A CNG fuel conversion is a package of equipments that can transfers high pressure natural gas from the vehicle’s storage tank to the engine compartment where pressure is reduced to the operating pressure of the engine’s fuel-management system. There are basically 3 (three) types of conversion engine system to CNG.
- Dedicated Conversion
An engine being converted to CNG called as a dedicated system when the vehicle after being converted can only runs on natural gas. A dedicated conversion is commonly done for a diesel type engine, whereby It can be either done by replacing the entire engine block with a natural gas engine, which is know as Repowering, or the original engine itself have gone through a limited modification towards its engine piston cylinders. The advantage of using this type of conversion is that the vehicle owner can obtain fully of the economic benefit whenever natural gas cost less than the alternate fuel. The disadvantage, however, because the vehicle can no longer use other fuel then natural gas, availability of CNG stations must be available through its driving coverage. Depending on the size and type of the diesel engine, this Dedicated Conversion System can range from US$10,000 – US$15.000 (excluding the storage tanks).
- Dual Fuel
A Dual Fuel system is mostly used only for diesel engine conversion. Through this conversion the diesel engine is modified to be able to use natural gas together with the diesel fuel. The engine is basically unchanged and continues to use compression ignition of diesel for ignition of the natural gas fuel. Unlike the dedicated system, whereby the engine now can only burn natural gas fuel, the dual fuel system the engine will burn natural gas and diesel fuel simultaneously. The ratio mix between natural gas and diesel fuel when the truck is in operation very much depend on factors like road condition, traffic condition, driver behavior, engine performance, engine type compatibility, etc. The advantage of using the dual fuel conversion, the engine is still be able to operate 100% diesel fuel, or alternately, on a mixture of diesel fuel and natural gas. The disadvantage, however, is that the vehicle owner might not be able to obtain fully the economic benefit of the lower cost of CNG fuel as the engine will still require a mixture of diesel fuel from 40% at best condition, up to 100%. Depending on the size and type of the diesel engine, this Dedicated Conversion System can range from US$7.500 – US$10.000 (excluding the storage tanks).
The Bi-fuel systems are also called “switchable” systems is a CNG Conversion used only for gasoline type engine. Through this conversion system the driver can freely switch the engine to run on gasoline or natural gas fuel. No modification is done toward the engine. With the Bi-Fuel CNG system, the natural gas is injected into the engine intake air the same way gasoline fuel is injected into the gasoline type engine. Thus, the engine will functions the same way as a gasoline engine where the fuel-air mixture is compressed during the piston upstroke cycle and ignited by a spark plug where the expanding gases produce mechanical energy in the form of rotational forces that propel the vehicle. There CNG Bi-Fuel system that can work for carburettor and sequential injection system engine. The installation for the Bi-Fuel conversion kit is pretty much simple, in which typically require less than a day to install to a vehicle. Because of this simplicity and cost of an injection type gasoline engine Converter kit range from US$700 – US$1.000 (excluding the storage tank), owners the vehicle can easily obtain the maximum economical benefit from the conversion. The only disadvantage from this Bi Fuel is that because typically are installed to a small-medium size vehicle, the owner of the vehicle must give up a partial of its space for its storage tanks.
CNG Cylinder tanks or CNG Storage tanks typically will take up a portion of the total CNG Cost conversion. It all depends on how many volume of gas that the owner wants to be installed to the vehicle with consideration such as available cylinder space, weight concerns, budget and desired travel range. Cylinders are available in a large range of sizes and configurations. It is also possible to install multiple tanks within one vehicle. CNG is stored on board vehicles in high working pressure rated at either 3,000 psi (+200 bar) or 3,600 psi (+250 bar).
There are 4 (four) types of CNG Cylinder available in the market. What differentiates the four types of CNG cylinders is the type of materials used to create the basic structure of the tank, the materials used to line or wrap the inside and outside of the tank, and how they are manufactured. The type of materials used to create the structure of the tank will determine the weight and cost of the tank. Heavier tanks are typically the least expensive and the lighter tanks are typically more expensive.
- Type 1 Cylinders
This type of cylinder is made from all metal steel in the shape of a cylinder. These types of tanks are the heaviest tanks on the market. At the same these tanks are the most affordable or cost-effective. Type 1 tanks are typically painted with a protective coating on the outside of the tank.
- Type 2 Cylinders
This type of cylinders is made from metal liner reinforced by composite wrap (glass or carbon fiber) around the middle (hoop wrapped).Liner takes 50% and composite takes 50% of the stress caused by internal pressurization. This is what is called a "hooped wrapped" tank. The composite material wrapper is composed of a woven glass fiber or woven carbon fiber or a combination of both. Both the metal liner and the composite wrapper each take on about 50% of the internal stress created when the tank is fill with compressed natural gas. Type 2 tanks are much lighter than Type 1 tanks due to the reduction of metal and the use of lighter-weight composite materials. Because of advancements in technology, Type 2 CNG tanks, they are slightly more expensive than Type 1 tanks
- Type 3 Cylinders
This type of cylinder is made from an aluminum composite material. The aluminum composite material is wrappencompletely around the cylinder. This is what is called a "full wrapped" tank. The aluminum composite material wrapped around the metal liner is typcially composed of a woven glass fiber or woven carbon fiber. Type 3 tanks are lighter and stronger than Type 1 and Type 2 tanks, and are more expensive than Type 1 and Type 2 tanks.
- Type 4 Cylinders
Type 4 CNG tanks do not use any metal in their structural design. These types of tanks are made with a "gas-tight" thick rubber membrane. The plastic liner is then reinforced with a composite material using the "full wrapped" method, where the entire tank is wrapped. The composite wrapper is typically composed of woven glass fiber or a woven carbon fiber material. Almost all of the cylinders strength is provided by the composite reinforced wrapper. Type 4 tanks are the lightest CNG tanks on the market. Type 4 tanks are similar in weight and cost the Type 3 tanks.
Given the difference material of CNG Cylinders, it is to note that each cylinder have different reaction to heat and pressure. Each type of cylinders has its own ISO manufacturing standard that has to be followed.
||ECU (for Injection Type Only)
||Gas or Petrol Switch
||Mixer (for Carburetor Type Only)|
||Map Senor (for Injection Type Only)
||Harness & Accessories
||High Pressure Pipe|
||Low Pressure Hose|