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Bi-Fuel System FAQs

What does "Bi-Fuel" mean?
In simple terms, bi-fuel can be defined as the simultaneous combustion of two fuels. In the case of the GTI Bi-Fuel System, natural gas is utilized in conjunction with diesel fuel to operate the engine. After conversion, the engine is able to operate on either 100% diesel fuel, or alternately, on a mixture of diesel fuel and natural gas (or other methane based fuels). At no time is the engine able to operate on natural gas exclusively.

Will my engine have to be modified to operate on the GTI Bi-Fuel System?
No. The GTI conversion technology has been designed to allow for in-field retrofit of diesel engines without the need to change or modify the design of the engine. The GTI conversion hardware is mounted externally on the engine and does not require modification of the engine or alteration of any critical engine parameter.

Will the system affect my engine warranty?
Most OEM engine warranty programs do not prohibit the use of aftermarket parts or technologies. In brief, the policy of OEM's is that they neither recommend nor endorse aftermarket technologies; however, the use of these products does not automatically void the validity of the engine warranty. If the cause is unrelated to bi-fuel, the OEM's have historically honored the warranty and repaired the engine. Additionally, all GTI Bi-Fuel components that fail within the warranty period will be covered under the GTI Bi-Fuel warranty policy.

Why can't the engine use 100% natural gas?
Because of the very high ignition temperature of natural gas (approximately 1300 degrees Fahrenheit), sufficient heat is not generated during the diesel compression stroke to ignite 100% natural gas. As such, dedicated gas engines employ spark plugs and an ignition system to facilitate combustion of the air-natural gas mixture. In contrast, during bi-fuel operation, a reduced quantity of diesel fuel acts as the ignition source for the air-gas mixture; this process is often referred to as pilot ignition.

Will my engine lose power after conversion to the GTI Bi-Fuel System?
Under normal circumstances, engines converted to GTI Bi-Fuel do not suffer any horsepower losses while operating in bi-fuel mode. Because the system maintains OEM compression ratio values and does not incorporate an air-throttling device, peak horsepower and efficiency levels of the converted engine remain on par with 100% diesel operation.

Will my engine run hotter on bi-fuel?
GTI Bi-Fuel technology has been designed to maintain OEM specifications for all engine temperatures including engine coolant temperature, oil temperature, exhaust gas temperature and intake air temperature. The Bi-Fuel System replaces diesel fuel normally consumed by the engine with an equivalent quantity of natural gas, relative to the heat value of each fuel. As such, engine air-fuel ratios during bi-fuel operation remain largely an "equivalent gallon" of natural gas is consumed resulting in similar engine fuel efficiencies.

What about efficiency?
The GTI Bi-Fuel System replaces diesel fuel with an equivalent quantity of natural gas. This process results in the same net fuel burn vs. load as would be experienced during 100% diesel operation. For each gallon of diesel fuel displaced during bi-fuel operation, there is a corresponding consumption of methane-based gas. Thus, for each gallon of diesel fuel displaced during bi-fuel operation, an "equivalent gallon" of natural gas is consumed resulting in similar engine fuel efficiencies.

What effect will the GTI Bi-Fuel System have on the durability of my engine?
Generally speaking, operation in bi-fuel mode has no negative effects on engine wear rates and durability. As explained above, because engine thermal loads are equivalent to 100% diesel operation, no excess wear of combustion chamber components (pistons, rings, valves, injectors, etc.) occurs. In addition, many users of the GTI Bi-Fuel System have reported positive benefits relative to engine wear including extended oil change intervals and extended time between overhauls. This is primarily the result of the cleaner burning characteristics of natural gas compared to diesel fuel.

What are the economic benefits of operating on GTI Bi-Fuel?
Fuel cost savings resulting from operation in bi-fuel mode will vary according to the respective cost of each of the fuels. If there is a significant cost differential between the cost of diesel fuel (per gallon, liter, etc.) and the equivalent quantity of natural gas (heat value basis) in favor of the natural gas, significant fuel cost savings would result. The closer the fuels are in price, the lower the fuel cost savings will be during bi-fuel mode. In addition to fuel cost savings, engine maintenance savings (as explained above) and extended runtime (up to 3.4 times longer) also contribute to the economic benefit of bi-fuel operation.