How do you calibrate a flow bench

[user-17438]

Since Charlies diary is getting blasted in many ways, how about we just start new Threads for each subject mentioned.

Helgesen calibration plate?
2 map sensors?
a Head from soneones bench that may have been calibrated?
a metronome?
your side piece?
a tape measure and some bubble gum?

Sound away Internet gurus!

[GARY C]

Is it possible to include the power difference from an engine built using a plate calibration method vs others?

[ole4]

On my orifice bench I make sure to set the reservoir so inclined manometer reads 0. Then I remove bore adapter and install my Cameron ASME certified orifice to the top of the settling chamber tape it down to insure no leaks and see if at 28” of depression my inclined manometer reads 100%. If not I adjust the incline of the manometer check for 0 again and if it is off I do it again. One or two times usually gets it. I also have non certified plates I made on the lathe for various cfm’s i Check as well. Then replace bore adapter and go. Before I changed my bench to orifice I had a pitot element and that needed correction factors for air density. Needed to be calibrated evert time I used it.

[Rick360]

On my orifice bench I make sure to set the reservoir so inclined manometer reads 0. Then I remove bore adapter and install my Cameron ASME certified orifice to the top of the settling chamber tape it down to insure no leaks and see if at 28” of depression my inclined manometer reads 100%. If not I adjust the incline of the manometer check for 0 again and if it is off I do it again. One or two times usually gets it. I also have non certified plates I made on the lathe for various cfm’s i Check as well. Then replace bore adapter and go. Before I changed my bench to orifice I had a pitot element and that needed correction factors for air density. Needed to be calibrated evert time I used it.

What exactly is "certified" about the orifice?

Rick

[GARY C]

Here we go!

[jcisworthy]

When I purchased a digital measuring system for my homemade bench I got a plate with a hole in it that the instructions say flows 120 CFM so I laid it on my head deck and adjusted for 120 CFM @ 28" and put it away.

Once in a while I check it and it is always good

The bench is always consistent

[engineczar]

When I purchased a digital measuring system for my homemade bench I got a plate with a hole in it that the instructions say flows 120 CFM so I laid it on my head deck and adjusted for 120 CFM @ 28" and put it away.

Once in a while I check it and it is always good

The bench is always consistent

I pretty much did the same. So long as my bench was consistent to itself I could care less what someone else's bench read. I had heads that came back a few years later that flowed nearly exactly what they did when they left the shop.

[user-9274568]

A certified plate is normally made from Stainless steel. It has a temp reading stamped on it. A cd is usually stamped on it. It is a perfect sharp edge per industry standards. It has been checked for nicks and is perfectly machined. They are used in places that requires a standard.

Send in a torque wrench or a micrometer and you get a certified unit back. Why should this be any different?

[GARY C]

They are just tools to collect data.

If one person builds a race winning engine using CFD and another builds a race winning engine using a flow bench and another builds a race winning engine using a shop vac and another builds a race winning engine using a magazine article....Which one is right and which one is wrong?

Do you tq a rod bolt to the manufacture certified specs or do you over tq it to reach a stretch gauge even though though you have never had a rod bolt failure?... do you just disregard the manufacture spec even though they specifically say not to over tq their bolt?

[GARY C]

It's just another discussion that leads to an absolute that if you do it different then me you are wrong!... If I listened to everyone that said I couldn't do it that way I would have never competed.

[SchmidtMotorWorks]

They are just tools to collect data.

If one person builds a race winning engine using CFD and another builds a race winning engine using a flow bench and another builds a race winning engine using a shop vac and another builds a race winning engine using a magazine article....Which one is right and which one is wrong?

Do you tq a rod bolt to the manufacture certified specs or do you over tq it to reach a stretch gauge even though though you have never had a rod bolt failure?... do you just disregard the manufacture spec even though they specifically say not to over tq their bolt?

It isn't a question of "right and wrong", it is a question of which method is most informative and efficient.
For someone with equal skill in both methods, it isn't a close comparison; CFD is more informative.
When combined with CAD developed port shape, it is vastly more efficient to test and manufacture.

[user-17438]

They are just tools to collect data.

If one person builds a race winning engine using CFD and another builds a race winning engine using a flow bench and another builds a race winning engine using a shop vac and another builds a race winning engine using a magazine article....Which one is right and which one is wrong?

Do you tq a rod bolt to the manufacture certified specs or do you over tq it to reach a stretch gauge even though though you have never had a rod bolt failure?... do you just disregard the manufacture spec even though they specifically say not to over tq their bolt?

It isn't a question of "right and wrong", it is a question of which method is most informative and efficient.
For someone with equal skill in both methods, it isn't a close comparison; CFD is more informative.
When combined with CAD developed port shape, it is vastly more efficient to test and manufacture.

Thanks for pointing that out! That was the basis. Not what is right or what is wrong.

In my opinion, a Flowbench is a tool to measure changes from altering shape, cross section, intrusions, protrusions, angles.etc it is used as a Comparator.

And when used properly, can show you valuable information depending on how it is used.

[Rick360]

Why an orifice plate mounted on top of any given flowbench is not proof that your bench is "accurate".

1. Air thru an orifice plate is affected by its surroundings.

2. To get a definite/determined flow thru an orifice would require the surroundings to be the same.

Take 2 benches with different construction in these areas. Size and shape of the inlet box, the distance to the internal orifice, distance to other internal and external objects/surfaces, diameter of opening the plate is mounted, thickness of the opening the plate is mounted. When these parameters vary, the flow thru the orifice can change and may also cause the reading to change if the air velocity from the calibration orifice impacts the internal measurement orifice.

Within the confines of a given flowbench design (meaning the same exact construction) an orifice can give reasonable results for comparing cfm measurements from different flowbenches.

If you have a homemade bench or want to verify the original design of someone elses bench, how can a orifice help? Too many variables to say for sure what the flow is with an orifice on different flowbench designs.

If you want to calibrate a bench of any construction you would need to have a test flow section that would be mounted above the flow adapter with 2 straight sections of pipe and a measurement element in the middle. It should either expand the air or diffuse it as it enters the top of the adapter so the adapter discharge velocity into the entry of the flowbench would be similar to testing a head. It would require different calibration orifices to check all ranges. The flow element in the test section could be an orifice, nozzle, LFE, pitot or others. Inside a pipe with straight upstream and downstream sections makes the surrounds fixed so an orifice flow can be calculated.

I am not the only one here that has seen benches that measure flow of a head equally but read different with the same orifice plate.

Erland Cox and Eric Weingartner are 2 that come to mind that have posted of seeing this. Either of you correct me if I am wrong. How can anyone explain how that can be if test plates always flow the same?

Should you recalibrate your bench to an orifice and now the same head reads different between the two benches?

Rick

[user-9274568]

I'll tell you why. Because some benches see the air differently. I have two benches here that do the exact same thing. SuperFlow has two benches that do it as well. A SF600 and a SF1020.

This design see the air way more efficient that an SF600 style bench. How do I know? Because with a digital manometer you can see exactly what is going over the plate on both sides.

[Rick360]

I'll tell you why. because some benches see the air differently. I have two benches here that do the exact same thing. SuperFlow has two benches that do it as well. A SF600 and a SF1020.

But they "see" the air the SAME when its an orifice?

Rick