kenh3497

I'm sure there has been discussion before on this....

Has anybody plumbed the crank case drain/breather back into the intake manifold of their older 4C engine. I'm thinking it would be a much more elegant way of taking care of the "mess" of having a drain hose out the bottom of the plane.

I'm thinking about this on my Enya .90

Ken

w8ye

My Feedback: (16)

Many times and different ways

Only drawback is having a place to add after run oil

Kmot

My Feedback: (24)

I would rather have a 'fresh' fuel/air mix going up my intake manifold.

jeffie8696

The problem with plumbing it back into the intake is that the gasses that pass the piston ring are most oftem burnt and no longer capable of supporting combustion. If a pocket of these gasses surround the glow plug element it could cause a misfire. This is a common phenomenon with EGR equipped gasoline engines.
Is is less prevalent at high speed where the occasional misfire would not be noticed but at idle it may cause problems.
Regardless of that I see it being done on new production engines to promote a cleaner airframe. I would not choose to do it myself.

Campgems

Magnum 4 stroke of 70 and greater size plumb back to the intake. Ditto for O.S 120s. All of the new designed O.S engines do this internally. It's not a bad idea. Keeps the spit off your fuselage and doesn't seem to hurt performance any.

Don

Motorboy

Not correct as a EGR function (Exhaust into the intake manifold to reduce combustion temperature hence nitrogen oxide (NOx) emissions reduction). The returned unburned fuel gas/oil fog who is entered into the intake manifold is socalled as PVC (Positive crankcase ventilation).

kenh3497

Correct EGR = Exhaust Gass Recurulation. PVC = Positive Crankcase Ventalation

I see all points taken. I've also thought about plumbing a nipple at an angle VERY close to the outlet of the muffler. If done correctly the exhaust flow should help scavange the excess oil. It would operate like an eductor (sp) if everything goes acording to plan.

bogbeagle

I do this on my 4-strokes ... including an Enya .90.

Works a treat.

Engines run much cleaner.

spaceworm

If you have enough blow-by, this could be an alternative to a dedicated smoke system.

Richard/Club Saito #635

kenh3497

How about a picture or two if you don't have to tear off a bunch of cowling to get them.

Ken

bogbeagle

OK, I'll get that sorted for tomorrow.

bogbeagle

Here is my Enya .60.

I soft-soldered a steel patch to the inlet manifold, so as to provide enough material to accept a threaded nipple.

When the engine is running, you can clearly see the flow of "mostly-oil" from the crankcase to the inlet manifold. It's a surprisingly good flow rate ... and it guarantees that fresh lubricant is reaching those hard-to-lubricate timing gears.











Here is my Saito 2.20.

The manifold is an alloy casting, so I drilled a small hole into the flange and let in a piece of brass tubing. I carefully flared the end of the brass tubing such that the silicon tube is more securely retained.

kenh3497

DUUUH, Never thought about adding a bit of material to the intake manifold. With that said maybe just solder in a nipple directly???? Nice solution to a messy problem. I would also assume you had to slightly change your mixture settings?

Has anybody used a "low" or "lower" oil content fuel. It seems to me this would be a possibility with ready supply of oil being reintroduced into the engine. Right now I'm burning heli fuel with a slightly higher content oil as it is the only fuel I have and I don't want to stock two different fuels. That will change as soon as it's gone. I've given up the heli's for the time being.

Thanks for the pictures!!

Ken

bogbeagle

Ah, the oil.

I didn't mention that, but I've been using @ 13% for some considerable time, now. Been mixing 2 gallons of commercial fuel with one gallon of pure methanol.

'Spect I could go lower than 13% ... 10% would probably be fine. Some of the buggy guys use about 8%, I think.

kenh3497

What does OS recommend for oil content on their "new" 4C engines that have the PCV built in?

MetallicaJunkie

i drilled a hole and tapped a fuel nipple on to the header, and rerouted the crankcase vent to it..... it smokes more so thats a good thing

Kmot

My Feedback: (24)

I just looked up all the latest OS four stroke engine specs and they all are spec'd for 18% oil in the fuel.

kenh3497

Not surprised buy that number. You know they want the engine to live forever. As mentioned before some engines (car) use extremely low oil contend and seem to live a life. I know the car guys run the crap out of their engines and do rebuild often but I'm thinking they are running in the upper teens for RPM.

Anybody else out there beside bogbeagle running reduced oil fuel in their 4C with an oil return?

rcdude7

My Feedback: (264)

They run them 30-40K while racing, it's no wonder they have a short life compared to a plane engine.

bogbeagle

Well, the Saito petrol engines are now rated to run at 5% oil mix, afaik.

They started off with a 3.5% mix, but experienced premature failures of the big ends ... I think that's the story, anyway. The big ends are plain bearing, afaik; exactly as per the glow version of the engines.

Yes, they say that petrol has some lubricating properties; and that methanol has no such properties - so the effective "oil mix" of the Saitos would be a little higher than 5%.




We know that a 2% mix provides adequate lubrication on industrial petrol engines. Admittedly, these usually have needle roller bearing on the big-end and the little-end. But, 2% seems to provide adequate lubrication within the cylinder and also for any ball-races that support the crankshaft.