200+Hz air valve?

[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]

Why not just pump it out like is normally done?

That would be too simple 

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]

For use in car engine crankcase evacuation

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

[ELS122]

For use in car engine crankcase evacuation

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

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.

[Benta]

How old is your engine? I haven't seen wet sumps since at least 40 years ("the crankcase has the oil sloshing around it").
And the compression (say 10 bar) plus combustion pressure (much more) compared to perhaps 0.2 bar of vacuum during intake is a problem?
Wow! Talk about microscopic optimization (popularly: "quantum leap"). Put that "improved" engine on a dyno and you'll see... nothing. Same with fuel consumption.

[ELS122]

How old is your engine? I haven't seen wet sumps since at least 40 years ("the crankcase has the oil sloshing around it").
And the compression (say 10 bar) plus combustion pressure (much more) compared to perhaps 0.2 bar of vacuum during intake is a problem?
Wow! Talk about microscopic optimization (popularly: "quantum leap"). Put that "improved" engine on a dyno and you'll see... nothing. Same with fuel consumption.

You must be living in a more fun world where cars come with dry sump systems from the factory 
The compression is higher than the static compression ratio, usually around 14 bar for a 10:1 CR, plus >100% Volumetric Efficiency can boost it even higher.
Vacuum can go up to ~0.65bar absolute pressure. for a 10:1CR

An engine can be properly designed so it's efficient even without vacuum in the crankcase, the Honda F20C doesn't and it achieves like 154HP/Liter
Moving around a ton of air (The same amount of air as the engine's capacity / 2) at above 1km/s WILL add drag.

[joeqsmith]

Why not just pump it out like is normally done?

That would be too simple 

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...

Electric pump with a total loss system but the motors are small and they are only ran a short distance.    Looks like some are using belt drive. 

https://www.starvacuumpumps.com/products/STR.09.04.000

[joeqsmith]

The great George Bryce talks about the history and whys

[Haenk]

"aerodynamic drag"

Any idea about the loss you are talking about? 1/10000th of total motor power?

I assume the best option is to hone your motor, new sealing rings and low viscosity motor oil. For another PS or two, polish out your exhaust manifold.
If allowed, straightpipe & cat delete.
If going crazy, add (larger) turbo and/or compressor.

And somewhat older Germans know another trick: Adding a foxtail to your antenna adds another PS.

[AVGresponding]

"aerodynamic drag"

Any idea about the loss you are talking about? 1/10000th of total motor power?

I assume the best option is to hone your motor, new sealing rings and low viscosity motor oil. For another PS or two, polish out your exhaust manifold.
If allowed, straightpipe & cat delete.
If going crazy, add (larger) turbo and/or compressor.

And somewhat older Germans know another trick: Adding a foxtail to your antenna adds another PS.

In fact aerodynamic drag in the crankcase, known as windage, is a serious loss, and much effort goes into minimising it.
I recommend you to watch the recent Engineering Explained video on the new Corvette C8 Z-06 engine.

[ELS122]

"aerodynamic drag"

Any idea about the loss you are talking about? 1/10000th of total motor power?

I assume the best option is to hone your motor, new sealing rings and low viscosity motor oil. For another PS or two, polish out your exhaust manifold.
If allowed, straightpipe & cat delete.
If going crazy, add (larger) turbo and/or compressor.

And somewhat older Germans know another trick: Adding a foxtail to your antenna adds another PS.

aerodynamic drag for boxy components going trough heavily oil saturated air, moisture, and co2 at >1km/s isnt a thing.

20hp of loss in aero.
another 20hp of loss in pumping losses at idle without egr.
yeah i'd say pneumatic losses are a problem in engines

[CatalinaWOW]

I personally think this quest is silly, but if you really are going to pursue it a mechanical solution seems best.  Unless your engine is exotic enough to have variable valve timing the required openings and closings of the valves are fixed relative to crankcase rotation so a rotating disk on the crank with appropriately placed ports would do the job.  If you felt that transport times forced timing changes as a function of rpm a much slower responding servo changing the disk angle relative to the crank would do the job.