Pitot Tube Location - Pitot Tube Location

[Peter]

I know this might of been covered before, but as I'm constructing my bench I need help in knowing where to locate the Annubar in my 4" straight Sch 40 tubing. The bench will be suck only to 8 vacumn motors with flow straighteners before the annubar. Starting out with 6" tubing reduced to 4" tubing, then to a 4" 90 deg. elbow, then the 4" straight section into a 4" knife valve, then into the vacumn box.

Peter

[slr350]

I used 2inch tubing to fit the annubars in, testing sbc ports its a little on the big side to measure the low lifts. I thing 4" tubing would be to big.
Im not sure on the placement but i thinks its somthing like 10 times the dia of the tubbing after your flow straightners and 4 times after your annubar.

[bruce]

I agree, 4" pipe is going to be way to big to get low flow numbers. What I try and do is use a test pipe dia that is a little larger than the dia of the part I want to test. In my application I use a 1.5" dia PVC pipe and this allows me to see flow numbers easier in the .050 to .150 lift range. But I'm not working on SBC heads. My largest dia right now I am working with is 1.5".

[gaz]

So as I understan the annubar needs quite high speed of flow to get accurate results.? would it be ok if I used a straight tube( where the anubar is located) about the same diametre as on the test head's valve ( if there is only one valve) diam??

Another question about annubars or several...
1) is annubar just a simple 1/8" tube with certain amount of holes drilled not through the tube but only trough 1 waal of tube?
2) how do I get static pressure and total pressure with only one tube? how is annubar connected to inclined manometer?
3) how many annubars do I need for a flow bench?

A lot of questions but I ask them because I didnt find reasonable info from the internet...... yet

thanks anybody who bothers to answere!
I found a link where is some interesting formulas for calculating cfm and other things http://www.tsi.com/iaq/appnote/ti_107a.shtml

[bruce]

Gaz, Everything you seek is already listed in other posts on this forum. Just have to surf around and find it

[slr350]

All the info you need can be found but it does take a little time to find it.
Your on the right track with the annubars, for the location of the holes and static have a look here: