Polished combustion chamber
10-05-2006, 05:22 AM
#1
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Polished combustion chamber
I was wondering if any of you have any info/exp with this. I had a bike about 2 years ago that i built with a 13.8:1 CR that ran on pump gas. The only way i can see that as being possible was because of the polishing. If it is true, then why not use it on a boosted car?
10-05-2006, 07:43 AM
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Re: (boosted94cx)
alot of info i've seen says that Fuel does not like any polished surface.
it's best to have a slightly rough surface
i believe it's because of surface tension. like how a golf ball flies better because all of the dimples in it. where a smooth ball does not fly as well
roughness gives tiny localised eddy currents or swirl which improves fuel atomisation and thus power
or they say if you polish the chamber, to introduce a small step at the valve seat to force the wet flow over the resulting sharp edge. fuel will re-enter the air stream and give you the same affect as dimpling, only without losing the benefit of a completely polished chamber.
it's best to have a slightly rough surface
i believe it's because of surface tension. like how a golf ball flies better because all of the dimples in it. where a smooth ball does not fly as well
roughness gives tiny localised eddy currents or swirl which improves fuel atomisation and thus power
or they say if you polish the chamber, to introduce a small step at the valve seat to force the wet flow over the resulting sharp edge. fuel will re-enter the air stream and give you the same affect as dimpling, only without losing the benefit of a completely polished chamber.
10-05-2006, 10:25 AM
#5
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Re: (hybridmoments)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hybridmoments »</TD></TR><TR><TD CLASS="quote">alot of info i've seen says that Fuel does not like any polished surface.
it's best to have a slightly rough surface
i believe it's because of surface tension. like how a golf ball flies better because all of the dimples in it. where a smooth ball does not fly as well
roughness gives tiny localised eddy currents or swirl which improves fuel atomisation and thus power
or they say if you polish the chamber, to introduce a small step at the valve seat to force the wet flow over the resulting sharp edge. fuel will re-enter the air stream and give you the same affect as dimpling, only without losing the benefit of a completely polished chamber.</TD></TR></TABLE>
it's best to have a slightly rough surface
i believe it's because of surface tension. like how a golf ball flies better because all of the dimples in it. where a smooth ball does not fly as well
roughness gives tiny localised eddy currents or swirl which improves fuel atomisation and thus power
or they say if you polish the chamber, to introduce a small step at the valve seat to force the wet flow over the resulting sharp edge. fuel will re-enter the air stream and give you the same affect as dimpling, only without losing the benefit of a completely polished chamber.</TD></TR></TABLE>
10-05-2006, 10:51 AM
#6
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Re: (hybridmoments)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hybridmoments »</TD></TR><TR><TD CLASS="quote">alot of info i've seen says that Fuel does not like any polished surface.
it's best to have a slightly rough surface
i believe it's because of surface tension. like how a golf ball flies better because all of the dimples in it. where a smooth ball does not fly as well
roughness gives tiny localised eddy currents or swirl which improves fuel atomisation and thus power
or they say if you polish the chamber, to introduce a small step at the valve seat to force the wet flow over the resulting sharp edge. fuel will re-enter the air stream and give you the same affect as dimpling, only without losing the benefit of a completely polished chamber.</TD></TR></TABLE>
Yes I'm aware of this but the largest affect (to my knowledge) is from from the intake manifold. Im taking fluid dynamics right now and from what i do know about it, a smooth surface shouldn't affect flow. what I remember coming from a polished combustion chamber was said to reflect heat and get rid of hot spots thus having the ability to run more boost or higher compression.
also im aware that bike engines are different in that of cars but the same theory is there. If i can raise the compression on my bike X% after polishing the combustion chamber then a car should be almost the same way.
In the end this is all theory, as is all physics. The only real way to get true results is to test it in a real car rather then paper. do any of you have boosted motors with polished combustion chambers?
it's best to have a slightly rough surface
i believe it's because of surface tension. like how a golf ball flies better because all of the dimples in it. where a smooth ball does not fly as well
roughness gives tiny localised eddy currents or swirl which improves fuel atomisation and thus power
or they say if you polish the chamber, to introduce a small step at the valve seat to force the wet flow over the resulting sharp edge. fuel will re-enter the air stream and give you the same affect as dimpling, only without losing the benefit of a completely polished chamber.</TD></TR></TABLE>
Yes I'm aware of this but the largest affect (to my knowledge) is from from the intake manifold. Im taking fluid dynamics right now and from what i do know about it, a smooth surface shouldn't affect flow. what I remember coming from a polished combustion chamber was said to reflect heat and get rid of hot spots thus having the ability to run more boost or higher compression.
also im aware that bike engines are different in that of cars but the same theory is there. If i can raise the compression on my bike X% after polishing the combustion chamber then a car should be almost the same way.
In the end this is all theory, as is all physics. The only real way to get true results is to test it in a real car rather then paper. do any of you have boosted motors with polished combustion chambers?
10-05-2006, 11:35 AM
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Re: (hks85)
only problem with this is that on alot honda engines the fuel does not flow thru the intake manifold. the injectors sit at the very end of the manifold and spray directly into the intake port of the cylinder head. therefore all atomization happens thru proper injector spary patterns, the intake ports on the cylinder head, and in the combustion chamber.
so you would want to leave the intake ports on the head somewhat rough for sure. though by reading about surface tension is seems the best idea would be to leave the intake manifold rough also, because it actually creates less drag.
like on Race boats where they actually scratch up their hulls with like 300 or 400 grit wax paper. they DO NOT wax the surface, it actually makes the boats slower. the rougher surface allows them to travel with less drag thru the water.
i'm not sure what happens to the fuel/air mix floating in the combustion chamber upon the compression stroke. though i've read a few articles mentioned the importance of atomizing the mix inside the combustion chamber. it may act to seperate the air and fuel somewhat.
so a slightly rough chamber may help re-atomize it as the pressure builds in the cylinder on the compression stroke
from what i've read about hotspots, it seemed like people were more concerned with the pistons and smoothing out any rough edges on the piston tops to prevent hotspots, detonation, and piston failure
definitely alot of misinformation out there concerning porting & polishing. i'd definitely like to know the correct answer myself. but from what i've read it always seemed like the only place that benefited from polishing was the exhaust ports on the cylinder head. maybe the best solution is polished combustion chamber with roughen intake ports to atomize the mix correctly.
so you would want to leave the intake ports on the head somewhat rough for sure. though by reading about surface tension is seems the best idea would be to leave the intake manifold rough also, because it actually creates less drag.
like on Race boats where they actually scratch up their hulls with like 300 or 400 grit wax paper. they DO NOT wax the surface, it actually makes the boats slower. the rougher surface allows them to travel with less drag thru the water.
i'm not sure what happens to the fuel/air mix floating in the combustion chamber upon the compression stroke. though i've read a few articles mentioned the importance of atomizing the mix inside the combustion chamber. it may act to seperate the air and fuel somewhat.
so a slightly rough chamber may help re-atomize it as the pressure builds in the cylinder on the compression stroke
from what i've read about hotspots, it seemed like people were more concerned with the pistons and smoothing out any rough edges on the piston tops to prevent hotspots, detonation, and piston failure
definitely alot of misinformation out there concerning porting & polishing. i'd definitely like to know the correct answer myself. but from what i've read it always seemed like the only place that benefited from polishing was the exhaust ports on the cylinder head. maybe the best solution is polished combustion chamber with roughen intake ports to atomize the mix correctly.
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10-05-2006, 12:28 PM
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Re: (hybridmoments)
You think leaving the surface "rough" in the cc really contributes to power? Did you ever look at a head that had some miles on it, the cc is covered in carbon. I like the idea of the polished chamber, the reflection should give greater gains than just leaving the chamber rough--or at least let you run more compression.
10-05-2006, 12:55 PM
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Re: (d16dcoe45)
i don't know. but alot of info you find says to leave a unpolished slightly rough surface.
why do you think carbon deposits are bad? if anything they would slightly increase compression ratio also.
i've seen info where they say it's ideal to have some deposits inside the chamber and on the piston tops
with proper chamber turbulence you should maintain an acceptable amount of deposits.
"Turbulence, by speeding up the flame front, reduces the thickness of the boundary layer and reduces the buildup of combustion deposits. Turbulence increases efficiency as liquid fuel doesn't burn.Without a boundary layer protecting the aluminum piston, the surfaces are exposed to the combustion flame which melts through the piston. As we mentioned earlier, melting occurs on the edge of the piston next to the cylinder wall where pressure waves reflecting off the wall combine and amplify the pressure at specific locations. Sharp bends in the metal such as at the edge of the piston and along valve cut-outs in high compression pistons are difficult for boundary conditions to provide protection and are usually first damaged by detonation."
why do you think carbon deposits are bad? if anything they would slightly increase compression ratio also.
i've seen info where they say it's ideal to have some deposits inside the chamber and on the piston tops
with proper chamber turbulence you should maintain an acceptable amount of deposits.
"Turbulence, by speeding up the flame front, reduces the thickness of the boundary layer and reduces the buildup of combustion deposits. Turbulence increases efficiency as liquid fuel doesn't burn.Without a boundary layer protecting the aluminum piston, the surfaces are exposed to the combustion flame which melts through the piston. As we mentioned earlier, melting occurs on the edge of the piston next to the cylinder wall where pressure waves reflecting off the wall combine and amplify the pressure at specific locations. Sharp bends in the metal such as at the edge of the piston and along valve cut-outs in high compression pistons are difficult for boundary conditions to provide protection and are usually first damaged by detonation."
10-05-2006, 01:19 PM
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Re: (hybridmoments)
some more interesting info i found on some automotive engineering forums
"Control of boundry layer flow through intake ports is much better in a 'non polished' finish. Indeed a stock cast finish will flow better all other conditions being equal. I have my doubts about exhaust ports as well . I will restate the old example I was shown so many years ago---take a drop of water and put it on a piece of glass and try to blow it off, then do the same on a piece of fine sandpaper. I prefer a nice, smooth satin finish, myself. The shape is much more critical than finish.
I have seen many polished combustion chambered heads after extended street use and although the carbon buildup was less overall, they had areas where buildup was heavy AND had possibly detonation generating sharp edges. "
"Control of boundry layer flow through intake ports is much better in a 'non polished' finish. Indeed a stock cast finish will flow better all other conditions being equal. I have my doubts about exhaust ports as well . I will restate the old example I was shown so many years ago---take a drop of water and put it on a piece of glass and try to blow it off, then do the same on a piece of fine sandpaper. I prefer a nice, smooth satin finish, myself. The shape is much more critical than finish.
I have seen many polished combustion chambered heads after extended street use and although the carbon buildup was less overall, they had areas where buildup was heavy AND had possibly detonation generating sharp edges. "
10-05-2006, 04:15 PM
#11
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Re: (hybridmoments)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by hybridmoments »</TD></TR><TR><TD CLASS="quote">some more interesting info i found on some automotive engineering forums
"Control of boundry layer flow through intake ports is much better in a 'non polished' finish. Indeed a stock cast finish will flow better all other conditions being equal. I have my doubts about exhaust ports as well . I will restate the old example I was shown so many years ago---take a drop of water and put it on a piece of glass and try to blow it off, then do the same on a piece of fine sandpaper. I prefer a nice, smooth satin finish, myself. The shape is much more critical than finish.
I have seen many polished combustion chambered heads after extended street use and although the carbon buildup was less overall, they had areas where buildup was heavy AND had possibly detonation generating sharp edges. "
</TD></TR></TABLE>
If you go and get yourself a book on Fluid Dynamics it will explain all of this why it happens. I was just reviewing it last night which was part of the reason I posted this. Ill agree with the above post in that a smooth surface does slow down flow there are so many more factors then just flow. For instance, lets say you polish the C chamber and it ends up decreasing flow by 4%. so your loosing a little VE but lets say that 9% more heat was reflected and kicked out the exhaust ports. so you up the boost to compensate for the flow loss and in turn make more power.
(remember i just threw those numbers out)
We could sit here for months and debate with way is better and do all the equations in the world and still prob not know what way is really better until someone slaps a motor on the dyno.
"Control of boundry layer flow through intake ports is much better in a 'non polished' finish. Indeed a stock cast finish will flow better all other conditions being equal. I have my doubts about exhaust ports as well . I will restate the old example I was shown so many years ago---take a drop of water and put it on a piece of glass and try to blow it off, then do the same on a piece of fine sandpaper. I prefer a nice, smooth satin finish, myself. The shape is much more critical than finish.
I have seen many polished combustion chambered heads after extended street use and although the carbon buildup was less overall, they had areas where buildup was heavy AND had possibly detonation generating sharp edges. "
</TD></TR></TABLE>
If you go and get yourself a book on Fluid Dynamics it will explain all of this why it happens. I was just reviewing it last night which was part of the reason I posted this. Ill agree with the above post in that a smooth surface does slow down flow there are so many more factors then just flow. For instance, lets say you polish the C chamber and it ends up decreasing flow by 4%. so your loosing a little VE but lets say that 9% more heat was reflected and kicked out the exhaust ports. so you up the boost to compensate for the flow loss and in turn make more power.
(remember i just threw those numbers out)
We could sit here for months and debate with way is better and do all the equations in the world and still prob not know what way is really better until someone slaps a motor on the dyno.
10-05-2006, 04:35 PM
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Re: (hks85)
bike engines are smaller displacement then a car engine so the heat caused by the compression isn't as much as a car with more displacement the higher compression in a car causes more heat and it cant transfer out of the c chamber like a bike but since its smaller it doesn't cause as much heat and can transfer it out
that was the origanal question right
that was the origanal question right
10-05-2006, 04:49 PM
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Re: (hks85)
Carbon is like free heat barrier coating.Carbon is a very good heat insulator.But that's not why you can get away with high static compression in a bike.Small bore diameter requires less time for a complete burn.Long duration cams compared to cars because you don't need much low end torque to get a 400# bike moving compared to 2500# car.That's just some off the major stuff.
As far as chamber finish I think the shape/contour is what's important.Sanding is a good method to shape an aluminum chamber.But I think it is more efficient with a layer of carbon on it.
As far as chamber finish I think the shape/contour is what's important.Sanding is a good method to shape an aluminum chamber.But I think it is more efficient with a layer of carbon on it.
10-05-2006, 06:07 PM
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Re: (NJIN BUILDR)
Just like the intake ports on the head, I was always told that you should leave them rough for n/a to let the fuel and air mix properly.
BUT, when in a forced induction application the intake ports can be polished pretty good and very effectively.
Would be nice to see some real world tests in a Honda application
BUT, when in a forced induction application the intake ports can be polished pretty good and very effectively.
Would be nice to see some real world tests in a Honda application
10-05-2006, 08:41 PM
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Re: (NJIN BUILDR)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by NJIN BUILDR »</TD></TR><TR><TD CLASS="quote">Carbon is like free heat barrier coating.Carbon is a very good heat insulator.But that's not why you can get away with high static compression in a bike.Small bore diameter requires less time for a complete burn.Long duration cams compared to cars because you don't need much low end torque to get a 400# bike moving compared to 2500# car.That's just some off the major stuff.
As far as chamber finish I think the shape/contour is what's important.Sanding is a good method to shape an aluminum chamber.But I think it is more efficient with a layer of carbon on it.</TD></TR></TABLE>
Im aware of this, thats why i said in relation!
As far as chamber finish I think the shape/contour is what's important.Sanding is a good method to shape an aluminum chamber.But I think it is more efficient with a layer of carbon on it.</TD></TR></TABLE>
Im aware of this, thats why i said in relation!
10-05-2006, 08:43 PM
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Re: (Shmaa)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Shmaa »</TD></TR><TR><TD CLASS="quote">Just like the intake ports on the head, I was always told that you should leave them rough for n/a to let the fuel and air mix properly.
BUT, when in a forced induction application the intake ports can be polished pretty good and very effectively.
Would be nice to see some real world tests in a Honda application
</TD></TR></TABLE>
thats what im saying! I wish i had time and $ to do the testing my self but unfortunately i have a full time job and im going to school. I can only dream and hope someone else saves me the trouble
BUT, when in a forced induction application the intake ports can be polished pretty good and very effectively.
Would be nice to see some real world tests in a Honda application
</TD></TR></TABLE>
thats what im saying! I wish i had time and $ to do the testing my self but unfortunately i have a full time job and im going to school. I can only dream and hope someone else saves me the trouble
10-05-2006, 11:37 PM
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Re: Polished combustion chamber (hks85)
This head is done by a well known shop and look at the chamber, they're polished. I don't see anything wrong w/ that. Sorry for the big picture.
10-06-2006, 11:33 AM
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Re: (quicksilver1689)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by quicksilver1689 »</TD></TR><TR><TD CLASS="quote">I've heard polished combustion chambers resist carbonbuild up better. Just what I've heard no personal expierence.</TD></TR></TABLE>
It would make since. i see it like rock climbing, lots of cracks and crevices (un polished) easy to climb. 100% smooth? im sure you get my point
If any of you are interested in doing this on your next build, its far easier then you would ever imagine! I know some of you know this but im posting it hoping that someone gets inspired to to it for out benefit
supplies needed.
1. Wet sand paper 800, 400, 150
2. Bucket of water
3. Soap (dish soap works fine)
4. Drill (pref not a batt opp one)
5. cutoff arbor about $4
6. 2X - 3" or 4" buffing wheel about $3 or $4
7. one bar/stick of medium Jewelers Rouge
8. one bar/stick of super fine Jewelers Rouge
***stay away from the ones designed for hard metals like chrome***
9. Water
10. an hour or so
If you have never done this before id suggest doing some aluminum other then your combustion chamber first. Start sanding with the roughest paper until (ALL) the pits are gone. remember to use soap and lots of water (the soap will keep the paper from clogging up). when the pits are gone move to the next paper up and sand until the metal looks uniform. repeat until your done with the 800grit. put the arbor in the drill and the polishing wheel on the arbor. spin the wheel on the medium rouge and buff the chamber. when chamber is uniform switch to the super fine rouge. when your done assuming you follow directions it will be the shiniest metal you have ever seen!
total time for polishing should be about 1 hour. be careful not to scratch the surface of the head or the valve seat. Ive herd of people doing it with the valves in but then you worry about cleaning all the dust off and blah blah blah have fun
Modified by hks85 at 12:53 PM 10/6/2006
It would make since. i see it like rock climbing, lots of cracks and crevices (un polished) easy to climb. 100% smooth? im sure you get my point
If any of you are interested in doing this on your next build, its far easier then you would ever imagine! I know some of you know this but im posting it hoping that someone gets inspired to to it for out benefit
supplies needed.
1. Wet sand paper 800, 400, 150
2. Bucket of water
3. Soap (dish soap works fine)
4. Drill (pref not a batt opp one)
5. cutoff arbor about $4
6. 2X - 3" or 4" buffing wheel about $3 or $4
7. one bar/stick of medium Jewelers Rouge
8. one bar/stick of super fine Jewelers Rouge
***stay away from the ones designed for hard metals like chrome***
9. Water
10. an hour or so
If you have never done this before id suggest doing some aluminum other then your combustion chamber first. Start sanding with the roughest paper until (ALL) the pits are gone. remember to use soap and lots of water (the soap will keep the paper from clogging up). when the pits are gone move to the next paper up and sand until the metal looks uniform. repeat until your done with the 800grit. put the arbor in the drill and the polishing wheel on the arbor. spin the wheel on the medium rouge and buff the chamber. when chamber is uniform switch to the super fine rouge. when your done assuming you follow directions it will be the shiniest metal you have ever seen!
total time for polishing should be about 1 hour. be careful not to scratch the surface of the head or the valve seat. Ive herd of people doing it with the valves in but then you worry about cleaning all the dust off and blah blah blah have fun
Modified by hks85 at 12:53 PM 10/6/2006
10-06-2006, 11:36 AM
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Re: (hks85)
haha, you guys have to keep in mind porting and polishing is all trial and error. Sure some guys are fluid drynamic physics majors, blah blah bullshit, unpolished, polished, dimpled, cut/uncut,
its really all about the applcation, and you just need to get a flow bench and see what moves the air better for that certain app
golf ***** are not a honda civic head, nethier are a stream flowing water.
its really all about the applcation, and you just need to get a flow bench and see what moves the air better for that certain app
golf ***** are not a honda civic head, nethier are a stream flowing water.
10-06-2006, 11:55 AM
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Re: (GarageAlchemist)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GarageAlchemist »</TD></TR><TR><TD CLASS="quote">haha, you guys have to keep in mind porting and polishing is all trial and error. Sure some guys are fluid drynamic physics majors, blah blah bullshit, unpolished, polished, dimpled, cut/uncut,
its really all about the applcation, and you just need to get a flow bench and see what moves the air better for that certain app
golf ***** are not a honda civic head, nethier are a stream flowing water.
</TD></TR></TABLE>
yeah thats what im saying, physics can help get pretty good idea but in the end the only thing that matters is Trial & Error
its really all about the applcation, and you just need to get a flow bench and see what moves the air better for that certain app
golf ***** are not a honda civic head, nethier are a stream flowing water.
</TD></TR></TABLE>yeah thats what im saying, physics can help get pretty good idea but in the end the only thing that matters is Trial & Error
