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| Joined: | 03-13-2005 |
| Location: | Salt Point, New York USA |
| Posts: | 208 |
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Your having contact at hot conditions and not at cold is a reversal that is perplexing.
Definitely one to think about.
Jim
| View single post by Jim Ketcham | |||||||||||||
| Posted: 11-14-2006 12:29 am |
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Jim Ketcham
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This is interesting. Typically when the "squish region" (space between top of piston and bottom of head) is too small you first detect it when the engine is run cold. At idle it sounds like a diesel. As the engine warms the rap goes away. The reason, I have been told, is that a cold unexpanded piston rocks letting the edge make contact. As the piston heats up and expands it no longer can rock within the cylinder and the noise disappears. This was an issue in some mid- 90's Mazda engines (and Ford Probes that used the Mazda engine) when Mazda reduced the squish region to help lower emissions. A slight carbon buildup on the top of the piston resulted in "rap". Your having contact at hot conditions and not at cold is a reversal that is perplexing. Definitely one to think about. Jim
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