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200+Hz air valve?

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ELS122:
I'm looking for a way to get an air valve to respond extremely fast. For use in car engine crankcase evacuation, using the venturi vacuum in the exhaust, PLUS short scavenging pulses that should give me even more vacuum, but for those I would need an extremely fast acting valve, 200Hz is just so it reacts to each cylinder's full cycle but in reality it would need to be around 10x faster to react to the actual pulse itself.
it's gonna go on a 1/2" pipe fitting, for a very rough flow estimate.

I presume a mechanical valve is out of the question, I was thinking of maybe a pressure sensor and a fast acting solenoid. It would have to be able to handle around 200C temps, and the pressure sensor would need to handle basically fire, and also frequent backfires which are explosions in the exhaust.

Does it sound like a feasible setup?

joeqsmith:
Why not just pump it out like is normally done? 

ELS122:

--- Quote from: joeqsmith on May 21, 2023, 07:52:49 pm ---Why not just pump it out like is normally done?

--- End quote ---

That would be too simple  ;D

I want to put as little load on the engine/electrical as possible, even if it doesn't pay off it's just a habit of mine.
But yeah a fast response solenoid will probably draw more power than a belt driven vacuum pump ever will...

PlainName:

--- Quote ---For use in car engine crankcase evacuation
--- End quote ---

Can you explain further? Shouldn't there be the reverse too, to let the air back in?

ELS122:

--- Quote from: PlainName on May 21, 2023, 09:03:48 pm ---
--- Quote ---For use in car engine crankcase evacuation
--- End quote ---

Can you explain further? Shouldn't there be the reverse too, to let the air back in?

--- End quote ---

Well I decided I'm just gonna go for the venturi effect vacuum like most people do anyway. But FYI:
The crankcase of the engine will have gases pushed into it because of the inherent leaks in the piston rings.
So you need to vent these gases out, but then there will still be a bit of positive pressure there which will tend to form oil leaks over time (the crankcase has the oil sloshing around it)

But there's another thing, because the whole rotating assembly of the engine is inside the crankcase, aerodynamic drag starts to add a lot of frictional losses.

Also, the piston rings (they seal the piston to the cylinder) are sealed by the pressure difference between the combustion chamber (the explody part of the cylinder) and the crankcase, on one of the cycles - the intake cycle, ring seal is a problem because the combustion chamber will be at a vacuum, so the rings would be forced to move away from the sealing surface, and lead to poorer sealing.
It also will increase the pressure difference in the power cycle which will improve sealing, reduce pressure loss, Or allow for rings that have less tensile preload.

But if a vacuum is pulled in the crankcase, it fixes all three problems.



In production cars, pulling a rather high vacuum isn't practical for many reasons. Instead most engines will have a PCV system where there's constant circulation going on, the vacuum is pulled by the intake usually (the intake vacuum is produced by the piston in the intake cycle as mentioned previously), But air is let in at the same time, this will circulate the crankcase air.
This not only reduces oil leaks because there isn't a positive pressure anymore in the crankcase, but also I've read it reduces moisture absorption by the oil.

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