Converting NB to return fuel style
08-07-2015, 06:13 PM
#28
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<p>OK, I'm going to be doing this within the next 2 weeks. I need the AFPR? Why was G trying to get the euro FPR? I don't understand that, but I think I understand everything else. Thanks for the thorough pics and descriptions, flounder.</p>
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08-08-2015, 11:13 AM
#29
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Do most people follow this and use the evap line? I'd be seriously nervous about using a 1/4" return line and a 5/16" feed line. If you don't get rid of all the extra fuel volume carried by the larger feed line (in relation to the smaller return line), idle AFRs are going to naturally fluctuate.
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08-08-2015, 11:38 AM
#30
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Great question, I don't know what most have done since it seems there aren't many who have done this conversion and documented it well.
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<br />I have an extra NB fuel line though, I can just use that.
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<br />I have an extra NB fuel line though, I can just use that.
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08-08-2015, 11:45 AM
#31
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Ed, he went from a returnless 60psi system to a return 43.5psi setup with the stock NA FPR. He added the aftermarket FPR to get back to 60psi because his injectors weren't big enough for only 43.5psi.
Run your 5/16" return line, then size your fuel pressure according to your injectors. If they're big enough for 43.5psi, just run an NA FPR. If not, I'd either get bigger injectors, or skip the FPR and run an open adapter to an auxiliary FPR.
Run your 5/16" return line, then size your fuel pressure according to your injectors. If they're big enough for 43.5psi, just run an NA FPR. If not, I'd either get bigger injectors, or skip the FPR and run an open adapter to an auxiliary FPR.
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08-08-2015, 12:49 PM
#32
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<p>
</p><p>I wondered the same thing, but I do understand that most do exactly that (use the evap line for return). Want to hear from users, with stock pump flowrate, if idle was as hoped.</p><p>EDIT: What are the sizes of the supply and return lines on NA's?</p><p>EDIT 2: Actualy, I can see where it might raise the idle pressure above the desired 43+MAP, but I don't see why it would be unstable. </p>
Do most people follow this and use the evap line? I'd be seriously nervous about using a 1/4" return line and a 5/16" feed line. If you don't get rid of all the extra fuel volume carried by the larger feed line (in relation to the smaller return line), idle AFRs are going to naturally fluctuate.
Last edited by DNMakinson; 08-08-2015 at 02:02 PM.
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08-08-2015, 02:21 PM
#33
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<p>
</p><p> </p><p>Ah OK. So I can run the line straight from the NA FPR to the return line then?</p><p>If so, I mean... that seems super duper easy. Do you have an NA FPR laying around? 
</p>
Ed, he went from a returnless 60psi system to a return 43.5psi setup with the stock NA FPR. He added the aftermarket FPR to get back to 60psi because his injectors weren't big enough for only 43.5psi. Run your 5/16" return line, then size your fuel pressure according to your injectors. If they're big enough for 43.5psi, just run an NA FPR. If not, I'd either get bigger injectors, or skip the FPR and run an open adapter to an auxiliary FPR.
</p>
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08-08-2015, 02:43 PM
#35
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<p>No AFPR. Based on what Josh was just saying, I don't think I need one. Anyway, I'll stop posting here, this part of the discussion belongs in my thread, not here.</p><p>Thanks gentlemen.</p>
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08-11-2015, 04:03 PM
#38
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<p></p><p>I wondered the same thing, but I do understand that most do exactly that (use the evap line for return). Want to hear from users, with stock pump flowrate, if idle was as hoped.</p><p>EDIT: What are the sizes of the supply and return lines on NA's?</p><p>EDIT 2: Actualy, I can see where it might raise the idle pressure above the desired 43+MAP, but I don't see why it would be unstable. </p>
The idle fuel requirements vary with coolant temp, A/C/heater/fan/lights, etc. As you need more fuel at idle, the return line has to carry less fuel, and the pressure in the line drops. The issue is that fuel pressure fluctuation, which will cause all sorts of issues.
If I need to convert my car, I'll be using something other than the evap line.
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08-11-2015, 05:13 PM
#39
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<p>In my current state of disassembly and since I already had another main line, it was easy peasy to put the new line in.</p><p>Thanks for the input gents.</p>
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08-12-2015, 04:50 PM
#40
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<p>
</p><p>But, the CL idle takes care of the extra load by adding air. Fuel formula (MAP goes up) and VE table then handle the fuel for us.</p><p>I think most people use the evap line, so I still hope someone will publish results of what their fuel pressure looked like at the rail with this set-up. Maybe even @flounder.</p><p> </p>
Stock NA feed and return are both 5/16"</p><p> </p><p>The idle fuel requirements vary with coolant temp, A/C/heater/fan/lights, etc. As you need more fuel at idle, the return line has to carry less fuel, and the pressure in the line drops. The issue is that fuel pressure fluctuation, which will cause all sorts of issues.</p><p> </p><p>If I need to convert my car, I'll be using something other than the evap line.
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