Sunday, June 22, 2008

Biodiesel versus Vegetable Oil

In the 1890's Rudolf Diesel designed the original diesel engine to run on vegetable oil, but modern diesel engines are intended to run on petroleum diesel (NOTE:  If you buy your gas from Mobil, BP and/or Valero, you buy "terrorist oil".  Sunoco oil is not purchased from Saudi Arabia or Hugo "Butthead" Chavez.  See  Quit funding the Saudi's, Iran and Al-Quada!)

(And of course, I digress again....)

For those interested in making their own fuel for diesel engines, the world of biofuels offers two options; biodiesel or vegetable oil.  Using biodiesel requires modifications to the vegetable oil itself; using straight vegetable oil requires modification to the diesel engine.

Both biofuels have pros and cons, plus complicated nuances to their use and production.  But for those with enough patience and enthusiasm to embrace biodiesel or vegie oil fuel, the rewards can be great.

For starters, straight vegetable oil is too thick to burn in a standard diesel engine.  In cool weather, it becomes thick as butter, clogging fuel lines and injectors.  But a diesel vehicle can be modified to run on straight vegetable oil by using either a dual-tank or single-tank fuel system.

The dual-tank system requires one tank for diesel and another for vegetable oil - plus a system to switch from one fuel to the other.  The engine starts on diesel fuel, but switches to run on vegetable oil after heat produced by the engine warms the vegetable oil to about 160 degrees Fahrenheit.  Before shutting off the vehicle, diesel fuel is cycled through the fuel lines to purge the system of vegetable oil.  Because diesel fuel is required for starting the vehicle and clearing the lines before shutting down, a dual-tank system is better suited to vehicles that run for extended periods or distances.  A single-tank system preheats the vegetable oil using electric heat (plus the additional heat produced by the engine when it's running) and uses modified injectors and glow plugs that are optimally suited to ignite and combust vegetable oil.  (New diesel engines have precise fuel requirements that need to match the chemistry of the oil, but older engines have a better tolerance for a range of vegetable oils).  

(NOTE: How I wish'd I'd taken Shop in high school - but NO.....I was an art fag!)

Original article written by:  Derek Kanwischer

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