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Re: Quench
[Re: WannaRunner]
#512201
10/31/09 10:37 AM
10/31/09 10:37 AM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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You'd want the D dish that double R spoke of. A full dish (which has a thin perimeter of slightly raised material) would not be wide enough to give you enough AREA (not enough mixture would be squished out
live every 24 hour block of time like it's your last day on earth
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Re: Quench
[Re: 360view]
#512205
11/01/09 02:36 AM
11/01/09 02:36 AM
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Joined: Jan 2008
Posts: 299
Fitchbug, Mass.
WannaRunner
OP
enthusiast
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OP
enthusiast
Joined: Jan 2008
Posts: 299
Fitchbug, Mass.
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Quote:
Quench is still important with dished piston design, and the area outside of the dish needs to be as large as 50% of the total crown area for optimum quench.
1994 Magnum 5.9V8 factory pistons are over 40% quench area.
The small details in the design of the edge of the dish are important too.
If the edge is designed right,
the straight line inward moving fan jets of "squished out" air and fuel
then 'tumbles' as it goes over the edge of the dish and downward.
Diesel pistons in particular make use of this tumbling turbulence in addition to the squish turbulence.
Ok, I jacked this pic from source, it was easy to find. Is this a good ballpark of the shape I should be looking for? are flat top slugs better overall? would I have hotspots with this piston? looking for 10.5-11.0 compression.
The red lines show how I believe the mixture would "tumble" off the dome and into the lands on the opposite side of the piston when squeezed from the quench area, is this ballpark/kinda along the lines??
Bare with me on this learning curve guys, Thanks.
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Re: Quench
[Re: JohnRR]
#512206
11/01/09 02:38 AM
11/01/09 02:38 AM
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Joined: Jan 2008
Posts: 299
Fitchbug, Mass.
WannaRunner
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OP
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Fitchbug, Mass.
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Quote:
The performance pistons I have seen are D shaped dish and that's what you need unless you need a HUGE dish ...
I'm having Diamond make me a piston with a pop up quench dome AND a D shaped dish
John, is the pic. above considered a pop up quench dome and a D shaped dish??
Thanks.
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Re: Quench
[Re: 360view]
#512209
11/01/09 08:12 AM
11/01/09 08:12 AM
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Joined: Jan 2008
Posts: 299
Fitchbug, Mass.
WannaRunner
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OP
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Fitchbug, Mass.
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Quote:
It would be helpful if you would tell us what cylinder head you are planning to use with that piston, or post a picture.
CNC'd Stealths
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Re: Quench
[Re: RapidRobert]
#512210
11/01/09 09:57 AM
11/01/09 09:57 AM
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Joined: Jan 2008
Posts: 299
Fitchbug, Mass.
WannaRunner
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OP
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Fitchbug, Mass.
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Quote:
Quote:
is the pic above considered a pop up quench dome and a D shaped dish??
It is a D shaped dish and a quench pad (since it is a flat plateau). pad/dome is splitting hairs a bit but to help you a dome refers more to the sort of pyramid shape that the old pop up racing pistons had to get compression.
Is it best to run flattop pistons??
Thanks.
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Re: Quench
[Re: RapidRobert]
#512214
11/01/09 12:42 PM
11/01/09 12:42 PM
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Joined: Jan 2008
Posts: 299
Fitchbug, Mass.
WannaRunner
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OP
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Fitchbug, Mass.
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Source heads, with slight variations, give or take, are 84-86cc. The piston above is a -17cc dish, at .015 in the hole and a .039 gasket I'll get around 10.0cr. with the same chamber, .010 in the hole, .039 gasket, running a flattop I'll get around 11.2cr. a couple years ago, even with alum. heads 11.2cr was to much compression on pump gas, even with a good tune/setup. within the last 1.5 years or so every gas station around here is pretty much E85, where 10.5cr was the high end then, my machinest says now that 11.0cr is becoming the norm due to this gas. I can up the gasket thickness if needed to drop the CR. where I was getting lost, and you answered, was what piston top design would be the best? a full dish has no quench and a pop up would interfere with flame propagation. the piston above has a quench pad, valve reliefs, a reasonable CR and would aid in flame propagation. Thanks by the way for taking the time to answer my questions! 
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Re: Quench
[Re: RapidRobert]
#512216
11/01/09 01:46 PM
11/01/09 01:46 PM
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Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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Hey your welcome and here is a very simple & user friendly CR calculator. http://kb-silvolite.com/calc.php? EDIT I reread your specs and more than .045" quench is going to require you to run a significantly lower CR with any given pump gas. With your choice of cam decide on a static CR to get the right cranking CR for your intending octane pump gas. this leaves nothing on the table with your short block then consult with your machinist & get each cyl's CR and quench exactly where you want it.
live every 24 hour block of time like it's your last day on earth
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