FlowBench for 150 to 210 cfm heads - FlowBench Materials

[200cfm]

Hello. This is my first post and I hope to build a DIY flowbench orfice style to evaluate my cylinder heads. My cylinder heads currently flow about 135 to 140 cfm at .400 lift cam and I want to improve their efficiency hopefully to 175 to 225 cfm range. I have read and researched the forums here and believe I am ready for the project. I have bought a vertical Dwyer manometer. It is the folding type and reads 30-0-30 inches water or mercury. My first question is. Is this a good start for selecting the vertical manometer? I understand the vertical manometer is required for the bench "test pressue." I would like to test at a minimum of 10 inches WC and if possible as high as 28".

My second question is. Should I just build the incline manometer or is it possible to go dital on that instrument? Can the incline be digital or does it have to be a genuine incline manometer? I see very short ones on ebay but none so far that reach out to 24 or 30 or 31 inches. And a final question for now. The orfice plate. I plan on installing only one plate. My size should be what? I am thinking 1.500" to 2.000" range. And since this piece is critical for accuracy is there anyone that offers a one piece orifice size for purchase? Thanks.

[86rocco]

Welcome on board.

Check out the spreadsheets in , if play around by plugging different numbers into those sheets, you'll get a good idea of the design requirements that'll meet your needs, for both the inclined manometer and orifice.

Also, check out Mouse's FP1 at , it's received good reviews around here and if it's within your budget,it'll satisfy all of your manometer needs.

[bruce]

If you need orifice plates check here and help support the forum:

[200cfm]

Thanks for the spreadsheet and orfice plate source. Now on the spreadsheet. I selected an orfice plate diameter of 1.750." At a test pressure of 10" wc I net 140.4 cfm. Now I am thinking that since my stock intake head port should flow close to this at .400 lift then the vertical incline would reach 100% vertical if I designed a scale length incline of 28 inches and height of 13 inches at an angle of 27.664 degrees.

Is this thinking correct? Also if the motors are able to pull up to 28 inches WC the same 1.750" orfice should flow 235 cfm. Well above my DIY porting skills I am certain. At that pressure though I assume I have to view the 100% vertical or 13 inch rise in WC (if actually obtained on my intake) as the new 235 cfm reference point for the incline.

Is this thinking correct? Also, I left the discharge coeffieient at 0.663. Should I have changed this value?

Summary: I should order a 1.750" sharp edge orfice plate for my design needs. At 10" WC test it would offer the highest accuracy on the incline. And if an improvement in port efficiency is made I can simply adjust by increasing the test pressure and recalculate the cfm flow on the incline based on the new test pressure using the chart. Would that be correct?

One final question please. On the vertical incline design. I understand the tube I.D. size of 0.125." What is the reservoir size of 10" for. Is that value something I can select and change or is it fixed? Thanks again.

[larrycavan]

[200cfm]

Ok, I assume I should have use .62Cd in the sheet then. I went with what was already posted in that slot. Will recalulate with .62. Does this apply also to the I.D of the reservoir. Do I select that value?

So the incline 100% point has to agree with the calibration of just the orfice hole at whatever test pressure IT was calibrated at. Is that correct thinking?

And would a 1.750." orfice hole be the correct starting point for my heads?

Here is a summary of data on a standard intake port with 1.656 valve. These are at 28" wc so perhaps I need a smaller orfice for 10" wc minimun test bench.

.100 lift @ 50.2
.200 @ 87
.300 @ 120.5
.400 @ 137.2
.500 @ 146.9

Or perhaps I need more than one orfice. At this point I am looking for guidance on what size orfice to order based on the above and a DIY bench with a minimun of 10" wc and hopefully a potential test pressure of 28" wc.

Thanks for the feedback.

[bruce]

Orifice plates can be machined to any diameter so I would be more inclined to make my max cfm a round number and machine the plate to that ie 200, 210, 220cfm etc.

Just a thought, or me being anal . . .

[larrycavan]

[200cfm]

Ok, good, I will go with an orifice cut for the max of 200 cfm @ 28" wc. And gather motors to pull the test pressure to 28".
I am understanding the chart better now. The chart is interested in only the pressure drop across the orifice and not the straight vertical manometer test pressure.

Bruce, I believe you must be the gentleman who can cut the orfice. Will be in touch with you via the above link. Thanks and Happy Thanksgiving.

[200cfm]

Spent the day reading and researching. I started off thinking one sharp edge orfice for these heads to be evaluated. Now I am thinking at least 3 orifice plates plus a calibration plate. Please advice me if I am proceeding correctly.

Here is my reasoning. These intake port heads flow on a good factory valve job from about 50 to 140 cfm flow range using the factory cam which has a max lift of .400"
Using the spreadsheet calculator and the guidance of the forum posts to keep the incline manometer flow meter above the 60% inch level the following is what I calculated.

I have selected a 28" incline with a 12" vertical rise using .250" ID tubing.

First: a 1.300 inch orifice: to cover valve lift flow ranges of 47.6 to 79.4 cfm.

Second: a 1.650 inch orifice: to cover valve lift flow ranges of
76.5 to 127.9 cfm.

Third: a 1.950 inch orifice: to cover valve lift flow ranges of 107.2 to 178.6 cfm.

These are the 12" incline WC 100 to 60 % ranges for the .100 to .400 lifts.

Is my thinking correct on this so far???? Is this how I cover the factory range with hopefully port/valve improvements?

A question on the calibration plate. This is the plate that sits on top of the completed bench in place of the head when the total bench is to be calibrated with the above three plates installed in the bench. Is my thinking correct on this so far? Is this my fourth plate requirement?

And here is where I get confused. The calibrated plate at XXXcfm is referenced to 28" WC test vertical manometer. Should it be larger in size than the largest installed orifice plate ( the proposed 1.950" orifice). And if so, what is going to keep the incline manometer from peaking far over 100% (spill over). For some reason I am thinking the incline manometer will be maxed out since it can only rise to 12" vertical incline wc.

One final question. What is the ratio of the tube ID to the reservoir value ID. I am not understanding the resevoir ID or ratio on the spreadsheet.

Thanks in advance for clarification.

[larrycavan]

[200cfm]

Thanks Larry, Currently researching how to mount or install the three sharp edge orfice plates in the chamber. Should they each be a separate plate or all three cut into one plate? And do they have to be centered or moved to a certain location in the chamber when selected. Don't like the sealing problems of the disc that I keep reading about. Like the rubber stopper approach but uncertain on the how to gain guick and simple access for range change. Trying to researach everything carefully and build only once.

[Thomas Vaught]

Using a large chamber with a single plate and three holes
120 degrees apart will work fine. Same deal for access if you use a "deck plate" from Beckman. Rubber stoppers from Mcmaster Carr will work well too.

Go for it.

I would make the chamber much like a SF 1200 is for the chamber
volume. 2 feet by 2 feet by 18 inches for each side of the chamber with the orifice plate in the middle.

Tom V.

[200cfm]

Ok, will go with the port hole access design and three orfices holes in one port. Boatersworld is nearby so will get the deck plates from them. Thanks.

[larrycavan]