Adding CNG To A Diesel Engine


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The factors that will affect the power produced in a diesel engine will depend on the volume of air, which is greatly enhanced by turbo-charging, as well as a the volume of diesel used for combustion producing expanded gasses and resultant pressure to drive the piston.


Increasing the diesel component in an engine can greatly affect the power as the heat energy is increased expanding the gasses further. The expanded gasses increase both exhaust heat and volume resulting in an increase in turbo boost. The upper limit will be governed by the need to keep exhaust gas temperatures in a safe range.


The addition of CNG into the air stream achieves a number of benefits to the overall power, efficiency, and emissions of the engine. When the CNG mixes with the intake air charge it becomes combustible gas. This will effectively increase cylinder pressure being a denser mixture to compress than straight air (the molecular mass of air being 28.97, compared to that of CNG which is 19.5). The vapor pressure of CNG will also increase cylinder pressure, as the rate of expansion is greater than air based on temperature. The air charge now mixed with CNG becomes a combustible mixture on its own, and will enhance the flame propagation of the diesel burn once ignited. The high auto-ignition value for CNG allows the ignition timing (critical compression) to remain unaffected for the initial diesel combustion. Once ignited the CNG/air mixture will enhance flame propagation of the rest of the diesel charge increasing the cetane level.  Low cetane levels can cause rough engine operations.  They are more difficult to start especially in cold weather or at high altitudes.  Low Cetane levels can also accelerate lube oil sludge formation.  Engine deposits increase which emit more smoke, emissions and tremendous wear on the engine.


Because the diesel conversion replaces air with denser and high octane natural gas (130 octane) and the air/natural gas mixture is condensed (cooler and more dense) , CNG diesel dual-fuel conversions increase the HP on most vehicles.   We R CNG’s dual-fuel CNG diesel conversion system’s patent pending technology takes advantage of this extra energy to pull back on fuel and provide just what the vehicle demands.  This helps to avoid overheating issues and in addition to the 70/80% diesel replacement with $2.11 natural gas (approx a 35% fuel savings) adds even more savings due to the reduced fuel demands.

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