Converting a diesel engine to run on natural gas requires careful modifications to the engine and control system, including adjusting the compression ratio, installing spark plugs, and modifying valve seats. Additional considerations include managing thermal issues, meeting emission regulations with catalytic converters, and potentially improving cooling system efficiency. Structural changes to accommodate spark plugs and an ignition system are also necessary for a successful conversion.

1. CNG ENGINE
CONVERSION

2. DIESEL TO NATURAL GAS
Diesel to natural gas conversion requires careful engineering
on the base engine modifications as well as the control system
• Compression Ratio: A typical diesel engine has a
compression ratio of between 16 and 18 to1. CNG usually
works best between 10 and 12
• Spark Plugs: Diesels don’t have spark plugs; instead they
have diesel fuel injectors.
• Valves: Natural Gas is a dry fuel so valve seats in a
converted engine need to be hardened to prevent
abnormal wear
• Thermal Issues: Spark ignited engines run hotter than
diesels

3. • Catalytic Converter: A catalyst will generally be required to
meet emission regulations. The exception is lean-burn
engines, which, if carefully engineered, can meet certain
emissions targets without a converter.
• May need to improve cooling system efficiency
• May need engine oil cooler
• Ignition system must be installed
• Cylinder head modifications are needed to install spark plugs