×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

converting to 28h2o

converting to 28h2o

converting to 28h2o

(OP)
Hope someone can help.  I know there is a formula to convert a flowbench reading from 10" H2O to 28" H2O.  The flowbench I have access to is 10".  Thanks.

David

RE: converting to 28h2o

David,

New_Flow = Old_Flow * ( New_Pressure / Old_Pressure ) ^ .5

334.664 CFM = 200_CFM * ( 28 / 10 ) ^ .5

334.664 CFM = 200_CFM * 1.673320053
===================================================

example for Holley 500 cfm 2-barrell carb
at 2-barrell rating at 3.0 inches Hg. -VS- 1.5 inches Hg
4-barrell rating

353.55 CFM = 500_CFM * ( 3.0_Hg / 1.5_Hg ) ^.5

As you can see ..a Holley 2-barrell 500 CFM carb is really a very small carb ( 354 cfm ) ..when compared to a Holley 4-barrell 500 CFM carb

  

Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers
http://www.mindspring.com/~meauxracing/

RE: converting to 28h2o

David , if you want to go the other way , then just calculate the "Reciprocal" which is 1/x  

10 to 28 = 1.673320053 conversion factor

1 / 1.673320053 = .597614305

28 to 10 = .597614305 conversion factor


Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers
http://www.mindspring.com/~meauxracing/

RE: converting to 28h2o

Hi Larry, in practice do you need to worry about laminar flow effects or other non linearities possibly caused by Reynolds number when you do a run at two different pressures?

Cheers

Greg Locock

RE: converting to 28h2o

Previous Post in ERROR
353.55 CFM = 500_CFM * ( 3.0_Hg / 1.5_Hg ) ^.5
===============================================

Should be
353.55 CFM = 500_CFM * ( 1.5_Hg / 3.0_Hg ) ^.5
=================================================

Greg, there is another small correction factor used by SuperFlow with the normal conversion factor
this might be a small Reynolds type correction ???

Most people just use the Test Pressure Conversion equation i just posted as its pretty close (Linear)

if you use the additional SF correction factor , its
even closer

if the Test Pressure is too low , the air speed will be low
and if theres a bad curve or any problem area in port or valve area , it won't show up at low airspeeds because air is flowing slow enough to follow bad curve , but at higher speeds (Test Pressures) , the same port will flow different numbers or in a live engine make less HP than the flow bench predicts.   







Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers
http://www.mindspring.com/~meauxracing/

RE: converting to 28h2o

Greg ,
additional info ;
SuperFlow doesn't use a Laminar Flow Element
they use Orfices.

When flowtesting on SF bench
especially above 20 inches of water
the flow is always in turbulent range (> Reynolds laminar value )

Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads
MaxRace Software
ET_Analyst for DragRacers
http://www.mindspring.com/~meauxracing/

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources