fuel mileage test tank

[moTthediesel]

While many of you with newer gas powered cars can use a Scangauge or similar to get some idea of real time fuel mileage, those of us with diesels or carbureted gas cars are stuck with a more difficult task. Our test results are dependant on our ability to get consistent refills at the pump. As we all know, this makes it very difficult to accurately quantify our fuel usage, especially as filling at anything less than a nearly empty tank only increases errors in computations.

At events like the recently run Green Grand Prix, not having a very exact means of quantifying fuel used over the very short (85 miles) distance covered makes getting fair and consistent results difficult. I think maybe it’s time to consider putting together a real dedicated testing tank.

What I have in mind is something that can be assembled from common, easy to find, and inexpensive components. It should be made so that it is easy to install and plumb into the fuel system, and just as easy to remove again. It needs to handle both supply and return lines (at least on a diesel) and it should be able to be installed/removed safely, without leaking or introducing air into the fuel system.

I first I looked into using a graduated vessel, but they are expensive in large (say ten liter) sizes, and could also introduce some error in reading. I think a better way would be to use a common small red plastic “jerry jug” and measure the fuel used by weight with a common postal scale.

I’m planning to use biodiesel safe translucent hose with an outboard motor priming bulb on the supply line from the tank. This will make it easy to prime the line and check to see that there is no air that could be introduced into the system. I’m looking into quick connectors now, and I think I will use some of the type that are made for motorcycle tanks. Outboard motor connectors would work as well, but they are a bit more expensive and bulky in size.

I’d like to hear input from anyone else interested in building such a tank, and I’d also like to see any ideas about the construction and use of it posted here as well.

Thanks,
Tom

[D.O.G.]

I've thought along similar lines in the past, but didn't follow up on it.
I was looking at using an old metal lawn mower fuel tank. It already had fittings rated for petrol and was small enough to fit under the bonnet (I drive a hatchback and didn't want fuel in the cabin with me).
I was going to simply run it from full to empty, but then realised the fuel in the carby float bowl would throw out my calculations.
I think your idea of a jerry can with quick connects sounds good. It could be mounted anywhere convenient, and the larger capacity (and not running empty) will reduce measurement errors.

Pete.

[moTthediesel]

Originally Posted by D.O.G.

It already had fittings rated for petrol and was small enough to fit under the bonnet (I drive a hatchback and didn't want fuel in the cabin with me).

Yes, where to put the tank when in use is a problem. There is no way I could get any kind of tank bigger than a beer can into my crowded engine room

I'm planning on making a bracket that will hold the tank on the trailer hitch at the back of my car. I don't think it will have much of a negative aero effect there.

I picked up a 2 gallon gas jug yesterday for $12 at Harbor Freight, and some barbed fittings at Lowe's.

Then I ordered 3 pairs of these quick connectors:Tusk Fuel Line Quick Connect | Rocky Mountain ATV/MC

As soon as those come in I'll get busy on putting it all together and post some pictures here.

Tom