some article
Why Not Polish The Ports ??
Doesn't Air Flow Better on a Smooth Surface ???
Remember that the ultimate goal isn't "flow" ... it's POWER !!
The intake port is going to flow both fuel and air. The problem with fuel is that, since it weighs more, it's difficult to keep it evenly mixed with the air as it follows the contours of the port.
Boundary Layer
The next time you drive a car in the rain, notice that when the car is going 60 MPH, the rain drops go up the hood of the car at walking speed. That's because the smooth surface of the car creates what's known as a boundary layer, and the portion of that layer of air that's nearest to the surface is almost still.
The same thing happens inside an intake port. Except instead of raindrops, it's fuel droplets that will run down the port wall slower than the air. That causes a serious change in the fuel air mixture by the time it reaches the cylinder, ruining much of the engine's potential power.
Polishing the port walls will ensure that this happens.
The phrase "Port & Polish" always makes me laugh ... I think the idea came from 70's Hot Rod magazines or something. Anyways, the last thing you want to do is polish your ports !!!
Instead, by making a series of rough 60 grit lines that purposely go against the flow, the "boundary layer area" will be turbulent, and the fuel will stay suspended in the air.
Remember: Rough is Good !!
http://www.mototuneusa.com/homework.htm
imho maksud d teori artikel atas di mesin mpi atau karbu fuel di mix di dalam intake, smooth intake menciptakan boundry layer analoginya di kaca dan hood kendaraan saat ngebut waktu ujan, dimana tetesan ujan geraknya pelan... jadi dengan rough surface mencegah terbentuk boundry layer,udara justru bergerak lebih cepat dan bisa mixing lebih baik dgn fuel................. disitu juga tutorial ngecilin lubang intake dan bikin roughsurface wkwkw
nah jika mesin sudah GDI, which is fuel sudah di inject di dalam ruang bakar sih kayanya uda g se sensitif mpi atw karbu.... intake uda g berfungsi juga untuk mixture,which is focus on cfm aja..
jadi kaya diesel... dan err jarang dgr ada diesel yg di pnp wkwkwk
ntah ya gw k pnp kurang sreg.... resiko dgn gainnya kya ga sebanding.
kec tunernya uda sering ngerjain mbl tersebut dan hasilnya terbukti baik.
pnp asa mending naikin kompresi sekalian....
apa ikut di cabut jga? dulu waktu SMA bbrp taun yg lalu sempet bermasalah sama ni sensor,. sampe mogok,. lupa d tret mana
,. nah klo yg freeflow kan g ad CC lagi,. mohon pencerahannya,.
dia dipindah sensornya oom...
untuk IHE dibiarkan standar...mentok di intake manifold pabrik dipoles dan dipapas(jika perlu untuk kelancaran airflow)
mira dan KWR dong bil? 
untung masih massal di econoboxes...coba m3 pake plastik 
gw kira itu cover luar doang...taunya bener manifold dari plastik 
pikir pikir jago juga bikin plastiknya...tahan sama pemuaian di perbatasan plastik/metalnya...
....taunya airbox doang yang plastikan 
....dan manifoldnya juga iya 
![:big_smile]](./images/smilies/big_smile.gif "Big Smile"){kind=small}
