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Posted:
Mon Apr 10, 2006 6:11 pmby DRAGRACER
am i on the right track i have the mercdog blueprints and i am going to use the flow performance software on my bench. i was wondering on the orfice can i use just one size orfice with the flow performance and how do i arrive at the size for the orfice or do i still have to have several different size holes as in the rotating disc. thanks in advance for your help.
Posted:
Mon Apr 10, 2006 8:13 pmby Thomas Vaught
A lot of people are getting away from the Rotating disc deal due to leakage. Some have gone to fixed orifices with stoppers to open certain ranges.
Others have gone to Pitot tube designs.
My opinion is, unless you are in an extreme hurry to build a bench tomorrow, read the previous posts on the board and also read all of the new posts and then build your bench the way YOU want it to be.
Good Luck.
Tom V.
Posted:
Mon Apr 10, 2006 11:25 pmby Tony
The answer is that a single sized measurement orifice only works over a fairly limited range of flows with any sort of real accuracy. For cylinder head work, where you want to measure flow over the full range of valve lift, a single orifice is just not up to the job.
A rotating turret with multiple orifice holes is one way. Another way is multiple orifice holes with rubber stoppers. A quite different approach is the pitot flow measurement method, perhaps with some electronics.
A lot depends upon your budget, fabrication skills, and personal preferences. They all work, and can all be just as accurate, the final results will depend mainly how much care you take in building and calibrating your bench than anything else. There is no one "best" design to adopt.
As with many things, understanding, knowledge, and experience are the most important factors in building and using a flow bench.
Posted:
Tue Apr 11, 2006 12:00 amby cspeier
Posted:
Tue Apr 11, 2006 2:46 amby Tony
You may be right, but it is still very bad practice. A 50:1 flow range is a 2500:1 pressure range you will need to measure accurately. That is a rather tall order.
Much better to switch orifice sizes, and maintain the full resolution and accuracy from huge flow numbers right down to residual leakage.
Posted:
Tue Apr 11, 2006 8:35 amby Jesse Lackman
Posted:
Tue Apr 11, 2006 10:04 amby larrycavan
Posted:
Tue Apr 11, 2006 2:21 pmby bruce
Save your money buying plans, read the forum here for all your info and feel free to make a donation 
Posted:
Tue Apr 11, 2006 5:53 pmby DRAGRACER
thanks guys for all your help. i already have the mercdog plans and i have been reading as many post here as i can their is some really smart people here. so if i make multiple orfice holes not a rotating disk what is the best way to access plugging them or swapping one plate to another.