Vacuum motor check valves

[jcisalive]

I have my depression fitting in the top of my plenum box.

It matters where you pull it from?

[1960FL]

Then i would say most likely you are running up against the limitation of the design.

Rick

[Brucepts]

I would not be able to use two 3" pipes because the air flow sensor is in the 3" pipe

What kind of flow sensor?

Is that blocking flow?

[jcisalive]

Thanks for the replies

It is like a mass air sensor.

It goes through center of the pipe and has a diameter of a pencil if I recall correctly.

I have two pieces of honycolmb air straightener before and two after the sensor. Maybe I will try flowing with one and see if it makes a difference. If it does I will take the other two out to see how that works.

[1960FL]

as Bruce leading to, if you test the pressure at the motor box and compare it to your test pressure i am sure you will see the 3" tube at high flow starts to become a restriction.

[jcisalive]

Thank you for the replies. I am very busy these days but I will test a few things in the next week or so and report back what I come up with.

[jcisalive]

I increased the size of the vacuum exhaust to 4" thinking that maybe the 3" could have been a restriction and did not make a difference.

I took both pieces of honeycomb air straighteners, before and after the air measuring pipe out and I was able to pull 28" on 450, up 45 CFM.

It seems the 3" from my plenum to vacuum box is the restriction as was suggested and the air straighteners do not help.

I will upgrade to 4" in the near future and report back.

[1960FL]

Great news, pain in the butt but progress.

Rick

[jcisalive]

I did a test to see if the 4" would help before investing in an upgrade.

I set a calibration plate on my head deck and adjusted it until I had max cfm and 28" with all 8 motors running. It came in around 435 CFM @ 28"

Then I took out the 3" from the plenum to the vacuum box out and replaced it with 4" striaght PVC pipe and turned on all 8 again to see if the depression changed.

Without the measuring pipe I can only see depression.

Depression went from 28" to 34" with the 4" pipe. I ordered a 4" measuring pipe.

I will post then CFM and depression with the 4" when it comes in.

[Brucepts]

Sounds like you are moving forward with your progress . . .