[urq] Too much Crankcase ventalation?

[djdawson2 at aol.com]

Engage Maverick... Engage!!



I wasn't implying that there would be enough vacuum to "suck" oil... just that oil control, in general, isn't so great... so much so that a lot of oil gets burped through the breather system when used hard.? This isn't fun, and may not be a problem with said 10v engine.



A standard PCV system isn't even supposed to utilize "much" vacuum... just enough to keep fresh air flowing through the crankcase to evacuate unburned hydrocarbons, water vapor, and reduce the risk of long term sludging.? In fact, to this day, large diesel equipment uses a tube that extends to the underbody of the truck to take advantage of the tiny amount of vacuum generated by airflow across and perpendicular to the tube opening itself... and that does the job just fine.

My only point is that the time spent trying to design the "perfect" sizing of orifices to make it work well might be a PITA with no tangible return on that investment in time and effort... no performance or reliability gain, etc...

Stack on top of that the fact that a traditional PCV system design operates on the principle that positive pressure is never achieved in the intake manifold.? Throw a hairdryer on your engine... and now your breather system has to accommodate a much broader range of scenarios... both vacuum and pressure.

IMO, trying to "homegrow" a system that works really well on an engine operating well outside of its original design parameters may be interesting... but not very rewarding in real world results.

I tend to analyze things from a cost/benefit perspective.? Redesigning a breather system (to me) represents a high cost/no benefit scenario.? Therefore I would ask... why bother?


my .02 from Folsom, CA...

Dave


-----Original Message-----
From: QSHIPQ at aol.com
To: quattro at audifans.com; urq at audifans.com
Cc: benswann at comcast.net; Djdawson2 at aol.com
Sent: Tue, 4 Sep 2007 8:59 pm
Subject: Re: [urq] Too much Crankcase ventalation?





Dave

A proper crankcase>valve cover oil vapor PCV system, won't suck oil, there?shouldn't enough vacuum to do so.? IME, oil from launches is a problem innate to the v8's and S cars?with the PCV?breather hoses?at the back of the head.? PCV pickup and/or vent?should be dead center in?a cam cover to avoid the hard launch and hard braking sloshing of oil.? The reason for a tie-in of the crankcase ventilation with the valve cover, is exactly to act as a?dead-air?oil return chamber for crankcase oil.? IMO, the 5k's with the double walled valve cover had a better design for PCV than either the later flagship v8's or the Scar.

?

Regardless, the urq has the same basic system as the 5k's, without the problem of oil sloshing.? Ben's issue is strictly too much vacuum IMO.? To fix the S-car or v8 problem of oil sloshing in the valve cover, it should be pretty easy to install a traditional ball type PCV valve and gasket dead center in the valve cover, with the vent line placed on top too.

?

SJ

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?

In a message dated 9/4/2007 8:58:00 P.M. Central Daylight Time, Djdawson2 writes:

I would agree that the noise you are hearing is air being sucked past seals.? Idle = high vacuum = noise.? Revs higher = low/no vacuum = no noise.

I guess recirculating crankcase gasses is an option, but I don't see it as a requirement.? A catch-can is an OK solution, but if you use the car aggressively, it will fill fast.

Even an AAN engine, with its windage tray, will push a very large amount of oil through the breather system during an aggressive launch.? No good.

I don't know if I'd want to make a project out of properly sizing the breather system.? To me, a good solution involves a breather device that allows the oil to return to the crankcase.

If you've built an engine with serious performance potential in mind, no matter how good the system works, you're going to be pushing a lot of oil through it... not just gasses.? To me it was only important to properly vent the crankcase, and return the out of control oil flow back to where it belongs... the pan.

Unless you redesign around some of the limitations inherent in the stock oil supply system, I think that a PCV approach will always leave you with oil in places that you don't want it... FWIW.

Dave




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