Crankcase Breathing

[FJCamper]

Hi Piledriver,

No, I havn't done anything special to try and reroute pressure, but your idea sounds good.

Porsche made some factory-engineered efforts in the 356 days that were technically interesting, but none were kept. Once they put slot vents in the tops of their valve covers with screen mesh and baffle covers (messy), and finally vented the head itself rather than vent the valve cover.

Something interesting about the 356 was the pushrods were of a much larger diameter than the VW, but filled with wood to control oil flow outward to the rocker arms.

A good side effect of the boxer configuration is that the crankshaft slings enough oil to either side to splash-cool the backs of the pistons. Upright engines have to have special oil squirters to achieve this.

Remember, the heads both pressurize and depressurize as the pistons move, and gradually suck in the valve cover gaskets. At least half the time, we have negative head pressure.

Something I have considered, just thinking about it, is anti-windage splash shield lips or baffle rings around the inside of the inner pushrod tube mouth, to further limit the oil intake area.

Maybe even helical "windage rings" on the pushrods themselves, to "screw" oil back towards the case.

FJC

[spongeworthy]

Back in the day, "windage tubes" were available for VW engines.

These looked just like stock VW pushrod tubes, but had an extended lip on the end that went into the case. The longer lip was supposed to keep more oil in the case and less flowing up to the heads if I remember correctly.

I have not seen a set of those in many years.

[sideshow]

In theory, you only need half.

http://www2.cip1.com/ProductDetails.asp ... C-C10-5370
What I noticed is that they make the engine easier to assemble

[spongeworthy]

Oh! Well I guess windage tubes ARE still around.

[FJCamper]

Hi Guys,

Give credit where credit is due. The very effective "windage tube" was developed by Porsche for the 356 engine wwway back in the early 1960's.

It took it a few years to make it to VW, but it did and it's the only thing to use. I just wonder if an even deeper tube extension would be better?

FJC

[Scott Novak]

How brand critical are those woven stainless steel pot scrubbers.

The two nearest stores only had the Chore Boy copper pads. The woven stainless steel pot scrubbers that they had were a generic brand called Home Best.

I am cringing at the possibility that there could be loose stainless steel bits in there that could get into the oil.

When you put these into the oil tower, do you leave the baffle in place?

Scott Novak

[melville]

FJC--not to hijack, but when you mentioned Krankvents it reminded me of what jamestwo posted on TS:

http://www.thesamba.com/vw/forum/viewto ... highlight=

He drilled and tapped the case above the 1/3 side and ran a line with a Krankvent to his breather box.

This appeals to me in that we can evacuate the crankcase from both sides without having to get our excess pressure from the front through the center main web to the back. With Krankvents I'd wonder if it would be possible to pull a vacuum like my BMW MC almost does.

[Scott Novak]

If the Krankvents really work that well, it would seem like the best place to put them would be through the top of the engine case, one on each side of the center main bearing.

Leave the inside of the case alone to minimize the pressure escaping to the other side of the center main bearing. Or perhaps even block the passages through the center main bearing area.

Then use a vent hose on each valve cover connected to a fresh air filter. The negative pressure that the Krankvents would develop would help suck the oil from the rocker arm area back into the crankcase.

The fresh air vent hoses on the valve covers would reduce the negative pressure in the valve covers and reduce the possibility of the gaskets being sucked in.

Any thought on this?

Would this be likely to contaminate your oil more quickly because of ultra fine dust that wasn't filtered by the air cleaners for the valve cover vents?

Scott Novak

[Piledriver]

How brand critical are those woven stainless steel pot scrubbers.

The two nearest stores only had the Chore Boy copper pads. The woven stainless steel pot scrubbers that they had were a generic brand called Home Best.

I am cringing at the possibility that there could be loose stainless steel bits in there that could get into the oil.

When you put these into the oil tower, do you leave the baffle in place?

Scott Novak

I think I suffered from a little bit of dain bamage, the copper Chore-Boy ones slightly corroded a bit over the winter... (easy to pull and inspect in a stock cooling T4) I plead "It's been awhile..."

I ended up with a larger, different brand of pot scrubber in SS, took it out of the package and gave it a good beating & shake over some sheets of white printer paper to make sure nothing was loose.

The woven ones are not like Brillo pads or normal steel wool, the second one in the 2-pak is still going strong in the sink many months later, sees the dishwasher every day or so...

I'm using some tiny in-line air filters, they double as my restrictors. They are for airbrushes.

On a T1, I'd absolutely leave the directional splash baffle in place. (no baffle on a T4, the "baffle" is designed into the block)

[FJCamper]

Gentlemen,

The KrankVent is extremely effective. When we just used one, and sealed up the engine everywhere except the standard vent hole but with a KrankVent on it, it began sucking oil right out of the engine. I put clear plastic line on it just to watch and it was amazing. I don't mean oil froth, but oil as if it were being sucked right out of the sump. It would pull out a quart in no time.

It was, if anything, too effective on such a small diameter single tube.

Two KrankVents, one on each valve cover, stopped that and made it all work.

I like the idea of tapping off from the case top. I actually considered that but thought it might tend to suck oil rather than vent pressure.

As to the pot scrubbers, I use the factory splash baffle, and the stainless steel scrubbers, not Brillo pads. They really helped suppress oil spray.

I don't know why VW didn't do what Porsche did in the 356 and just cast in a spray guard over the cam gear to keep the oil from being slung right up into the generator tower. Instead, they went with the generator stand baffle.

The cam gear is right there spinning in a pool of oil, spraying it almost straight up into the generator tower. Almost. A shield over the top of the gear would fix that.

FJC

[mike thompson]

Great post FJ, Old Kohler engines use a reed/check valve to retain vac in the case. If it gets buggered up the engine smokes.

[Scott Novak]

At what level of vacuum do the benefits of a crankcase vacuum reach diminishing returns?

Scott Novak

[Piledriver]

At what level of vacuum do the benefits of a crankcase vacuum reach diminishing returns?

Scott Novak

Probably 7-10" or so from a performance/$$$ standpoint.

There is a point >~14"+ when it's too much, and you end up losing more power running the pumps than you could possibly ever gain... Also can cause oiling issues (piston pins, wet sump fails to suck etc)
Less of an issue running dry sump, but the pins still need help.

From a financial standpoint...Whatever theh crankvents or such will give you is great

ANY average level of vacuum is going to help, by keeping the oil in the engine where it belongs, and by assisting getting the nasties (water, ex gasses) out of the oil.

I imagine a 2 stage krankvent setup >> exhaust evac valve (with a evacuated catch can in between to act as a damper/catch oil) could generate some pretty decent vacuum on a race car.

[sinistervw]

ok ok....so how would a crank case venting setup above do with a stock 1600 T1 with Kadrons?

I am running a 34 P3 right now and i got oil on my air filter and around my single vent on the common after market none baffled oil filler w/Nipple.

Already got my case sand sealed, and i think its tight!

[Piledriver]

Should work fine, but I feel the pot scrubber(s) are a BIG part of the system, as they act as very effective air/oil separators.

Living (effectively) in the block, they are heated, which helps.

Another biggee is ... do you have a thermostat?
Are theh bottom tins in place?
Are you running fake K&N filters, or real air filters that actually stop stuff?

The stock filters (oil bath OR paper) rocked as filters.

The controlled temperature & decent filtration can double (or more) your ring/cylinder life, reducing the blowby that this whole arrangement is built to combat.

If it gets bad enough, nothing will help.