stu999 Posted November 12, 2003 Posted November 12, 2003 In theory at least, Matt is right. It's not what fuel the engine is consuming, but how much is being constantly pumped around the system (i.e, via the fuel return). But in practise, there are folk who have plumbed the fuel return back into the tank, seemingly with no ill effects. The question is, does the injection fuel pump actually deliver 44 GPH @ 50 psi around the complete system, or is it merely capable of 44GPH? I know a substantial amount of fuel is returned, but the pressure regulator does stem the flow quite a bit arouind the system..... P.s. I think you will always need another overflow back from swirl pot to tank, because otherwise the system pressure could potentially be lifted by 7 psi or so (or whatever the 'carb' pump is capable of delivering) and *could* play havoc with with fuel metering.... Quote
Blatman Posted November 12, 2003 Posted November 12, 2003 P.s. I think you will always need another overflow back from swirl pot to tank, Never said you wouldn't. I was postulating a point of view....... And I'll do it again....... Surely "system pressure" will only increase if the pressure regulator is b*******ed? Quote
Matt Seabrook Posted November 13, 2003 Posted November 13, 2003 Surely "system pressure" will only increase if the pressure regulator is b*******ed? Not if the Swirl pot has no return to the fuel tank pressure could build up if there is no wear for fuel to go The question is, does the injection fuel pump actually deliver 44 GPH @ 50 psi around the complete system, or is it merely capable of 44GPH? I know a substantial amount of fuel is returned, but the pressure regulator does stem the flow quite a bit arouind the system..... Fair point Stu and I would agree with you if the injection pump delivery were lower I would not have a problem returning the fuel to the tank. A correctly sized pump for a 180-200ish bhp engine would be ok on that pluming set up. I over speced the pump for my 210BHP engine as I plan for more power at some stage and did not want to have to get another pump. It may be possible for my pump to over come the red top pumps capacity and as such a swirl pot with a return from the engine then to the tank would over come this. As you have to have a return to the tank for an injected car anyway it would only mean one extra hose for a more reliable set-up than has been described earlier. After all the whole point of a swirl pot is to stop fuel starvation. If this set up is good enough for Steve Broughton (SBD) then its good enough for me. Quote
Blatman Posted November 13, 2003 Posted November 13, 2003 Not if the Swirl pot has no return to the fuel tank pressure could build up if there is no wear for fuel to go But would that matter? In hot weather, the fuel tank will pressure up anyway (may not be 7psi though). I can see possibly that equal pressure either side of the lift pump *may* cause the pump to stall, but Red Tops need at least *some* pressure (from gravity, normally) which is why you mount them as low as possible. I guess it's possible that presure on the "wrong" side of the pump may also break rather than just stall it, but who knows..... I can also see that if fuel backs up all the way to the pressure regulator along the return line, then yes, there will definitely be a problem, which I guess is what Stu was getting at........ That'll be my eureka moment for today then....... Whatever.....don't want to start another row, just an interesting discussion.......... Quote
windy Posted November 13, 2003 Posted November 13, 2003 This system works for me: Standard tank modified with additional tank on base in centre. Drill a 1" hole in the base of the tank first then weld a tank to fit inside the squareof the chassis tubes underneath. Careful to ensure clearance around sides for allowing installation / removal of tank. To this additional tank weld feed & return. Delete the low pressure pump. Gravity feed the fuel through a 1/2" bore pipe to filter & then staight into high pressure pump. -6 hose to fuel rail, return from regulator back to base of pump. Advantages: 1) No need for lots of expensive fittings to a seperate swirl pot. 2) Returned warm fuel is cooled by cooler fuel in main body of tank 3) Existing wiring for low pressure pump can be used to power high pressure pump. 4) Your existing fuel tank now has a reserve tank. Hope this helps Windy Quote
Matt Seabrook Posted November 13, 2003 Posted November 13, 2003 Whatever.....don't want to start another row, just an interesting discussion. No problems with me mate just the way I see as being the best solution Quote
stu999 Posted November 13, 2003 Posted November 13, 2003 That'll be my eureka moment for today then....... *sound of penny dropping* Quote
Matt Seabrook Posted November 13, 2003 Posted November 13, 2003 That'll be my eureka moment for today then....... *sound of penny dropping* I think he has got it now Quote
ray wilson Posted November 13, 2003 Author Posted November 13, 2003 Thanks for all the info,I'm glad I'm not confused , but I think the seperate swirl pot is the best for me at the moment, I do not know anybody local who would weld a used alli tank.The SBD drawing seems a straight foward, may not be perfect solutoin but it is a solution to get around the welding part. Does SBD sell the pots ?. I still think I can use the same power to the low pressure pump to power the high pressure, So thanks again for all the input on this matter. Yours thankfully Ray. P.S. Blatts do you read a lot of books? Quote
Matt Seabrook Posted November 13, 2003 Posted November 13, 2003 Blatts do you read a lot of books? I think he just spends too long on the net Quote
george Posted November 14, 2003 Posted November 14, 2003 Joining this late, but . . . I'm with Matt on this one. If you route the return from the engine's pressure regulator to the main tank, then you've set up a race between the low pressure pump filling the swirl pot and the high pressure pump emptying it. Sometimes the high pressure pump will win. Bad. If you route the engine's return back to the swirl pot, then the race is between the low pressure pump filling the swirl pot and the engine's fuel consumption emptying it. The pump should always win. Regarding a return from the swirl pot back to the main tank, it's always necessary (even if, with a very high volume low pressure pump, you decide to run the engine's return back to the main tank.) The return from the swirl pot to the main tank is the only way to purge the air that you will pick up in the low pressure feed when cornering hard. And you expect to pick up air --- if you didn't, then you wouldn't be fitting a swirl pot. Quote
Mike H Posted November 14, 2003 Posted November 14, 2003 But surely one of the main purposes of returning fuel to the swirl pot is because it's a SWIRL pot designed to remove air bubbles from the fuel. The bits welded to the bottom of fuel tanks are best described as 'surge pots' - ie a small pot of fuel that your pump can draw on which won't spill out on long corners. They serve different purposes it's just that a swirl pot doubles up as an anti surge mechanism. IMHO Mike Quote
Blatman Posted November 14, 2003 Posted November 14, 2003 P.S. Blatts do you read a lot of books? Not really, although I have read several....... Westfields have been my "hobby" since 1989, so I've tried *lots* of bits/suppliers, spoken to *lots* of engineers, spent (and wasted ) lots of money, and generally done lots of "research"........ I think he just spends too long on the net I do also spend *a lot* of time on the net........I discovered Blatchat back in early 2000, and I used to, until very recently, read everything that was posted. The tech section of their web site has several *very* knowledgable people, and lots of the info is as relevant to us as it is to them. I also read everything that gets posted here, and I seem to have a good memory for digging up info that I've previously read It also helps having a Le Mans GTP engineer in the family..... Quote
Matt Seabrook Posted November 14, 2003 Posted November 14, 2003 I do also spend *a lot* of time on the net........I discovered Blatchat back in early 2000, and I used to, until very recently, read everything that was posted. The tech section of their web site has several *very* knowledgable people, and lots of the info is as relevant to us as it is to them. I also read everything that gets posted here, and I seem to have a good memory for digging up info that I've previously read It also helps having a Le Mans GTP engineer in the family..... Mornin mate Quote
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