Hows my porting coming?

[deflator]

Learning to port my junk. Just got through with the manifold today. I made some mistakes, like matching to the bigger stainless gasket that made the ports huge, but I think it went well.

I tried to smooth out the bottom of the collector, but that didn't work all that well. The collector area is a lot smoother than the pictures look though

Comments? Suggestions?

[Freerevving]

well, it's actually better to over-port the exhaust manifold a little... there should be at least a little step. I could explain why, but don't feel like it...

but... You could have concentrated on porting the roof, since that's where most of the air pressure will be... but hey, I'm one of those nit-picky people.

Actually it looks very good, especially for a first port... looks much more experienced than that...

[fwdmaster]

Porting came out great deflator, what kind of porting carbide did you use?

[deflator]

Freerevving- Actually its about a quarter and inch larger than the head exhaust ports, kinda overkill, but I hope it won't matter much.


fwdmaster- I used a double cut tree shaped carbide bit.

Now I just have to do my turbo

[Freerevving]

no it won't matter much, in fact the step helps eliminate back pressure and reverberating soundwave pressure... the "pocket" will matter if it's long and creates a pressure drop, but from what I see in the pictures, it won't hurt performance. The main thing you want to stay away from is a step going up into the manifold (head ports too big)... that would create a lot of turbulence.

take a picture of the bit! more pics more pics

[deflator]

Thats good to hear Freerevving, I was worried I did more work than necessary and would end up with a worse performing manifold.

As for the bit, it was this one from carbidebur.com, $15 to my door and it feels the same as before I started on the manifold
Finished it off with regular grinding stones and then sanded it

[Freerevving]

I haven't got around to the manifold yet... but here's a picture of the port shape I'm using (I've whored this picture out 1000x ....lol)

[deflator]

That looks very nice but I hope you know what you're doing porting the head like that. I don't see how to learn something like that, trial and error with junkyard heads?

[propeine]

Be careful not to "knife edge" the divider in the exhaust port too thin. It can have trouble dissipating the heat enough and melt/burn off. This isn't from experience but a general rule I have read in the past.

[ApexVIII]

looks pretty good!! lol like you stated just a little to large thought

[Freerevving]

Originally Posted by deflator

That looks very nice but I hope you know what you're doing porting the head like that. I don't see how to learn something like that, trial and error with junkyard heads?

Originally Posted by propeine

Be careful not to "knife edge" the divider in the exhaust port too thin. It can have trouble dissipating the heat enough and melt/burn off. This isn't from experience but a general rule I have read in the past.

Yes I definitely know what I'm doing... but no need to brag

The center divider on both intake and exhaust is knife-edged and then extremely dulled... I have a special method for this... The main thing is to graduate the divider, as most ports have the two paths meet suddenly. Here' a better shot to show how dull it is:


funny you mention this, I have warned people in the past of knife-edging it too sharp for that exact reason... But yet I see many professional looking ports with a long, sharp edge... sure to melt off some metal within 30k miles. Think about paper thin aluminum exposed to a flame.

The reason you dull the intake is you don't want to create a "whistle"... a whistle is unwanted turbulence, so you want a certain amount of roundness to control the flow... Airplane wings work on this principle

Another misconception people have is leaving the intake port rough... that method dates back to carburetion, where gains were actually seen on the dyno from better fuel atomization... ANY fuel injector atomizes fuel 100-1000+ times more than carburetion ... totally negating the need for further atomization .....and laminar flow only applies to hydrodynamics! It's purely theory that the moisture in the air creates a laminar flow.. It has become common practice to use these terms with gases, but the behavior of gases is different.
Furthermore, I have seen dyno charts, before and after, of ports brought from rough to polished... very small, but definite, gains were seen with polished intake ports on fuel injection.

No wonder most airplanes have smooth coatings (with the exception of stealth)... there's turbulence at the surface! the boundary layer is clinging to the surface and moving!... anyway... with carburetion, having very rough intake ports is a small sacrifice for a large gain. Anyone who insists on leaving the intake ports rough... has probably never seen a dyno test proving it's worthlessness on fuel injection, is doing it for carburetion, or is doing it to satisfy what other people want to see.

Porting a head is not rocket science... but if someone is ignorant or has a shaky hand, I advise they let someone else do it....

Do not over-port unless you have A LOT of experience porting: always under-machine the ports.

Do not ever flatten-out any large surface that is rounded. If you wish, you can exaggerate that feature but make sure you don't create a low spot. Do not exaggerate features that run parallel to flow

Create an even taper from gasket to valve seat... If you have no way to protect your valve seat, stay the hell away from it!

When removing the casting marks/flashing: don't create low spots (pockets) just because you want to completely eliminate a casting mark... If you have to go deep to remove it, be prapared to make all the ports that deep (with an even taper) and be prepared to do a lot of work. You might have to leave faint casting marks on a light or mild port.

If you can, flatten out the radius on the short side... If someone doesn't know what this means, then they definitely should stay away from this step.

Make sure your ports match each other between cylinders. Stock ports are pretty uneven to begin with, but don't make it worse. Improvise a way to measure if you're too cheap to buy some tools.

Use common sense and remember, less is more

[propeine]

Originally Posted by Freerevving

...and laminar flow only applies to hydrodynamics! It's purely theory that the moisture in the air creates a laminar flow..

You gave a lot of very good tips on porting in there. Even the fuel atomization for the carburator vs fuel injector thing is easy to follow especially with real results. I'd like to see the theory on laminar and turbulent flow being caused by moisture in the air. Not because I think its wrong but because thats the first I've heard that. 5 years in Mechanical Engineering classes make you curious about dumb things. We were always taught that gases being fluids as well exhibited similar behavior to liquids. Reynold's numbers and all that jazz for aero and fluid dynamics. If you happen to have a paper on this I would love to see it. Might be able to go back and teach the professors a thing or two.

[Freerevving]

Originally Posted by propeine

I'd like to see the theory on laminar and turbulent flow being caused by moisture in the air.

Sorry I'm not presenting the theory, I'm actually against rough ports, but I make them rough by default if someone is paying me (I don't like to hear people bitch).

Laminar flow exists in aerodynamics, but it's much different and can cause (a very small amount of) drag... Gasses and liquids behave very similarly, but sometimes they have significant differences. For instance, you can't compress a liquid.

Laminar flow/boundary layer is just one of the reasons that people present for why they do it... also "pooling" fuel (somewhat impossible), and other marginal/rediculous reasons.

btw... In the picture I posted, the port shape at its edge is not very far from stock. It's more gradual inside, but there is an optical illusion with the slight arch at the bottom, making it appear very different.

[propeine]

Damn you got me all excited. You're talking to a guy who did research on Helmholtz resonance for intake design which led to control theory and differential equations blah blah blah. I just like to try and make some use of my school considering I could really give a rats ass about most of it.

[Freerevving]

Originally Posted by propeine

I'd like to see the theory on laminar and turbulent flow being caused by moisture in the air. Not because I think its wrong but because thats the first I've heard that.

not sure if moisture was the right word... sorry if I made a mistake there... but more accurately, the unfounded theory claims that the compression at the surface makes the gases "wet". Here is more info from Wikipedia:

Originally Posted by http://en.wikipedia.org/wiki/Cylinder_head_porting

A mirror finish of the port does not provide the increase that intuition would suggest. In fact, within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished intake port and a rough textured port is typically less than 1%. The difference between a smooth to the touch port and an optically mirrored surface is not measurable by ordinary means. Exhaust ports may be smooth finished because of the dry gas flow and in the interest of minimizing exhaust by-product build-up. A 300 - 400 Grit finish followed by a light buff is generally accepted to be representative of a near optimal finish for exhaust gas ports.

The reason that polished ports are not advantageous from a flow standpoint is that at the interface between the metal wall and the air, the air speed is ZERO (see boundary layer and laminar flow). This is due to the wetting action of the air and indeed all fluids. The first layer of molecules adheres to the wall and does not move significantly. The rest of the flow field must shear past which develops a velocity profile (or gradient) across the duct. In order for surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this.

So much in this article is either self-contradictory... or just doen't make sense

Fuel deposited: have you ever seen fuel "pool" at 200cfm and 250 degrees??? Not to mention the warm/heated air. The tempuratures alone is enough to keep the fuel evaporated. The velocity of the air is enough to keep it evaporated. A smooth surface would make it even harder for fuel to get trapped in the first place! (since the boundary layer becomes so thin). I dare you to get your hair dryer and mist a smooth surface with gasoline.

"energize" the boundary layer? where do they come up with this stuff? Golf balls use air foils for hang time... the air foils actually resist the force of gravity... we don't really want that added resistance since we aren't fighting gravity... we want maximum velocity!.. If dimples create less drag and more lift, then I'm wondering why every aeroplane isn't coated with bed liner (!?)
"possibly increasing flow" ? rediculous! there is no way that could happen, and the word "possibly" proves that it's someone's speculation.

"Flow bench testing shows that the difference between a mirror finished intake port and a rough textured port is typically less than 1%" :
So even their flowbenching proved that the mirror finish flows better by 1%... Well they don't really explain but you can assume if they are using proper English... but even if they're trying to say that there's practically no difference, then they just contradicted the theory that rough ports flow better.

"The first layer of molecules adheres to the wall and does not move significantly"...
What? with liquid it moves zero... with gas it moves significantly, only much slower than the rest. Plus we are talking "MOLECULES"... they are not enough to completely fill your rough port. While a smooth port is not that much better, there is still no argument in favor of rough ports.

This artical claims over and over the wetting action of the intake air, while the exhaust gas is dry. First off, exhaust gas is not dry, it's just hotter.
Secondly, if the "wetting" action is what creates the laminar flow... then it's depending on pooling to create its laminar flow. It says later in the article that very rough ports will affect the rest of the flow... Well then that would be the only way to get the fuel evaporating (in this theory).

"In order for surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this."
And this is the very principle behind carbureted porting... to create a very rough surface that protrudes enough to create turbulent air and atomizes the fuel... pretty simple, really.

This article relies on no solid fact or sound theory. Everything in it is presented as "possibly" or "could possibly".

there is so much more I want to pick apart in this article... but I've already written a book lol.
The most convincing theory to a rough surface is that the surface turbulence creates a "breaking" foil, but since intake flow happens in pulses a small amount of flow is lost to this turbluence.

Weather you want a rough intake port, or a smooth one... it will make almost NO difference with fuel injection. In my experience with smooth intake ports, there is a very slight performance advantage... In addition to that, you can't hide a wavy surface with a mirror polish.

--Mac

[bastarddsm]

Originally Posted by propeine

You gave a lot of very good tips on porting in there. Even the fuel atomization for the carburator vs fuel injector thing is easy to follow especially with real results. I'd like to see the theory on laminar and turbulent flow being caused by moisture in the air. Not because I think its wrong but because thats the first I've heard that. 5 years in Mechanical Engineering classes make you curious about dumb things. We were always taught that gases being fluids as well exhibited similar behavior to liquids. Reynold's numbers and all that jazz for aero and fluid dynamics. If you happen to have a paper on this I would love to see it. Might be able to go back and teach the professors a thing or two.

Best as I know turbulent flow isn't well understood yet. I remember chatting with a guy who was a forerunner in hybrid rocket engines, about approximations to turbulent flow. It was long enough ago I don't really remember what he had to say tho.

But yes I do agree that rough intake ports are a thing of the past. On carbed dirtbike stuff I tend to leave them with about a 80 grit finish.

[propeine]

Originally Posted by Freerevving

not sure if moisture was the right word... sorry if I made a mistake there... but more accurately, the unfounded theory claims that the compression at the surface makes the gases "wet". Here is more info from Wikipedia:



So much in this article is either self-contradictory... or just doen't make sense

Fuel deposited: have you ever seen fuel "pool" at 200cfm and 250 degrees??? Not to mention the warm/heated air. The tempuratures alone is enough to keep the fuel evaporated. The velocity of the air is enough to keep it evaporated. A smooth surface would make it even harder for fuel to get trapped in the first place! (since the boundary layer becomes so thin). I dare you to get your hair dryer and mist a smooth surface with gasoline.

"energize" the boundary layer? where do they come up with this stuff? Golf balls use air foils for hang time... the air foils actually resist the force of gravity... we don't really want that added resistance since we aren't fighting gravity... we want maximum velocity!.. If dimples create less drag and more lift, then I'm wondering why every aeroplane isn't coated with bed liner (!?)
"possibly increasing flow" ? rediculous! there is no way that could happen, and the word "possibly" proves that it's someone's speculation.

"Flow bench testing shows that the difference between a mirror finished intake port and a rough textured port is typically less than 1%" :
So even their flowbenching proved that the mirror finish flows better by 1%... Well they don't really explain but you can assume if they are using proper English... but even if they're trying to say that there's practically no difference, then they just contradicted the theory that rough ports flow better.

"The first layer of molecules adheres to the wall and does not move significantly"...
What? with liquid it moves zero... with gas it moves significantly, only much slower than the rest. Plus we are talking "MOLECULES"... they are not enough to completely fill your rough port. While a smooth port is not that much better, there is still no argument in favor of rough ports.

This artical claims over and over the wetting action of the intake air, while the exhaust gas is dry. First off, exhaust gas is not dry, it's just hotter.
Secondly, if the "wetting" action is what creates the laminar flow... then it's depending on pooling to create its laminar flow. It says later in the article that very rough ports will affect the rest of the flow... Well then that would be the only way to get the fuel evaporating (in this theory).

"In order for surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this."
And this is the very principle behind carbureted porting... to create a very rough surface that protrudes enough to create turbulent air and atomizes the fuel... pretty simple, really.

This article relies on no solid fact or sound theory. Everything in it is presented as "possibly" or "could possibly".

there is so much more I want to pick apart in this article... but I've already written a book lol.
The most convincing theory to a rough surface is that the surface turbulence creates a "breaking" foil, but since intake flow happens in pulses a small amount of flow is lost to this turbluence.

Weather you want a rough intake port, or a smooth one... it will make almost NO difference with fuel injection. In my experience with smooth intake ports, there is a very slight performance advantage... In addition to that, you can't hide a wavy surface with a mirror polish.

--Mac

Nothing terribly new there and I agree most of it is contradictory at best. Old tech for carbs. Better time is spent on port length, shape and size. Fluid dynamics is a crazy field. Place I worked for used to do a lot of Fluent simulations and hand calcs. Everything is based on assumptions and fudge factors to make it match real world data. Then we tried to extrapolate findings to new projects. Not really a better way to do it other than try and see but still. We've got halon colliders, been to the moon (maybe), and yet can't explain such simple things. Flow benches aren't even accurate due to the pulses. Helmholtz resonation is effective at the RPM its designed for. I'm interested in some of the dual throttle plate designs that some bikes are running with one of them right at the valve. The one near the valve is computer computer controlled and designed to keep velocity up at low RPMs.