|
|
|
|
| Author |
|
|
Registered
Join Date: Feb 2005
Location: Hartsville, SC
Posts: 624
|
Fuel Return Line Question
What do you do with the fuel return line (the one to the tank) when you use carburetors instead of the FI system? Is it just stopped up or is some sort of "breather" put on the end.
Jack |
||
09-23-2010, 05:18 AM
|
|
|
Registered
Join Date: May 2004
Location: New Hampshire
Posts: 6,159
|
 Usually you tie it in to make it a recirculating system so you have the coolest fuel possible to the motor. Len
|
||
|
09-23-2010, 05:26 AM
|
|
|
Keepin' it Simple...
Join Date: Sep 2007
Location: MO, 63141
Posts: 1,663
|
If you got it, use it! Lots of ways to tie into it... depends on the hardware in your setup. The PMO FPR makes it easy if you go that route.
__________________
-Doug 1968 911R Clone; 11/07-?? (forever the project car  )1978 911SC Midnight Blue Metallic Coupe; 7/05-11/09 (so long impact bumpers) 1973.5 911T Sepia Brown Coupe; 9/98-8/99 (went to a great home) 1973.5 911T Gulf Orange Targa; 5/97-11/02 (went back to Germany) Last edited by R_Builder; 09-25-2010 at 06:00 AM.. Reason: typo |
||
|
09-23-2010, 05:53 AM
|
|
|
Registered
Join Date: Feb 2005
Location: Hartsville, SC
Posts: 624
|
Return Line
Would love some details on such a "tie in." What is the line connected to?
Jack |
||
|
09-25-2010, 04:13 AM
|
|
|
Keepin' it Simple...
Join Date: Sep 2007
Location: MO, 63141
Posts: 1,663
|
Here is a picture of a typical PMO fuel pressure regulator (FPR) install. This happens to be on a 73T:
 The bottom line on the side of the FPR is the supply line, the top line is the return. The ports on the front (covered with blue tape) go to the carbs. The pressure is set to 3-4 psi by adjusting the needle valve on the top of the unit. The needle valve is basically changing the orfice size on the return side to create the desired operating pressure. This is just one of many ways to do it, but what is stated above is what PMO recommends when installing their units. Hope that helps,
__________________
-Doug 1968 911R Clone; 11/07-?? (forever the project car )1978 911SC Midnight Blue Metallic Coupe; 7/05-11/09 (so long impact bumpers) 1973.5 911T Sepia Brown Coupe; 9/98-8/99 (went to a great home) 1973.5 911T Gulf Orange Targa; 5/97-11/02 (went back to Germany) |
||
|
09-25-2010, 06:11 AM
|
|
|
Registered
Join Date: Feb 2005
Location: Hartsville, SC
Posts: 624
|
Return Line
That loots like a good set up. How about if the original fuel pump is replaced with one having the correct pressure and a FPR is not needed?
Jack |
||
|
09-25-2010, 08:12 AM
|
|
|
|
Keepin' it Simple...
Join Date: Sep 2007
Location: MO, 63141
Posts: 1,663
|
... then it gets a little trickier IIRC. You need to get different fittings for the carbs and create a continuous fuel line loop from one carb to the other then back to the return line over on the LHS.
__________________
-Doug 1968 911R Clone; 11/07-?? (forever the project car )1978 911SC Midnight Blue Metallic Coupe; 7/05-11/09 (so long impact bumpers) 1973.5 911T Sepia Brown Coupe; 9/98-8/99 (went to a great home) 1973.5 911T Gulf Orange Targa; 5/97-11/02 (went back to Germany) |
||
|
09-25-2010, 04:49 PM
|
|
|
Senior Advisor
|
That sounds like a great idea but if you have 3.5 psi @ idle, what is the VOLUME of fuel flowing through the carbs at idle? Will you have 3.5 psi @ 6k down the back straight? See, volume is the key, just like the FI guys, you want to have max volume set at max power and anything less (fuel flow) is bypassed to the fuel tank. Always maintaining that all important 3.5 psi. The PMO fuel regulator does that as long as the fuel pump is good enough. And it looks cool!!
__________________
08 Cayenne Turbo |
||
|
09-25-2010, 05:05 PM
|
|
