"Oil Drain Valve" fuel recovery on a Big Twin

[Paul Moir]

Chinewalker speaks of a member over at AOMCI that has modified the drain valve on his engine to dump the excess puddled fuel from the bottom of the crankcase and behind the left reed into a can so he can dump it back into his fuel tank. He, the AOMCI member, claims to recover a worth-while amount of fuel this way that would otherwise be simply dumped into the water.<br />This got me thinking. Although a tidier way to recover the fuel would be to simply route the fuel that would otherwise be dumped back to the gas tank, that would mean running an extra fuel line back to the tank and the complications that brings. What about instead running the fuel directly into the carburetor's bowl, bypassing the needle valve? This could be done simply by pressing a fuel barb into a hole drilled into the carb's bowl vent passage. I'm thinking that there couldn't possibly be enough gas coming from the drain valve to really affect the fuel level in the bowl.<br />What do you think?<br /><br /> Original Thread

 

[jimmbo]

Re: "Oil Drain Valve" fuel recovery on a Big Twin

Most of the puddled stuff is oil, sending it back to the carb will just mess up your gas-oil mixture plus pressurize the float bowl messing up the air/gas mixture . Sending it back to the gas tank will mess up the gas-oil ratio too, and only some pre 1960 tanks were designed to be pressurized.

 

[Paul Moir]

Re: "Oil Drain Valve" fuel recovery on a Big Twin

First, thank you for your reply jimmbo.<br />I had read your reply in that thread and thought about what you wrote there about the puddled fuel/oil being mostly oil. And I think you're right - that most of that suff would be the heavier fractions since the lighter ones would be more likely to vaporize and get burnt. But if the recovery rates are anything like what the AOMCI member claimed (6:1) there must be a large ammount of still viable fuel being dumped.<br /><br />I should clarify that I don't intend to pressurize either the carb bowl (that would be disasterous!) or the fuel tank. Both would still be vented to the atmosphere as they normally are. I was just proposing to use the carb bowl vent as a handy passage to return fuel to the carb, but not block it off from the atmosphere. It's true though that this would affect the fuel level slightly which would vary the air/gas mixture.<br /><br />I appreciate your comments. As it stands it looks like this idea's getting religated to the "Dumb idea, don't bother" catagory.

 

[jimmbo]

Re: "Oil Drain Valve" fuel recovery on a Big Twin

The newer outboards recirculate the oil to the upper crank bearing and to the crankcase sealing rings.

 

[Paul Moir]

Re: "Oil Drain Valve" fuel recovery on a Big Twin

Yeah, these ones recirculate a bit too. There's a hose running from the bottom main bearing to the top for just the purpose. But the drain valve assy takes and dumps it only from odd puddling locations (ie, back of reeds, and a crevice in the bottom crankcase chamber).<br />This would be more like those ones where you see it being sent back to the intake manifold or into one of the bypass covers.<br />Don't forget we're in the $0.91+ per l range down here. Not like the 0.75c range you got there today...

 

[tgissel]

Re: "Oil Drain Valve" fuel recovery on a Big Twin

Paul, I tried the fuel recovery into a can that Chinewalker was talking about. Either I did it wrong or the guy over @ AOMCI is running too rich, I captured very little if anything and most of it did look like oil. I gave up hope on this project. Good Luck.

 

[Paul Moir]

Re: "Oil Drain Valve" fuel recovery on a Big Twin

Great, thanks!<br /><br />I'm glad I didn't go too far with it then. I gotta admit, I was a little suspicious.<br /><br />Thanks Jimmbo and Thad!

 

[Chris1956]

Re: "Oil Drain Valve" fuel recovery on a Big Twin

I created an oil recovery system for my '59 Johnson 50HP outboard. I routed the rubber hose from the bottom of the intake manifold to a plastic container I mounted next to the carb air intake. This plastic container had the top cut out and the bottom had a hose connected to an extra fuel tank. The pressure from the crankcase forced the unburned fuel up into the container, where the fuel vapor was drawn into the carborator and burned, while the liquid drained under gravity to the fuel tank.<br /><br />If you run the hose from the intake manifold directly to the fuel tank, you will stink up the boat with gasoline fumes, hence the intermediate container near the carb.<br /><br />I did find about a 1::6 ratio of unburned to burned fuel. Although the recovered fuel was richer in oil, it was mixable with fresh fuel and could be recycled. Remember my carb was in bad shape. I hope most of carbs are in better shape.

 

[billbass9]

Re: "Oil Drain Valve" fuel recovery on a Big Twin

i dont think you wold want to recycle the used oil its going to be thicker and full of carbon

 

[jimmbo]

Re: "Oil Drain Valve" fuel recovery on a Big Twin

Paul, gas isn't that cheap here, Calgary where Ghengus Klein lives perhaps, up here in Edmonton it is about 77c per l, and it's comes from around here. A couple of months ago it was about 90c. I walked into a gas station with my hands in the air and asked if they had a gun behind the counter and if they did to please point it at me because it would be appropriate cause I felt I was being robbed.

 

[Paul Moir]

Re: "Oil Drain Valve" fuel recovery on a Big Twin

Haha - I guess it's bad all over then Jimmbo. I lived in Edmonton for a short time a few years ago and I remember seeing a sign for somthing under 50c/l. I guess the memory just stuck. <br /><br />That's some interesting information, Chris. I might try just collecting what drains into a bucket to satisfy my curiosity some time. But I suspect the fuel efficiency of my '62-'63 28hp is somewhat better than your fat fifty. Are they really as hard on gas as people make out? IE, like twice what they ought to be?<br /><br />Bassinbill - there shouldn't be any carbon in the stuff from the crankcase. It just doesn't get into there unless there's something wrong with the engine.

 

[jimmbo]

Re: "Oil Drain Valve" fuel recovery on a Big Twin

Actually there is some carbon inside the crankcase. Carbon builds up in the ring grooves and some of it works its way into the crankcase. The piston tops get pretty hot and the underside of the piston top often shows a buildup of carbon from oil burning off.