Introducing a new series of fascinating interviews of Master Mechanic Chris Hill by Eric Sandstrom. Read what Mr Hill has to say about biodiesel, alternative fuels and historic road rallys!
Check back often for new content!
Here's our first installment:
On Alternative Fuels. . . Veggie Oil, Biodiesel and Kerosene. . .
Eric Sandstrom: I just don't understand it. How does veggie oil combust? Is it like diesel? Put it under enough pressure...
CH: Yeah, diesel fuel is an oil. Vegetable oil is an oil. Motor oil is an oil. They're all fuels. It all combusts.
ES: Can you explain the difference between veggie oil and biodiesel.
CH: Well, that's an entirely different thing, but the diesel engine was designed as a multiple fuel engine. It uses compression for ignition rather than spark plugs and a bundle of wires. Then all you need to do is heat up the air in the cylinder - which is what it does – and then spray any number of fuels in there and that fuel will combust immediately. So you can use heavy oils and light oils. You can use lighter fuels like thing close to gasoline but gasoline is just too volatile. It burns too fast. A diesel will run on gasoline as long as a very low compression diesel, and, in fact, they have them. They use them on farms. They were tractors that started on gasoline, then when they warmed up they were switched to diesel fuel. So they ran both fuels. They were, I want to say, 15:1 compression or something like that. That's really low for a diesel. You see, just about anything will run in a diesel engine as long as it's warm. It has to be warm and it has to have relatively high compression. 15:1 or 14:1 is the lowest it can be.
ES: So that's why they can switch over as tractors.
ES: I have a '96 Pontiac Sunfire GT, 2.4 li. It's a pretty high compression engine, I think.
CH: It's probably only about 9 or 10. High for a gas engine is usually 10 to 11. Some cars run as high as 11.8 and that's really high. I've built engines that were 14:1 that were gasoline powered, and that's really high for a gas car [laughs]. That's really high, but it's a lot of power. A whole lot.
ES: Can you just not convert a diesel engine and run other types of fuel into it?
CH: Yeah, you can. If you live in Florida, you can put vegetable oil right in the tanks, no problem. Just pour it in the tank.
ES: Why can you do it in Florida but not elsewhere?
CH: Vegetable oil is thick and it won't pump through the lines in New England and in cold weather. In the warm weather you can pour it in the tank in New England, but the problem is that it's so thick. It'll run on kerosene. It'll run on it but you won't get the same mileage because it doesn't have the same BTU content.
So yeah, you can pour those things into it. Biodiesel you can pour right into it. Any engine that runs diesel can run biodiesel.
ES: Biodiesel is what, exactly?
CH: All it is, is trans-esterfied vegetable oil. What that means is, if you take vegetable oil and you remove the glycerin (soap) from it. That's pretty much it. You mix the vegetable oil with lye (caustic soda) and methanol. When you mix it together and warm it up a touch it creates a chemical reaction where it changes the oil into another type of oil. It takes all the soap out (it settles to the bottom – that's actually how we get soap, by the way). It's made of fat. Oil is fat.