Tank type heater problem

[vtec-e]

As the title suggests, i have a problem. I recently made a tank type heater with a 400W heater cartridge in it. After 1.5 hours of heating it has heated up my engine to 38.8c. and holding. It is thermosiphoning but i fear that 400W is not enough to get the heat into the engine this way.
I have a plan B though. It involves the use of a central heating pump...
I bench tested the pump and it has a good flow at its lowest setting. I don't think it will cause any harm to the engine if installed. The wattage is 45W so i would hope to have a toasty engine within an hour.
There is room in the engine bay in front of the gearbox so that wont be a problem.
Should i remodel the tank heater to take a 1kw heater element? No doubt it would thermosiphon better but maybe not well enough. Combined with the pump and it should kick ass!
Ideas?

ollie

[Daox]

In my experience with my Matrix and its block heater which is 300 or 400W, I would have liked it to have been a more powerful heater. I'd rather have the heater one for a short duration of time and heat up quickly. With that block heater, I had to keep it on for 3-4 hours every morning to get the car up to ~90-100F in the morning, ambient was normally around 20F. I can only imagine I lost a ton of heat through the aluminum block and head during 3 hours of sitting there.

[vtec-e]

Yeah the heat loss from the block must be a lot. I stuffed some fibreglass lagging in front of the block and it helped raise temps by 2 or 3 deg. Not a lot but it helped all the same.

I can't imagine a 1kw heater is very long. Depends on its intended use i guess. I'll look around.

I still like the pump idea though, might just try it and see. If only to show it doesnt work!

ollie

[vtec-e]

2 hours and its up to 104f. The 400W heater cost me 11.2c to heat it this far. I would hope to save more than that in my commute. By my calcs i would have to go from 3L/100k to 2.8L/100k to break even. Hmm....pumping the heater might be better able to offset the heat loss due to it (hopefully) heating quicker.

ollie

[orange4boy]

Hi Ollie,

I want to do this with my Prius which has two coolant pumps. I have installed a 1500watt tank heater on the transaxle coolant lines and want to do it on the engine too. 1500 watts is too much. 750 would probably be about right.

I would like to heat up the heater core too so the inside is nice and toasty. That way I can justify the cost as part of my heating bill and the lady of the house is warm and happy too. I just have to hack the pump and install a manual switch.

To keep the heat in I have installed a thermal blanket over the engine and sealed off all gaps with foam tape. After an overnight soak at 5˚C the engine is still at about 12˚ This also helps keep the car warm when you stop to do an errand.

Those 400 watt block heaters were never meant for what we are doing.

[vtec-e]

Originally Posted by orange4boy

To keep the heat in I have installed a thermal blanket over the engine and sealed off all gaps with foam tape.

Good point. Even with my factory belly pan there are quite a few gaps, sorry cavernous openings!
I've started the pump installation and it is proving to be tricky. I had hoped to join the heater to the pump but there is not much room as it turns out. So i will have the heater up behind the engine at the firewall and the pump under the gearbox, with the relevant pipework connecting the two. Pics tomorrow and hopefully some decent temps.

ollie

[orange4boy]

The top of the engine compartment is where I concentrated my sealing efforts. I even have two removable upper grille blockers to finish the job that I only take off for long trips.

The 1500 watt number gets my transaxle into the 60's! (˚C) My goal is to get the motor there too so I can be at full operating temperature before I turn the key.

Cool that you are doing a pump install too. Can't wait for the pics.

[vtec-e]

Marcus, what does the extra water pump in the prius look like? Is it part of the engine like all other cars or is it external to the engine? If it is external then a scrapyard one would suit me perfectly. The central heating pump is a bit of a beast actually! Couldn't find anything suitable, ie: temperature,pressure and affordability.....hmmmm

[MetroMPG]

Originally Posted by orange4boy

To keep the heat in I have installed a thermal blanket over the engine and sealed off all gaps with foam tape. After an overnight soak at 5˚C the engine is still at about 12˚

I wonder: did you measure it without the insulation? I assume the engine would be at ambient after sitting over night.

[orange4boy]

Yes, the engine and transaxle get to ambient overnight without the blanket and sealing. I have to get busy and post some pics. Think of you engine bay like an inverted grocery floor freezer. The hot air rises and gets trapped in the engine compartment if it can't escape through any holes in the top. The opposite of a freezer where the cold air sinks. It helps to have a belly pan bit isn't essential unless it's windy. I used my face to feel for warm leaks.

I learned from building my house that tiny leaks can cause a lot of air to escape over time. If you have them, eliminating air leaks is way more important than improving insulation and leaving the air leaks.

There are two external plastic coolant pumps on the 2000-2003 prius and three on the 2004-2009. (one for the coolant thermos) The best one for your use would probably be the cabin heat/heater core pump. It has a one way valve and it's meant for full temperature and pressure. It's probably cheaper than the inverter pump which is often replaced around 100,000 miles. It sits under the inverter and is easy to identify from the 5/8" ID hoses coming off it. The inverter pump is in front of the inverter behind the driver headlight.