Purpose and Function.

Fuel injectors perform an important role in the accurate metering and atomisation of fuel. These electro-mechanical valves react in milli-sec- onds to open and close giving the electronic control unit optimal control
over fuel flow to the engine.

Method of Measurement.

Fuel flow specifications are given in grams per minute, as this is an inter nationally accepted standard at vehicle manufacturing level. As vehicle development engineers deal with the weight or mass of air inducted by an
engine not its expected power rating, the weight of fuel that an injector can provide is the pivotal measurement. Bosch does not rate fuel injectors related to expected engine power outcomes for this reason.

Power Ratings of Fuel Injectors. [Horsepower]

It has become an aftermarket performance industry practice to rate fuel injectors in relation to expected engine power outputs, mainly Horsepower. As this method of measurement has many issues in relation to various cal-
culation methods, accuracy, individual interpretation and overall relevance, Bosch as an Original Equipment supplier of fuel injectors, does not sub-scribe to this specification method. EV6 - Standard Version There are many design requirements taken into account when under- taking the design and manufacture of a fuel injector to suit a particular
application. Further explanation can be found under the “Method of Measurement” heading in this section.

Effects of Fuel Pressure on Pintle Type Fuel Injectors

Fuel velocity through a pintle type fuel injector [type code EV 1] can dra matically affect its ability to atomise fuel. The profile of the pintle used in a fuel injector has a direct relationship to the operating pressure it is designed to operate under. Whilst Bosch produce various fuel injectors that may flow
the same amount of fuel at a given specification, the system operating pres sure will influence the pintle profile. Correct pressure will result in a well atomised spray, while insufficient pressure will result in a “hosing” effect. Excessive pressure will result in either “hosing” or a spray angle that is too large for the targeted area dependent on the pintle profile.
The consequence of excessive fuel pressure on a pintle type injector may well be that as the pressure is increased the mixture values of the engine may appear to get leaner. This is of course not the case, but the fuel being
injected is no longer atomised and is entering the cylinder as a liquid mass. This will typically cause the Hydrocarbon [HC] values to rise due to the raw fuel exiting the cylinder, and the Carbon Monoxide [CO] to drop due to insufficient combustion.
Later design fuel injectors [type code EV 6] use “director plate” multi-ori fice technology to better atomise fuel across various operating pressures. These injectors allow more flexibility in relation to operating pressures without compromising spray efficiency or fuel atomisation.

APPLICATION NOTE Fuel Injector 0 280 150 842 is designed for CNG operation only.

Bosch EV6 - Long Version has not tested this fuel injector for permanent service using liquid fuels; therefore it is not recommended for liquid fuel control systems. Control issues may result due to internal valve group sensitivity to viscosity dif ferences between liquid and gaseous fuels.

* IMPORTANT NOTE
Bosch fuel injectors have their flow rates defined in N-Heptane as part of their engineering specification. N-Heptane is a pure chemical and does not have the same viscosity and density as standard petrol. Hence the N-Heptane flow rate figures stated should be used as a general guide for comparison purposes only