Crank case ventilation (PCV)

[1964-M20E]

So as not to derail the other topic.

I asked the question why we do not have PCV valves on our airplane engines?  This seems like it would solve some of our theorized and real corrosion and oil contamination issues.

I think a PCV valve would eliminate if not reduce oil on the belly of the plane from our current breather tubes not getting into the pros and cons of oil air separators.

It would reduce moisture in the oil thereby reducing all the ill effects of that moisture.

It would remove blow-by combustion gases and un-burnt fuel from the crank case as well.

I think the current breather tube could be used for the air inlet adding a filter.  A place to allow the gasses back into the manifold would be needed and then a good place to attach the PCV valve to evacuate the gases from the crankcase

Below is a great explanation of what a PCV valve does with graphics.

http://www.agcoauto.com/content/news/p2_articleid/197

 

In an experimental category aircraft I would be investigating the best ways to achieve this on our engines and implement it.  The biggest drawback is without enough $ you really cant evaluate what it really is really going on i.e. making any claims of benefit are much harder.  You only end up with one data point and that is your engine.

[Piloto]

I have an M20 oil separator that works very well. But I do not how well the PCV concept will work on aircraft engines since they are not engine blocks but individual cylinders. How well the PCV will work above 10,000ft (power output) is another issue.

José

[Guitarmaster]

Interesting

Sent from my XT1585 using Tapatalk

[Yetti]

Last time I checked the PCV system uses an Air pump.  so that is another accessory robbing horsepower.   air pumps go out pretty regularly... they would take your alternator with them when the belt breaks. more weight
   Keep it simple.

[1964-M20E]

The air pump was for the EGR and catalytic converter system.  The PCV valve is just a check valve that regulates the flow of gases from the crankcase to the intake manifold.

My questioning and theory is just to remove the unwanted gases and moisture form the crankcase the entire time during the flight.

[Piloto]

11 minutes ago, 1964-M20E said:

The air pump was for the EGR and catalytic converter system.  The PCV valve is just a check valve that regulates the flow of gases from the crankcase to the intake manifold.

My questioning and theory is just to remove the unwanted gases and moisture form the crankcase the entire time during the flight.

A PCV is like having a hose to inhale your own flatulence. 

[carusoam]

Negative John...

we derailed and debunked in the other thread...  I wrote a nice piece there...

PCV is a spring loaded vent that dumps the block's pressure back into the intake.  Our existing system is not interrupted by anything (no valve) and dumps directly overboard.  Cold weather makes this vent system problematic if it freezes.

On the other topic, EGR (exhaust gas recycle) valve this is an engineering solution for a problem we don't really want to use.  It requires the air pump (for the cats) , and the O2 sensor and additional cubic inches to get the same power.... it's efficiency is up a few percent, but the LL in 100LL kills O2 sensors.  10% added weight to get the same power...

Recycling these messy streams back into your intake leaves a sticky mess behind the butterfly valve.  When the Firebird gas pedal gets difficult to push,  the butterfly valve is sticking.  Not something to deal with on a go around... expect needing 10% more cubic inches to handle 10% more intake volume.  This 10% is based on chemical reactor design theory.  More recycle = more efficiency, doubling the engine size is really efficient.  10% makes an interesting compromise....

PP ideas only, not a mechanic.

Best regards,

-a-

[N201MKTurbo]

The PVC was put in to keep crankcase gas out of the atmosphere. The thought is that burning the oil and fuel vapors was less polluting than the unburnt products. The PVC requires a pressure differential between the crankcase and intake manifold large enough to overcome the spring pressure in the valve. A car will get this differential pressure every time it pulls up to a light. Even cruising down the freeway is done at a relatively low manifold pressure. Our engines are run near WOT all the time so the valve would only open during taxi or if the crankcase pressure increased.