My 1970 Mercedes 220D Veggie Car

As part of my “no nonsense” series on bio and alternative fuels, I covered biodiesel and straight vegetable oil (SVO) and waste vegetable oil (WVO) diesel conversions.  Since I believe in experimenting first-hand with topics I discuss, a few years ago, I worked with a local company to convert a restored 1970 Mercedes 220D to run on vegetable oil.  I have had one other veggie car before “Helga” the Mercedes and you can read about the “Veggie Ranger” conversion on Greasology.com.

Restored Vintage Mercedes 220D Diesel

Why did I pick an old Mercedes?

Even though the first diesel engines built by Rudolf Diesel in the late 1800′s ran on plant oils, modern diesel engines are far removed from those first engines.  They use direct injection with high pressure common rail fuel systems with computerized injection and timing.  They use sensors everywhere that expect a fuel that has the same viscosity and cetane rating as diesel fuel.  They are also not very tolerant to water in the fuel

Helga the Veggie Mercedes interior

The 2.2 liter, indirect-injected, mechanical diesel in the Mercedes 220D is much closer to the first diesel engines and is a much more forgiving and tolerant engine for burning alternative fuels.  There are no computers or sensors.  Combustion occurs in a “pre-combustion” chamber off the side of the main cylinder (there are four of them).  This helps prevent carbonization of the piston rings in the cylinders since unspent fuel is carbonized in the pre-combustion chamber instead of in the cylinder.  This is very important for diesel engines that are run on vegetable oil.  It is common for veggie fuel to enter the combustion chamber at lower than optimal temperature which causes the fuel to be sprayed in a less than optimal pattern.  This causes some of the fuel to carbonize on the walls of the combustion chamber.  In modern diesel engines, fuel is injected directly into the cylinder.  Therefore, the carbonization occurs on the head of the piston and eventually on the walls of the cylinders.  This causes carbonization on the piston rings which eventually fouls them causing breakage and a dead engine.

Helga's Converted Engine Bay

There are some sophisticated and well-designed vegetable oil conversions such as the Frybrid and Vegistroke conversions that are designed to perform on modern, direct injection diesel engines but still require a very careful fuel preparation system.  This is a highly debated topic in the Grease Community but my recommendation would be to go with an older indirect injection diesel engine if you want to experiment with veggie fuel.

Helga's Veggie Fuel Tank

How Does the Conversion Work?

Helga has a coolant-heated, two tank system with a looped return.  There are two parallel fuel systems that connect before the injection pump on the supply side and after the injection pump on the return side.  It was designed by Rob del Bueno of Vegenergy Fuel Systems and installed by Dezso Gavaller.  Rob is an experienced resource in the biofuel industry and is the star of the VegMyRide Instructional DVD on converting a diesel vehicle to vegetable oil.  You can order the video direct from Rob if you want a copy (link coming soon).  It includes all of the conversion fuel diagrams including the system installed in Helga.  Here is a brief description of the system:

1. A custom-welded tank with an integrated heat exchanger.  Coolant from the engine is looped through the heat exchanger welded into the tank to heat the vegetable oil.
2. Hose on hose (HOH) fuel lines from the fuel tank to the heated fuel filter. The coolant lines that take engine coolant to and from the engine are wrapped together with the vegetable oil fuel line as it runs from the tank to the fuel filter.  This keeps the fuel heated from the tank to the fuel filter
3. Coolant-heated fuel filter on the vegetable oil side of the fuel system. The head of the filter is a coolant-based heat exchanger that also uses waste heat from the engine to heat the oil coming from the fuel tank.
4. Arctic fox inline coolant-based heat exchanger. This is the last point of heating the fuel before it flows through the valve and into the injection pump.  Coolant that leaves the engine is at its hottest point so it flows first through the arctic fox, then through the fuel filter and then onto the fuel tank through the HOH lines to the tank.
5. Switching valves. One switches the fuel source from diesel to vegetable oil.  The second valve switches between returning diesel to the diesel tank and looping the return back into the fuel supply line.  The loop is used when the system is running on vegetable oil and during the diesel purge process.

How do I Operate the System?

When you first start the engine, the fuel system should be set to diesel and return. (there are two switches)  the engine is cranked and warmed up on diesel fuel.  Once the engine reaches operating temperature, both switches are flipped to the right simultaneously switching the fuel system to veggie and the return to a looped return.  You can now drive on veggie until you’re approaching your destination or you start to run out of vegetable oil.  When you are a few minutes from your destination, you need to begin the diesel purge process.  Flip the fuel selection switch back to diesel but leave the return switch on looped return.  Diesel enters the fuel system and return loop diluting the vegetable oil until it is almost completely diesel fuel.  This is usually about 1-2 minutes in Helga when driving on the highway at 65mph.  Once the system is purged, the return switch is flipped back to diesel return.

Helga's Veggie System Control - diesel/veg on left, return on the right

Pro’s and Con’s?

My overall experience with this car was positive.  However, I was very meticulous in doing research on the right vehicle, picking a well-designed conversion and performing proper filtration and dewatering of the fuel.

Pro’s

• Once I had the operating procedure down, the system was easy to operate.
• I used approximately 90% vegetable oil fuel on my 80 mile daily commute to and from work.
• I didn’t have any vegetable-oil related problems with the vehicle or fuel system during the year and a half that I used Helga as a daily commuter
• I only replaced the veggie filter one time during the time I owned her.
• The exhaust smells like french fries.
• There is no particulate in the exhaust so it doesn’t bother folks with breathing issues like asthma.

Con’s

• The conversion cost around $1700 installed.
• Fuel acquisition from restaurants is competitive, time consuming and messy
• Fuel preparation is messy and time consuming
• Most diesel mechanics won’t work on your veggie car or truck

Overall, I enjoyed running my two veggie vehicles and didn’t have any issues with the conversions or driveability.  However, they were well-designed and I took the proper precautions and procedures when preparing the vegetable oil for use.  I also perform most of my own vehicle maintenance and would consider myself an advanced “shade tree” mechanic.  I would not recommend veggie cars to someone that is not mechanically-inclined unless you find an installer that will provide all of your vehicle maintenance for you.

For more information on using vegetable oil as a diesel fuel, see the following “NotPetroleum-approved” internet sources:

Greasology.org

InfoPop SVO forum

Frybrid Forum

Vegistroke site