Bosch debuted its common rail fuel injection system in the United States in 1999, and soon after, expanded its Charleston, S.C., plant to manufacture common rail systems for GM trucks. The common rail system was designed to help manufacturers optimize fuel consumption and comply with emissions regulations by separating pressure generation and injection. Today, common rail systems have led to significant achievements in diesel engine technology.

It is calculated that by 2015, 90% of new diesel vehicles will incorporate Common Rail injection systems and 10 million such systems will already be on the road.

A common rail engine is designed to supply constant fuel pressure to electronically controlled injectors through a shared fuel reservoir. This means that the fuel supply is not dependent on the engine rpms. A common rail system is built around four basic components:

• A high pressure pump with pressure regulator and inlet metering valve.
• A rail which contains a pressurized reserve of fuel.
• Injectors which inject precise amounts of fuel into the combustion chamber as required.
• A Diesel Control Unit – the ‘brain' of the system, which precisely controls injector flow and timing as well as rail pressure while continuously monitoring the operating conditions of the engine.