*Boostwerks*

I have been told several times that a Domed piston is not favorable in Forced induction. Why is this?

Is the most efficent style of FI piston a flat top?....If so..... why?

Thanks for any info....

falcongsr

compression. its not about effeciency, its about compression ratio. stock GSR pistons are pretty much flat. domed pistons would give you 11:1 or higher compression ratio...not good for forced induction on pump gas.

*Boostwerks*

well, I have a ZC engine, so to get a 10:1 CR the piston would have to be inturn a dome variety....

I know for a fact that the piston geometry does in fact change the burn rate and efficency of combustion....

falcongsr

yeah, the floor of the combustion chamber is indeed the piston top. but what are you asking? is a dome better/worse than flat or dished?

*Boostwerks*

for the most part yes thats what I'm asking....

I am basically asking, why are domed pistons not favorable in a forced induction car?

mos

With a domed piston the flame has harder time reaching all areas of the chamber. In some engines with very steeply domed pistons, the use of multiple spark plugs per cylinder can help to complete combustion. Other than that I'm not sure what effect it has.

edit: I'd imagine when you exacerbate the above conditions with forced induction, it gets even harder for the spark to do its job. So if you take a domed piston that pushes the limits of what the spark/flame can do, but still performs well, and put it in a forced induction engine- it might not perform as well?


[Modified by mos, 2:27 PM 10/9/2002]

falcongsr

i am having a hard time seeing how adding boost would change any of that though.

mos

The same thing that causes people to run smaller plug gaps with boost probably has an effect here. It becomes more difficult for things to get lit off under boost, and on top of that you've got this chamber which is essentially cut in half as far as the spark is concerned.. and while you might be able to get away with one or the other... when you put the two together the thing doesn't want to light up the mixture.

I dunno tho. Maybe you can run high boost and high domed pistons. I've never tried myself.

*Boostwerks*

Bump....

need some more people to respond

MiraiZ

Its all about compression dude...higher domes mean that air compressed more...physics dictate that the more air is compressed, the more heat it produces...heat in the combustion chamber equals higher tendousy to combust prematurely which is the definition of detonation...hope that helps

DSF

http://www.racingsecrets.com/article_racing-10.html

Some good reading. Key words to think about...squish, quench, flame front, burn time, detonation...