Newbie design help

[bearwen]

I am totally new and have read a lot of the posts. I have to say I am still very confused on the DIY manometers. Anyway I am looking at building a flow bench for go kart engines I will be flowing heads, carbs and exhaust. The largest opening I will be flowing is the exahust which is in the 1" to 1 1/4" dia range. So I have seen some designs other places and well heres the design that I feel is the simplist so please give feed back as to your opinion remember I am flowing 22mm carbs and 1" exahusts for single cylinder 4 stroke motors in the 6.5 to 15hp range. Ok the design is basically just a pvc pipe size in the 1" to 1 1/4" depending on flowing carbs heads or carbs with restirictor plates for the Jr classes with a valve ( the valve becomes the controlable orifice of the system) on one end of the pvc we have the fixture for what ever I am flowing on the other end of the pvc pipe is a large shop vac with the valve in between as the orfice that is adjustable very simple and controlable I think. The questions I have are what do you think of the design will it work 2. how do I hook up and where do I hook up the manometers 3. How do I make the manometers with the proper scales. when I build all of this how do I actually use it and understand what I am seeing on the meters? 4. What should the vacuum meter be at for test 8" 12" 28"? This is not my design i found it on a go kart forum the guy says hes been using for years but he says that he runs his tets at 8" of pull I am assuming that is because the shop vac cant pull 28" with the 1" or 1 1/4" pipe depending on what he is flowing. Please give input as I am looking for simple, cheap but effective and I am not nor do I intend with this bench to flow anything larger than what I have stated above. I do intened in the future once I learn this stuff to build a larger and much more professional bench perhaps with Bruces DAQ as my son will be getting into cars in about 4 years so I will be ready.
Thank you all in advance for your help and thank you Bruce for starting and maintaining this forum.

[RACEPUMPER]

Welcome to the forum.
Buy Bruces plans, their great value for money.
read all you can on manometers in the forum and keep asking questions, these guys know heaps.

Jim

[bearwen]

I have been reading a lot and its starting to come together. I do plan to buy Bruces plans in the future but for know I need small flow and cheap. Once I get the hang of it and understand everything then I will look at build a bigger bench to flow car parts but for just need the go kart stuff.

[bruce]

Checkout John's bench he built using just the plenum area of my plans. Nice simple bench that can be upgraded by adding a blower box at a later time:



I've been giving some thought to making another set of plans for a setup like this as a simple starter bench.

[106-1194218389]

It was quick easy and cheap! I bought Bruce's plans and as he said I just built the chamber side. On a small block Chev head flowing 263 CFM it will still pull and honest 10" H2O.
Bruce's plans simplify the whole process and you can actually build the one like I have in a weekend.

John

[bearwen]

Ok I have came up with a design no offense bruce for not buying the plans. I wil probably buy the plans and build a much bigger unit in the future but for now I just want to get started and learn this stuff. Ok I have a few questions. I hope the pic posts. 1. does the size of the box on the two sides of the orifice plate matter if so what size should they be? 2. what should or does it matter the distance of the baffles from the orifice plate? 3. does the smaller pipe and elbow matter on the carb adapter? 4. where do you put the tube for the 28" H2O utube and where do you put the tube for the incline manometer? 5. can a single shop vac pull 200cfm @28"( that is most more than I need) if not will the test be wrong if I only pull 10" @200cfm? 6. I used the spread sheet to caculate the orifce size I came out with 2.5" orifice for 200cfm and the incline scale well i am not sure how long or at what height I am going to use. I did notice that on the spread sheet if i used 24" long and 6" rise with Marvel oil gravity that the scale read 100% at only5.14" or something like that it was not 6" is this right? if someone could look at the pic and draw or explaine where to put the manometer tubes and the deminsions of the box and answer the other questions i have I would be really greatful as i would like to start building this thing this weekend so that i can figure this all out and do some flow test befor race season starts back up in mid January. I figure i will need time to get the hang of it and know what I am doing.

Thanks soo much for the help.



Edited By bruce on 1229546019

[49-1183904562]

Bearwen,

Why would you not just use a AVG pito tube and a settling chamber alot less work and you will be up in a afternoon.

Rick

PS. Buy the plans, or read more and you will find the answers as they have all been answerd many times before.

[bearwen]

Ok I have done more reading I figured out that i need an orfice of 2.25" for 168cfm which is more than i need since I am working with 196cc motors or roughlly 12 cid motors the valves are around .95 and the veturi of the carb is .625 I have read that a .95 carb dia in another post will flow roughlly 70cfm at 10" or 105cfm @28" I would like to get a little higher water to make the readings more accurate so i figure 168 cfm would be a good target @28" this will be difficult with shop vacs but we will see what we can do I may have to buy a few motors. I have also learned the placement of the manometer tubes except for the 28" water as I have seen some that are in a plenum box on the top of bench before the first side of the orifice box and i have seen some that dont have a plenum and have the tube going into the the first side of the orifice box and the incline is set with one tube on both sides of the orifice box. The really big questions I have that i cant seem to find an answer to are 1. does the intake and exhaust ports of the bench need to be the same bigger or smaller than the orifice I assume the same or larger or should the intake to the box be the dia of the cylinder of the motor what about exhaust? Also the carb or head adapter to the box this should have a size as close to the cylinder as possible bore and stroke correct? 3. Do you need to have a plenum box or can I build one large box with a divider in the center and the orifice plate mounted to the divider does the divider need to be angled, vertical, horozontal or does it matter as long as the input air is not going straight to it ie a baffle ? I dont think I am really concerned with actual cfm flow it would be nice to know what the numbers really are but more so concerned about getting a reading of my carb then working it a little and seeing a positive (hopefully) or negative difference in the reading so as to adjust the heads and carbs valves etc to get max potential from them we have size limits for everything and are very limited as to any machine work but if nothing else i can blue print them and see the flow differences to say yes its better or lets blue print another one and maybe adjust the venturie shape to get max flow within the spec rules. As well as to go through all the spares and find the best and worst and know what to put on first.
I will get Bruces plans to build a bigger and better bench once I get this first one working as I am one of those people who have to search and read for the info then draw conclusions and get feed back from others then progress and I figure the more I try to learn this on my own through the forum the better I will be when I do get it going as I will better understand the principles and why.

[bruce]

1. Make you ports larger than your orifice plate holes.

2. You can use one large box and simply add in a divider as you suggest. The orifice plates needs to "see" flow from all directions so keep that in mind when you install the baffle (this is my personal opinion) from working with my design.

[bearwen]

Bruce thanks for the reply. How big should they big should the intake port be the size of the cyclinder of the motor or just use a 3" piece of pipe cyclinder bore is 2.25" i think it is smaller than 3" an then use a plate like the head plates I have seen here where there is a flat plate on bottom to seal to intake of bench then a tube of the same size as the motors bore and stroke and then a plate on top to actually mount the head to. I assume I would use the same kind of head adapter to flow the carb as well just have the top hole reduce down to the size of the intake port on the head of the motor correct? I think I am getting my head around this now. as for the pressure utube put one side to atmosphere and one side to the intake side of the box and then on the incline one side to the intake side of the box and the other to the exhaust side of the box this is correct? Thanks again Bruce for the help and the great forum. One thing I am unsure of is if I have an orifice of 2.25" and an intake port of 3" and all is set to flow at 100cfm then when I put the cylinder AKA head adapter of 2.5" without the head on it would that make the incline automatically read lower than 100% then with the head it will be really low correct or do I need to calibrate the incline to the bench with the head adapter on? These numbers are not exact I will work the numbers out once i get the spec of the bore. Just how much bigger or smaller should the intakes be compared to the orifice and what if the cylinder of the head adapter is really close to the same size as the orifice is this a problem?

[49-1183904562]

Bearwen;

The incline only reads the difference in pressure across the orifice plate. So the only time a bore adapter could effect depression on the upstream (test side) is if it is smaller than the orifice plate. I/E your bore is 2.25" and you have an orifice plate that is 2.75" at full unrestricted flow your bore adapter is the restriction. But it is assumed you would have something like a head or intake or carb upstream further with a greater restriction, thus your bore adapter would not have any effect all be it you would probably be better served with a smaller orifice plate. Also in reading your ideas you may have the wrong Orifice plate for what your doing right now, to conserve motor power you want the smallest possible orifice this will use less motor power and make the incline more sensitive during testing.

Rick

[bearwen]

thanks for the reply I get what you are saying. I am not sure about the size of the orifice plate though as you said smaller would be better but dont I need to be able to flow the max or actually more than the max of what ever I am testing such as a .95 bore carb according to a post I read earlier I think Larry said it that he calculated that a .95 bore carb has a cfm of 104 @28" now the bore of my carb is .625 so I have more than I need however the valves are .95 and the exhaust is .75 id. so wouldnt I need to be able to flow over 104cfm as that is what the valve orifice will flow with nothing in it not counting runner design losses etc so any work I do I wouldnt be able to flow enough at 28" to even see it. I think perhaps since the valve is the largest but it has many obstructions that i could get away with a bench that flows 115 to 125 cfm @ 28" if the vac will do it. If the vac wont do it then perhaps i will buy a couple of motors and then do a second larger orifice plate so that I can flow larger stuff later on as we grow in motor sizes and then into cars but I amsure I will build anew bench before we get to cars I have 5 years till myson is 15. So other than that does everything seem right I am hoping to get the replies by tomorrow so that Saturday i can start on the bench and be flowing by Monday. Oh last question to make a sharp edge orifice plate can I cut lexan with a hole saw and then use a router with a 45 chamfer bit to give it that sharp edge if so how thick does the lexan need to be I think Bruces are 1/8" but they are aluminum does it matter? I read somewhere that different angles or edges of the orifice plate have different coeficents and that a orifice plate with a rounded edge on the intake side is roughlly .98 or so so would this be better than a sharpedge with a coeficent of .62 andagain does the thickness matter if so how thick? I read the coeficent of the orifice plate stuff in the service procedure pdf from superflow. Are all the info in the spreadsheets set for a sharp edge if so can you change it or would I be better off using the sharp edge and leaving everything alone for now? Also any way to easily convert the incline graph from the spread sheet to metric as i think it would be easier to measure?

[bearwen]

Ok I ma not sure about what i am getting in the spread sheet.
Pressure difference is the hight of the fluid in the incline at max or 100% for example I have a incline meter that is 24" and has a vertical rise of 10" than on the spreadsheet I would put in for pressure difference 10 correct? Ok if you go to the scale section and look at the scale I have a.25 id tube with a 1" resovoir and the meter is 24" long and has a rise of 10" and i am using the fluid of.83 which I believe is what I read was the gravity of Marvel Mystery Oil that makes my ^p (WC in) 9.55" at 100% now this 9.55 that is not what the vertical is set at correct that will be different such as 10" or 28" so how do I know and how can I figure out if my motor will pull 28" as I have read you want to test at the highest possible to get the most accurate and to see small changes correct? i have tried this out in the spread sheet and based on the numbers above it says I need a 1.75" orifice to get 131 cfm at 10" pressure difference and a .62 coefficent. does this sound right? and I still not sure how the 28" vertical meter is calculated or is it not a factor in this. I think I am getting confused with the WC in in the incline scale and the WC in of the vertical as i dont get how one is 28" and the other is only 10". As I am building this bench to learn and get a visual of all that you guys are talking about as well as set my Kart motors up a little better so I am trying to DIY everything even the orifice plate so how do I go about making the plate lets say out of lexan how thick and what angle does the chamfer need to be or can I just bore a hole with the lath and change the coefficent in the spread sheet to adjust the numbers right? I am looking at the SF sevice procedures PDF and it is showing that a hole with no beveling rounding or chamfer has a Cd of .86 I am unsure as to what part thickness plays but I am sure it does and also they are showing that a hole with the intake side of the orifice being rounded over and the straight at the back like a regular hole has a Cd of .98 so if i want to get the CFM up and use a smaller orifce to try and get 28" with out killing the vac wouldnt I want to use a plate with a higher Cd? If so anyone know the specs to build one of these higher Cd plates such as thickness to diameter and angle of the rounding over etc...?

Once again a long winded post I am sorry I just start typing and then more questions come up.

[49-1183904562]

[color=#000000]Bearwen,

First off at this point don

[Otto]

back up boys i believe Bearwen might be slightly confused, ok the speadsheet calculates for your incline and for oriface plate sizing your 28" test pressure has nothing to do with what is being calculated {unless you are making a calibration plate}. The Depresion input is the pressure differencial across your oriface plate. say 10"

test pressure + oriface pressure {or Dp} = total vacume power required

28"+10"=38"

as for the plate if you just have to make one use allu or steel brass would work {better hobby shops} 1/8" it would be easeir to make a square edged plate and use the cd listed in superfow paper work. but sharp is best bruces are inexpensive but you could do that later if you have to flow today