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Re: pistons.. Posted by 900 Aero [Email] (#425) [Profile/Gallery] (more from 900 Aero) on Wed, 15 Dec 2010 12:06:26 In Reply to: pistons.., derf, Wed, 15 Dec 2010 08:50:16 Members do not see ads below this line. - Help Keep This Site Online - Signup |
In years past I would have agreed however now days Polycrystalline Diamond (PCD) and of course CNC machining is why quality forged piston manufacturers are able to maintain identical tolerances. On the other hand the OEM has controlled their tolerances by grading their pistons and finished bores (usually with a letter) and then making sure each cylinder and piston have the same letter. PCD and CNC technology has also allowed the forged piston companies to hold better tolerances along with more precise forging dies also because of modern day machining. As far as "greater expansion than cast" we use a high silicon 4032 forging that has a low expansion rate for most of our street driven turbo Saab applications unless it's a heavily modified one where we us a 2618 alloy that will withstand more serious horse power. Also now days there has been much accomplished in piston skirt design which allows for tighter tolerances therefore we can have our cake and eat it too when it comes to building turbo Saab's that can intimidate most other cars they come across and not have noisy pistons at start up! I'm also not sure about your "explosion a forged piston on top of a 'lowly' cast one in a hyd press"??? Out of curiosity I put one each in my press and the cast ones skirts kind of exploded where the forged ones skirts bent straight out before they even fractured! As far as an "AA fueler engine" I cut my teeth on top fuel dragsters, Alan and Blaine Johnson practically grew up in my shop in their early blown alcohol sand dragster days throughout Blaine's cut short career in top fuel. Even though all that's way out of my league now I am still very familiar with what a top fuel piston goes though, they're pretty much only expected to make one burnout (on alcohol) and one 1,000 foot fuel run so that comparison doesn't really even count.
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