Montero Diesel Conversion

Making the choice to run biodiesel in your car can be difficult for the average driver.  As we all know, almost all passenger vehicles run on gasoline in the United States. There are very few diesel-powered cars such as the Volkswagen/Audi TDIs and Mercedes diesels, so most consumers that want to run biodiesel end up driving a large pickup truck like a Ford F250 or Chevy Duramax.

One option that is interesting to me is converting a car to diesel power. Is this difficult? How can it be done? How will I get a license tag and title for a diesel conversion? These are a few of the questions that came to my mind when I first considered the project. I decided a few years ago to embark on a research project to convert a gas car to diesel to see how it could be done.

This is the first of a series of blog posts where I will document my conversion of a 1987 Mitsubishi Montero from a 4 cylinder 2.6 liter gas engine to a 4 cylinder 2.3 liter turbo diesel engine.  Stay tuned… this should be a fun ride!

Since I advertise my use of biodiesel with bumper stickers, I’m often asked about what new vehicles are good for running biodiesel.  For this reason, I’ve done some research on new diesel cars and trucks and what I’ve found is disturbing for the biofuel movement.  Since about 2006, the Volkswagen diesels will only warrant biodiesel at a blend of B5.  I would hardly even call that biodiesel since it is really only using it as an additive.

From what I’ve read on forums of real biodiesel users, this limit is for good reason.  The electronics that control fuel flow and injection on the newer diesel engines don’t appear to be designed to run anything except for petroleum-based diesel.  According to some experts, the minor differences in viscosity and cetane rating cause problems for the newer engines and can lead to mechanical issues.

The new BMW 335d diesel here in the US also only warrants up to B5 in their diesel engine.  Experts on the BMW forums indicate that the BMW diesel uses a high pressure injection system similar to the VW TDI and will have trouble injecting biodiesel blends greater than B5.  Higher blends contaminate the oil requiring much more frequent oil changes.  They can also cause problems for the emission systems.

As US manufacturers begin offering domestic diesel cars, we need to make sure they use fuel systems compatible with at least B20 blends of biodiesel.  If this issue concerns you as well, reach out to the manufacturers and ask them to engineer support of bioidesel into their engines.  GM just announced yesterday they will bring the Chevy Cruze diesel to the US so let’s start with them and tell them we want biodiesel-compatible diesels here!

For now, it looks like I’ll need to continue maintaining my older VW diesels to preserve them for the future.

Diesel Fuel
Diesel fuel is made from petroleum and is a very efficient and energy dense fuel when used in a compression ignition engine. (diesel) It takes less energy to crack petroleum into diesel fuel than it takes to make gasoline. It also burns more efficiently in a diesel engine more miles to be traveled per gallon and producing less heat.

Biodiesel Fuel
Biodiesel is another form of diesel fuel that is made from plant oils or animal fats instead of petroleum. I run several of my personal vehicles on biodiesel including VW TDIs, a Dodge RAM and a Ford Excursion.  In order to make the oils or fats close to the same consistency as diesel fuel, it is chemically modified using an alcohol as an additional reactant and a catalyst. Typically, the alcohol reactant is methanol and the catalyst is Sodium Hydroxide or Potassium Hydroxide.

Manufacturing Process
The oil is heated to facilitate the reaction. The alcohol and catalyst are mixed together and mixed into the oil causing a chemical reaction called transesterification. Transesterification creates biodiesel fuel and a waste product called glycerine. After the reaction, the glycerine separates from the biodiesel and drops to the bottom of the reaction vessel. The biodiesel is removed, washed and dried before using it in a vehicle as fuel.

Naming Convention
Biodiesel is used in several different ways and there is a naming system to identify its type. In its purest form, biodiesel can be used without dilution direct in a diesel engine. When it is used as 100% biodiesel with no diesel mixed in, it is called B100. (‘B’ for Biodiesel and ’100′ for 100%) The more common way to use biodiesel is to dilute it with diesel fuel in several different ratios. B20 is a mixture of 20% biodiesel and 80% diesel. B50 is a mixture of 50% biodiesel and 50% diesel.

Diesel Fuel Additive
When the dilution of biodiesel drops below 10% it is usually considered to be a fuel additive similar to the way ethanol is used as a 5% additive in gasoline. B5 is the most commonly used dilution for a diesel fuel additive. 5% biodiesel and 95% diesel.

Waste Vegetable Oil
Waste Vegetable Oil or WVO can be used directly in a diesel engine by using heat to reduce the viscosity of the oil to make it closer to the consistency of diesel fuel. (Straight Vegetable Oil (SVO) can also be used in the same method described here. It is just unused vegetable oil so it is not a waste-stream-based product) Reducing the consistency allows it to flow in the fuel lines and combust properly in a diesel engine. For this to work, the fuel system on the diesel vehicle must be modified to heat the oil before combustion. Typically, WVO at temperatures of approximately 160 degrees Fahrenheit is the same consistency as diesel fuel.  I have personally run a Ford Ranger and a Mercedes on two tank WVO fuel systems.

Heat Source
Systems either use waste heat from the the engine to heat the fuel or an electric heater run off of the electrical system in the vehicle. In the case of the waste engine heat system, the vehicle is started on regular diesel and then switched to WVO once the vehicle is up to operating temperature. (typically 180-210 degrees Fahrenheit)

Two Tank Systems
The system described above for heating the fuel is typically used with a separate tank for diesel fuel and another tank for WVO. A switch mechanism is used to change the tank source once the vehicle is at operating temperature or the electric heat source has heated the fuel to the proper temperature.

One Tank Systems
There is a practice that some drivers use that leverages a one-tank system for WVO. Instead of relying solely on heat to reduce the viscosity of the oil, they mix it with diesel and/or regular unleaded gasoline (RUG) to thin out the oil. They pour the mixture into the single stock tank of the vehicle and run it in this manner. The one-tank method can be problematic in colder weather and since proper dilution of the oil can be difficult to maintain if the fuel is blended in the tank itself.

I hope this helps you with understanding the differences in the types of diesel fuel

The goal of this site is to share both experiences I’ve had in the biodiesel industry and to report on current news related to the biodiesel industry.  I hope that you will find this site informative and will share it with others.  We also encourage feedback on our posts via our comments section.

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- Veggie Ranger