Testing question?

[bruce]

I've taken notice the last couple of times while testing my ports that the flow numbers while opening the valve are a tad higher (.5-1 cfm) than while doing the same test closing the valve? Has anyone else experienced this on their bench? Why would this make a difference? I show the same reading on the dial indicator and I make no changes in the setup.

[Mouse]

Yes, no idea.

[Rick-360]

I think it is from the manometer fluid not draining down fast enough. A small amount will stay behind as the flow increases and the fluid lowers in the inclined tube. It has had time to completely drain to the level line by the time you are going back down in flow (fluid rising).

Rick

[bruce]

My bench is all digital, I use Mouse's FP1 setup. The only manometer I have hooked up is the flow depression one which is T'ed into the line for quick reference.

Its a good answer though.

[Mouse]

I have seen even greater degrees of difference. I do know that on ports that I can hear turbulence cutting in and out, even the turbulence will occur at different lifts when dialing the valve up and down. For instance, a port will go turbulent at .485" when opening the valve, but the turbulence will stop at .465" when closing the valve.

It may be similar to the time I was driving down the road and a long thread that was stuck on my windshield wiper blade was streaming up my windshield. The thing I was wondering is why, on a perfectly still day, would it shift to the left side, then shift straight up, then shift to the right side. No wind, steady cruising speed, straight road. Why was it changing directions?

[RRBD]

Bruce, have you ever checked your indicator for accuracy in both directions as well as your indicater set up? It would be simple to set up another just to verify. I have a couple of brand name 1" travel indicators that have some "backlash" so to speak. I have also had problems with my indicator mount being "springy". I'm also trusting that you dont have an enormous amount of guide clearance and changing direction is actually moving the valve head (not insinuating anything here, I refer to this as "trust but verify")

Mouse, could changes in air temp or "therms" be causing your thread to move around on your windshield??????

forgive the spelling

Scott

[bruce]

Scott, Some definite thoughts to ponder and do some "test and verify". The valve guides in this ole block are pretty loose. Quess I'll have a "look see" on my indicator setup to verify that it is giving me accurate numbers up and down.

What I do when I test something is take 2-3 sets of readings both up and down and then average all of them to give me a final number at various lifts. I really need to setup a spreadsheet to do all of this and make a nice chart in the end (anyone happen to have one they'd like to share?). I'll do that sometime when I'm not to busy . . . . er I mean lazy