Quote:
Originally Posted by JonL
I think there is one more reason why gallery pressure may affect injection performance, and that is cavitation. Even if the supply pump provides sufficient volume to satisfy the injection pumps maximum delivery, if it cannot maintain sufficient pressure in the gallery the plungers may cavitate. The pressure in the gallery must be sufficient to fill the plungers quickly through the very small inlet ports while maintaining sufficient pressure within the plunger to prevent cavitation during filling.
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My experience with this is that in 5 years working in a Fuel Injection shop I have never witnessed any cavitation inside of a Element/Plunger and Barrel on any make of inline IP.
Cavitation is a result of the pressure and more specific the pressure waves created by the begining and ending of injection.
If your Delivery Valve is funcitong properly it closes and isolates the Plunger and Barrel from there end of Injection Pressure Wave coming back to the IP.
I have seen cavitation on all of the parts past and including the Delivery valve seating area and all the way to the Injector itself. It is also one of the reasons Fuel Injection Hard lines develop pin holes.
The other place that I have read there can be cavitation in an inline IP is the IP housing opposite the fuel inlet holes in the Plunger and Barrels.
After filling the plunger rises shooting a stream fuel out of the fuel inlet hole at a high velocity until the fuel inlet hole is closed off at begin of injection.
The high velocity stream of fuel can erode/cavitate the Aluminum IP housing.
Some makes of IPs have Steel Plugs across from the Plunger and Barrel inlet hole so that the high velocity fuel is deflected on the harder steel plugs.