In Japan the range gradually received upgraded motors which could pass the 1978 emissions standards; these models carry 811 series chassis numbers. Japanese market 811-series vehicles replaced the Bluebird badge on the rear decklid with a NAPS badge, identifying emission control technology as having been installed. The process of meeting the 1978 standards began in October 1977 and continued until August 1978 and meant replacing the earlier L-series engines with the new crossflow Z engines, based on the L. From March 1979 until the end of production in November that year, the NAPS badge was once again removed from passenger cars (although taxis featured a "NAPS-Z" badge as they wer now equipped with the new Z engine).