Porting Efficiency
05-12-2005, 01:06 AM
#51
Fabricator
Join Date: Jan 2004
Location: Central Ohio (Hebron) Zephyrhills Fla.
Posts: 1,322
[quote name='Rub20B' date='May 11 2005, 12:31 PM']So regarding to that, you need to ge the sides as smooth as possible so the less as possible air is "sticking" to the sides?
Sorry for bad english:/
[/quote]
Not entirely.
The inside of runners is generally enlarged slightly to form a flater shape like the flat side of a "D". This gives a more uniform velocity, and a slightly lower velocity so as to keep the flow attached to the inside of the turn. The flow will want to stay on the outside of turns, (Newton) so the outside of turns should have the smoothest finish. The inside of turns should have a less than smooth surface on the order of a 50 grit flapper wheel.
The thinking here is that the courser finish will produce small vortex turbulance and that causes a local lower pressure that helps hold the flow against the inside of the turn. So the effect is that the port flows as though it were a straight line than a turn. Interested?
Look at the vortex generators on the tail fin of any airliner.
They keep flow attached to the fin so it acts as though it were taller than it is for better control and higher speed. There are some installed just ahead of the rudder and on some planes, ahead of the ailerons.
On Paul Yaws site you can see the port face of one of his engines. See the "D" shape?
Lynn E. Hanover
Sorry for bad english:/
[snapback]711361[/snapback]
[/quote]
Not entirely.
The inside of runners is generally enlarged slightly to form a flater shape like the flat side of a "D". This gives a more uniform velocity, and a slightly lower velocity so as to keep the flow attached to the inside of the turn. The flow will want to stay on the outside of turns, (Newton) so the outside of turns should have the smoothest finish. The inside of turns should have a less than smooth surface on the order of a 50 grit flapper wheel.
The thinking here is that the courser finish will produce small vortex turbulance and that causes a local lower pressure that helps hold the flow against the inside of the turn. So the effect is that the port flows as though it were a straight line than a turn. Interested?
Look at the vortex generators on the tail fin of any airliner.
They keep flow attached to the fin so it acts as though it were taller than it is for better control and higher speed. There are some installed just ahead of the rudder and on some planes, ahead of the ailerons.
On Paul Yaws site you can see the port face of one of his engines. See the "D" shape?
Lynn E. Hanover
05-12-2005, 08:03 AM
#52
Fabricator
Join Date: Jan 2004
Location: Central Ohio (Hebron) Zephyrhills Fla.
Posts: 1,322
[quote name='Lynn E. Hanover' date='May 11 2005, 10:06 PM']Not entirely.
The inside of runners is generally enlarged slightly to form a flater shape like the flat side of a "D". This gives a more uniform velocity, and a slightly lower velocity so as to keep the flow attached to the inside of the turn. The flow will want to stay on the outside of turns, (Newton) so the outside of turns should have the smoothest finish. The inside of turns should have a less than smooth surface on the order of a 50 grit flapper wheel.
The thinking here is that the courser finish will produce small vortex turbulance and that causes a local lower pressure that helps hold the flow against the inside of the turn. So the effect is that the port flows as though it were a straight line than a turn. Interested?
Look at the vortex generators on the tail fin of any airliner.
They keep flow attached to the fin so it acts as though it were taller than it is for better control and higher speed. There are some installed just ahead of the rudder and on some planes, ahead of the ailerons.
On Paul Yaws site you can see the port face of one of his engines. See the "D" shape?
Lynn E. Hanover
[/quote]
In addition: Brian cannot move in with me, sorry. And your english looks better than some of these clowns born here in the good old USA.
I am up to my ears in aligators this month, first race, moving to new (old) house, moving shop, finish guest engine, fix up van to sell, fix up new purchase chevy tow vehicle and mow 5 acers.
The cross section of a runner should be kept the same cross sectional area from end to end. Any time you change the velocity of a flowing mass, you remove energy (slow it down and change its temperature) so you maintain a constant cross sectional area. Not shape, just area. So then velocity remains constant.
The common thinking is just make it bigger. And this works just fine so long as the design was a bit undersized to start with. When we rev the engine through the HP range we need to have the maximum amount of HP unser the curve as is possible, because we are nut cases and love the feel of mind numbing thrust as we pass through 100 MPH in third gear. Only in an off the road situation under controlled conditions of course.
Runner velocity kept high gives you a better bottom end in that HP curve. It gives you a car that jumps out of a turn. It gives you some power where you can use it rather than having to get to 45 MPH in first before any fun begins.
Think about how long that port is open at points along the RPM range. It starts off in thousandths of a second and gets smaller as you rev the engine. So think about low flow velocity vice high velocity. Sounds like high velocity has it every time.
For us NA guys (and gals) there is only 14.7 PSI of boost available, and only then if you race on a beach somewhere (sea level). So almost always less than 14 pounds available to push stuff into the port, and even less than that because we cannot produce a perfect vacuum inside the chamber so as to take full advantage of even that.
So at first as we go bigger on the runners from stock, things perk up a bit. So the next time we go bigger yet and that engine seems a bit soft on the bottom, so next time we go real big, bigger is after all better yes?
This time the engine is a pig. Mixture is all over the place. No power at all until after maybe 3,500 RPM. And even from there on up it really isn't pulling hard until maybe 5,500 RPM and then it seems fine. But now it sucks down low and is no fun to drive to work. You cannot even autocross it on a short course in low gear.
So runner velocity as high as is possible at any RPM. The runners in my Drummond built 245 HP 12As is the same as the stock gasket. They are smooth as silk. Not shiny just smooth. My closing line is radiused and polished like chrome. Although he is not supposed to be below about 8,000 RPM, the engines still have over 212HP at 7500. So the runners don't need to be enlarged very much at all. I must add here that the 12A center iron has good sized ports in stock trim should you want to build up a special street engine.
This power is from a 48 IDA with 36MM chokes.
You are not that limited with any stock Mazda induction system.
Let me try that picture again.
Lynn E. Hanover
The inside of runners is generally enlarged slightly to form a flater shape like the flat side of a "D". This gives a more uniform velocity, and a slightly lower velocity so as to keep the flow attached to the inside of the turn. The flow will want to stay on the outside of turns, (Newton) so the outside of turns should have the smoothest finish. The inside of turns should have a less than smooth surface on the order of a 50 grit flapper wheel.
The thinking here is that the courser finish will produce small vortex turbulance and that causes a local lower pressure that helps hold the flow against the inside of the turn. So the effect is that the port flows as though it were a straight line than a turn. Interested?
Look at the vortex generators on the tail fin of any airliner.
They keep flow attached to the fin so it acts as though it were taller than it is for better control and higher speed. There are some installed just ahead of the rudder and on some planes, ahead of the ailerons.
On Paul Yaws site you can see the port face of one of his engines. See the "D" shape?
Lynn E. Hanover
[snapback]711576[/snapback]
[/quote]
In addition: Brian cannot move in with me, sorry. And your english looks better than some of these clowns born here in the good old USA.
I am up to my ears in aligators this month, first race, moving to new (old) house, moving shop, finish guest engine, fix up van to sell, fix up new purchase chevy tow vehicle and mow 5 acers.
The cross section of a runner should be kept the same cross sectional area from end to end. Any time you change the velocity of a flowing mass, you remove energy (slow it down and change its temperature) so you maintain a constant cross sectional area. Not shape, just area. So then velocity remains constant.
The common thinking is just make it bigger. And this works just fine so long as the design was a bit undersized to start with. When we rev the engine through the HP range we need to have the maximum amount of HP unser the curve as is possible, because we are nut cases and love the feel of mind numbing thrust as we pass through 100 MPH in third gear. Only in an off the road situation under controlled conditions of course.
Runner velocity kept high gives you a better bottom end in that HP curve. It gives you a car that jumps out of a turn. It gives you some power where you can use it rather than having to get to 45 MPH in first before any fun begins.
Think about how long that port is open at points along the RPM range. It starts off in thousandths of a second and gets smaller as you rev the engine. So think about low flow velocity vice high velocity. Sounds like high velocity has it every time.
For us NA guys (and gals) there is only 14.7 PSI of boost available, and only then if you race on a beach somewhere (sea level). So almost always less than 14 pounds available to push stuff into the port, and even less than that because we cannot produce a perfect vacuum inside the chamber so as to take full advantage of even that.
So at first as we go bigger on the runners from stock, things perk up a bit. So the next time we go bigger yet and that engine seems a bit soft on the bottom, so next time we go real big, bigger is after all better yes?
This time the engine is a pig. Mixture is all over the place. No power at all until after maybe 3,500 RPM. And even from there on up it really isn't pulling hard until maybe 5,500 RPM and then it seems fine. But now it sucks down low and is no fun to drive to work. You cannot even autocross it on a short course in low gear.
So runner velocity as high as is possible at any RPM. The runners in my Drummond built 245 HP 12As is the same as the stock gasket. They are smooth as silk. Not shiny just smooth. My closing line is radiused and polished like chrome. Although he is not supposed to be below about 8,000 RPM, the engines still have over 212HP at 7500. So the runners don't need to be enlarged very much at all. I must add here that the 12A center iron has good sized ports in stock trim should you want to build up a special street engine.
This power is from a 48 IDA with 36MM chokes.
You are not that limited with any stock Mazda induction system.
Let me try that picture again.
Lynn E. Hanover
05-12-2005, 11:20 AM
#54
Senior Member
Join Date: Nov 2004
Location: Europe, Belgium
Posts: 147
great info!
As my engine is a 20B, runners are huge from stock so just cleaning up will do..
When I have more time I'll make some plexi and enlarge the ports a little and check that the side seal kept supported and I don't create overlap.. Should I open up a bit earlier or close a bit later or both? But I won't make them much larger..
Why the pics aren't working?
As my engine is a 20B, runners are huge from stock so just cleaning up will do..
When I have more time I'll make some plexi and enlarge the ports a little and check that the side seal kept supported and I don't create overlap.. Should I open up a bit earlier or close a bit later or both? But I won't make them much larger..
Why the pics aren't working?
05-12-2005, 12:05 PM
#55
Senior Member
Join Date: Jun 2003
Location: Grand Prairie, TX
Posts: 917
I'm glad someone agrees with me here albeit you've got much more technical know-how when it comes to flow dynamics than I do, Lynn. That's why I wanna rent a room at your place for a couple of months. 
I'm not a fan of 'bigger is better'. I never have been. The guy who originally taught me what I know (from several years back) was and still is a proponent of velocity. His aim was more towards the removal of turbulent flow points where the charge may hit 90 degree angles or walls, other obstructions, etc. as well as doing chamfering and radiusing work to reduce pressure drop points. He was never, ever about going large on anything. The original porting work I had done to my S4 Turbo engine in 1998 reflected this. To this day, with that combination, nobody has yet to match the power and torque it produced. The ports on it weren't dramatically large at all. Infact, I don't remember him putting much of any effort into making for larger port outlets like alot of other porting guys do. He kept them small and, instead, focused more on the port runner walls and the transitioning points from runner to outlet at the short and long radiuses.
My porting work is an evolution of his original theory and idea. I still follow the exact same methodology that he inspired in me. I don't chrome finish the edges of the port outlet like you've suggested Lynn, but I do medium-fine finish everything. I don't mind having some visible scratches or patches on the intake as I am trying to keep a bit of a boundary layer there anyways. On the exhaust ports, I tend not to enlargen them much past their shape but I do open them slightly earlier and close them slightly later. I put alot of effort into making those as mirror finish as possible. I ultra-fine sand and polish by hand every one of those things. What are your thoughts on that, Lynn?
Have a peek: http://bdc.genxracing.com/GarretLievens/index.html
B
I'm not a fan of 'bigger is better'. I never have been. The guy who originally taught me what I know (from several years back) was and still is a proponent of velocity. His aim was more towards the removal of turbulent flow points where the charge may hit 90 degree angles or walls, other obstructions, etc. as well as doing chamfering and radiusing work to reduce pressure drop points. He was never, ever about going large on anything. The original porting work I had done to my S4 Turbo engine in 1998 reflected this. To this day, with that combination, nobody has yet to match the power and torque it produced. The ports on it weren't dramatically large at all. Infact, I don't remember him putting much of any effort into making for larger port outlets like alot of other porting guys do. He kept them small and, instead, focused more on the port runner walls and the transitioning points from runner to outlet at the short and long radiuses.
My porting work is an evolution of his original theory and idea. I still follow the exact same methodology that he inspired in me. I don't chrome finish the edges of the port outlet like you've suggested Lynn, but I do medium-fine finish everything. I don't mind having some visible scratches or patches on the intake as I am trying to keep a bit of a boundary layer there anyways. On the exhaust ports, I tend not to enlargen them much past their shape but I do open them slightly earlier and close them slightly later. I put alot of effort into making those as mirror finish as possible. I ultra-fine sand and polish by hand every one of those things. What are your thoughts on that, Lynn?
Have a peek: http://bdc.genxracing.com/GarretLievens/index.html
B
05-12-2005, 11:38 PM
#60
Senior Member
Thread Starter
Join Date: Oct 2001
Location: Peoria, AZ
Posts: 10,906
[quote name='Rub20B' date='May 12 2005, 03:18 PM']Damn, that looks nice, what do you use to get them so shiny?
If you lived in an acceptable range of me I brought my housings to you..
[/quote]
This was the whole reason behind me making this thread. My port only flows 10% more than stock, sure it looks good and is big, but that doesn't mean anything..........
If you lived in an acceptable range of me I brought my housings to you..
[snapback]711783[/snapback]
[/quote]
This was the whole reason behind me making this thread. My port only flows 10% more than stock, sure it looks good and is big, but that doesn't mean anything..........