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 Brand "X" flow bench? 
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Joined: Fri Feb 17, 2012 10:18 am
Posts: 81
I have a question about a pitot style bench . Is there a way to cheat the CFM's reading?Is there a way it will show a higher un-true reading?


Sun Jan 26, 2014 8:54 am
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Joined: Thu Dec 19, 2013 10:34 pm
Posts: 20
any bench can be made to lie. just like a butcher can put his thumb on the scale. lol


Sun Jan 26, 2014 10:48 am
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Joined: Fri Feb 19, 2010 7:36 pm
Posts: 1628
Location: Grantsville, Utah 45 min west of Salt Lake City
I had a Flowquik system for a while. It had a calibration knob on the side of the unit and you could crank it way up and make it really happy. It also had honeycomb plastic in end of the tube that normally was a fair distance from the sensor in the tube. One day when I was not paying attention I sucked a rag I to the tube and it pushed the flow straightening honeycomb right up against the sensor. I was in a hurry and did not reposition it. With out doing any grinding I gained 30 cfm :D


Sun Jan 26, 2014 1:32 pm
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Joined: Fri Feb 17, 2012 10:18 am
Posts: 81
jfholm wrote:
I had a Flowquik system for a while. It had a calibration knob on the side of the unit and you could crank it way up and make it really happy. It also had honeycomb plastic in end of the tube that normally was a fair distance from the sensor in the tube. One day when I was not paying attention I sucked a rag I to the tube and it pushed the flow straightening honeycomb right up against the sensor. I was in a hurry and did not reposition it. With out doing any grinding I gained 30 cfm :D

Now thats funny . The Flow quick system is why I asked this question . On a differant site I have posted some flow numbers on some heads I did . There is a guy on there that claims he gets more flow than my heads and he has a flow quick .But on all the dyno runs I have seen the engine do not build as much HP as my engines .Now I know why .I looked at there flow bench once , sure glad I went with a PTS flow bench now .Thanks for your comment .


Sun Jan 26, 2014 10:15 pm
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Joined: Wed Aug 25, 2010 7:54 am
Posts: 427
Location: Riverina Australia
All the pieces of equipment that we use are useless if we don't know how to use them. A screwdriver is a great tool but if you don't know which way to turn a screw its worthless. A flow bench is the same and so is a dyno.
A friend showed me on his superflow dyno one day.
A Chevy made 550 hp, then he changed the humidity compensation only.
620. No other change.
I think that's scary in the world of quoted hp and flow figures.
Another guy I know has a very old 10" flowbench, he figured out about 5 years ago that his correction factor to 28" was generous by about 20%. Never mind the 10 years before that!

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Tue Jan 28, 2014 2:24 am
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Joined: Wed Mar 03, 2010 3:40 pm
Posts: 1271
Location: Melbourne, Australia
As soon as you start adding correction factors to any measurement, you can get into really deep doo doo.

The best measurements are very simple direct measurements that can be calibrated directly against a known physical standard.

Its when you start assuming that 1+1 = 2.04 because.....

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Wed Jan 29, 2014 5:01 pm
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Joined: Wed Aug 25, 2010 7:54 am
Posts: 427
Location: Riverina Australia
Tony wrote:
Its when you start assuming that 1+1 = 2.04 because.....


This is so true Tony, old post I know but correction factors caught out a mate yesterday and I remembered you saying this.

Jim

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Mon Oct 26, 2015 5:43 pm
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Joined: Fri Jan 08, 2010 10:36 pm
Posts: 1148
Location: Maryland
I will post this here as I think it fits,

I have noticed that some of the Digital Monometers offered out there even some of the newer ones just coming out are using a correction factor for calibration, years ago Bruce and I discussed just how do you represent good calibration to the end user? Don't get me wrong a lot of these devices are nice better than the DIY PTS DM from some points of view. But using and displaying CD as the adjusting factor for calibration has two valid advantages, 1.) Once you have a basic understanding of CD and what it is and means you are more opt to recognize when adjusting the CD to calibrate is masking another problem (leak, etc.) with your setup. 2.) As you progress with the flowbench you learn just how important understanding CD is in how the flowbench works but more, how important understanding the role of CD in porting and using your bench to determine port CD for good, better, best port is in your work.

Adjusting the knob on the bathroom scale to lose weight has never seamed to work for me :mrgreen:

Rick


Tue Oct 27, 2015 7:35 am
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