High flow numbers

[Mousehouse1]

I have been getting some ideas from Larry on changing the current top on my bench and the location of the pressure probe. My orifice disk is a straight shot to my cylinder head fixture. I am going to add another top to the bench so the air isn't a straight shot into or out of the bench. This should help with turbulence if there is any. I am also going to put a few small holes in the pressure probe. Currently they are just straight brass tubing.

John & Larry if I have some turbulence problems do you think a baffle and the new top will take care of them?

[Mouse]

Martin,

Hard to say. A sharp edge calibration orifice will usually diffuse the air flow enough to not effect the measuring orifice too much. It is when you are flow testing things like a head or manifold that the air can influence the measuring orifice by forming air streams and biased air flow patterens inside your bench. A good way to test for this (balance test) is to glue a short section of 1.5" pvc pipe into a flat board and flow test it. Move the board around the test fixture so that you can flow test the edges of the fixture as well as the center. If your flow reading change depending on where the pipe is located in your fixture, you have some turbulence problems.

Keep in mind that your FP1 can also be a very usefull tool in trouble shooting and designing your flow bench. Set your FP1 to manometer mode (mode 3) to probe and do experiments in trouble shooting your bench. Both FP1 pressure sensors can be used as single ended or differential pressure measuring.

John

[Mousehouse1]

I decided to test my bench again and while checking the FP1 settings I noticed when I tested the leakage of my bench I had the FP1 set on C orifice instead of A orifice. This made a huge difference. The FP1 is reading 13cfm at 28". I still don't know why I can't get the bench to flow over 300cfm.

I was going to install another pressure tube but when I tried to drill another hole I got to close to the orifice disk and the bit broke. Not to bad of a problem except the bit is stuck in the wood behind the orifice disk and not allowing it to turn. I guess I am going to cut the top of the bench off and make another top chamber with a baffle. While I am in there I am going to redesign my orifice disk since I don't need all of the orifice holes using the FP1.

Maybe that will solve my high cfm problem.

My luck has to improve it can't get any worse.

[Mousehouse1]

I finished the new top chamber, installed the deck plates on each side and installed a baffle. I have between 12-18cfm of leakage. Is this in the range it should be with an orifice disk at 28"? I know I probably have some leakage between ranges. I am trying to come up with a way to change or seal that better.

I have two calibration plates. I cracked the one John sent me and can't get it close at all. I wonder if the crack has something to do with that? I have another one made out of steel that is suppose to flow 114cfm at 28". I used it and the cd numbers are in the .80-.95 range.

I made a 2.30" hole and tested it on the biggest orifice size (3.068) at 28". I believe someone above said it should flow 360-370cfm. Can it flow more? I need to put one of my cylinder heads on and see if I can get the numbers close.

John if you read this can you send me another calibration plate? I promise not to break this one.

[larrycavan]