Crankcase Vapors - Vent or burn?

[veggie]

Yesterday I gave my Listeroid a 4 hour maintenance run at 80% load.
At the end of the run, my garage smelled like the inside of the crankcase.
I do have a working check valve on the crankcase breather and there is no visible vapors emitting from the case.
However, the place was thick with the smell of sump oil vapor.

So my question is....
Can I route the crank vapors to the inlet port and burn them?
Or do I have to vent the case to the outdoors ?

I have read some discussion in the past about the possibility of a "runnaway" if vapors get too heavy from excessive ring blowby but I have never heard of this actually happening to anyone.
Opinions ? recommendations ?

thanks,
veggie

[BruceM]

Good question, I also wonder about the viability of venting the crankcase to the intake manifold too.

I couldn't stand the crankcase stink in my engine room, so added the brass water type check valve with reduced spring and gravity to close the valve, vented outdoors.  I got that idea from some folks here.  It works fine.

I've seen photos and read about others piping to the intake manifold.  That seems like a better way to dispose of (burn) the oily vapors, though I wonder about effectiveness since the power stroke crankcase positive pulse doesn't happen during intake. Wouldn't the crankcase vapors be partially pushing out of the air cleaner, thus still stinking up the engine room?

I have no worries about a runaway, since my standard shutdown also decompresses, like the SOM, and my Picaxe engine monitor monitors engine for over and under speed.

[mike90045]

I'd think, using loose coupled 4 or 5 inch lightweight drain line, you could plumb some sort of collection hood over the crankcase and route to the vicinity of the intake.  It may suck up 80%,  the tighter the coupling, more efficient.

[Jens]

I vented my crankcase to the input manifold and was quite happy with the results. The one thing that I would do different in retrospect - make sure there is a slope in the manifold towards the engine (BTW, manifold because I was running a twin). Anyway, I found that the vapour condensed to some extent in the manifold and upon shutdown the soup had a chance to leak back into the air filter. Over time the air filter literally filled up and started leaking black goo onto the generator. A rag fixed that but it was messy. Every once in a while I emptied the air filter.
BTW, I have come to belief (WAG) that a lot of my oil burning and veg oil leakage to the crankcase issues were caused by me neglecting to hone either the factory sleeves or the replacement sleeves. This might have also caused my big soot issues.

[veggie]

BTW, I have come to belief (WAG) that a lot of my oil burning and veg oil leakage to the crankcase issues were caused by me neglecting to hone either the factory sleeves or the replacement sleeves. This might have also caused my big soot issues.

Yep ! without honing, your rings probably never seated. Takes forever to break in the rings/bore.

[veggie]

That seems like a better way to dispose of (burn) the oily vapors, though I wonder about effectiveness since the power stroke crankcase positive pulse doesn't happen during intake. Wouldn't the crankcase vapors be partially pushing out of the air cleaner, thus still stinking up the engine room?

Good point BruceM,

I think that would happen 50% of the time....

Intake cycle:
==========
On the downstroke the vapors would be forced from the crankcase, on the same downstroke the inlet valve would be open and drawing in air.

Combustion cycle:
===========
On the downstroke the vapors would be expelled from the crankcase, on the same downstroke the inlet valve would closed and vapor may fill the air cleaner housing.

Just not sure if there would be enough vapor to exit the air inlet system into the engine room.

veggie

[Cornelius]

Most of the wooden boat engines i've worked on (mostly Norwegian 1- and 2-cyl gasoline engines from the 40's and 50's) have a pipe/tube from the crankcase breather to the air-filter...



Wouldn't think diesel engines would be different?

[BruceM]

I think most diesels also do the crank vent to air cleaner approach- my MB 300D does.

The issue is the slow speed, poof of the CS crankcase the power stroke while the rather tiny intake is stopped.  A higher speed and/or multi-cylinder engine would typically have almost constant intake manifold vacuum.

Jen's engine was in an enclosure, so that would buffer/store the vented air until intake.  So that would not really let us know if it would really work well  in a more typical engine room setup. 

A larger intake buffer/box with filter would also do the trick to hold that power stroke crankcase vent pulse.

[Jens]

Jen's engine was in an enclosure, so that would buffer/store the vented air until intake.  So that would not really let us know if it would really work well  in a more typical engine room setup. 

I also ran it in a general engine room setup without enclosure with the same results. It is a twin though and running a bit faster than the typical single.
The standard vacuum valve setup on a twin is ineffective IMHO because one piston goes up as the other comes down so there is very little net change in crankcase volume. The connection to the intake (again IMHO) sets up a pulsating but always negative crankcase pressure assuming an air filter is in use and you don't have a large connection between crankcase and intake. I used something like a 3/16 id hose. I guess the fact that there are two intakes which are combined to give a larger volume also helps. I never really investigated the whole setup though and it is possible that a small amount of vapours escaped.

[glort]

I'll probably be the odd man out in that I hate plumbing the Crankcase vapors back into the engine.
It always results in filthy, black, dirty inlet manifolds where you don't know if it's dirt, condensed oil or what the heck is going into your engine.

Just last weekend I discovered my vehicle had puked oil out the PCV pipe which I had disconnected. Thank goodnees for that. I discovered my son had substantially overfilled he crankcase which would have gone back pre turbo before I disconnected the PCV and resulted in one hell of a runaway.  Instead what happened is I got a mess under the bonnet and a rust proofing treatment of the floorpan. 
Given the amount of oil that was ejected in the course of me going over a mountain range, I really hate to think what would have happened if all that oil went back through the turbo into the engine.

There are several Vehicle engines I know of here that are prone to failure directly caused by Crankcase fumes going back into the intake through residual Buildup.

In any case, I would Vent the crankcase to atmosphere and keep the intake air clean of the muck that comes from the crank case or at a very minimum, use an air compressor oil vapor trap before introducing them to the inlet .

[ArcticCogen]

Apologies for digging up an old thread.  My 6/1 is still patiently waiting on the to-do list for its first smoke and in my planning I hadn't bothered to consider crankcase vapors because I thought the crankcase on the Listeroid maintained a slightly negative pressure?  Is this not the case?

In the commercial world I always found the best solution for crankcase vapor was a rolled up oil absorbent pad with one end stapled closed and the breather tube stuck in the other end and secured with a cable tie.

John

[thomasonw]

I like the oil-zorb idea, will give it a try on our main engine.  I had thought of fastening on a quart plastic bottle with some oil-pads cut up and put in the bottom, but your idea seems oh-so much simpler 


Here is what I did for our small Kubota EA300 DC generator:



The original C-Case vent tub is the larger white one - with the sort of clear one heading over to the intake manifold after the air cleaner.  A blob of plumbers putty seals things up.  In use the alum can cools the gases a little, helping to drop out most the gunk.  I change out the can every year as part of the winter service and there is some bit of junk in the bottom of the can.  Must be working as the sort of clear tube is still - - - sort of clean.  We  just crossed the 600hr mark and I do not see any objectionable build up in the intake. 

Here is a larger view:


Can tell you w/o this bypass gasses are VERY noticeable (e.g., when the can fell off one time).

-al-

[playdiesel]

I thought the crankcase on the Listeroid maintained a slightly negative pressure?  Is this not the case?


John

Yes and it does so by venting the crankcase to the outside, where did you think the gasses went?
Adapting from the OEM vent is a bit difficult but if you remove the vent and make up an adaptor to 1" pipe you could plumb in a swing check so as to keep the needed negative crankcase pressure and after that go outside or simply plumb it to the intake as the fellow with the Kubota did.

[buickanddeere]

Check fleabay. They sell catch cans for direct injection gas engines to reduce the chances of sooting up the intake valves.  Then route the 1/2 burned gasses to the intake manifold downstream of the aircleaner. Plus if somebody chirps about the EPA. Tell them the pipe work is a Tier 1 emissions system.

[Dualfuel]

I am a diehard aircleaner, PCV, sealed systems, and even sealed gastanks fan. The caveat are these old FE engines. I worked at a junkyard where the owner used these FEs with no aircleaner/PVC. It was a place in the sand, so the oil fill cap area would get dust in the valve cover. These engines seem to handle this configuration better then the stock filters. I use this idea on the blower engine in the photo. With out the oil fill cap, I don't get that milky water condensation in the oil. The FE does spew drops and vapor all over the place, but it starts and puts out 100hp at the shaft, all winter, which is the point of burning all that hi-test in the first place.
I totally do not recommend this. I just thought it would be interesting to show the other side of the coin.