For many years four-stroke engine manufacturers have specified the honing of cylinder bores, but it is only recently that the low-speed designers have followed suit. With lubricant injected directly into the low-speed cylinder, honing has not been seen as necessary. But now with BMEP of 19 bar and P-max reaching 200 bar, much higher piston ring pressure is required to prevent blow-by. This means the liner must have a good running surface from the moment the engine first starts. With a liner made of a hard material, runnihg-in an un-honed liner would take thousands of hours off the piston ring life, and fill the cylinder drain oil with metal 'filings'. If the liner material were soft, the rings would bend the high peaks over and push them into the troughs, filling the areas where the oil collects. This would mean the first piston ring wipes the oil from the surface while the others run dry, and rapid wear will inevitably result.
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