How to Make your Own Fuel #4

So what sort of cars run best on biofuels?

Well, in principle any diesel will run on biodiesel or SVO (straight vegetable oil). Most people run older, indirect injection engines, and the best of the lot are the old Mercedes diesels.

One thing you need to take into account if you are running biodiesel is that it is a more aggressive solvent than regular diesel and can potentially chew out the rubber seals in your fuel injection pump. This is not a major problem, as you can get it rebuilt with Viton seals, which solves the problem.

This is not cheap, but as a one off expense it quickly pays for itself with the cost of diesel these days.

Can you run a modern, common-rail engine on biodiesel? I think the answer is yes, but there are lots of people that say no. I think this is for a couple of reasons. Firstly, the manufacturers warn against it, mostly because I think they don’t want people putting fuel into their cars  that they made in their backyard, and then coming to them for a warranty claim.

The second reason I think is that a lot of people that make BD in their backyard don’t know what they are doing, and can make fuel that can damage an engine. The issue with common rail engines is the higher injection pressure, and BD is more viscous than regular diesel, so this is another cause of concern.

But for 10 people who say you can’t run a certain car on BD, all you need is one person who says they can, and you have your answer. And I have yet to find a car that someone, somewhere, is not running on biodiesel

How to Make Your Own Fuel #3

Right, now we get into a bit of chemistry.

Your diesel car will run fine on cooking oil but it’s too viscous, so what we have to do is reduce the viscosity. This is the only reason you need to modify the oil. It’s all about viscosity, so that when your car starts from cold in the morning, the liquid is thin enough that your injectors can inject it into the engine.

So how do we modify it? Well let’s have a look at what an oil molecule looks like. Essentially it’s shaped like an uppercase E. The horizontal lines are long carbon chains and the vertical line is a three carbon glyceride. This is where we get that term triglyceride from. The physical structure of the molecule makes it quite bulky, and this is why oil is quite thick, as the bulky structure means that the molecules don’t flow over each other very easily.

So to reduce the viscosity, we need to break up this structure. Essentially what we are doing is splitting off the three horizontal carbon chains from the glyceride backbone.

This is done with a process called transesterification.

if you look on the web you will find plenty of information about it, but unfortunately, a lot of it is wrong. The standard method of doing this involves complex measurements of the oil content, followed by a process where the oil is heated, and then cleaning processes afterwards. The reason that people use these methods is that they don’t understand much chemistry.

For this reason, I designed my own method, which is foolproof and works at room temperature. Details are here. Tomorrow I’ll talk about which cars run best on bio diesel

How to Make Your Own Fuel #2

The only reason you can’t run your car on straight vegetable oil is the viscosity.
It’s OK when hot, but too thick when cold. So you have two choices – either you modify your car or modify your fuel.

If you are going to modify your car, you simply add an extra fuel tank for starting and stopping. You start the car on regular diesel, then when the motor is warm you switch over to the oil. Before you stop, you then just switch back to the diesel.

This is a little like having a dual fuel car, so all the switches and valves and solenoids are readily available. The only decision you need to make is where you’re going to put the extra fuel tank. Because it’s only used for starting and stopping, it doesn’t need to be very big – 10L is plenty. On older cars, a popular spot is inside the engine bay.

The only other modification you need to consider is heating your fuel lines, so the thicker oil can flow from your tank to the engine bay. This is generally done by branching off your cooling system, and it’s possible to get tube-in-tube designs where the fuel line is encased with a cooling line.

The acronym for this option is SVO (Straight Vegetable Oil) and there are plenty of online forums around where the logistics of this process are discussed.
The idea, of course, is that you use waste cooking oil as your fuel, which can be obtained from fish and chip shops and restaurants.

It’s not as easy to get as it used to be, however, as there are now lots of people making their own fuel, so you might have to do a bit of scoping around to find a supplier.

One option of course is fat. Fat is much easier to obtain than cooking oil, as it is more commonly used (and is cheaper).
There are two obvious problems with fat, however – how do you collect it, and how are you going to get it into your tank as fuel?

One option would be to fit an tank into the boot of your car with a wide mouth or clip on lid. Into the bottom of your tank you run a line from your cooling system, so it would melt the oil. With this approach, having a heated line would be mandatory, to stop the fat solidifying as soon as it left the tank.

Tomorrow we’ll look at the other option – modifying the fuel.

How to Make Your Own Fuel

I love diesels for several reasons. One reason is that you can make your own fuel.

A little known fact about diesels is that they were originally designed as an alternative to petroleum fuels. In fact, the very first diesel motor ran on peanut oil.
So what would happen if you tipped some vegetable oil into your diesel fuel tank? Well, nothing. That is, your motor would run fine, and your exhaust would smell like a barbecue. The only problem that would occur is when you turned off your engine and allowed it to cool. When you tried to start it again, it wouldn’t start.

The reason for this is simply viscosity. That is, the injectors in your engine are designed for low viscosity petroleum-based diesel, and not for the thicker vegetable oil.

So if you want to run your car on vegetable oil, this is the only problem you need to get around. There are two ways to do it – you either modify your car, or modify your fuel.

Tomorrow we’ll start looking at how to do it.