VW Krank-Vent oil control idea by Alpha_Maverick

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Joined: Sun Feb 08, 2015 5:05 am

VW Krank-Vent oil control idea by Alpha_Maverick

Postby Justin » Sun Feb 08, 2015 6:35 pm

OP: http://www.thesamba.com/vw/forum/viewtopic.php?t=552366&start=0
Posted: Tue Apr 16, 2013 6:17 pm Post subject: Krank-Vent oil control idea. Reply with quote
I've mentioned this in other threads, but I figured I should start my own now.

Most people in this sub-forum know about the Type I's propensity to fill the driver's side valve cover with oil, and the starvation issues that can exacerbate. Many people have come up with various ventilation systems to combat this, but I wanted to come up with something that still -looked- relatively stock, so I came up with this:

The boxer-pairs generate alternating pulses of high and low pressure inside the case as they alternate between BDC and TDC, respectively. This is due to the displacement of air in the crankcase. The two pairs, ideally, would move air back and forth inside the crankcase, but as RPMs climb, the case has trouble moving the air freely, and pressure pulses are generated.

If you drill and tap the case, you can give these pulses somewhere to go. Put a check valve or reed valve on those lines, and you can create a longer lasting negative pulse in the crankcase, assuming that you have a sand seal, and a very tight motor. Ideally, you would want to vent these pressure pulses into a catch can to isolate the oil, then vent the remaining air into the intake stream, before the carburetor. The negative crankcase pressure would be best regulated with a vacuum break/regulator in the valve cover. This would promote oil return to the crankcase, as well as control crankcase vacuum.

Since I don't want to use a sand seal, I'm not going to use the ideal. I'm going with a shortcut. Instead of using a catch can, vacuum breaks, and all that, I'm going to feed the high pressure pulses through Krank-Vent check valves into the driver's valve cover. This will use the high pressure pulses to directly force the oil back towards the sump, and the negative pulses in the crankcase to pull on that same oil. When I have time after getting everything sorted (probably never), I'll make a windowed valve cover to see if it actually works like it should.


That's the idea. I got my two Krank-Vent minis the other day, and was decently impressed. They're essentially poppet-style check valves with no spring, and some proprietary valve-disk material. They're not bad, and they flow nicely. I'm not sure they're worth the money, but... *shrugs* I have them. One interesting behavior I noticed: when there are no hoses attached, any detectable (using my breath) reverse flow caused the valve to close tightly. When a short length (<6") of hose was attached, behavior didn't change much. With a longer hose attached (~2.5'), I got the valve to flutter noisily, passing air in the reverse direction. The longer the hose, the more I could do it. When I tried to tap a magnehelic gauge to it, that altered the behavior like shortening the hose. With the magnehelic attached, I was able to maintain reverse flow, through the noisy flutter, up to 1.75" of water. I was able to maintain flow up to around double the pressure without the gauge attached. In all cases, rising above a certain pressure slammed the valve shut and stopped all flow.

Comments? Ideas as to why it's fluttering?

yes, I know this is overkill for a "stock" engine. I still wanted to do it, because I can.

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