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Guest Message by DevFuse
 

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fuel return placement


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3 replies to this topic

#1 scubaroo84

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Posted 23 July 2014 - 12:16 AM

On my ea81 I'm building I'm putting a factory 87 turbo on it with a weber set up for blow thru. I have a mallory 4309 boost referenced fuel pressure regulator and I will be running a spfi fuel pump, my return has to be bigger than the feed for the regulator to work properly and it needs to return to the top of the tank, it looks like the factory return goes to the bottom. Where should I plumb my return line to? I don't want to drop the tank. I saw on the instructions to ej an older soob to run the return to the tank vent box? Would that work? Where is it located? Also how much pressure does a spfi pump put out?

#2 wagonist

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Posted 23 July 2014 - 07:28 PM

Unless you already have factory EFI on your EA81, it is doubtful that your current feed line will be big enough to flow enough fuel for the EA82T.

 

When Subaru put the EFI into the 85- models, they removed the carb return line, used the carb feed line as the return line, and then installed a bigger line again for the feed.

 

That sounds so weird that the return line needs to be bigger than the feed line for the regulator to work properly. Why would you need a bigger pipe when most of the fuel coming through the feed line is burnt in the engine, leaving less to go back?

 

Just becasue a line goes into the bottom of the tank from the outside doesn't mean it stays there once its inside the tank ;)



#3 scubaroo84

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Posted 23 July 2014 - 09:24 PM

I'm putting just the turbo on it. It's an ea81 with ported heads and a weber. The spfi pump puts out more pressure than I need. I'm running a rising rate regulator so that I have adequate fuel pressure under boost. The pressure will be set at 3 psi at idle and for every lb of boost the regulator sees (via a hose from the boost pipe) the regulator allows an extra lb of fuel pressure. So at 7 lbs of boost it will let 10 lbs of fuel pressure through. The return line needs to be bigger so that there is no restriction or it will not regulate properly.

#4 wagonist

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Posted 24 July 2014 - 06:22 PM

ok, so I can't guarantee what I said about the lines then is accurate. I have no experience with carb turbos, only EFI, so my statements may or may not be relevant.






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