Test common rail piezo injectors

with DIT31 test bench

Massimiliano Gandini (IP)


Classic(Old) test Method


The most popular method to measure the flow of a common rail injector is to collect in a <strong>graduated glass</strong> the amount of liquid introduced during a known number of injections and compare this volume with the graduation of the container.

Deteq test  Method


An alternative able to provide <strong>higher resolution</strong>, is to split the flow in its two fundamental physical parameters: that is,

- the time interval between opening and closing of the nozzle (injection time).

- pressure difference during the injection time

 

Piezoelectric actuator control requires the additional CRP module to the  unit TC38.

Test 1:Minimum pressure

Activated the automatic triggering cycle, it is easy to find the minimum pressure which allows the chatter.

Test 2: Chatter

Activated the automatic triggering cycle, it is easy to find the minimum pressure which allows the chatter

Test 3: Return


With the injector pressurized, the pump is stopped and the pressure drops gradually, <strong>depending on the return</strong>.

Test 4: Seat Leackage

Known the acceptable leckage time, any lower value indicates a too high back leackage.

The injector on the left has an acceptable quantity of return; the other one on the right has an extra internal leakage.

Test 5: Opening Delay


Opening delay is the time to translate the electrical command into a mechanical movement

Injection time is the time elapsed between the opening and closing of the nozzle.

It is essential to determine the flow.


On the left an injector that pulverizes exactly on time, on the right an injector that responds with  a delay.

For each chatter, at constant pressure DIT31 calculates the difference between the level of pressure on opening and closing of the nozzle.

This parameter, together with the injection time, determines the amount of the injected fluid.

On the left, the injector injects the correct amount. The injector in the center has at least one of the nozzle holes with a reduced diameter by dirt or oxide while the nozzle holes of the injector on the right are expanded by wear.

The electromagnetic actuator control is delegated to the external unit TC38, which once synchronized with DIT31, generates the excitement command, via smartcards.

Piezo actuator control requires the addition of CRP module to the external unit TC38.  


Connection and test methods keeps unchanged contrary to the test of electromagnetic common rail injectors.

This component is an Upgrade.

PiezoDevice 87.20.116 is the specific device to be used on an exhisting DIT31 test bench for diesel injectors.     


The device has been developed to solve a particular situation rising when testing piezo common&#xD;rail injectors, as the piezo actuator must result lubricated before being energized. On the contrary the piezo actuator may be damaged