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 Can a Air bench flow detect small changes? 
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Joined: Sat Oct 03, 2015 1:38 pm
Posts: 75
Can a air bench flow detect small changes like a engine port being polished?
Can that be detected?


I just ran my 3/4 built air flow bench just to see what happens and the psi figure on the manometer was fluctuating a little.
Orifice roughly 2.5inch.


Anyway I put a allen key over the pipe hole and not much change on the manometer.
I was only running 2 out of 3 ametek 119666 motors.

I know I should fully build the bench but I thought i'd ask this question now before continuing as I feel like bringing the project to an end as I am only wanting to make slight modifications to the engine ports to try and gaing 1-2 hp per port.

I should have asked this before I even started lol but it never came across my mind at the beginning.


Thu Jul 06, 2017 1:53 pm
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Joined: Mon Feb 23, 2015 6:10 am
Posts: 264
Location: Northern NSW, on the wrong side of the Great Divide.
damunk wrote:
Can a air bench flow detect small changes like a engine port being polished?
Can that be detected?
Depends on the amount of improvement and the scale being used to see it. As an exaggerated example if your polished port only makes 0.4 cfm improvement and your measurement scale is in 1 cfm increments then no it wont be detected. However if your measurement scale is in 0.1 cfm increments then it will be detected but then the problem will be if you recognise it as an improvement or ignore it as an anomaly.

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Thu Jul 06, 2017 7:25 pm
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Joined: Sat Oct 03, 2015 1:38 pm
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I don't mind the anomaly bit aslong as it is possible to record it. I have a few replica engine heads to test against one n other.

The ebay digitial manometer measures in kgmm, mbar, bar, psi, cmg and a few others. This is where I am stuck.
The psi is measured in 0.000 so with one motor is is 0.020 , with two motors 0.080 psi. not tried with three yet. Damn thing makes so much noise, the neighbour must think there is a rocket launcher take off happening, will take it into garden after work today.

The calculator download from here tells you to only change the following :

Orifice diameter 2.10 inches
Pressure difference 16.0 WC in inches
Discharge coefficient 0.62


1) So you input orifice diamter which in my case is 2.5

2) Pressure difference: Is this the test pressure: which I should always keep to 16.If drop increase vacuum power. If lower higher than 16 then lower vacuum power?

3) discharge coeffient: leave that as it is?

So the psi measurement from the manometer I put into this calculator?


Fri Jul 07, 2017 1:49 am
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Joined: Mon Feb 23, 2015 6:10 am
Posts: 264
Location: Northern NSW, on the wrong side of the Great Divide.
I haven't used the software or the calculator so I can't advise on anything to do with them.

The point I was trying, probably poorly, to make is what gets detected depends totally on the resolution of the scale. The smaller the resolution the more will get picked up but the more that gets picked up can be actual improvements or momentary anomalies. If you use the software Bruce and others use you could at the very least write the measurements down so yes you can record it, if it saves the measurements or not I do not know.

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Fri Jul 07, 2017 2:03 am
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Joined: Sat Oct 03, 2015 1:38 pm
Posts: 75
Well I better get this to work atleast before I even decide to buy the proper data recording manometer with software because this way with recorded data you can get rid of anomaly if data taken over a wide range.

p.s my digital manometer resolution is Psi Range: ±2.000; Resolution: 0.001


Fri Jul 07, 2017 5:26 am
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Joined: Wed Aug 25, 2010 7:54 am
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Location: Riverina Australia
How large is your port ? Diameter?

Jim

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Sat Jul 08, 2017 3:16 am
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Joined: Sat Oct 03, 2015 1:38 pm
Posts: 75
The pvc pipe diameter is about 80mm(3inch)

16 valve engine:
The two inlet valve ports are 29.5mm diameter.
The intake port on the engine is small enough approx 45mm x 32mm

3 x ametek 1199966 motors

I just had all three motors on and the digital manotmeter was reading 0.200 psi
This was without a test piece. Just air being sucked through the main 3 inch pipe.

the digital manometer is brandnew.


Sat Jul 08, 2017 5:45 am
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Joined: Fri Jan 08, 2010 10:36 pm
Posts: 1148
Location: Maryland
Where did you purchase this digital Monometer, as i have a couple off eBay and they will measure in inches of water which is preferable to what you are doing.

Rick


Sat Jul 08, 2017 11:00 am
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Joined: Sat Oct 03, 2015 1:38 pm
Posts: 75
http://www.ebay.co.uk/itm/Fixkit-Digita ... SwXY5ZQsZ0

5 star rating.

I cannot detect any leaks and the suction was so strong that it sucked the air foam filter out of the pipe.
Selectable Units: H2O, pis, bar, mbar, kpa, InHg, mmHg, ozin², FtH2O, cmH2O


* I just tried it in Inch(H2O) full blast and the reading was 6.81 :(


Sat Jul 08, 2017 11:44 am
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Joined: Sat Oct 03, 2015 1:38 pm
Posts: 75
Attachment:
manometerproblem.jpg


Right okay. The 6.81 inches H20 was taken in the above config.

I then removed one of the manometer tubes and the reading shot up crazy well above 16.00 INches H20 but I had to cover most of the pipe with my hand to get that high reading.
This was with just two motors on.

But then when you put when connected both tubes back into the box the RANGE becomes so small.

Is that how it is supposed to be.


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Sat Jul 08, 2017 12:56 pm
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