Dreams of a Diesel MINI

Posted by murmini Fri, 01 Jun 2007 22:01:39 GMT

Having just spent a weekend converting my son's girlfriend's 2003 VW Jetta to veggie oil, I can't help but consider what fun it would be to have a MINI Cooper Diesel and do the same.

Tank.JpgThe conversion was quite simple. In principle, you add a second fuel tank for the waste veggie oil, in this instance we used the greasecar tank, which is custom made for the Jetta and sits directly in the spare tire well.

I should explain the principle of how this conversion works. Obviously one of the biggest differences between used veggie oil and diesel is viscosity. Diesel is thin, flows easily and is easy to pump and inject into a diesel engine. Veggie oil, on the other hand, has the viscosity of honey and would pretty quickly gum up the injectors, the pump and any filters or fuel lines.

So the answer is to heat up the oil until it is the same viscosity as normal diesel and this is achieved in two stages. Firstly, back in the fuel tank in the spare tire well and again just prior to injection. The best and most reliable source of heat is the car's coolant system.  Water and coolant is pumped around the engine block to take the heat out of the engine, cooled in the car's radiator and pumped back to the block. Most vehicles coolant temperatures are around 160 - 190 degrees so this is ideal. So we simply tap into the heater feed pipe with a T-piece and feed a water hose back to the veggie tank.

CoilInside the tank is a simple two-turn copper coil so that this hot water can warm up the oil in preparation to passing it up to the engine. The return water pipe goes back to the engine and inserted in this is a piece of plex piping which caries the veggie oil, kept hot by the flowing water. We made it a little bit more complicated by routing the water pipes back to the engine compartment by concealing them up under the exhaust heat shield for the full length of the floor. instead of just fixing it to the underside of the car, where it would be vulnerable to being damaged.
Vlcsnap-13085592So with the hot water lines and veggie oil line installed the next pice to install was the pre-heater that gets the veggie oil up to the final temp again, just before going into the fuel pump and injectors. Again, this is a water heated coil that surrounds the veggie oil filter. he hot water flows around the filter in a copper coil and heats the veggie oil to its final temperature prior to the fuel pump and the injectors.

Vlcsnap-13102747Then two electronic valves are installed and wired to a three-way switch that allows you to select diesel, veggie or purge. The purge function is imperative as you never what the engine to cool down with veggie in the fuel lines. Purging simply forces diesel back through the system to remove any veggie oil. Simply, you start on diesel, run until the engine and coolant is warmed up and then switch to veggie. When you stop, you simply purge for about 15 seconds, then switch to diesel and switch off.

Vlcsnap-13107944-2All this is conveniently controlled from the dashboard adjacent to the veggies tank gauge we installed under the center dash, just under the air conditioner controls. We tested everything, did some preliminary test on diesel then once everything was warmed up, we switched to veggie. On road tests we detected no significant change in performance and if anything, the engine seemed to run a little quieter. Subsequent tests have proven that we are getting about the same level of fuel economy on veggie as we are on diesel, about 50 mpg.  The car is capable of carrying 13 gallons of veggie oil as well as its normal diesel capacity giving a total range of about 1100 miles.

They seem to be getting good responses  from the restaurants they have approached once they actually believe what they are doing!  The used oil has to be filtered through a 10 and then 5 micron bag filter, but that's not much of an inconvenience for free fuel.

Now... if we could only get our hands on one of those MINI Ds.... just think of the fun we could have!!!

2 comments

Comments

  1. Ian C. said 2 days later:

    Excellent descriptions, thanks Murray!

    Did you see that one of the two New England MINI owners BABE Rally entries was a converted-to-veggie Mercedes?! http://vegginator.blogspot.com/ From Cambridge to New Orleans was 1,835 miles. Along the way we used 2 tanks of diesel and approximately 137 gallons of vegetable oil

  2. murmini said 6 days later:

    Great article Ian, thanks for the link…

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