increaseing fuel efficiency in a big twin...check valve?

[Saskatoon2005]

Hello all,

I have heard rumours about being able to make the old big twins more fuel efficient by redirecting some sort of check valve that would dump unburnt fuel into the lower leg and untimately into the water (lake, ocean..etc), back into the carb or cylinder to be burnt.

Is this true and what motors do this. i have an RDS-23 outboard. I am curious to know if I am able to make my 1961 Johnson Outboard 40Hp more fuel efficient.

 

[F_R]

Re: increaseing fuel efficiency in a big twin...check valve?

You are speaking of the crankcase drain valves, and yes they do dump into the lake. They are behind a little cover plate about an inch by an ince in size, on the lower/front of the crankcase, near the intake manifold & reed plate.

It is debatable how much fuel mileage would increase by capturing and recycling the drainage. But it would keep it out of the lake, I suppose.

 

[lark2004]

Re: increaseing fuel efficiency in a big twin...check valve?

These inlet covers came from a 74 or 75 40hp, as did the plate that replaces the drain valve. You can get them from any outboard wrecker and they are a simple swap over. Does exactly what you want.

 

[Saskatoon2005]

Re: increaseing fuel efficiency in a big twin...check valve?

Wow,

very impressive pic, lark 2004! It sure is true that a picture speaks volumes!!! Yeah, that is exactly what I was talking about. Have you noticed any increase in fuel efficiency, or decrease in fuel consumption? I would love to know how you managed to do this...can you give me the part numbers of the parts that I would need? I also would like the adhesives you used to get this back together including gaskets, and ther gasket part numbers. That is amazing. I LOVE this website! Awesome!

Patrick

 

[lark2004]

Re: increaseing fuel efficiency in a big twin...check valve?

can't help too much with gaskets and stuff.....I made all mine myself as the cost was too much for me over here in Australia.

The parts you need are the bypass covers, one upper and one lower Part #'s 0386364(lower) 0385107(upper),
And...
HSG. NIPPLE & VALVE ASSY part # 0385109.

Do NOT use silicon tubing. Use PVC tubing, it is available from any mower store. I used the tubing they sell for fuel lines on line-trimmers(weedwackers)

 

[WillyBWright]

Re: increaseing fuel efficiency in a big twin...check valve?

I like it for the sake of reducing pollution. Excess oil-rich fuel is pulled into the cylinders to be burned rather than dumped straight into the water. But there will be little to no effect on efficiency. Puddling only happens at low RPMs. When the throttle is opened up, those puddles are pulled in and burned in a few seconds. No puddling will occur again until the throttle is brought back down.

I worked on an old V-4 75Hp where somebody took that same idea, but sent the stuff back to the gas tank. It was dirty and oil-rich, so by the end of the tank the customer was complaining of excessive smoke and lack of power. Things seemed to clear-up with each fresh tank of gas (he was using 6 gallon cans and modified a cap with a nipple to transfer whenever tanks were changed). The puddled fuel contains more oil than gas and he was making the fuel in the tank richer with oil with each used gallon used. It's not a lot, but apparently it was noticeable.

 

[Saskatoon2005]

Re: increaseing fuel efficiency in a big twin...check valve?

Thank-you guys for your input...it's best to try and do our parts to keep the environment clean for future generations...Thanks again.

Patrick