Bosch Unit Injector System (UIS)
With the unit-injector system, injection pump and injection nozzle form a unit. One of these units is installed in the engine’s cylinder head for each engine cylinder, and driven directly by a tappet or indirectly from the engine’s camshaft through a valve lifter.
Compared with in-line and distributor injection pumps, considerably higher injection pressures (up to 2050 bar) have become possible due to the omission of the high-pressure lines. Such high injection pressures coupled with the electronic map-based control of duration of injection (or injected fuel quantity), mean that a considerable reduction of the diesel engine’s toxic emissions has become possible together with good shaping of the rate-of-discharge curve.
Electronic control concepts permit a variety of additional functions.