Porting head
The only thing i would do by myself is to polish the ports with some sandpaper to prevent from messing up the head... Getting the intake side of the head glass smooth is a bad idea since the fuel would not stay airborne!! (Allready tried on a DOHC neon and ended up gaining 6Whp and way better driveability when we putted it back slightly rough with sandpaper...) I dunno what it could do for the Fit but i have polished the inside of that very same DOHC Neon manifold with really great results... Anytime the inside of a manifold is rough, there is something that could be gained or that is left on the table!!
Marko!!
Marko!!
i see what you are trying to see. what would happen if i opened up the intake manifold bigger than the head ports? i think that would reduce air pressure but increase volume. would that do harm to this little motor?
Member
Joined: Sep 2008
Posts: 622
From: Québec city
If you open the manifold bigger then the head (at the ports!), it will create excessive turbulence and decrease performance... the best would be to compare the sizes on the head and manifold using a gasket and try to make them the same size or a tiny little bit smaller (Manifold!)...
Marko!!
P.S. The motor will not take more air that it can if the runners are biggers then the head, just polish it up and call it a day!!
Marko!!
P.S. The motor will not take more air that it can if the runners are biggers then the head, just polish it up and call it a day!!
Last edited by DOHCtor; Oct 11, 2008 at 08:08 PM.
I am very curious if it is at all possible to port the L15a. I have seen pictures of top fuel and noblesse fits and they are the only ones that i know of to actually open the head up and work with the cams. is it possible to take the head and give it a mild port job and then polish it up?
well without knowing what they used this seems useless.
i dont know what your goal is with the L15 but doesnt seem like this motor is worth going N/A
wouldnt that be like blowing through a coffee straw?
that is true. the head would be the coffee straw. i just got done porting the manifold. there is quite a bit of material there. it opened up real nicely. so at least there is enough air flowing to the head. i took it for a test drive and there is a huge differance. it feels like i gained 20-30 horsepower......NOT!!! i didnt see any differance. didnt really expect to. i will just wait and see if the fuel efficiency has changed at all. at least i know that my engine is running that much more efficient.
its hard to tell without a dyno to prove anything but i feel that it does pull a little better. it was cheaper than going with the weapon r manifold that is for sure!
im sure you did nothing.
port matching your intake manifold to your head would be the best gain over all.
how would making the ports on the intake side of the head glass smooth decrease performance??? that would restricte less air flow which to me would be a gain. Also if you had the Throttle body bored out a little bit that would be even better with both those mods but in the end result probably would have only made 5hp
port matching your intake manifold to your head would be the best gain over all.
how would making the ports on the intake side of the head glass smooth decrease performance??? that would restricte less air flow which to me would be a gain. Also if you had the Throttle body bored out a little bit that would be even better with both those mods but in the end result probably would have only made 5hp
im sure you did nothing.
port matching your intake manifold to your head would be the best gain over all.
how would making the ports on the intake side of the head glass smooth decrease performance??? that would restricte less air flow which to me would be a gain. Also if you had the Throttle body bored out a little bit that would be even better with both those mods but in the end result probably would have only made 5hp
port matching your intake manifold to your head would be the best gain over all.
how would making the ports on the intake side of the head glass smooth decrease performance??? that would restricte less air flow which to me would be a gain. Also if you had the Throttle body bored out a little bit that would be even better with both those mods but in the end result probably would have only made 5hp
Member
Joined: Sep 2008
Posts: 622
From: Québec city
Didn't made sense for me either at the beginning as i tought mirror like ports would ultimately acheive better flow, so i tried it, the power was actually good but i had driveability issues and after i tried just almost everything else, i took some 200grit sandpaper and roughened it a little, little bit.... ...and it worked!! Still don't know why but i read something about fuel suspention and atomization somewhere else so maybe it explains the case!! I will research more....
Marko!!
Marko!!
Member
Joined: Sep 2008
Posts: 622
From: Québec city
found it on wikipedia!! -> http://en.wikipedia.org/wiki/Cylinder_head_porting
The "Porting and Polishing" Myth
It is popularly held that enlarging the ports to the maximum possible size and applying a mirror finish is what porting is. However that is not so. Some ports may be enlarged to their maximum possible size (in keeping with the highest level of aerodynamic efficiency) but those engines are highly developed very high speed units where the actual size of the ports has become a restriction. Often the size of the port is reduced to increase power. 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.
Marko!!
The "Porting and Polishing" Myth
It is popularly held that enlarging the ports to the maximum possible size and applying a mirror finish is what porting is. However that is not so. Some ports may be enlarged to their maximum possible size (in keeping with the highest level of aerodynamic efficiency) but those engines are highly developed very high speed units where the actual size of the ports has become a restriction. Often the size of the port is reduced to increase power. 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.
Marko!!
hmmm... that explains alot. on my previous car (79 toyota celica) my intake port was ported and then rifled which was uber cool, but the exhaust port had a mirror finish on it. well it looks like it is ok to put a mirror finish on the intake manifold all the way until it reaches the spot where liquid is introduced by the injectors.
Member
Joined: Oct 2008
Posts: 27
From: MN
that is true. the head would be the coffee straw. i just got done porting the manifold. there is quite a bit of material there. it opened up real nicely. so at least there is enough air flowing to the head. i took it for a test drive and there is a huge differance. it feels like i gained 20-30 horsepower......NOT!!! i didnt see any differance. didnt really expect to. i will just wait and see if the fuel efficiency has changed at all. at least i know that my engine is running that much more efficient.
i have not done any port work to the head. i just ported the aluminum section of the intake manifold. i wanna research more about the head so i know how much i could open it up.