In conventional injection systems, such as the use of distributor and sequential injection pumps, only a principal injection takes place. An exception to this is the VP44, which is a solenoid valve activated distributor-type fuel injection pump.
In conventional systems, pressure generation is coupled to injection volume preparation. This has the following consequences for the injection characteristics:
• The injection pressure rises as the engine speed and injection quantities increase
• The injection pressure increases during injection
As a result:
• Small injection quantities are injected at low pressures
• The peak pressure is more than twice as high as the average fuel injection pressure
Peak pressure determines the load which can be applied to the components of an injector pump and its drive unit. The average injection pressure is, however, important for the quality of the fuel/air mixture in the combustion chamber.
