Plantoil/diesel conversion basics
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danalinscott

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The following is a list of components in a VO conversion kit adaptable to any VO/WVO and easily operable in any climate.

VO fuel tank
Except in the case of single tank "conversions"  separate tanks are needed to hold VO fuel AND diesel fuel. It is most common to continue to use the existing fuel tank for diesel fuel and add a tank to hold VO fuel. A plastic tank is preferred over any metal tank.

Heated VO fuel pickup
Since wvo becomes thick (or even solid) at low temperatures a heated VO fuel pickup is needed to allow use of VO when outside temperatures drop. Optimally a heated fuel pickup will not add so much heat to the VO tank that the VO in the tank is heated to over 100F.

Heated VO fuel lines
Before VO fuel can flow through fuel lines it must be liquid. If the VO in the lines is too viscous (or even solid) no flow is possible so all VO fuel lines must have a provision to add a small amount of heat to the (possibly solid) VO in the lines. Insulation is desirable since it allows lines to heat up faster and retain more heat in cold weather. High quality flexible synthetic polymer "rubber" fuel line is preferred over metallic fuel lines.

Flat Plate Heat Exchanger
These are extremely efficient low cost units that transfer heat from engine coolant to VO fuel. While heated fuel pickups and lines only need to liquefy VO fuel enough to flow easily a great deal of heat must be added before it has the same viscosity of diesel fuel at the injectors. The FPHE is capable of raising VO fuel temp to near 160F which is close to the maximum safe pre IP (Injector Pump) fuel temp in most case.

Heated VO fuel filter
Unless one is willing to use a great deal of diesel fuel and time to accomplish the "purge" of VO from the IP, injector lines, and injectors, a separate fuel filter must be provided for each fuel. Similar to the fuel lines the VO fuel inside the VO fuel filter must be liquid enough to flow before the switch to VO fuel is made. In addition (since the VO fuel filter is often located between the IP and the FPHE) enough heat must be added to the VO fuel filter to prevent significant cooling of the VO fuel passing through it during operation. The micron rating of the VO fuel filter must be equal to or finer than the engines stock fuel filter.

3 port fuel switching valves and/or Electric fuel pump(s)
The use of two electric fuel pumps (one for each fuel) can allow a simpler and more trouble free conversion configuration. But since fuel pumps which provide adequate pressure and durability may be very expensive it is more common to use the existing fuel pump for both fuels. In either case "three way" valves are usually used to switch from one fuel to the other. Most choose "remote" valves which can be controlled with a dash mounted switch or automatically controlled.

Fuel pressure  gauge
Since IPs can be damaged by low fuel pressure it is important for the operator to quickly become aware if the fuel pressure drops during operation. A dash mounted fuel pressure gauge tied to the "common" fuel line prior to the IP provides a visible warning should a low fuel pressure condition occur.

VO temperature indicator/gauge
Although (for optimal engine longevity) the switch to VO fuel should not be attempted prior to the engine reaching normal operating temperature it is best to also be certain that the VO fuel is at optimum temp at all times during engine operation. The addition of a temp sensor and dash gauge (or light) will provide the operator with a visible indicator that the VO fuel is sufficiently heated prior to switchover and during operation.

Injector Line heaters and/or insulation (for engines with injector lines)
Although the optimum temperature for VO fuel prior to injection is in excess of 200F it cannot be heated this high using ONLY coolant heat. While additional heat CAN be added to the fuel utilizing electrical resistance heating before it passes through the IP doing so wastes much of the limited available alternator capacity since the IP tends to absorb and dissipate some of the heat carried through it by the fuel. It is significantly more efficient to add resistance heat produced with electrical resistance heaters to the fuel AFTER it has passed through the IP. Injector line heaters are the only practical way to reliably heat VO to pre-injection temperatures of over 200F.  If injector line heaters are not used light foam insulation should be used on injector lines since a great deal of the heat added to VO fuel prior to the IP will be lost as it passes through unheated and uninsulated metal injector lines. 

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Dana danalinscott@yahoo.com
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