winter approaching I thought I'd do a test similar to MetroMPG's. I plan to test warm-up times both for the heater, and for idling (starting with cold engine) to see the difference. Yes, it's a waste of fuel (and a source of pollution), but it is in the name of scientific research. Plus I'll do it before a planned drive, so that should partially offset any bad side effects. If I install an oil pan heater, then I'll also test it with and without the coolant heater.

I would like my results to be comparable with MetroMPG's, but before I start I'd like to know if I should pay attention to anything else. Wishlist, anyone?

In his tests MetroMPG idled for 30 seconds every 15 minutes to pump the coolant throught the block, but it turned out that even that added enough energy to skew the results towards the end of the test (and maybe in the beginning too, but that's hard to quantify without an electric water pump). So, maybe I should idle for only 15 or 20 seconds to reduce the effect of combustion heat? But is that enough to thoroughly mix the coolant inside the engine?

I did the test today. It was around 0°C (32°F) this morning when I started, light drizzle. I idled for 30 seconds every 15 minutes, recording the coolant temperature on the ScanGauge when starting and when stopping the engine. I noticed that right after starting the engine the 'old' (when the engine was previously stopped) temperature showed for 5-10s before it was updated. I also recorded the total energy used by the heater.

During the test the grilles were blocked, but I removed my thermal insulation. I replaced it after 2:30h, so the last 30 minutes of the test were with the insulation.

time	coolant temperature - start (°C)	coolant temperature - 30s later (°C)	total energy used (kWh)
0:00	1	1	0.00
0:15	1	9	0.15
0:30	10	17	0.27
0:45	18	23	0.40
1:00	23	27	0.54
1:15	25	31	0.67
1:30	28	33	0.81
1:45	31	35	0.93
2:00	33	37	1.07
2:15	35	39	1.20
2:30	36	40	1.33
2:45	38	42	1.49
3:00	39	42	1.60

http://ecomodder.com/forum/attachmen...1&d=1292190365

Good experiment.

Did you discover anything that'll change how you use your coolant heater?

Not really anything I didn't already know from your experiments, but I do have hard numbers for my engine that I can crunch. I'll have to sit down and use my fingers and toes to count a few things once I do an idling warm-up test.

It may seem that plugging in isn't worth while past 90 minutes, but the truth may be different: Short durations of heating only warm up the coolant, but the more time that goes by, the more heat is soaked up by the engine block. So even though the coolant's temperature isn't rising as fast, there is still heat being accumulated in the engine. Of course, once the block gets warm it starts to radiate more heat, and an aluminum block is probably better at radiating than at accumulating, so for now I'll work on better thermal insulation.

I also learned that going outside to the car every 15 minutes is not compatible with doing lots of other things at home at the same time (cooking, baking, cleaning, etc.). Thankfully I'll only have to do this one more time (when I get a heating pad installed).

Ha! I forgot about that. It was a big time-waster. (I mean, not counting the gains in the name of science!)

I'm wondering if another experiment might be needed...

When we start the car every 15 minutes to check temperature, we're likely lowering the coolant temperature in the vicinity of the heater. This will improve the thermal transfer by increasing the temperature difference between the heater and the coolant surrounding it.

How much does convection/conduction mitigate this? I have no clue.

In actual usage, I turn on my block heater and only crank the engine after 1-2 hours (when I'm ready to go to work.) In theory, would less heat have been transferred to my coolant than if I had cranked the engine every 15 minutes?

As someone mentioned earlier, the intermittent idling will also contribute some amount to heating the coolant.

To redo this experiment would require several nights with consistent outdoor temperature:

Day 1: run heater for 15 minutes, crank engine to mix coolant, check temp.
Day 2: run heater for 30 minutes, crank engine to mix coolant, check temp.
Day 3: run heater for 45 minutes, crank engine to mix coolant, check temp.
...
...
Day X: run heater for 15*X minutes, minutes, crank engine to mix coolant, check temp.

Maybe This is something I can try soon! =)

My car came with a 400 Watt true block heater from the factory. The elements are right in the block underneath the head. I find that just 15 minutes of use makes all the difference in the world as far as getting the thing started. I get no white smoke from incomplete diesel combustion and the starter spins the crank much faster. If I leave it on for 30 to 45 minutes I get heat out of my heater a lot quicker. I might mention that I have a 3.0L diesel with a cast iron block and head.

I guess this shows what putting the heat where it matters most can do. :D

That's a good idea! I've been making a mental note of outdoor temperature, heating time and coolant temperature, but my mental notepad got a memory overflow error (I've got the old model with only a few bytes of memory:rolleyes:). I should make a habit of writing it all down in my trip log.

Looks like you've got a big ol' AC powered glow plug. :jealous: