Tuesday, January 30, 2007

COCONUTS HILUX - Efficiency of running on coconut oil blends

In my private life, I have been experimenting with the use of coconut oil in our vehicle. It is a Toyota Hilux 2.4l and it has become some sort of a hobby to fiddle around with the car an trying different blends. I have recently posted an update on the coconuthilux pages which is a set of web-pages that display the trouble and the fun I went through with using coconut oil as a fuel.

My findings on the efficiency go:

The most frequently asked question by people when they see my 'cocopowered' sign at the back of the Hilux is what them mileage is on coconut oil. In the beginning, I could not see any change so I would respond that it is actually the same.

During the course of time, man grows wiser. Theoretically, the calorific value of coconut oil is lower than diesel. The average energy content for a litre of diesel is 42 MJ/litre and coconut oil typically shows an energy content of 38 MJ/litre. On the sole basis of these numbers, you would expect 8-9% less energy in a litre of diesel. Of course the energy content of diesel varies (with its distillation curve) and so does the energy value of coconut oil.

In addition, if the moisture content of the coconut oil you use is 2% (an analysis shows most Pacific island copra oil has 1-2% moisture), during combustion, 2% of the volume of the fuel must be evaporated out of the cylinder, absorbing energy. This obviously decreases the total efficiency, as diesel is normally 'dry'.

So it would be expected on the basis of these basic physics facts that the mileage on coconut oil is at least 10% less than diesel.

Coconut Oil proponents (Coconutters) would argue that diesel burns with a 'bang' whereas coconut oil burns more slowly, creating a more subtle force in the cylinder, increasing the overall efficiency. Laboratory tests in PNG indicate that the energy content is a good predictor of the fuel efficiency (in Litre per kWh or litre per km) so that theory is the only one standing.

Now my own experiences. It is very difficult to scientifically assess the efficiency of a vehicle if you don't equip it with a multitude of electronics and data loggers. The operational characteristics of an engine change significantly if you drive through town stopping at traffic lights and going up-hill versus off road driving or hundreds of kms driving over flat tar-sealed roads. For the coconut hilux, in the past years, all of the above apply. And all I logged is kms and litres. In addition, I've had to clean out my tank, losing fuel. We've had criminals stealing fuel from the bottom of our tank while we were relaxing at a resort. We've had a multitude of filter changes.

Nevertheless, the graph below shows the efficiency of various periods of driving (typically 1,000 - 1,500 kms) with the average percentage of coconut oil in the fuel for that period. The total period is from January 2004 through to November 2006, that is almost a three-year period.

Findings for the last three years:

The trendline, calculated with Excel shows a negative correlation with coconut oil percentage (as expected) but much higher than theory suggest! A 30% blend of coconut oil gives almost 6% less mileage in litres per km. If it is a complete linear correlation (which I do not expect), it would mean that 100% coconut oil leads to 24% less efficiency in km/litre.

The other observation one can make is that the hilux consumes a sh^&*$%*t-load of fuel to get anywhere, really.






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