makasih banget um..... smuga berguna ..... buat konco2 BCI.... cmiiw, lagi dechhh.....
________________________________ Dari: "[email protected]" <[email protected]> Kepada: Baleno Email <[email protected]> Terkirim: Senin, 29 Juni, 2009 13:09:13 Judul: Re: [baleno] <SHARING> "The Port and Polishing Myth" Ntar di bantu terjemahannya ya om. Lg di jalan nih... :) Powered by Telkomsel BlackBerry® ________________________________ From: robert marlino Date: Mon, 29 Jun 2009 13:56:30 +0800 (SGT) To: <bal...@yahoogroups. com> Subject: [baleno] <SHARING> "The Port and Polishing Myth" thulong bantuin dunkzzzz.... . buathin terjemahan na...... skedar nambah pengetahuan aje..... sual kebenaran na...... terganthung tuner mesin masing2 yachhh.... meth baca yachhh...... cmiiw, thapi yachhh..... 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 reducedto 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 balldo. 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. ________________________________ Menambah banyak teman sangatlah mudah dan cepat. Undang teman dari Hotmail, Gmail ke Yahoo! Messenger sekarang! Terhubung langsung dengan banyak teman di blog dan situs pribadi Anda? Buat Pingbox terbaru Anda sekarang! http://id.messenger.yahoo.com/pingbox/
