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Type 1 breather theory and operation
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busdaddy
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PostPosted: Wed Sep 28, 2016 6:40 pm    Post subject: Type 1 breather theory and operation Reply with quote

Like many systems on our VW's the crankcase breather is often misunderstood and few take the time to fully understand just how many things it really does, once again those shmartypants German engineers made a simple device do many important things that the untrained eye never spots.

The 68-71 breathers we find on our buses separate oil from the crankcase fumes with the louvered gasket at the base as well as the trip up the generator tower (thanks gravity), the upper stamped sheet metal "bulb" is exposed to cooler air entering the engine compartment and the interaction where the warm fumes meet the cooler inner surface condenses the water out of the fumes and drains it away via the draft tube leading down beside the dipstick, that's why the draft tube has got the pinched rubber boot on it, drip drip drip.
The fumes continue on through a hose to the inlet snorkel of the aircleaner and are force drawn out of the system by a weighted flap that chokes off the snorkel at idle and maintains a slight atmospheric depression on the hose right up to near full throttle, as air flow increases with engine speed the flap closes off the breather hose to prevent sucking up more than just fumes, but even at full flow when the flap is fully open it's still got a divot in it to maintain flow and not completely block the breather hose.

Now here's where the science ends and the questions begin, VW continued to use the 1600 in buses after 71 (but not in North America), the oil bath was retained for a few years and even featured a bimetal valve that controlled a vacuum operated flap for the preheat air opposed to the wax pellet thermostat on the 71 and the cable controlled system on the 68-70 models.
When they changed over to the plastic aircleaner with the paper element (mid 73?) they ditched the draft tube and increased the size of the hose between the bulb with the filler cap on it and the aircleaner, this system no longer used the weighted flap in the snorkel. The old system was a full time flow PCV system, did the newer system act in a similar manner using the resistance of the filter element to extract fumes?, and what about the water?, oil formulas didn't change, so what happened to it, was it suddenly OK to recycle it through the engine?, did oil change interval recommendations change with the introduction of the new air filter?

On a side note I've also noticed there's no flame trap on later systems (although there doesn't seem to be many cases reported of exploded aircleaners due to a backfire).

New replacement breathers are the later large nipple style with no drain tube, they can be made to work with an oil bath by adapting the hose to fit 2 different diameters. But they seem to make alot of moisture under the cap (white milkshake scum), it's getting sucked out by the smaller bore bobweight flap on the snorkel but why isn't it working and keeping that oil dry?, is there another hidden puzzle piece I'm missing?

Maybe some of our UK or Euro based members with later plastic aircleaner 1600 buses who drive thier bus 20+ miles daily and reach oil temps of 200f+ can share thier experience, any goo under the oil filler cap?, is it all white down inside the filler neck? (especially when the ambient temp is ~ 15 degrees C)

*This is spurred on by a customers bus that gets the sh*t driven out of it and reaches good oil temps daily for extended periods, it shouldn't be making the milkshake, WTF?
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PostPosted: Wed Sep 28, 2016 7:44 pm    Post subject: Re: Type 1 breather theory and operation Reply with quote

All worthwhile questions. Sorry I'm going to muddy the waters: we're any changes in the non-US T1 bus specifications correlated with the bug's adaption of fuel injection breather systems? I know the road draft tube was eliminated eventually, and I think there was a difference in bug and bus L-Jet breather systems. Any correlation here?

Robbie
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skills@eurocarsplus
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PostPosted: Wed Sep 28, 2016 7:49 pm    Post subject: Re: Type 1 breather theory and operation Reply with quote

and, the system would also draw in fresh air via the crank pulley...no seal there.

EPA is what did the "closed loop" system and made it so you have to suck vapor into the intake tract and burn it
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PostPosted: Wed Sep 28, 2016 8:38 pm    Post subject: Re: Type 1 breather theory and operation Reply with quote

Always questioned that floppy bobber flap. Makes sense now that it's just pulling from the case, but why not increase vacuum with engine speed?

I guess the divet in the flap is enough, as airflow increases it also has a more powerful draw from the breather hose. Nevermind.
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busdaddy
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PostPosted: Wed Sep 28, 2016 8:38 pm    Post subject: Re: Type 1 breather theory and operation Reply with quote

No doubt the EPA had a hand in this, yet the Euro delivered models also got the no tube/big hose system and there didn't seem to be any smog laws there. And yes, I should have included where the air gets in to allow flow through ventilation, the gap around the pulley it is. Although too large a gap may cause excess flow and suck oil up the generator stand, consider the gap when tracing down excess oily blowby issues. Moving the bob weight to make the flap lighter (reduce flow) may help with that issue.

Feel free to muddy the waters all you like Robbie, I want to figure this out and learn all I can in the process, I've gotten my head around the early system but the later one still makes me go "Hmmm..." now and then. Is it better?, or just another cost saving measure to reduce parts count and speed up the production line?
The L-jet bug used a simple breather like the later carb models, except for some (I'm guessing California) models which had the same vacuum regulator diaphragm as the L-jet bus has on top of it's breather tower and a hose to the S boot, the bug's was incorporated into the side of the airfilter, most have the blank for it, it looks alot like the EEC valve we are used to on buses.
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PostPosted: Wed Sep 28, 2016 8:47 pm    Post subject: Re: Type 1 breather theory and operation Reply with quote

You guys make me feel pretty stoopid
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