Hoss 350
My GSP, Dutch
High Pressure Common Rail Fuel Injection. It is as simple as that. The newer Cummins (no "g" at the end) has HPCR, and the Duramax has always had it. The benefit of HPCR injection is almost INFINITELY controllable timing, and precise and multiple injection events.rustinator said:
The Powerstrokes HEUI (Hydraulic/Electric Unit Injection) setup has EXTREMELY poor timing control, and can only provide two very crudely controlled and executed injection events (Three, if you cound PI, but Ford took that away, didn't they...). The HEUI system's multiple injection events are provided by a mechanical modification to the injectors, not a PCM-controlled actuator as in HPCR. What this means is that, all other things being equal, EVERY first injection event is the same, and EVERY second event is the same, with no adjustability for engines conditions, etc. HPCR can adjust the number of events (up to a certain number, depending on the PCM. I have heard of HPCR setups that can do 7 different injection events per powerstroke) both in the number of events, and also duration/quantity in an almost infinite way, to consistantly provide the quietest operation possible.
Since the event creation in HEUI is mechanical, provided by a bleed hole that "backwashes" the fuel in the middle of the event (creating the "split" in "splitshot"), it pushes 21,000 PSI fuel back into the fuel rails, int eh form of foam, undoubtedly. Now, factor in the dead-ended fuel rails on our trucks (thank you Ford
) and you have a situation where the foam has nowhere to go but back into your injectors in the next injection cycle, which means you CANNOT accurately control injection timing in an HEUI system. Even without this foam, the fuel system sucks air along it's entire route, and has restrictions that free up entrained air in the fuel. Since HEUI systems do not pump the fuel into the rails at or above the miscibility point of the air/fuel mixture (the pressure at which the air dissolves back into solution, instead of remaining bubbles in the rail), all of this air is fed to your injectors. This wrecks any chance for your injection setup to accurately control timing.Why? you might ask? Have you ever turned on a hose that has air in it? How long until water came out? How long then until it was a steady stream instead of a spurty mist? This is why air destroys injection timing in HEUI systems. And to make matters worse, as descrined above, HEUI systems, by their nature, create air. Can you say SNAFU? Can you say Catch-22?
Bad timing equals NOISE. No other way around it. Many people have quieted their PSDs down considerably by modding the fuel system to not suck in of free up air in the fuel, and have put regulated return lines off of the heads to circulate air bubbles back to the tank, instead of allowing them to go through your injectors. Net result? A MUCH quieter PSD...
Sorry so long, my .02...
it is just what I've heard...
