An Understanding of the 4port Fuel Filter w/regulator

[q_dubz]

Hello All,

So i got bored tonight and decided to carefully open open my fuel filter and get some better damn photos than whats floating around the internet.

So here it is, a 4port filter with labels:



So yea we all get that fuel goes in, gets filtered and gets regulated to 4bar/58psi. The question for me was how does it flow, internally and what all the ports allow.

Without further adooooo....

Here you see the top carefully opened with angle grinder, hammer and screwdriver And voila there's your everyday FPR. One thing to note; the filter is separated into two chambers. A filter chamber and a pressure chamber.



Now here is a look down the filter, Fuel enters the VL port where it then surrounds and goes through the filter pleats entering the center of the filter chamber and THEN flowing into pressure chamber the via the 3 long slits surrounding the center return (RL) tunnel.



Popping the FPR out reveals an oring sealing it off from the rest of the filter and that the "EJ" port is merely a vent for when the diaphragm of the FPR is pushed up by incoming fuel pressure.



Now what happens here is that filter fuel pressurizes the upper pressure chamber, fuel line, and fuel rail. Once 4bar pressure is reached the FPR lifts and fuel flows through the 4 slots in the bottom of it and OUT THE CENTER into the plastic straw. From there it exits the filter via "RL" and goes to the top of the fuel tank on the driver side transfer pump fuel hat.



Now that's that. Time for beer and dinner.

P.S. I discovered that the regulator is capable of holding vacuum so that makes me wonder IF we applied vacuum/boost to the EJ port instead of sending it back to the tank would the FPR act as a rising rate?

hmmm...

[924Carrera]

Awesome information. It's great to see things explained like this, as it helps with diagnosing problems and dispels some of the "black box magic" notions that people have about cars and their operation in general.

[q_dubz]

Thanks

[q_dubz]

For those of you that go to a larger pump with the factory filter. That plastic "straw" goes all the way to the RL port. It has a very small opening. Because of that restriction your fuel pressure will rise if you install a larger pump due to inadequate return flow. You need simply only to run a 1/8 to 3/16 (I don't recall if a 1/4 would fit) drill down the port to open up the end of that plastic tube. Takes two seconds. I had to do it on my turbo build.