PTS Flowbench Forum

Rick, thank you for the word variac! I was actually trying to find/make/buy this exact type of device for the reasons stated + a few ways to make the rig much more versitile.

I agree that the line voltage is a biggie on variables, although I am still failing to grasp the need for a line voltage correction factor if i am only using or considering results from the same(to a small tolerance) voltage in my testing.

I am planning as time and $ allow to obtain some of the PAP copies to use as another standard in my testing. I think this will come after I get the new rig put together. I actually had to partially reassemble the other one for the pics. right now i am not doing any testing, the few engines i work on during the winter are racing right now.

This brings me to my next point of consideration. Not trying to downplay its imporatance or negate anthing connected with what people are doing on this site (the site is great!), but I am interested in flow benches only a little farther than it makes the engines i build more powerful. at what point do i say i am swatting flies with the thing? I also have to consider at what point i just break down and buy a flow quick instead of messing with the other. If i do that the line voltage variable is not a problem and the supposed only winky in the works is making sure that there are no leaks between the test piece and the flow tube. this coupled with the added selling point of a computer printout is probably the way to go......

Jason

OK,

I will see if i can explain what is going on in my head with this experiment. As I said you are not flowing air through a known restriction thus the motors direct vacuum is a variable in your test results. Lets use this example you flow the head and at 115VAC and .250 valve opening it will pull
25" of depression. Now based on the theory less ability to pull depression at all things equal would mean that the restriction (The Port) is flowing more air. But lets say you do some work and test again and now at this test the line voltage is 113 but your depression is now only 23"? Do we contribute this improvement to port work? or is it because the motors can now not pull as hard?

113/115 = .9828 so do i just take my prior 25" x .9826 = 24.56" but we pulled 23" so 24.56 - 23 = 1.56" of depression, equating back to my original 25" 1.56/25 = .0624 or 6.24% improvement ?????

Do you see where i am going with this. I do not believe the motors ability to pull vacuum is linear across the voltage scale. That is why you need to build some type of voltage correction factor based on a known good orifice.


Just more thinking

Rick

Jason,

Also i would not jump on the flow quick yet Bruce and i are working on porting FlowSoft work with a Pito application, i just need to get off my ass and stop working 7 days a week. With this you can build your own flow elements (Bruce will supply APT's) and use the PTS DM.

Rick

Also i would not jump on the flow quick yet Bruce and i are working on porting FlowSoft work with a Pito application

I think there is still a lot of interest in this.
FlowSoft/Pito style bench.

I see what you are driving at Rick. I think we are approaching the same problem from two different angles. I definately agree the motors are not linear with voltage. even with my simple setup i could see this effect. While you are (i think) wanting to devise a way to correct for different voltages, i simply did not include results from different voltage, which can leave me offline at times and is a priority issue i also wish to resolve! Is the variac device not capable of just providing a stable voltage? or does the output voltage on the variac also change with line voltage? Vizard had written that his friend had overcome this variance by using a transformer to step line voltage up to 140 and use a rheostat to nock it back to 125v. I admit to not being up on the electrical (or any other for that matter) engineering. Just glancing at the variac i ASSumed (stress on the first syllable) thats what it was in a neat package.
best
Jason

Jason,

Yes any good variac will have the ability to step voltage up to 140VAC +/_, as long as the unit is rated for your power requirements then this should all be fine. Please remember DV's approach to this hole concept was to do it on the cheep and that a good variac is not. But that said in the learning process once you go to the dark side and build a Pito or orifice bench the variac is a nice easy way to control electric die grinder speeds. Also, one of the big issues you will have with this setup is if you ever change vacuum source (or it wares out) all historical data is pretty much useless. All that you are still learning something useful.

Rick

Interesting about voltage and not being linear, I was looking back through notes i made while playing around with the thing on different days about voltage and weather/ temp. Different days, same temp +- lil' bit. 80 cfm orifice open. line voltage one day 110vac the depression was 32.5" h20. Different day same scenario only change line vac 114 the depression was 33". in this range of depression around a 5 cfm variance for 4 vac. At higher flow cfm for this thing (315cfm, whole orifice plate open) 9.5" @ 110vac and 10.25" @ 114 vac. or should correlate to around a 15-20 cfm variance in this basic range for the same 4 vac. I say in this basic range because if you plot the points on the graph, the cfm and depression form a neat graph like x^2 decay if measured while at the same voltages. interesting. J

Jason,

Yes, that is probably very close, and i bet it would correlate to the inverse of performance graph of the motor being used.

I understand what you are doing and here with this setup but what are your ultimate goals with flowing heads, pipes, bongs, whatever one likes to flow. You mentioned a flowquick? are you just looking for a simple setup?

Also i am not sure how you are correlating to CFM is this just through extrapolation?

Rick

I mean really, my ultimate goal is to learn more about the heads and intake systems of the engines i am working on (sorry,No bongs, i'm not into that ) The engines i work on now are about 99.9% 2bbl cirlcle track engines. I only do 2 or 3 per anum so just a hobby that i take way too seriously. the engines have (if the rules are followed) serious choke flow issues. nothing i wish to do is breaking any known technology or physics barriers thats for sure! one thing i have found though is that my own knowledge can help bridge the gap between very small budgets and endless ones a bit. my own budget is definately on the small side. Currently, at 37 yrs old i have quit the automotive trade to stay at home with my kids(2 and 5) and am going to college as time and $ allow. been about three years now. after my wife gained tenure at the university where she teaches we decided that paying 80% of what i make out in childcare was not a bargain.

The idea of testing at differing or floating depressions ( especially high dep for low lift) does hit a soft spot with me. The engines i work on hve a restricted intake but not exhaust. I know from my own experiance that on these engines the overlap period and intake valve closure are paramount. the idea that the exhaust scavenge pulse during the overlap period is at a high depression and low valve lift is where i want to concentrate my efforts on the cylinder heads because of this scenario.

Yes, the flow is all extrapolated from testing the orifice plate in the picture. I made it to the print Vizard published with permission from Helgesen, it was his design and SHOULD? flow the numbers sharpied next to each hole when the hole is open if pulled to 28", thus use it at different depressions and correlate to flow at 28". what i was seeing is that as i tested Around any given amount of open orifice the mano would drop in a pridictable fashion as more holes were open in increments of what should correlate to 5cfm@28"h20. so my extrapolation for being off an amount of cfm comes from manometer readings being different at a certain voltage with the same amount of orifice opening. if the mano was say 1/2" different between voltages
you could see that at around that flow amount it give about so many cfm difference on the graph i had made at that voltage. i have a number of graphs that i did while messing around that were not quite complete over the entire range of operation but i always noted the voltages and temp/ weather conditions. It seemed that the voltage was way more relavent.

sorry for the lifelong story post but thats my direction with all of this. Thanks for all insight in advance,
Jason

Jason,
First, repeatability is of the most importance to me and that has also been stated by Rick. I also like to know how I compare to other benches as I work with a lot of other people and we share information back and forth. When you asked if your head was in the ball park I find that it compares very reasonably to what I was getting, but now you have to wonder if your bench and mine would calibrate the same with the same orifice. I found the post about the Pass Around Plates very interesting.

I have tried the FlowQuik, orifice in a tube and a venturi bench and now I am using an orifice bench built with Bruce's plans. By far the orifice bench built with Bruce's plans is the easiest to use, build and is the most repeatable. I can go with out touching it for a couple of months and come back and it is still calibrated the same. The one I am using right now is just the chamber side with the orifice plate that I plumbed two of my shop vacs to it as I did not have all the motors at the time. It will pull 12" on a set of 180 cc Dart heads at .700" lift. I threw it together in a weekend also.

I hope this gives a little helpful info to you. Good Luck!

John