No Oil Filter???

it flows both ways in that tube Jan. It flows from crankcase to air filter when the crankcase is pressurized (when the engine is making power), but it flows the OTHER WAY during high vacuum decelleration (downshifting). That's why it's important that hose is connected on the filtered side of the air filter. Our engines don't have that PCV valve which prevents flow one-way.

this isn't arguing, it's discussion. :-D

John Aircooled.Net Inc.

[one idea propounded snipped] [rejoinder snipped]

To the best of my tiny ability, I want to summarize the two thoughts on this ventilation discussion, remembering that this branch of the thread started when I said that after I put a good oil filter on the Wonderbus's engine, I would not need to change oil as frequently. My mistake was corrected when it was pointed out that there is a sufficiently large opening behind the pulley to allow a lot of contaminants to be pulled into the case. Using a sand seal, the pulley end of the crankshaft can be sealed to keep this crud out. Now we have a case that has only one real opening: the hose leading up to the carb side of the oil cleaner/filter.

Viewpoint 1: The "that's all that is required," view. Water vapor and blow-by will all vent out of the crankcase into the carb to be burned naturally. No additional inlet is created to provide flow into the crankcase. Now you're good to go with fewer oil changes.

Viewpoint 2: The "you want to have flow" view. This view says that the single opening at the top of the case is insufficient to draw all the evil fumes out from the case. To assure complete ventilation, an inlet into the case needs to be provided to replace the one the sand seal closed off. This inlet wants to be filtered.

Sidebar: Additional outlets from the case, in the valve covers, have been suggested. In Viewpoint 1, I reckon some fumes would be drawn out of the heads in a somewhat lazy fashion; in Viewpoint 2, a faster flow might be expected, as there is an easy source of outside air to replace the fumes leaving the heads.

I can easily see how providing an inlet of filtered air into the case would increase flow. But getting carried away and doing more than is needed to accomplish the job is silly. As Bob Hoover says, I am the Mechanic In Charge of this vehicle. Which, in my case, is like handing a loaded pistol to a chimp.

Anyone else got any thoughts about this inlet needed / not needed discussion?

Sounds like your rings are shot John ;) Either that or you converted to

2-stroke :D

Please explain to me where the vacuum inside the engine case comes from? Reversed blow-by during engine braking or deceleration? That's the only possible channel. Is that enough to overcome the suction of the carburator, inside the air filter, to create airFLOW back into the case? (Granted, there shouldn't be much of VACUUM in the aircleaner, just FLOW.. as the aircleaner itself is wide open to the athmosphere.)

Even with the flaps "closed" (as far as they will close, leaving a gap and idle circuit open for air to get through), there's still quite a bit of suction through the carb.

(you could use the brake booster one-way valve from a baywindow bus....LOL)

I just don't see how you get enough air to enter the otherwise sealed case to make noticeable FLOW possible. In either direction. Pressure pulses are easily relieved through that one hose. It's still not flow.

Good :)

I would already have performed tests with a vac/pressure gauge hooked up to one of my engines, but the damg gauge fell on the floor months ago and broke. ARGH. It would have told me the pressure/vacuum conditions inside the case during normal operation of a non-sand seal engine that was just broken in. (assuming fairly minimal blow-by)

Jan

what is the MAP during decelleration? Is this more or less then the crankcase pressure? Is this more or less then atmospheric pressure?

Hint: MAP and crankcase vacuum are very strong during decelleration, so much so that the engine can suck oil thru worn valve guides, or oil up thru worn rings. Rings seal most, but not all, pressure differential in either direction. Put a gauge on the crankcase, you'll find it goes into a vacuum condition under decelleration, and this would suck air from the air filter into the crankcase. Why else would they have put the vent on the filtered side of the air filter?

John Aircooled.Net Inc.

Well, I'm glad they are all doing okay. Still it's a shame about the store. When I moved here there were many stores - Knights, Southern Volks, Red Baron, etc. I do most of my shopping online already so I guess I will be doing a bit more of it that way now.

As we all know, hot air, and lightweight particles suspended in it, have a natural tendency to travel UPWARDS without assistance. The stock crankcase ventilation system leads more or less straight up from the depths of the crankcase, where the hot air, oil mist and water vapors rummage.

Then there are the pressure pulses pushing and pulling this air mass in the vantilation tract back and forth. My reasoning says that these pulsations pretty much cancel each other out, resulting in almost zero absolute airflow in either direction. For that you'd need a) outside suction, by way of the carburator and air cleaner housing and b) replacement air to enter from someplace else to allow air to really move in the desired direction, in a continuous flow.

Now, even if no replacement air was present, I wonder if the hot air along with the hot water vapors could travel upwards and into the air cleaner ANYWAY, since that's what it would try to do even if there's no other activity in the system (When the engine is turned off). Self-cancelling pulsations, and carb suction added on top of that, and EVEN a marginal pushing effect from blow-by. Hmm. Could it be enough to vent the fumes anyway? Just not as effectively as I would hope, but adequately so anyway.

This still leaves us with John's claim that the "replacement air", or air in general, enters the case the same way it exits it: the same breather hose, only it would o it only when the engine is decelerating. Pistons drawing vacuum but carb butterfly closed.. rings give up and allow crankcase air to slip by, into the cylinder? I understand how this could happen to some extent, but what I keep wondering is is it enough to make a difference, i.e. strong enough vacuum and enough FLOW again to create reverse flow, to make this pillar of hot air in the vent tract travel downwards, AGAINST it's natural path?

One can't but wonder, until one buys another vacuum/pressure gauge to replace the one one stupidly dropped on the garage floor.

in addition one would need a sensitive flow meter installed in the vent hose. Since, as we know, pressure does not equal flow ;)

Jan

"Mike Rocket J. Squirrel Elliott" wrote:

but that's not what I said. I said that vapor travels both ways in that hose. I never said that hose was the ONLY way air entered the crankcase.

It enters from

entering near the open crankcase pulley, sealed off when you install a sand seal entering thru the breather hose entering by getting past the piston rings.

None of these only allow flow "one-way". Travelling from the filter to the crankcase is not a normal path, it only happens when you decellerate. But it does happen.

John Aircooled.Net Inc.

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Narley Dude®

Of course the vac is strong during deceleration. In the manifold, and in the cylinder. But for it to be seen in the crankcase, the rings would need to leak pretty bad. A healthy engine doesn't burn noticeable amounts of oil during deceleration.

I'm dying to do this. :D

It's not, on the earlier oil bath models. Only on the later paper element models. (oil and the horsehair is the "filter", and from there you only had the internal velocity stack between it and the carburator.. nothing connected to that)

Only on the later paper element models. I tried to run the breather hose on the unfiltered side once, above the paper element. The element got soaked with black motor oil. EWW.

Jan

I reckon we can speculate about this all we want. Empirical evidence -- John? -- seems to suggest that things are just hunky-dory when the sand seal is installed and no other inlet provided. Jan reckons that things could be improved upon.

Leaving the measurement of air flow and pressure aside, which don't really prove anything except air flows and pressure exists, the real test would be to monitor the chemical composition of the oil to see if stuff we hope would escape does or does not and is building up in the case. Is there anything else that matters?

Which is the situation we were talking about? Getting replacement air from someplace else when the sand seal was installed.

Ok.

Jan

I say it probably is not an issue that would require a dozen or more newsgroup messages and extended debate over it :)

You'll be fine. The most important thing in my opinion will get adequately taken care of: pressure relief.

Precisely.

That could be witnessed by examining the underside of the oil filler CAP for yellowish-white creamy mayonnaise-like substance. That would be water that got mixed with oil and it collected there because it didn't have a path to exit. Or the engine was never allowed to run at it's normal operating temperature long enough for the water to evaporate.

Jan

Is there anything else that matters?

I've been wondering where the vacuum during deceleration in the crankcase comes from. I didn't know that happened. I can understand the vacuum in the intake manifold during deceleration, but not in the crankcase. I mean the throttle closes so air/fuel isn't dumping into the intake, but the pistons are still going and sucking in what they can through the intake valve on the intake stroke so that would cause vacuum in the intake area. I don't get it for the case, though.

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Narley Dude®

Don't worry, I planned to investigate V-Dubfolks after seeing you mention it previously. :)

Aw, c'mon -- with very little effort we could keep this discussion alive for a few more days!

Here, lemme show you -- watch a master:

Adding a sand seal to the pulley end of the crankshaft closes off the "inlet" into the case (I am assuming that air generally goes /in/ through the opening and gases vent out through the oil filler vent hose

-- especially during the still-being-discussed vacuum-in-the-case condition). I don't have my engine apart right now, but maybe someone does: how big is the inlet? The cross-sectional area?

Give the man a cigar -- CB Performance finally got back to me and confirmed what you, and others, have said: use the later style. Thanks for the help!

This, I reckon, is a Bob Hoover or Jan kinda question.

OK, then I won't answer it... :-)