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© Green Car Congress / A comparison of combustion chambers in Diesel engine and CNG engine pistons poprzednie następne
Sector: CNG

Mercedes CNG models

Mercedes CNG models  

OM904 and OM906 Mercedes engines have been used all over the world in compact and mid-size Mercedes models as well as in buses that used MB truck chassis.
A Mercedes diesel engine converted to run on CNG with an Omnitek system© Green Car CongressA Mercedes engine converted to run on CNG

Omnitek created a kit that allows these popular engines to be converted to CNG. The system uses one controller that is responsible for gas injection, motor control and ignition. Combustion is controlled by a lambda probe in the exhaust system.

The conversion kit includes all the necessary components – pistons with enlarged combustion chambers that lower compression to the level that allows the engine to run on natural gas, a gas injector, components of ignition system, an electronic controller and proper sensors. In the case when Euro IV or Euro V emission standards apply, the set can be supplemented with appropriate catalytic converters.

A converted bus with OM904 engine has been in use in Mexico since the beginning of 2012. Its users praise it for lower operating costs (estimated at around 40%). Another important factor is lower emission of harmful components in exhaust gas (90% reduction in particulate matter emission and 30% reduction in carbon dioxide emission).

Good to know

Total cost of a Diesel-to-CNG conversion is 7-12 thousand USD (the conversion kit, engine modification and labour costs, doesn’t include the gasholder).

Truck and bus drivers were hit by the increasing prices of diesel oil particularly hard. For many of them, the conversion to CNG might be the only way to stay afloat. Adapting the engine for CNG not only reduces fuel costs but also contributes to reducing air pollution levels.

During the development of this conversion kit, the priority task was to create an inexpensive system that would pay off after roughly a year of operating.


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Piotr Złoty
source: GNV Magazine, Green Car Congress 2012-2018 All rights reserved. By using this site you acknowledge that you accept its Terms and Conditions