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"Pimpin aint easy"
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I am going thru a big bore build right now and am going stay completetly generic on this question. In researching my head options, I have looked at several porters work. Some are mirror finish combustion chambers, smooth intake ( emery finish ) with no noticeable humps and bumps in the ports etc and some are actually quite rough in my opinion. All are top of the shelf porters and all highly recommended. My question is, what is the benifit to the smooth almost art work type porting that brand A offers versus the more noticeably hand worked ports of brand B ? None of my choices were NC cut versions and all claim big gains. Is the only benefit visual upon opening the package? I know that in the auotmotive performance world horsepower is not always pretty. Same goes here?
 

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Theoretically polishing the combustion chambers helps reflect heat and the more heat you can keep in the charge, the more power it can offer. Also, polished combustion chambers helps keep carbon from building up.

Both of those theories apply to the exhaust ports also. Hense the reason we polish the exhaust port.

The intake is better with a rougher surface. A polished intake promotes the fuel to collect into droplets and that reduces the efficiency of the combustion process. A rougher surface it more turbulent and helps keep the fuel atomized. The amount of roughness (finish on the surface) is somewhat debatable. You want the surface to have turbulence but not enough to effect the port.

Additionally, polishing the piston top can add to this effect. The gains can be minimal but every little bit helps.
 

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Addicted to American Iron
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The guy I use to for all my machine work (Big Al Performance) gave me this answer when I asked him the very same question: Pretty polished chambers are like pretty fishing lures. They do not do anything more to catch fish, but are that way to catch more customers.
 

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On the intake port.

Is there still a difference on an EFI bike? Don't the injectors already atomize the fuel?
 

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yes you still get fuel drop out in the charge and still need to pick it up off the walls being the port is not straight and there is a valve , stem guide in the way plus cam timing ect
 

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claydbal said:
damn, springer, could yu be a little more specific?
Yes.

A surface that has a greater surface area can transfer or absorb more heat. In raw cast form, the surface is very rough and that creates more area to absorb heat into the head. A polished surface is flat and has less surface area to absorb heat. Again this keeps the heat in the charge. Also the rough area allows the carbon to hold on better and build up. A polished area is hard for it to build up on. Why do we care? Carbon build up can promote detonation and it actually takes up space. The space it takes up changes the size of things and the flow. Like the combustion chamber and exhaust port.

Back to keeping the heat in the charge. When the charge is putting pressure on your piston during the power stroke, you want to keep pressure as high as possible, as long as you can. Heat is a it part of what makes the gasses expand putting pressure on the piston. The more heat you can keep in the charge, the more pressure you can apply to the piston. A polished piston top and combustion chamber helps promote this.


davemhughes said:
The guy I use to for all my machine work (Big Al Performance) gave me this answer when I asked him the very same question: Pretty polished chambers are like pretty fishing lures. They do not do anything more to catch fish, but are that way to catch more customers.
I agree to an extent. The customers do like to see a shiny polished surface. At $299 we do it for the above mentioned reasons and not for aesthetic reasons. I have seen Beans ported heads come off a bike and have very little carbon build up because of the polishing. BUT it also depends on the way you ride and the tuning.


niget2002 said:
On the intake port.

Is there still a difference on an EFI bike? Don't the injectors already atomize the fuel?
A carb also atomizes the fuel. On an EFI bike, the injectors do. On both bikes, the Air/Fuel mixture has to pass threw the intake port. On it's way threw, it is desirable to have as much of the fuel stay atomized or suspended in the AF mixture as possible. A turbulence on the surface of the port wall helps this for both a carberated and EFI engine. I forget the name of the principle off hand.


HDWRENCH said:
Ok maybe gun shy but does it feel "dark here??"
I think I understand what you are saying. Feel free to PM me anytime you have suspicions. But I don't think it applies here.
 

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I also believe a polished chamber, piston top, and exhaust port assist the burn process and help keep the heat in the charge after combustion and in the exhaust process which assists the exhaust to go out the pipe to atmosphere.

Part of the reason why ceramic coatings inside exhaust pipes work so well..............some car type heads have this same ceramic lining also in the exhaust ports.

BUT BUT BUT......................A polished finish inside the intake manifold and the T/Body on EFI equipped bikes gives higher CFM flow due to a thinner binery layer and because it flows air only will not effect fuel drop out at all.

Surface roughness inside a manifold or port produces a binery layer between the wall and the medium flowing through it, the rougher the surface finish, the thicker the binery layer.

The thicker the binery layer, the smaller the diameter the manifold and/or port appears to the charge coming in (and going out) So looking at the cross section of a pipe, you would see the pipe wall thickness, then you would "see" a layer of turbulent air that is passing along the inner surface of the pipe, then you would "see" the mainstream column or air and then the binery layer and then the pipe wall again.

Now dependant on how much surface roughness there is determines how thick the binery layer becomes and how small/large the port actually is to the flow. More flow creates better V.E., better V.E. creates better power............to a point.......

.........You also need high port velocities at low rpms to assist in cylinder fill at these low rpms. Hence the need to combine good port velocity with flow to achieve an efficient head design, and not all head porters think the same on this.

In the 60`s and early 70`s polishing the ports, chambers, pistons, etc. was the rage and it was always believed that this polishing gave great improvements in performance. Wrong!

In the mid 70`s, various racing teams discovered that a surface finish of approx. 60 grit gave optimum results with the air/fuel charge because experiments were finding that the fuel was seperating from the air and fuel droplets were forming on these highly polished surfaces inside the port which effected V.E. and of course the burn process as the fuel was not at the designed A/F Ratio and also was not mixed efficiently, the net result was the engine was less eficient.

The port still needs to have a 60 grit finish to maintain the turbulence at the edges of the mainstream column of the charge and to stop or minimise "fuel drop out".............but I believe the intake manifold on EFI Engines can be polished mirror smooth to give a higher CFM number without impacting lower rpm performance.

There a nice long one for a change..........................Ozzie
 

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Off topic but....

springer- said:
Yes.

A surface that has a greater surface area can transfer or absorb more heat. In raw cast form, the surface is very rough and that creates more area to absorb heat into the head. A polished surface is flat and has less surface area to absorb heat. Again this keeps the heat in the charge. Also the rough area allows the carbon to hold on better and build up. A polished area is hard for it to build up on. Why do we care? Carbon build up can promote detonation and it actually takes up space. The space it takes up changes the size of things and the flow. Like the combustion chamber and exhaust port.

Back to keeping the heat in the charge. When the charge is putting pressure on your piston during the power stroke, you want to keep pressure as high as possible, as long as you can. Heat is a it part of what makes the gasses expand putting pressure on the piston. The more heat you can keep in the charge, the more pressure you can apply to the piston. A polished piston top and combustion chamber helps promote this.



I agree to an extent. The customers do like to see a shiny polished surface. At $299 we do it for the above mentioned reasons and not for aesthetic reasons. I have seen Beans ported heads come off a bike and have very little carbon build up because of the polishing. BUT it also depends on the way you ride and the tuning.



A carb also atomizes the fuel. On an EFI bike, the injectors do. On both bikes, the Air/Fuel mixture has to pass threw the intake port. On it's way threw, it is desirable to have as much of the fuel stay atomized or suspended in the AF mixture as possible. A turbulence on the surface of the port wall helps this for both a carberated and EFI engine. I forget the name of the principle off hand.



I think I understand what you are saying. Feel free to PM me anytime you have suspicions. But I don't think it applies here.
Springer....how do you do the multi-"quote" thing? On some forums I visit, it is an option with a button right next to the reply and quote buttons.

Clay
 

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Seahag said:
Springer....how do you do the multi-"quote" thing? On some forums I visit, it is an option with a button right next to the reply and quote buttons.

Clay
I right click on the "Quote" button in the post I want to quote and select "Open in new window". I then do this for all the ones I want to quote. Then I copy the quoted text from each window to the window I am going to use as my reply.

You can also copy and paste the text and add the quotes yourself. I quote the FAQ's all the time but there is no quote option to do this.

FAQ's said:
I typed "quote=FAQ's" with brackets then copy and paste the info in.
Anything I Type Here said:
just another example
 
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