Piezo injectors use piezoelectric technology to open and close fuel injectors at extremely high
speeds and precision to inject fuel into an internal combustion engine. These injectors are used in both
petrol and diesel engines to improve their persformance and efficiency
Piezo electricity results from squeezing or applying pressure from certain crystal like materials or
certain ceramics. If this process is reversed and electricity is applied to these same materials they will
expand and return to their original size as soon as the electricity is cut off. The expansion of one crystal
is too small to see with the naked eye.
How piezo electricity make piezo injectors work is by using the expansion of the crystals to open the
injector. The expansion of one crystal is much too small to open the injector so there are several hundred
little piezo crystals placed one above the other covering a length of more than half the injector.
Because of their operation piezo injectors can open and close much faster than mechanical injectors which
allow more precision in the injecting of fuel during the four stroke cycle.
Just the right amount of fuel can be used for each stroke whatever conditions the engine may be operating under.
When electricity passes through these hundreds of crystals their combined expansion is enough to open
the injector and as stated before they return to their original size as the electric charge stops. The crystals
expand downwards and an upward movement is required to open the injector so two very small levers are used to
reverse the process and open the injector and a spring closes it as the crystals retract.
Piezo injectors are not used any petrol or diesel engine but electrically controlled direct injection
engines such as gasoline direct injection (GDI) or
common rail diesel engines.
The ECU determines at exactly what stage of the compression and/or
power stroke the piezo injector should be opened and closed. This is monitored by the ECU to the millisecond. In
addition to having the right amount of fuel, the engine receives that fuel at the right time, as determined
by the engineers of the engine when they were designing it.
Piezo injectors have the ability to inject fuel into the cylinder several times in one stroke (as many as seven times).
This is very useful in a diesel engine where a spark is not used to ignite the fuel. Multiple injections allow a pre, main and
post explosion and ensures no fuel is wasted.
Piezo injectors have greatly contributed to the effectiveness of common rail systems in offering better performance
with increased fuel efficiency and has definitely improved the way the internal combustion engine functions.