Posted By: Fishmarket
Polishing Piston Tops? - 01/06/11 09:35 PM
Any benefits to this? Obviously it would be more difficult for carbon to stick... here is an excerpt from the kb-silvolite website,
"Tests have shown that polishing the combustion chamber, valves and piston top can increase Hp and fuel economy by 6%. So far it has proven difficult to keep a coating on a polished piston."
Anyone doing this on their engines or have tested the practice on a dyno?
Its more a case where you are trying to control detonation by eliminating areas that can cause pre-ignition. any sharp edge sticking out will often be a place for a hot spot to develop. Polishing keeps this to a minimum. You'll see boosted motors often polished very smooth, as they are worse.
Posted By: jcc
Re: Polishing Piston Tops? - 01/06/11 11:05 PM
However you can have polished sharp edges, Seems to me polish is just more heat reflective, and that would likely be a small power boost, but only as long as it stayed reflective, wonder how long the dyno tests lasted that showed a boost.? What kinda of fuel, ie carbon/lead buildup? If coatings don't last why would polishing?
Posted By: Fishmarket
Re: Polishing Piston Tops? - 01/07/11 12:16 AM
Here's the link referring to the testing that united engine and machine (kb-silvolite) has done
http://kb-silvolite.com/article.php?action=read&A_id=36The article states that the polished piston doesn't transfer heat to the intake charge as much as a non-polished one, thus the increase in performance. Here's another quote,
" A smooth polished piston runs cooler than a non-polished piston even after combustion deposits have turned both pistons black. A cool, smooth piston will transmit a minimum of heat to the incoming fuel air mix."
Posted By: moderncylinder
Re: Polishing Piston Tops? - 01/07/11 01:44 AM
when you look at castings or forgings that are not machined on their surfaces,, they have more area due to all the little bumps, edges, ripples,, or whatever,, polishing that surface then reduces the total surface thus allowing more heat to be retained in the chamber, or less heat reflected into the intake charge,, thats probably what they mean...
also,, usually fluids do not like to flow over mirror polished surfaces,, there is no friction on the surface to create a boundary layer,, so the fluid flow is chaotic,, rather than uniform if a boundary layer is there,,, though with that said,, you want the thinnest layer possible