Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
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Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
Bob, that is not what happens.
Texturing the surface activates the boundary layer and keeps it thinner longer so that the air can follow the surface.
If the boundary layer goes upp in thickness it greates a wake and as the pressure is higher where flow is slower
that wake can be pushed against the flow and cause separation.
Erland
Texturing the surface activates the boundary layer and keeps it thinner longer so that the air can follow the surface.
If the boundary layer goes upp in thickness it greates a wake and as the pressure is higher where flow is slower
that wake can be pushed against the flow and cause separation.
Erland
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Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
I like to think of chatter finishes creating a variable rate and thickness boundary layer which acts like tiny ball bearings for the mass to run against. And since the mass is compressible the boundary layer can thicken and thin depending on port speeds and pressures. Sort of acts like a smaller port at lower mass flow rates.. and then goes towards a larger port when the mass movement gets higher. This is the way a few engineers and pro head porters have also explained it to me.
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Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
I did those tests with a cylinder head.groberts101 wrote: ↑Wed Mar 21, 2018 7:20 pmThis is with that straight pipe right, Erland? Or within a bent port?Erland Cox wrote: ↑Wed Mar 21, 2018 7:15 pm I have done tests in my bench between 3" and 48" and the result was the same.
The only difficulty being at low lifts and reading low on the scale makes for larger errors.
As long as you have fully developed turbulent flow the result will stay the same up until you get where you must make compressible calculations.
Erland
Either way I find that strange to wrap my head around when a fully mirror polished port has ALWAYS picked up flow by about 1-2 cfm. My usual testing regimen was to always sneak up on the proper shape as best the available material, abilities and tools would allow, work at slowing the mass/to meet speed requirements, and then when happy enough I would full mirror polish both intake and exhaust for one last test. Assuming no major issues with the short turn, which of course was not always the case and sometimes I had to have another go at them, I would finally do the full polish prior to the final test. The polished ports ALWAYS picked up.
Different parts of the head react differently to surface texture.
Texturing parts where the flow is slow should help flow which I also have seen and polishing fast parts also helps.
I once tried to texture a restrictor and it lost more than 10% flow and there was a high noice from the flow.
Erland
Last edited by Erland Cox on Wed Mar 21, 2018 7:37 pm, edited 1 time in total.
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Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
OK, I see. In reality I believe much of this stuff can be like working on carbs. Change too many things between tests and you can gain in one area and simultaneously hurt in another to cancel out any one gain that may have been effective at producing better results. I also believe the pitot is still highly underutilized around the valve curtian. IMO, that's the real proof in the pudding right there.Erland Cox wrote: ↑Wed Mar 21, 2018 7:26 pmI did those tests with a cylinder head.groberts101 wrote: ↑Wed Mar 21, 2018 7:20 pmThis is with that straight pipe right, Erland? Or within a bent port?Erland Cox wrote: ↑Wed Mar 21, 2018 7:15 pm I have done tests in my bench between 3" and 48" and the result was the same.
The only difficulty being at low lifts and reading low on the scale makes for larger errors.
As long as you have fully developed turbulent flow the result will stay the same up until you get where you must make compressible calculations.
Erland
Either way I find that strange to wrap my head around when a fully mirror polished port has ALWAYS picked up flow by about 1-2 cfm. My usual testing regimen was to always sneak up on the proper shape as best the available material, abilities and tools would allow, work at slowing the mass/to meet speed requirements, and then when happy enough I would full mirror polish both intake and exhaust for one last test. Assuming no major issues with the short turn, which of course was not always the case and sometimes I had to have another go at them, I would finally do the full polish prior to the final test. The polished ports ALWAYS picked up.
Different parts of the head react differently to surface texture.
Texturing parts where the flow is slow should help flow which I also have seen and polishing fast parts also helps.
I once tried to texture a restriktor and it lost more than 10% flow and there was a high noice from the flow.
Erland
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Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
This thread is about pitoting around an intake valve: https://www.speed-talk.com/forum/viewtopic.php?f=1&t=34978
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Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
Right, I'm a little rusty here.
A turbulent boundary layer results in higher drag at the surface. It does have the effect of speeding up airflow, which results in the less wake (as it can resist the adverse pressure gradient).
However, that's for a blunt object.
We're interested in skin friction drag in a port. Look up Rayleigh Fow (pipe loses heat to surroundings) and Fanno Flow (pipe is insulated).
A turbulent boundary layer results in higher drag at the surface. It does have the effect of speeding up airflow, which results in the less wake (as it can resist the adverse pressure gradient).
However, that's for a blunt object.
We're interested in skin friction drag in a port. Look up Rayleigh Fow (pipe loses heat to surroundings) and Fanno Flow (pipe is insulated).
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Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
Thank you Erland. I will read it later on tonight. Seems like too much to learn with far too little time!Erland Cox wrote: ↑Wed Mar 21, 2018 7:36 pm This thread is about pitoting around an intake valve: https://www.speed-talk.com/forum/viewtopic.php?f=1&t=34978
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Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
It works the same for a port wall and keeping rhe boundary layer thinner helps in several ways.
But where the velocity is high the boundary layer is thin or nonexistent and the flow touches the surface.
Erland
But where the velocity is high the boundary layer is thin or nonexistent and the flow touches the surface.
Erland
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Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
Repost to go along with Erlands second to last post before it gets buried.groberts101 wrote: ↑Wed Mar 21, 2018 7:25 pm I like to think of chatter finishes creating a variable thickness boundary layer which acts like variable sized ball bearings for the mass to run against. And since the bulk of the mass is compressible the boundary layer can thicken and thin depending on port speeds and pressures. Sort of acts like a smaller port at lower mass flow rates due to thicker boundary layer.. and then goes towards a larger port when the mass movement gets higher and thins out the layer due to greater cross sectional demands. This is the way a few engineers and pro head porters have also explained it to me.
EDIT.. I write too damned fast sometimes and edited my previous response quoted above. Anyone have input to blow holes in that theory then I'm all ears. Stupid aluminum heads cool so quickly that I lost my welding window. Lol
Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
What does a flowbench being ratiometric have to do with calibration plates being a bad way to calibrate a flowbench.cspeier wrote: ↑Wed Mar 21, 2018 11:15 amThis is the beauty of an Ratiometric orifice style bench.Rick360 wrote: ↑Wed Mar 21, 2018 11:11 amThinking that two different flow benches that are "calibrated" using so-called "Calibration plates" will measure flow thru a head the same is absolutely wrong. Calibrating flowbenches in this manner, that are the same exact model, might get you within a few percent of each other. When the flowbenches are different design, you have no idea how close they will truly be.
Calibration plates can't have a Cd or a flow rating unless they are "calibrated" in a system. Then they will only flow that amount in that same system arrangement.
Rick
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Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
A few things to keep in mind:
1. Laminar boundary layer and flow needs steady flow over a minimum distance to develop, this can be achieved on a flow bench but never in an engine, the flow is way too unsteady and short for that except maybe on the exhaust side far from the head,
2. A turbulent boundary layer is what we should aim for, it adheres to turns better and is thinner than a laminar one, Erland's first picture shows it quite nicely, it also allows more flow in a pipe,
3. The requirement to test a port with a turbulent boundary layer is one of the reasons why it is important to test at higher pressure ratios as working a port with the wrong boundary layer can give misleading results.
1. Laminar boundary layer and flow needs steady flow over a minimum distance to develop, this can be achieved on a flow bench but never in an engine, the flow is way too unsteady and short for that except maybe on the exhaust side far from the head,
2. A turbulent boundary layer is what we should aim for, it adheres to turns better and is thinner than a laminar one, Erland's first picture shows it quite nicely, it also allows more flow in a pipe,
3. The requirement to test a port with a turbulent boundary layer is one of the reasons why it is important to test at higher pressure ratios as working a port with the wrong boundary layer can give misleading results.
“Ignorance more frequently begets confidence than does knowledge.” -Charles Darwin, The Descent of Man
Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
Rick, if you have a more accurate method to calibrate a flowbench I would be interested in the procedure. Thanks, CharlieRick360 wrote: ↑Wed Mar 21, 2018 11:11 amThinking that two different flow benches that are "calibrated" using so-called "Calibration plates" will measure flow thru a head the same is absolutely wrong. Calibrating flowbenches in this manner, that are the same exact model, might get you within a few percent of each other. When the flowbenches are different design, you have no idea how close they will truly be.
Calibration plates can't have a Cd or a flow rating unless they are "calibrated" in a system. Then they will only flow that amount in that same system arrangement.
Rick
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Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
Rick360 wrote: ↑Wed Mar 21, 2018 8:54 pmWhat does a flowbench being ratiometric have to do with calibration plates being a bad way to calibrate a flowbench.cspeier wrote: ↑Wed Mar 21, 2018 11:15 amThis is the beauty of an Ratiometric orifice style bench.Rick360 wrote: ↑Wed Mar 21, 2018 11:11 am
Thinking that two different flow benches that are "calibrated" using so-called "Calibration plates" will measure flow thru a head the same is absolutely wrong. Calibrating flowbenches in this manner, that are the same exact model, might get you within a few percent of each other. When the flowbenches are different design, you have no idea how close they will truly be.
Calibration plates can't have a Cd or a flow rating unless they are "calibrated" in a system. Then they will only flow that amount in that same system arrangement.
Rick
Rick
I had this big long post typed up then I went back and re-read the flow around plate test from 2010. Talking the same thing. So I realized nothing has changed for me and deleted it..
Re: Ported Dart 215 pro1 platinum with port energy discussion 2.0
Your doing it right! Just like everyone in this country. Just like Harold Bettis will tell you to do it.Carnut1 wrote: ↑Thu Mar 22, 2018 12:52 pmRick, if you have a more accurate method to calibrate a flowbench I would be interested in the procedure. Thanks, CharlieRick360 wrote: ↑Wed Mar 21, 2018 11:11 amThinking that two different flow benches that are "calibrated" using so-called "Calibration plates" will measure flow thru a head the same is absolutely wrong. Calibrating flowbenches in this manner, that are the same exact model, might get you within a few percent of each other. When the flowbenches are different design, you have no idea how close they will truly be.
Calibration plates can't have a Cd or a flow rating unless they are "calibrated" in a system. Then they will only flow that amount in that same system arrangement.
Rick