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 Subject: Hydraulics Category: Sports and Recreation > Automotive Asked by: gimmemorepsi-ga List Price: \$5.00 Posted: 13 Dec 2005 12:55 PST Expires: 12 Jan 2006 12:55 PST Question ID: 605408
 `Will a concaved face on a Piston produce more force than a Piston with a flat face?`
 Subject: Re: Hydraulics Answered By: redhoss-ga on 13 Dec 2005 13:16 PST
 ```Absolutely not. The pressure acts on what you might call the projected area of the piston. The projected area being the area that would project onto a plane perpendicular to the axis of the piston. I don't have any links to submit as proof, but I do have years of hydraulics and engineering experience to draw from. You will just have to trust me on this one. Redhoss```
 ```Redhoss, I am speculating that Gimme is wondering why the added surface area of a concave (or convex, for that matter) piston head would not produce more force, or same force with less input. Darn, now I gotta go read up on hemis...```
 ```I believe a concave face would actually reduce the effective pressure by increasing the space in the cylinder chamber, thereby reducing the compression.```
 ```Gimmemorepepsi-ga, I'm commenting on a quote below that mentions extra power produced; unfortunately, the issue is confused because the quote mentions only reduced friction and increased charging efficiency explicitly in connection with increased power. The relation to a concave piston is more implicit. Perhaps your question is related to the effect of using a concave piston as quoted below? If I read the following correctly, a concave piston can result in more complete lean combustion; if so, this extra combustion _might_ (I'm extrapolating here since it doesn't say extra power specifically) produce extra power compared to a flat piston in the same circumstances. However, as redhoss-ga stated, once a given amount of pressure is produced, there is no difference between the two pistons in the total force exerted in the direction the piston moves. "Nissan Improves Power, Emissions with Effective Intake System and Piston Crown Design [Nishizawa et al.]: Nissan?s RB20DE, a 1.998-liter, in-line six engine, powerplant of a sport sedan called ?SkylineTM,? has been revised to consume less fuel and produce more power. Engineers at Nissan de- veloped lean-burn technology for a short-stroke en- gine which has been known to be difficult compared to application in a long-stroke engine. Tumble air motion was effectively generated by the low-restric- tion intake system called the ?Air Jet Swirler? (AJS). The uniquely configured, concave piston crown re- tained turbulence intensity longer near top dead cen- ter (TDC). Both the AJS and the concave piston crown successfully increased the burn rate of lean mixture in a short-stroke engine. In addition, engine friction was reduced by 20 percent at all engine speeds ..." "Engine power output was increased by improving charging efficiency. The peak torque increased to 186 Nm at 4400 rpm, and the maximum power increased to 114 kW at 6400 rpm compared to those of the previous model." http://www.itepsa.com/samples/SIET199907_ES.PDF```
 ```Folks, we gotta remember Ginne was asking about hydraulic pistons. Brix, Nissan's AJS sounds a bit like Honda's Controlled Vortex Combustion Chamber (CVCC) of the early 70's. It was so efficient it allowed the Civic and Accord to avoid the need for a catalytic converter for about a half-dozen years. And the Skyline-- ah, what a car! I had a '78 or '79 when I lived in Japan and a colleague had an '87. It was a doozy of a design, flew like the wind and was a pleasure to drive. It was my first introduction to heated leather seats. *sigh*```