Commonrail explained
Common Rail Direct Injection,
Modern diesels owe their resurgence in popularity to advances in fuel delivery and engine management systems that allow the engines to return power, performance and emissions equivalent to their gasoline counterparts, while simultaneously producing superior fuel economy.
It's the high pressure fuel rail and the computer controlled electronic injectors that make all the difference. In the common rail system, the fuel pump charges the fuel rail at a pressure of up to 25,000 psi--but unlike indirect injection pumps--it is not involved in fuel discharge. Under the control of the onboard computer, this fuel quantity and pressure accumulates in the rail independently of engine speed and load.
Each fuel injector is mounted directly above the piston within the cylinder head (there is no pre-chamber) and is connected to the fuel rail by rigid steel lines that can withstand the high pressure. This... Commonrail explained More.
How To Tune Commonrail Diesels
A modern diesel engine's functioning is almost completely controlled by the electronic system that manages the fuel injection and ignition functions. These systems have a number of sensors which are controlled by the vehicles ECU. These signals are processed many thousands of times each second to keep the vehicle running at its optimum efficiency, and also to keep the engine's emissions at acceptable levels.
The idea behind a diesel tuning box is to intercept the signal between the ECU and the injection system, and basically allows it to inject a more optimal amount of fuel into the cylinders thus producing more torque and power. Because of this the engine runs more efficiently. Fuel economy is also improved because you would have to use less throttle to achieve the same performance level, and because the engine is tuned to burn its fuel more efficiently.
To understand how the tuning box works it is important to understand the workings of a diesel engine.
