Smooth vs Rough cylinder head intake ports on FI
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Smooth vs Rough cylinder head intake ports on FI
Ive been having this discussion with a friend of mine who told me my head intake ports were kinda rough and need porting.
This is what I pulled off Wikipedia, I always knew there was a reason for rough intake ports, but how true is this, discuss?
This is what I pulled off Wikipedia, I always knew there was a reason for rough intake ports, but how true is this, discuss?
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.
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Im not defending them, but I guess the argument there is that PORTING is not simply enlarging the ports and having them be smooth mirror-like.
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I'm not so sure on this, i believe the machining on a port actually helps flow, same reason why a golf ball has dimples in it and is not completely smooth, it travels farther because there is less drag- allows for more velocity. I remember reading a really good post on this site a long time ago, but have no idea where it is now...
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^the reason why golf ***** are smooth has little to do with velocity. It has a lot more to do with spin, and allowing the ball to lift (however, this allows the ball to travel further). You were partially correct. Anyways I'm hoping someone with credentials and experience wants to join in this discussion, definitely would be interesting to find out.