How it works
Low Pressure Direct Injection
The ECI SIP natural gas conversion is designed for the EMD 645 2-cycle diesel engine. It utilizes a low-pressure direct injection system, a prechamber spark ignition system, and an advanced full-authority electronic engine controller.
By means of an electro-hydraulic valve incorporated into the head, natural gas is injected into the cylinder near the bottom of the piston's stroke when cylinder pressures are low. This requires far less injection pressure than late-cycle injection, and allows fuel and air to mix thoroughly during compression. The system achieves full rated engine horsepower with only 120-150 psi of injection supply pressure.
The ECI Spark Ignited Prechamber is installed in place of the EMD diesel injector, and at the top of the piston's stroke provides enough ignition energy to light the lean mixture of natural gas and air in the main combustion chamber. This oil-cooled prechamber is supplied with natural gas separately from the main chamber, and the engine controller is called upon to continuously adjust the prechamber air-fuel ratio for ideal ignition.
In order to reduce emissions and improve the quality of combustion at low engine speed and load, ECI employs innovative control techniques to manipulate combustion characteristics. The spark ignited, 100% gas EMD 645 runs smoothly from Low Idle to Notch 8.
ECI chose to use low pressure injection over a high pressure system for a number of reasons. Low pressure injection:
Extends the life of injectors and other fuel system components
Improves the safety of the working environment on and around the engine
Makes the fuel system simpler and more cost effective
- Avoids the complexity and energy consumption of a fuel pressure boosting system
These benefits of the ECI design translate into cost savings in both the initial investment and the operation of the equipment.