Crancase Venting Question- GM90

[veggie]

Can anyone shed some light on this crankcase vent system for the GM90.?

The GM90's comes with two crankcase vents.

One is the typical listeroid reed valve vent located on the crankcase inspection cover.
I dismantled mine and confirmed that the reed is positioned to let air OUT but not in.

The second vent is an external steel tube rising from the crankcase to the top of the engine.
At the top of the tube is a check valve ball which is also positioned to let air OUT only.

I have attached the parts picture which confirms the positioning of the check-ball flow direction.

So.....why have two vents which both vent outward.?

Any ideas ?

veggie

[Henry W]

I believe it works like the following:

Top vent is for venting on intake and power stroke. (down stroke)

Bottom vent is for venting on comperssion and exhaust stroke. (up stroke)

Henry

[mobile_bob]

dang veggie, who knows why those indian thumpers are built the way they are?

just use a changfa call it a day already!



besides i really liked your work with the slowspeed changfa, what ever happened to that project?
i wanna know more about how that worked out.

bob g

[billswan]

Well good question?

Maybe it gives the option of sending the blow by outside if the engine is run in an enclosed space. That takes into consideration the upper valve is large enough. And a large enough hose is put on after the valve, and the lower vent is plugged? That is all I can think of.

Now both my 10/1 and the 16/1 were drilled for access to the crankcase by me in the same spot as the pix of the gm90. I did it to give a vent to a murphy oil level sensor and I can say that that spot has a lot of oil vapor particles in it as the clear line I am using is constantly full of fine black oil vapor that ends up making the glass in the murphy sensor almost to dark to see through. I even extended this line up above the top of the engine thinking that the particles would surly not make it up over the top of the loop and back down to the murphy sensor but no that only helped for a couple of days. After about so much time the sensor just gets black......... I am wondering if the stand pipe that is supplied is large enough to get the vapors to drain back before they get past the ball check?

One other thing to note veggie I see in the pix labeled plate 2 that it says 14, 16, 18 hp. Is that a indian misprint or are these engines made that large?

Billswan

[Henry W]

GM-90 engines  were made up to 22 hp. They are HUGE!!! Everything about them will make a Redstone and Lister/Listeroid twin look small. Total weight of both flywheels weigh over 600 LBS. I seen one fire up and
it was a trip!!! I watched Mike M. hand crank his over. And once it fired it seemed like it took only a few revelotions to reach set speed. The sound and power pulse was amaizing!!!

Henry

[Crofter]

Could the plumbing up to the top have anything to do with plans for oil feed and return for the valve mechanism?

[Ronmar]

Thats interesting.  Nothing like that on my 6/1...  Only the case door vent and reedvalve.

[veggie]

Both valves are positioned to open on the piston downstroke.
It seems redundant to have both valves in operation. There must be a reason for two vents but I have no idea why.
I was considering closing off the vertical tube vent and just using the standard inspection port crankcase breather.
Indoor location so I want to control fumes.

Is it not the case that a properly working vent valve in the inspection cover will keep the case under vacuum ?

veggie

[veggie]

what ever happened to that project?
i wanna know more about how that worked out.

bob g

Hi Bob,

I will post an update in the Changfa section shortly. Stay tuned 

veggie

[veggie]

Another advantage of using the vertical vent tube is that it has an NPT thread on the end.
It would be very easy to add piping and route the fumes A] to the intake or B] to the outdoors.

veggie

[Ronmar]

Another advantage of using the vertical vent tube is that it has an NPT thread on the end.
It would be very easy to add piping and route the fumes A] to the intake or B] to the outdoors.

veggie

I was just thinking the same thing, maybe that was what it was intended for, and that it would be very easy to route that upright pipe to the aircleaner, and just burn the blowby gasses.

I replaced my reedvalve assembly with a flat plate and 3/4" pipe nipple.  On to that I screwed a bronze inline checkvalve assembly mounted vertically with the spring removed(closes by gravity).  This gives me a 3/4" NPT port to rout the fumes elsewhere.  I have yet to do this though.  I just keep an old sock pulled over it for now, and it collects quite a bit of oil vapor...  Don't know how well that port would work as an oil filler, as I have no way of gauging the oil level in the lower sump without removing the access hatch to look down inside.  The dipstick on mine only dips the upper sump.

[rcavictim]

I had a noticeable issue with crankcase oil vapor contaminating the air in the workshop from my new Changfa 1115 engine.  I solved it by running a 1/8" pipe tap carefully into the crancase breather hidden behind the side cover next to the protruding fuel rack shaft and installing a brass hose barb and clear plastic line to a port brazed into the top cover of the oil bath air cleaner.  Voila.  No more oil vapor in the air.  The plastic line stays pretty clean.

[Crofter]

I really think for the engines sake that you should not try to keep the condensed products of combustion. Also not a good idea to breath it. Piping it to the outside would almost certainly result in hoar frost freezing and plug up or even sludge plugging unless you are in a warm climate.

The line into the intake seems a good way to dispose of the blowby and keep the crankcase negative but has the slight possibility of engine runaway on crankcase oil. That would likely be non existant in a single.

[XYZER]

Maybe on the big bores they felt the crankcase breather could not handle the volume of air being forced out causing a positive preasure increasing oil weap in the seals. Adding another vent would increase the flow and reduce crankcase preasure.....? Easier to do that than cast a larger breather assembly.......Indians fix things as afterthoughts.....

[veggie]

here's a picture of the breather tube.
Because the orifice in the check valve is smaller than the area allowed by the conventional inspection plate reed valve, I suspect the velocity through this pipe to me much higher than the standard breather.
The tube extends quite high (to the valve cover) which might help eliminate liquids from being carried outside the system.
This setup looks like a good candidate for an air intake connection setup.
I will make a blanking plate to block off the conventional breather port.
At first I could use rcavictim's idea of a clear plastic tube to monitor liquids.

veggie