zstalker Posted September 2, 2007 Share Posted September 2, 2007 ok, small snag: I'm getting the finishing touches on my SPFI build of an EA81 in my Brat. I've got the fuel supply line plumbed, but now I'm looking at the return that the old Hitachi carb used, and it's really tiny. Has everyone else who's done this swap just gone ahead and used the tiny return, or what? I was also thinking of maybe seeing if the Brat original vent line is a little close to the size of my high-pressure fuel hose I have, and just switching the vent and return lines at both ends to utilize that size difference. Worst case scenario, I would get some tubing and make a new return line at the supply line size. Also, if people have just used the original return, did you make an adapter like the one for the huge fuel pump inlet, just smaller? ~Erik~ Link to comment Share on other sites More sharing options...
GeneralDisorder Posted September 2, 2007 Share Posted September 2, 2007 Stock return line works fine. My write up details the sizes of adaptors I used. The bigger problem is that your carb fuel tank won't have baffles - so you need to build a surge tank. Believe me it's better if you just do it now. Without the surge tank you will run out of gas before the low fuel light comes on. Very annoying. GD Link to comment Share on other sites More sharing options...
zstalker Posted September 2, 2007 Author Share Posted September 2, 2007 ok cool, I guess my mind is still calibrated for feeding fuel to a significantly larger and more powerful engine. The return line just looked too small...but if it works, then sweet! Thanks... ~Erik~ Link to comment Share on other sites More sharing options...
carfreak85 Posted September 2, 2007 Share Posted September 2, 2007 The bigger problem is that your carb fuel tank won't have baffles - so you need to build a surge tank. Believe me it's better if you just do it now. Without the surge tank you will run out of gas before the low fuel light comes on. Very annoying. GD Why wasn't that gone over in your conversion guide? Are turbo EA81 tanks suitable? Link to comment Share on other sites More sharing options...
zstalker Posted September 3, 2007 Author Share Posted September 3, 2007 yeah, I'm kicking around the idea of using a large-diameter pipe (like 4 or 5 inches)...cap at both ends. drill the caps in a few places and thread in some pipe fittings. doesn't have to be pretty, just has to keep air out of the EFI pump (and seal tight) , right? ~Erik~ Link to comment Share on other sites More sharing options...
GeneralDisorder Posted September 4, 2007 Share Posted September 4, 2007 Why wasn't that gone over in your conversion guide? Are turbo EA81 tanks suitable? Didn't notice it till later, but I should add something about it. I haven't yet built one though. And yes - turbo tanks have the baffles already because they are EFI vehicles. I found an article by someone that used a plastic housing for a tap water filter from home depot - modified of course. but it's nice because they are plastic and there's no chance of corrosion. Also it's desireable to feed the EFI pump using a tube fed down from the top to *near* (1 inch or so) the bottom of the surge tank (like a drinking straw). This way crap won't get sucked into the pump - it will just settle on the bottom of the tank. And it allows the bottom to have a drain cock instead. GD Link to comment Share on other sites More sharing options...
mikeshoup Posted September 4, 2007 Share Posted September 4, 2007 From what I can tell in the FSMs, the Turbo and non-Turbo have the same damn tank. My Turbo doesn't run out of fuel with a quarter left in the tank. Link to comment Share on other sites More sharing options...
Phizinza Posted September 4, 2007 Share Posted September 4, 2007 My EA81 tank has issues with the cornering thing and running out of fuel thing now I run EFI (EJ22.) It starts at about 42L down, and I think the tank is a 55L. I ran a full sized 5/8th rubber pipe (through the door trip strip with the other fuel feed hoses) because I didn't want anything bursting off. I also used one of the tank vent hoses and the original return line. I have noticed you can squeeze the return hose and the engine doesn't mind so you probably would be fine with the little 3.2mm return line. I just wasn't sure and didn't want to blow a hose with 40psi of fuel in it in the engine bay. (yes, although I am talking EJ I still used the EA82 pump so it all is basically the same stuff.) Link to comment Share on other sites More sharing options...
GeneralDisorder Posted September 4, 2007 Share Posted September 4, 2007 The EJ fuel rail must use more fuel - if you crimp the return line on the EA82 SPFI the fuel pressure spikes to 50 psi (dead head capacity of the pump) instead of the correct 21 psi. This results in it running super rich. The return is there to bleed the pressure down to the correct rail pressure. Think of the SPFI as an Antelope drinking from a never-ending river of fuel. GD Link to comment Share on other sites More sharing options...
Phizinza Posted September 4, 2007 Share Posted September 4, 2007 Is that crimping the 3.2mm size or the 8mm size hose your talking about GD? I was talking about the 8mm size which is what I have.. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted September 4, 2007 Share Posted September 4, 2007 Is that crimping the 3.2mm size or the 8mm size hose your talking about GD? I was talking about the 8mm size which is what I have.. That's just crimping the return right after the regulator on the SPFI TB. GD Link to comment Share on other sites More sharing options...
Phizinza Posted September 4, 2007 Share Posted September 4, 2007 I really need to get myself a AF ratio gauge and a fuel pressure gauge.. Oh and a surge tank.. Sorry for going slightly off topic Link to comment Share on other sites More sharing options...
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