Re: Forged pistons - Saab NG900 & OG9-3 Bulletin Board - Saabnet.com
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Re: Forged pistons
Posted by Dean (more from Dean) on Fri, 17 Dec 2004 07:57:27
In Reply to: Forged pistons, Jeff in ATL, Fri, 17 Dec 2004 05:58:43
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According to "Maximun Boost", HO turbo applications sometimes need to avoid forged pistons because of typically higher expansion rates that require larger wall clearances, which can shorten the life of the piston during warmup when the clearances are too large. Hypereutectic (high silicon) alloys have lower expanstion rates. So the forged pistons are stronger, but can present other serious issues. There may be some good forged pistons that have the alloy and expanstion rates under control.
"Unless circumstances are highly unusual, street cars with stock readlines will prove more successful with cast pistons. Forgings should be reserved for the high revers [where inertial loads start to become the limiting factors], while T6 hypereutectic alloys can cover almost all requirements." + "Do not rush to the forged piston every time a turbo engine need preparation".
Also, in this situation, I don't see that the failed engine has been modified from stock. If the HG was distorted and mislocated, the piston rings might have been kissing an intrusion of the HG metal ring. But as guessed, perhaps the engine has been 'repaired' once already. I am concerned by the color of deposits at the 3-4 end of things and wonder if loose head bolts were responsible for first problems. Could combustion gases have blown through from one cylinder to the next one.
posted by 66.142.222...
Posts in this Thread:
- Broken piston pics!, Tom, Thu, 16 Dec 2004 17:14:49
- +, Dean, Thu, 16 Dec 2004 18:56:34
- ++, Dean, Thu, 16 Dec 2004 19:10:20
- Re: ++, Tom, Thu, 16 Dec 2004 20:59:59
- Re: Broken piston pics!, Dean, Thu, 16 Dec 2004 18:53:57
- Re: Broken piston pics!, Mark, Thu, 16 Dec 2004 18:07:32
- oh yeah - where can I get an engine in Canada?, Tom, Thu, 16 Dec 2004 17:25:00
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