MoTeC Global Forum

Hi,
I have measured opening time using a probe wich displays the current waveform on the oscilloscope display. The waveform shows the core rebound and I can measure the timings at different voltage. But this is done in my lab, without fuel, thus no pressure inside injector.
Will the timmings be different when injectors are fitted, with fuel pressure ?

Angelo

Hi Angelo,

Do you mean you can see when the actual pintle is opening?? And you want to know if the pintle opening time will change with different fuel pressures?

I can tell you it does change, obviously with a change in voltage, but also with a change in fuel pressure and that is why we have a 3D table for injector 'dead time' so you change your fuel pressure and know the 'dead time' comp is always correct.

Typically the 'dead time' is longer for more pressure but not always.
Here is dead time at different fuel pressures for an injector we have characterised.
At 14 volts the dead time is -
At 3 bar = 584mS
At 4 bar = 646mS
At 5 bar = 679mS
At 6 bar = 755mS

This is calculated from actual fuel flow so takes into account injector closing time also.

Cheers,

You might want to contact Paul Yaw at yawpower.com. He tests and characterizes the non-linear behavior of injectors over a range of voltages and operating pressures.

DarrenR wrote:Hi Angelo,

Do you mean you can see when the actual pintle is opening?? And you want to know if the pintle opening time will change with different fuel pressures?

I can tell you it does change, obviously with a change in voltage, but also with a change in fuel pressure and that is why we have a 3D table for injector 'dead time' so you change your fuel pressure and know the 'dead time' comp is always correct.

Typically the 'dead time' is longer for more pressure but not always.
Here is dead time at different fuel pressures for an injector we have characterised.
At 14 volts the dead time is -
At 3 bar = 584mS
At 4 bar = 646mS
At 5 bar = 679mS
At 6 bar = 755mS

This is calculated from actual fuel flow so takes into account injector closing time also.

Cheers,

Darren - are those units mS (milli seconds) or uS (micro seconds)?

Holmz wrote:Darren - are those units mS (milli seconds) or uS (micro seconds)?

Ahh yes, micro seconds ofcourse... So should be

At 14 volts the dead time is -
At 3 bar = 584uS
At 4 bar = 646uS
At 5 bar = 679uS
At 6 bar = 755uS

Thanks for pointing that out.