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  #11  
Old 28th October 2019
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Quote:
Originally Posted by Tomcatt View Post
Is this supposed to "prove" something?
No I'm not trying to prove anything.
I'm just playing around with my new tool.
bustert's testing interested me enough that I wanted to try it myself.
I'm just trying to see what I can learn and I realize it's just one of many tools.
You normally have more vacuum than positive pressure.

As I mentioned earlier,
Even though there is a positive 'push' on internal pressure through piston downstroke, the overall internal pressure is still negative.
It's just less negative than it was before the downstroke. This creates a pulsing effect on oil in the sump which helps shift the oil toward the scavenge port.
Even though there is normal blowby throughout the RPM range, the vacuum created buffers that.


But it's the positive push that creates the pulsing air (constant differential) that helps move oil and air around in the crankcase.

It's OK to have vacuum as long as it's not too high.
The higher the vacuum, the less differential that takes place inside therefore the less pulsing pressure to move things around.

I had to build this homemade rig since I don't have money for a used Dwyer not to mention a pressure sensor and data logging capabilities.
But I think I can learn something from it.
So it's a win-win for me.

Vacuum deters high oil suspension. In other words the air/oil mix that gets pushed around will be less dense.
If the pulsating air is great enough on downstroke (even though the mean pressure is still negative) , the oil in the sump is kept in the rear to be scavenged.
But vacuum can also lower the pulsations if it creeps too high.

So my degree of vacuum wasn't high enough to hinder scavenging.
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