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LESSON 4 Putting together all of the pieces. Now that you have a basic understanding of how vegetable oil can be used as fuel in a diesel engine, now we need to learn how to modify a diesel engine to burn vegetable oil as a fuel. (otherwise known as, "how to install an auxiliary heated fuel system for a diesel engine!") Two Tank vs. Single Tank Systems There are two schools of thought on how to build a veggie conversion for a passenger vehicle or truck. In warmer environments, some pioneers modified the existing tank and fuel system to add heat to the fuel before injection. This is still done today but there is much controversy on whether the fuel is hot enough for proper combustion. The Fuel Tank In order to heat the fuel, the existing fuel tank is often modified to add a heat source within the tank. This is accomplished either by inserting a heat exchanger into the tank usually by attaching it to a replacement assembly that contains the fuel pickup, return line, fuel level indicator and heat exchanger. This can be heated either by circulating engine coolant through the heat exchanger or, more commonly, adding 12v power to a heating coil. Both systems, if properly designed, are efficient at heating the oil enough to keep it flowing into the fuel lines to be delivered to the engine bay. In colder climates, most tanks are insulated to keep in the heat by wrapping an insulated "jacket" over the tank that uses an efficient insulating material. Properly heating the oil in the fuel tank is an important part of the heated fuel system as it insures that the oil will flow into the fuel lines to the engine bay in the front of the vehicle. The Fuel Lines Once the oil is in the fuel lines and on its way to the engine bay, it is also very important to keep the oil heated as it travels through the hoses to the injection pump. There are several options for accomplishing this: Hose On Hose (HOH) - The "hose on hose" method involves running heater hoses containing coolant next to the fuel line carrying the vegetable oil. This is often done in conjunction with a coolant-based in tank heat exchanger. New hoses are added by tee'ing in to the main heater hoses in the engine bay and routing the new hoses back to the fuel tank. The coolant flows through the tee'd hoses into the tank heat exchanger and returns through hoses to the engine bay and is tee'd back into the vehicle's stock heater hoses. The tee'd heater hoses are wrapped together with the fuel line using an insulating material. This uses the heat radiated from the heater hoses to keep the vegetable oil heated as it flows to the engine bay through a fuel line. (if your heated fuel system uses a fuel return line to return excess vegetable oil to the fuel tank, then this line should also be wrapped with the heater hoses to keep it from congealing in the fuel line before reaching the tank.) Hose In Hose (HIH) - The "hose in hose" method involves special hoses that are either custom-made or fabricated by vegoil conversion companies. The heater hoses that are tee'd off of the engine's cooling system contain an internal fuel line that runs the length of the hose. With this type of system, the vegoil travels in the fuel line completely contained in hot engine coolant. This is the most efficient heating method and is very useful in extreme environments such as Northern Canada, Iceland and other sub-arctic and arctic environments. It is also used in more moderate climates to make sure that the vegoil is heated in the most efficient manner. One drawback to this type of system is that it requires the use of compression fittings that can be problematic if they are not installed and tightened properly. (improper installation can cause fuel/coolant leaks and/or mixing of coolant and fuel) Last Chance for Clean Fuel before Combustion! Once the vegoil arrives in the engine bay, it's time to prepare it for flowing into the injection pump and on to the injectors and combustion chamber. This is the last chance to remove any particles or water before the fuel reaches the injection pump. Particles can clog the screen on the injection pump and smaller particles will pass through the screen and clog the injectors. Water will rust the internals of the injection pump and/or injectors. These are very expensive problems to repair so a little extra filtering and dewatering will save you $$$ in the long run.
Let's first address final filtering and dewatering. Installing a diesel filter/water separator in the engine bay in the vegoil fuel lines before the injection pump is the best way to remove any remaining particles large enough to clog the injection pump or fuel injectors. However, don't expect a fuel/water separator to remove water from contaminated vegoil! According to testing done by several experts on SVO conversions, fuel/water separators don't work to remove water suspended or emulsified in vegoil. If you suspect that there is water in your oil, you should concentrate on removing this from the oil before placing it in your fuel tank. (see lesson 6 for information on preparing your waste vegetable oil for burning in a diesel engine.) There are many brands and types of filters from companies like Racor, Davco, Bosch and others. Some just filter oil and do not have a water separator bowl. Others provide electric or coolant-based heat to further heat the fuel before combustion. Some filters designed specifically for alternative fuels, use centrifugal force to help remove particles and moisture from the fuel. (one example is the Vormax filter from Racor) The best filtration will have a filter element of 10 microns or less, will apply some heat and will have a bowl at the bottom with a drain for removing water that is separated from the fuel before it reaches the filter element. While these filters are very efficient at removing particles from liquids, the dewatering capabilities are specifically designed for water emulsified in petroleum diesel fuel. There is a lot of discussion of whether these fuel/water separators will work with water that is emulsified in vegetable oil. Your best option is to spend the bulk of your time designing an optimal filtration/dewatering setup before you put the vegetable oil in your fuel tank. See Lesson 6 to get more detail on how to properly pre-filter and dewater your fuel. Time to Get that Oil Hot enough for Combustion Once the vegoil reaches the engine bay, it should still be hot enough to flow through the fuel lines if you have properly designed and installed your fuel tank and lines. However, it is not nearly hot enough to reach the proper consistency for atomization in the combustion chamber. (review: the vegoil must reach at least 160 degrees fahrenheit to properly atomize for complete combustion. 160-180 degrees is optimal) If you have an electrically-heated fuel filter, your oil is probably around 100-120 degrees Fahrenheit. Coolant-heated fuel filters may get the oil a little hotter but, in most testing you will find, there is not enough heated surface area in a filter to properly heat vegoil that is flowing through it to the injection pump. Proper heating requires the use of a more efficient heat exchanger that uses either engine coolant or 12v power to heat the oil over a longer distance before it reaches the injection pump. One of the most popular heat exchangers uses a large coil of tubes that are similar in function to the HIH setup for heating fuel lines. A coil of tubes made from a highly conductive metal contains coolant circulating around an internal fuel line. When the fuel leaves the coil it should be very close to the temperature of the coolant in the engine. (>160 degrees) As long as the distance from exiting the heat exchanger and entering the injection pump is less than a few feet, the fuel should be at the optimal combustion temperature if the engine is warmed to operating temperature. One example of this type of heat exchanger is the Frybrid FRYHE050 from Frybrid, LLC of Seattle, Washington. (http://www.frybrid.com) Another option for heating the fuel to combustion temperatures is an electric inline fuel heater. This uses a long length of highly conductive metal heated by electricity from the engine that surrounds the fuel with heat. It is important that the heat is in contact with the flowing coolant for a long enough period for it to reach the minimum combustion temperature. This often requires more wattage than a heated fuel pickup in a tank or a heated fuel filter. This will draw significant amperage from the battery and should not be operated unless the engine is running and properly charging. In some cases, a high output alternator may be needed to provide enough amperage to the engine, vehicle and fuel heater. One example of this type of heat exchanger is the "Vegtherm" by Neoteric Biofuels of Canada. (http://www.plantdrive.com) Switching Fuels As you can imagine, when a car is off and sitting, both fuel systems are at the temperature of its surroundings. This is not going to be hot enough to start the engine on vegoil. For this reason, two-tank systems start the cold engine using the stock tank with diesel or biodiesel fuel. This fuel is the consistency that the engine expects at normal temperatures. (Note: biodiesel should be blended in cold climates where the temperature drops below 45 degrees Fahrenheit. Otherwise, the biodiesel can gel, preventing your engine from starting) Once the engine reaches operating temperature and the vegoil is heated, the engine is ready to switch to vegoil. This is accomplished using valves that switch from the diesel tank to the veggie tank. These valved are either solenoid-driven, motor driven or manual. The most common valves are made by Pollack and switch using an electric signal to a solenoid. However, some users claim that the Pollack valves malfunction from the heat of the vegoil at different intervals. We are still waiting for more information on this reasearch. Another autmated switching option are the custom valves for vegoil conversions designed by Frybrid and Greasecar. If you prefer, you may also use a simple, manual ball valve to switch over manually. Some conversion designers will use manual ball valves to isolate the coolant tees for the auxiliary fuel system so they can isolate the conversion when troubleshooting coolant leaks and heating issues. Burn, Baby, Burn! Well, if you have followed this lesson and install a conversion, the oil is now in your injection pump, into the injectors and combusting in your engine! Congratulations! You now have a Veggie-burning machine! One final word on monitoring the temperature of your veggie oil. I have an electrical fuel temp sender tee'd into the fuel line right before the injection pump with a gauge mounted inside my truck. It allows me to monitor the temperature of the fuel just before it enters the injection pump. You may want to consider installing one of these so you can make sure that your heated fuel system is running optimally. Better safe than sorry. If something fails in your system and the fuel isn't heating properly, you will know before you damage your engine.
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