Krank-Vent oil control idea.

[Alpha_Maverick]

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.

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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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[modok]

things with a tuned length and one way valve? hmmm.
trumpets
bagpipes
buzz bombs?


Probably any time the tuned length is tuned lower than the resonant frequency of the valve itself you can make it do that
Even breathers can be harmonic systems!

[Alpha_Maverick]

Kinda what I figured... so how would I kill the resonance, without adding a restriction?

catch can/Vizard~esque pulse termination chamber?
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[modok]

or maybe you can take advantage of it. If the tuned length is tuned near to the frequency of say, 3000 rpm, then it will aid pumping!

[Alpha_Maverick]

yeah, but only at -that- rpm, and at any other, it'll just be air going back and forth in the tube... Not really the goal here...

I think I'll look into the smallest chamber necessary to kill the reversion... we'll see what I come up with.
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[modok]

No, it would be helpful over a large range of rpm. Do headers work at only one RPM? and headers have no one-way valve.......

I'd have to think about that for awhile to say what it would and would not do, but when dealing with pulsating flow.......it's easier to just "go with the flow" \

if you approximate a taper with the flow from big to small, or just simply a step or two, such as using a hose bigger than needed, and perhaps a fitting with 50% of the crossection of the hose, then that should be enough to break it up enough for all practical purposes.

Design a trumpet that cannot be played

[Alpha_Maverick]

hmm... valid point on the tuned length-header comparison. Unfortunately, going only into the driver's valve cover makes it untenable to get a single tuned length. From my bench testing in the last few minutes, I just need two different lengths of hose terminating at the same locations to bring my resonant frequency -WAY- above the valve's natural frequency (lowest common multiple). I should be able to do that fairly easily.

I still wanna throw something at you for the pun, though...

ETA: I think my best bet is to make a "pulse termination chamber" (PTC) just outside the tin, on the driver's side. The 3-4 hose is short enough to not resonate (or only at fairly high frequency). Then split the 1-2 side just outside the tin, and run two slightly different hose lengths there, to bring the frequency up. Then dump the outlet of the PTC into the 3-4 valve cover. No restrictions, and as little as possible showing "under the hood".

Edit #2: Scratch the earlier edit. All I need is a short loop in each of the tubes, to totally screw up the resonant frequency, then there's no need for a PTC, or multiple lines from one location. I'll get a couple Tees tomorrow to check this idea.
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[Alpha_Maverick]

Ok, second idea failed. I guess the standing wave is just bypassing the non-resonant part of the tubing.


AND I'M A RETARD! Quokka, Dale, Dave: you can say it now, and I'll agree.

I was/am way overthinking this. Here's why:





The first harmonic of 4500rpm, one pulse every rotation is ~45"

My current resonant frequency for the passenger side hose (longest, 39") is ~87Hz, which is ~5,200rpm. Extend the hose a little, and it'll peak right around 4500-5k, which is right where I would want it...Modok, once again, was right on the money... I just had to figure out why/how.

My current driver's side resonant frequency is ~308Hz, or ~18,500 rpm. That won't be doing anything helpful for me, but it also won't be experiencing reversion, and it'll work better at lower RPMs. I can live with that. Then again, it wouldn't hurt to extend the tube over the transmission, to get a good frequency response, so that both tubes are at maximum flow when I need maximum flow. Use a wye, instead of a T, and then the alternating pulses would further aid in "scavenging". This might work...

Thoughts on this one?
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[mark tucker]

so , push on the 34 side and pull on the 12 side and let the oh never mind my motor dosent have an issue with that. what I cant understand is with all the pushing&pulling why dont both vave covers fill up & empty as fast as oh never mind.just run your motor 3 qt low and it wont have that issue.

[modok]

[Alpha_Maverick]

Uh... second harmonic? why?

I was using the formulas for an open-closed pipe, assuming that one rotation would yield a single wavelength pattern. With this in mind, I was using a 1/4 wavelength as the fundamental/1st harmonic. Why would I want to use a second harmonic? The first would give me a stronger resonance signal, wouldn't it?

Agreed on the friction, but I need the 39"+ to get from where I tapped the case, around the shroud, out the tin, and to the valve cover. The driver's side, I could probably tune to the second harmonic, but I might want to keep it on the first... who knows.
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[modok]

As far as intake tuning is concerned, that means two cycles in one engine cycle. 1 engine cycle is 720 degrees crank rotation

[Alpha_Maverick]

ah, so your "second" is what I'm calling "first"?

Either way, I think I'm gonna get both sides equal length, around 40", put a wye leading into the valve cover, and see what happens. When I get around to doing the window, if I find that it's -more- effective than I need, I'll move one over to the passenger's valve cover, just to balance things.
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[mark tucker]

hmm have you seen rockrussers thread where he drilled holes all over his raised roof aluminum case & plumed it with clear hoses to see whats going on.rearsearch it it may help some in this useless indever...oops who said that?? I mush of been hacked!!
hmm where is RC??? HEY RC WHERE ARE YOU!!! I HAVE A FRESH TUBE OF JB WELD!!!!

[Alpha_Maverick]

I'm guessing you meant "rockcrusher". Was that documentation on Shoptalkforums, or here on the samba?
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[fabricator john]

OOOOOO,,, a PCV valve ......
fabricator john

[SoCalJes]

You can shorten the length of the pipe and alter the pulse with an empty chamber T'd of the pipe.
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Jesse
71 Ghia
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Just because it didn't come that way, doesn't mean it shouldn't have.

[modok]

[Alpha_Maverick]

So... you wanna run those numbers for me?

Random point of thought: I found the calculated resonant frequency and plugged it into a tone generator, then got the valve to flutter while it was playing, and it's damn close, so I might make it a little longer, to bring the RPMs down, but I'll probably just make them equal length, and run it.
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[modok]

a tone generator? COOL

I could probably run the numbers, but I'm fairly sure it will work just fine anywhere between 3 and 4 feet. Frequency could be a little lower than organ pipe due to more actual flow transmitted through the tube, of course, we don't really know how much it will be flowing anyhow.....

Need to put a probe in the case and measure the pressures