Dual-Fuel engines operate on both natural gas and diesel fuel simultaneously, majority of fuel burned being natural gas. Diesel fuel acts essentially as a ‘spark plug’ as it auto ignites under compression and then ignites the gas. The use of diesel fuel allows the retention of the diesel compression ratio and its efficiency while the natural gas contributes to economy and is responsible for lowering emissions.

The Fumigation Principle

Natural Gas can be introduced to the combustion chamber by either mixing it with the airflow or injecting it into the manifold/chamber. In the Fumigation process, the gas is blended with air and both enter the inlet together in correct proportion whereas in direct injection the gas is introduced into the engine just prior to burning. The latter is an expensive and complex process whereas the fumigation method is not. More importantly, gas is not the primary fuel in a dual fuel engine and therefore the fumigation process works perfectly well, even for very large engines.


The EXCLAIM kit has operated at a replacement ratio of 92%. However, the average substitution of diesel by gas ranges between 50% to 80%.


The EXCLAIM kit will not derate an engine if used with standard Natural gas or LPG. The kit ensures that full power remains available by adjusting ratios and providing necessary BTU energy to the engine. In gases such as LPG where the BTU content is higher than normal, dual fuel operation provides superior energy efficiencies whereas when the gas being used has a low heat value (coal gas, biogas or other gases having BTU content of less than 800) there is a proportional de-rating of the engine.


Unlike dedicated natural gas engines, dual fuel engines do not run hotter. Indeed, in some cases engines may actually run a few degrees cooler.

Changeover between fuels

The EXCLAIM kit is designed to switch seamlessly between full diesel and dual fuel operation without any surge or loss of power, frequency or speed.

Maintenance costs

Because gas is a better, cleaner fuel, the engine oil life is extended. Oil and filter change intervals are normally extended to generate additional savings.


  • Attractive operating economics; replaces expensive diesel with low cost gas.
  • Greatly reduced emissions
  • Retains torque and power characteristics of the original diesel engine
  • Emergency diesel fallback for safety
  • Excellent long term reliability record
  • Same heat rejection as diesel

This website is relevant to the following topics:
1. Dual Fuel conversion,
2. Diesel to Dual Fuel, Diesel to BiFuel,
3. Diesel to Bi-Fuel conversion,
4. Conversion of Diesel Generators to Bi Fuel,
Outside links to similar content:
Cummins Generators Dual Fuel Website
Caterpillar Dynamic Gas Blending