squish area - technical discussion
17-03-2005, 09:29 AM
#1
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squish area - technical discussion
The way I understand it:
Squish is an area trapped between the cylinder head and the piston that DOESN'T form part of the combusion chamber.
So you want the actual volume to be very small to prevent detonation in this area which can be caused by cool cylinder walls, the advancing flame front, and the trapped end gasses.
To make this volume small you run the pistons very close to the cylinder head (ie small clearance) and this pushes most of the end gasses into the main combustion chamber.
The BIG advantage to this is that as the piston comes up the bore the squish area forces the gasses at high speed towards the centre of the combustion chamber... this movement can be used to create swirl... which is a shole subject in itself... but the A-series certainly has very high swirl for a production engine!!
so my question am I getting turbulance and swirl confused?
Alex
Squish is an area trapped between the cylinder head and the piston that DOESN'T form part of the combusion chamber.
So you want the actual volume to be very small to prevent detonation in this area which can be caused by cool cylinder walls, the advancing flame front, and the trapped end gasses.
To make this volume small you run the pistons very close to the cylinder head (ie small clearance) and this pushes most of the end gasses into the main combustion chamber.
The BIG advantage to this is that as the piston comes up the bore the squish area forces the gasses at high speed towards the centre of the combustion chamber... this movement can be used to create swirl... which is a shole subject in itself... but the A-series certainly has very high swirl for a production engine!!
so my question am I getting turbulance and swirl confused?
Alex
17-03-2005, 09:41 AM
#2
Other thing you havent mentioned of course is the simple fact that you want all the charge in one place, not in nooks and crannyies around the edge of the piston etc.
So that the flame front is all one big explosion and heading the same way.
I dont know enough about the semantics of swirl and turbulance to comment though, i have a pretty good understanding of how engines work but i dont know all the trendy terms, lol
Karl norris is the man to ask, i will wager he knows more about piston shape and chamber design etc than all the rest of us on this board put together (except IMA of course
)
So that the flame front is all one big explosion and heading the same way.
I dont know enough about the semantics of swirl and turbulance to comment though, i have a pretty good understanding of how engines work but i dont know all the trendy terms, lol
Karl norris is the man to ask, i will wager he knows more about piston shape and chamber design etc than all the rest of us on this board put together (except IMA of course
)
17-03-2005, 10:11 AM
#4
Yeah i did 
https://passionford.com/forum/viewtopic.php?t=105670
Maybe continue it there and it can go to tech essays as well
https://passionford.com/forum/viewtopic.php?t=105670
Maybe continue it there and it can go to tech essays as well
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