In the mid-1980s, automotive engineers "discovered" multi-valve engines. A regulatory push for lower exhaust emissions and higher fuel economy, coupled with customer demand for cars that could and would perform as well as cars from a generation earlier, led car companies to designs of powerful and efficient four-cylinder engines. A horsepower race of sorts had developed, and small-displacement engines could produce big numbers if they ran at high engine speeds.Four Are Better Than TwoTo help these small engines breathe at high speed required large intake and exhaust valves. But the combustion chamber size limits the size of the valves, and it was found that two small intake and two exhaust valves would breathe more efficiently than a single large intake and large exhaust valve. This was especially true in the short-stroke high-speed engines that were popular in Europe and were starting to show up in America.
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