| Yeah strange isn't, whats worse is I can't find where i read it again. I always just thought it was to stop the fuel coming out when you disconnected the tank, as per the manual.
Ok the fuel system. The pump puts out somewhere between 3-5 bar constantly. it draws from the bottom of the tank. Fuel leaves the tank and feeds the injectors. Next in the circuit is the pressure regulator, the pressure regulator bleeds off any pressure in excess of 3 bar to the return line. (Aftermarket can be set to 4.5. This gives more fuel per injector cycle, and hence more go. FIM). 3 bar is 44 ish psi. So the the return pressure can be any where from 0 to 2 bar depending on injector demand. Max pump pressure 5 bar minus system pressure 3 bar.
The degaser just removes any air that may be in the circuit, from cavitation or maintence.(In avaiation we use to call them swirl cans.)
The tank needs a breather to allow for over and under presurisation. Use the fuel you get negative pressure and pump will starve for fuel, and cavitate. Add heat and tank will have positive pressure. Tank will get fat and burst. A little positive pressure means the pump doesn't have to work so hard. So you would think that this is a good thing. But it will cause more pressure on the back surface of the pressure regulator diaphram, thereby effectively increasing the regulators spring force and raising regualted pressure above 3 bar.
So our non return valve now has two jobs. Stop fuel ****ing out all over the place when you take the tank off. (Fuel pump has its own non return valve), and stops an increase in fuel pressure regulation in the event of a fuel tank increase in pressure, by maintaining a set return line pressure using the opening spring force in the Non return valve.
How about that then? Sound better.
[Edited on 4-3-2006 by jgriff]
[Edited on 4-3-2006 by jgriff]  |