forced crankcase ventalation

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would it be a good idea to use a small rotary air pump to suck crank case air out of the crank case. and NOT push air into the intake of the engine. but just dump the crank case air to the atmosphere. and DONT even talk about the environment, I am thinking out loud.
 
I don’t think we’d see a difference because it’d have to be a variable speed thing in tune with the engine. Too much or too little may cause seal failure.

With the “normal” way, you have the increased vacuum as the RPM’s increase.
 
Many race cars use a system like this:

357610d1338920321-crankcase-evacuation-system-evacsysteminstallsy2.jpg
 
Originally Posted By: red7404
would it be a good idea to use a small rotary air pump to suck crank case air out of the crank case. and NOT push air into the intake of the engine. but just dump the crank case air to the atmosphere. and DONT even talk about the environment, I am thinking out loud.


Yes. I have this on 4 vehicles now, although I do route back to the air intake, via the filter box. Neither air filter or intake tract ever get oily at all.

Crankcase emissions can smell. For some reason, Rotella oil stinks it up the worst by a large margin.

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Why forced though? The old school valve cover breathers worked fine right?


They don't circulate fresh air into the crankcase. I let a little bleed air come in through a filtered inlet, but the system still maintains 9" of vacuum at all times.

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I don’t think we’d see a difference because it’d have to be a variable speed thing in tune with the engine. Too much or too little may cause seal failure.

With the “normal” way, you have the increased vacuum as the RPM’s increase.


Only if the pump is belt driven. I use Ford electric emissions pumps.

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A properly designed PCV system does exactly this.


It doesn't. When the engine is under the most load, the crankcase gases increase, and the amount of vacuum decreases.

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A rotary pump would work but would also be electrical or mechanical load.

This device http://www.jegs.com/i/Moroso/710/25900/10002/-1 uses waste exhaust energy to perform the same function.


That system works good if you have open headers with no mufflers. Otherwise, the one-way valves pretty much remain closed at all times and the system does not function.
 
Years ago there were vacuum pumps made for the crankcase ,I haven't followed hot rodding for years.
 
well OK my friends here have some very good ideas. and some info i didnt know. thanks.
 
As stated earlier, race cars do this. There are belt driven and electrically driven vacuum pumps. It's regulated by a valve that controls the amount of leakage back into the engine.
Race guys do it for improved ring seal. In some cases the horsepower increase is fairly significant.
 
Originally Posted By: BrocLuno
Pro-Stock and other classes use vacuum crankcases. Worth maybe 5 HP net at 9,000 RPM. On the street at 2,700 - worth nothing - might even be parasitic ...


Actually, it depends on the engine design. Pumping crankcase air under and between each cylinder can take significant work. Manufacturers now strive to reduce losses by designing in airflow management.

An inline 4 can have quite a bit more losses than a V8 depending on design.

Evacuating a crankcase is a time tested method to reduce losses. It can be done on a single cylinder engine with just a one way reed valve. Lets the air out, but not back in. The pressure quickly stabilizes at about 1/2 atmosphere.

bikecylinders.jpg
 
Evacuating a crankcase is a time tested method to reduce losses. It can be done on a single cylinder engine with just a one way reed valve. Lets the air out, but not back in. The pressure quickly stabilizes at about 1/2 atmosphere.

OOOh, thats the thingee that fills the carb up with oil when you tip the mower the wrong way.
grin2.gif
 
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Originally Posted By: BrocLuno
Pro-Stock and other classes use vacuum crankcases. Worth maybe 5 HP net at 9,000 RPM. On the street at 2,700 - worth nothing - might even be parasitic ...


In much lesser classes, running 1000HP engines, the gains are 10HP per 1" of vacuum. This has been solidly demonstrated over decades.
 
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