Fired Up! Testing the fuel heater

by Ben N on February 7, 2016

As much as I like the all electric Mitsubishi iMiEV car, it’s Achilles Heel is the heating system. The combination of a small battery pack and inefficient heater just slays winter driving range.

So, it’s time to upgrade the heating system!

Several other iMiEV owners have experimented with “parking heaters” – fuel-burning heaters to supplement the existing electric heating system. You can read about that here.)

IMG_7664I ordered the heater a couple of weeks ago and it finally showed up the other day. Inside the box was the heater itself, radiator hose, a wire harness, and more tiny hose clamps than I care to count. I spread the items out on my living room floor to see what was there, and how it would all go together. The “Made in China” documentation was NOT particularly good, but it’s pretty obvious where the radiator hose should connect. Likewise, the wire harness isn’t hard to figure out – the four pin male connector goes to the four pin female connector, etc.

iMIEV_gas_liter

Before going through the major steps of taking the car apart, I wanted to try out the heater and see how it works. To do so, I mocked up an installation by mounting the heater and its associated parts to a wooden pallet. For fuel, I stopped by my local gas station, which sells E85 fuel. That’s 85% ethanol and 15% gasoline. In the long run, I’m planning on running the heater on 100% ethanol, but it was pretty nice to have E85 so easily available locally. I bought one-fifth of a gallon, which came to a cost of 32 cents.

IMG_7677

To mount the mock-up, I screwed the mounting bracket to the pallet, then set the furnace onto that. Next, I began connecting the fuel line, going from the heater to the 12V fuel pump, and finally to the temporary fuel tank. For that, I drilled a 1/8″ hole into the cap of a camping fuel bottle. The rigid fuel pickup goes through the hole and down into the bottle.

I also hooked up the aluminum tubing air intake into the bottle of the heater. An air filter went on the opposite end. On the exhaust side, I installed the larger aluminum exhaust pipe.

I cut the large radiator hose into two equal pieces. Those went onto the two connections on the side of the heater, one for cold water in and the other for the hot water out. I ran both hoses to a bucket of water.

The wire harness was easy to connect. One plug went to the fuel pump, and one to the small control panel. Two other wires were obviously for 12V + and – connections. I hooked those up to a large 12V battery I had around.

IMG_7679With that, the fuel-burning boiler was ready for testing. I pressed the “Heat” button on the control panel and I could hear various sounds of the heater, but mostly, I heard the shriek of the internal water pump. Many pumps are lubricated by the fluid traveling through them, and not all pumps are “self-priming”. Just turning the heater on did NOT mean that it would be powerful enough to suck water out of the bucket. I lifted the bucket up onto a stool, to make it the same height as the heater, and moments later, I could hear the water being pumped properly, which was confirmed by a sudden steady stream of water back out the other water hose.

I had NOT yet installed the muffler, as that required cutting the exhaust pipe, and I didn’t know what length I would need to cut it to for installation in the car. So, the sound of the heater was rather loud. It sounds like a jet engine – a steady roar, rather than the putt-putt-putt of an internal combustion engine.

The fuel pump makes a little noise too. It’s a “pulse” 12V pump, which makes a steady, repeating, clicking sound. It was interesting to see the fuel pumped up from the bottle with little air bubbles in it at first, then slowly going away once the fuel fully filled the line.

IMG_7710I shot some stills and motion video with my thermal camera. The exhaust pipe does get very hot, as one might expect. The water in the bucket started off at room temperature and fairly quickly heated up. It didn’t take long until there was steam rising from the top of the bucket. The rubber radiator hose is an insulator compared to the metal components. I measured water coming out of the hose at over 170 degrees F. I believe that the heater in the iMiEV tops out at 140 degrees.

Overall, it was a great first test, and I’m fairly impressed. Next, maybe I’ll just install the muffler at the very end, so I can hear what a difference it makes WITHOUT having to yet cut the exhaust pipe. I also need to measure how much fuel I used. I started with a full bottle and ran the heater for 30 minutes, so I should easily be able to calculate a volume of fuel per hour of heating.

I’m hoping to install the heater in the car sometime later this week. I also need to make an appointment to go visit the friend who makes his own ethanol, so that I can run the heater on home-brew!

Till next time, stay fired-up!
-Ben

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