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-   -   Sportster Crankcase Pressure / Engine Breathing / Wetsumping and Mods (http://xlforum.net/forums/showthread.php?t=2073932)

Hippysmack 5th August 2019 16:04

Ok, that makes sense.
I've never used one so lots of dumb questions. :geek

dieselvette 5th August 2019 16:43

To be clear, this is a pressure test and not a flow test. It is imperative that the fluid height be enough to prevent air from coming in/out - the fluid acts as a moving "air blocker" and this apparatus does not act like a second vent. Hence to need to buffer it with some kind of restriction, lest a sudden pulse blows the tube empty. 60Gunner do you suppose in this scenario, the tank vent line could be tapped into?

Depending on the amount of restriction (and air volume in the tubing etc) connecting the manometer, you will get different results in terms of fluctuations or pulsing. But in any case you'll get an overall average of CC pressure/vac which is repeatable with any manometer setup (assuming the same fluid). Ideally you would open the needle valve as far as possible, without your manometer going crazy.

60Gunner 5th August 2019 17:08

Quote:

Originally Posted by dieselvette (Post 5767828)
To be clear, this is a pressure test and not a flow test. It is imperative that the fluid height be enough to prevent air from coming in/out - the fluid acts as a moving "air blocker" and this apparatus does not act like a second vent. Hence to need to buffer it with some kind of restriction, lest a sudden pulse blows the tube empty. 60Gunner do you suppose in this scenario, the tank vent line could be tapped into?

Depending on the amount of restriction (and air volume in the tubing etc) connecting the manometer, you will get different results in terms of fluctuations or pulsing. But in any case you'll get an overall average of CC pressure/vac which is repeatable with any manometer setup (assuming the same fluid). Ideally you would open the needle valve as far as possible, without your manometer going crazy.

It will take oil with it.

Tomcatt 5th August 2019 17:45

Quote:

Originally Posted by 60Gunner (Post 5767836)
It will take oil with it.

Based on what?

You'd be tapping a vent line and the only "flow" would be the amount you see the manometers' column moving.

bustert 5th August 2019 17:49

the slack tube is a dwyers 1723-72 which will measure to 72" of water.
orifice size is based off piston diameter
my chosen size was 7/64
interestingly, there was no oil mirgration through the orifice.

to be honest, i see no issues with using the c/c to bag line since there is no flow out the manometer. only issue i can see is if there was oil being pushed through the line.
you could even modify an oil cap, this is done on automobiles, matter of fact, cooper has an article for doing so on their r5 engines.
the issue here is that the further from test point, time factors in travel effects readings with larger diameter lines adding more skew.
they do have handle bar mounts that will hold a vac/press gauge, they even have hand held digital units that can record. dwyers sells them.

60Gunner 5th August 2019 18:26

Quote:

Originally Posted by Tomcatt (Post 5767845)
Based on what?

You'd be tapping a vent line and the only "flow" would be the amount you see the manometers' column moving.

Based on numerous accounts of people trying to vent there. Go ahead and tee there.

Tomcatt 5th August 2019 18:30

Quote:

Originally Posted by bustert (Post 5767846)
they do have handle bar mounts that will hold a vac/press gauge, they even have hand held digital units that can record. dwyers sells them.

Yep, a gauge/meter taped to the bars could be seen as you ride so you could see pressure/vacuum under real conditions. Just need an "inches of water" gauge with a useful range that will read pos and neg pressure. Then damp it well enough to not kill the gauge. Big diameter analog gauges with needles can be easier to read.

Tomcatt 5th August 2019 18:34

Quote:

Originally Posted by 60Gunner (Post 5767852)
Based on numerous accounts of people trying to vent there. Go ahead and tee there.

We're not talking about venting, just a pressure tap. Two different things. Now you've read that on the internet too.

needspeed 5th August 2019 18:43

I've used an automotive vacuum gauge, usually used to measure intake manifold vacuum, to measure crankcase vacuum on my old ironhead. It will read negative and positive pressure.

For what you're trying to find out, wouldn't that work just as well as a manometer?

Hippysmack 5th August 2019 18:45

Can't take him anywhere. :laugh

Quote:

Originally Posted by Tomcatt (Post 5767857)
We're not talking about venting, just a pressure tap. Two different things. Now you've read that on the internet too.

Judging from the balloon test, Aaron's and bustert's testing, there shouldn't be any reason you couldn't use the vent line.
If it turns out bad, you may have other problems to address anyway.
The vent mods folks do there are different in that air is allowed to vent.
As mentioned, as long as the water is not blown out, it's just a pressure test point.
No different than installing a pressure gauge there.
I've got to get around to getting a flow meter as well.


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