Tractorsport Flowbench Forum Archive

Posted: **Mon Jan 31, 2005 9:42 pm**

This has probably been asked a thousand times, but does anyone have a spreadsheet already done for calcuating cfm with an orifice type flowbench. My bench is similar to the performance trends. It is 4" pvc to a 1.5" orifice.

Thanks for the help.

Posted: **Thu Feb 03, 2005 6:38 pm**

I probably wasn't specific enough. I was wondering if anyone had an excel spreadsheet to convert differential pressure to cfm. I have been using an online calculator. I would like to have one without going online each time.

Thanks[B]

Posted: **Thu Feb 03, 2005 7:31 pm**

I'm sure you will find all the math to do this calculation here in the forum. You can use the search feature to find it . . . another way to find past posts is to use google.com and limit your searches to this site by adding this to your search:

"what you are looking for" site:tractorsport.com

This will allow you to see posts from the old archived forums that were crashed thanks to SPAM.

Edited By bruce on 1107474368

Posted: **Wed Feb 16, 2005 2:41 pm**

[color=#000000]Well vwrcr, i do haver such a spreadsheet set up for no particular testpressure, just needs orificediameter, valvediameter and lift, should ba fairly accurate even though i have lower numbers then those published in lets say harley aftermarket suppliers, but mybe they test in refrigerators to get higher numbers lol, Well let me know how i can send it, oh by the way you need a linear(perhaps vertical) manometer for orificecolumn or you

Posted: **Thu Feb 17, 2005 7:58 pm**

I will PM you. Thanks

Posted: **Fri Feb 18, 2005 4:54 am**

Christian I wonder why you need the valve diametre for calculating flow through orifice?

vwrcr: have a look at . it seems to me that the formula given there is quite OK. only the flow coeficient varies with different differential pressures and is dependant (a little) of the tube orifice diameter/tube diametre where it is located.

Posted: **Fri Feb 18, 2005 8:03 pm**

I created a worksheet using the supplied formula from budman
(shown from the previous forum) and found it to be very accurate.

The cd will need to be adjusted for the orifice system you have but the calcs work great on any test pressure/ orifice size.

Tom V.

My previous computer crashed with my info so I had to register again

Posted: **Fri Feb 18, 2005 9:23 pm**

Sounds great. Can I get a copy???? Any help would be great.

Thanks.

Posted: **Fri Feb 18, 2005 10:20 pm**

Here's one I made based on the earlier link.

Posted: **Sat Feb 19, 2005 12:16 am**

Yours is a lot simplier than mine but EXACTLY the same accuracy.

Good Job!

Tom V.

I would use his vs the one I have really.

Posted: **Sat Feb 19, 2005 12:25 am**

What can I say, I'm a math grad, formulae are my life :laugh:
Anyways, thanks.

Posted: **Sat Feb 19, 2005 9:50 am**

That is Awsome. Just what I was looking for. Thanks alot.

Posted: **Sat Feb 19, 2005 9:15 pm**

Question for 86Rocco about his other spread sheet for calculating
the fluid movement on the incline manometer.

Can you e-mail me to discuss further?

Tom V.

boostengineer@comcast.net

Posted: **Sat Feb 19, 2005 11:40 pm**

The math behind the inclined manometer scale for an orifice type flow bench is very simple. You just take the percentage of maximum flow square and multiply it by the total length of your scale.

For example lets say you're using a manometer with a scale that's 25" long and your want to know how far up the scale the 75% flow mark should be: it's 0.75 * 0.75 * 25 = 14.0625" up from the zero of your scale.

I think the same scale will also work for a pitot tube bench but I haven't thought through that part of it well enough to say for certain. Of course, with that type of bench compensations for air density may need to be made as well.

If you want to know the actual pressure at any particular point on your scale, the calculation is a little more complicated because you need to take into account the fact that as the fluid level in your tube rises, the level in the reservoir drops but both the tube and the reservoir are a consistant diameter, the rate at which the fluid level in the well drops compared to the rise in the tube is a constant ratio.

I have a spreadsheet for that too but for some reason, the forum won't let me upload that today.

Posted: **Mon Feb 21, 2005 8:02 pm**

Uploading works now so here it is.

Tractorsport Flowbench Forum Archive

Flowbench Spreadsheet???