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The kei car regulations were revised in March 1990, allowing engines an increase of 110 cc (6.7 cu in) in displacement, and the overall car length to be increased by 100 mm (3.9 in). These changes occurred during the 1990s Japanese economic bubble, and all manufacturers quickly developed new models to suit. Within five months, all the major models of kei cars had switched from 550- to 660-cc engines.[26] For the first time, a power limit was also applied, in addition to the limit on engine size. This power limit of 64 PS (47 kW; 63 hp) matched the highest output reached by any kei manufacturer at the time and was a gentlemen's agreement amongst the manufacturers in an effort to avoid a kei-class horsepower war.[27] The only kei-engined car to have exceeded this limit was the Caterham 7 160, a lightweight British sports car that was not expected to qualify as a kei, though it is small enough (in dimensions and displacement) to fit the regulations. Its engine is rated at 80 hp (60 kW; 81 PS), and since that is how the car is homologated in the United Kingdom, the Japanese authorities told the importer that its power should remain unchanged.[27] The addition of a power limit was a response to the ever-increasing power outputs available with turbocharging and multivalve technologies popularized in the late '80s. Engine technology was also shared with sport bikes, which are designed for rider enjoyment, and less so for fuel economy – going against the idea of small, people's cars and putting the kei cars' tax and structural advantages at risk of a governmental backlash. The Japan Automobile Manufacturers Association also self-imposes a speed limit for kei cars of 140 km/h (87 mph).[28] In a rare example of an overseas mass-produced model being sold as a kei car in Japan, a kei version of the Smart Fortwo (called the Smart K) was sold at the Yanase dealerships in Japan from 2001 to 2004. The Smart K used revised rear fenders and reduced tire dimensions and track width to conform to kei-car regulations.[29] The model was not a success, and it sold the fewest examples of a kei car when it was marketed.[3] The Suzuki Wagon R was the best-selling kei car in Japan from 2003 to 2008.[30] Starting in 2011, Toyota entered the kei-car market for the first time. The resulting Toyota Pixis Space, a rebadged Daihatsu Move Conte, was expected to increase competition in that market.[31] Currently, Nissan and Mitsubishi jointly produce the Mitsubishi eK (also sold as the Nissan Dayz or Nissan Otti). Honda's kei-car line-up, the N-one, N-Box, and N-WGN, accounts for around a quarter of its overall sales.[31] In April 2014, the Japanese government significantly reduced advantages for kei-car owners, imposing higher sales tax, higher gasoline tax and higher kei-car tax – the last of which was raised by 50% – greatly reducing their tax benefits, compared to regular-sized cars.[5] Daihatsu, Honda, Suzuki and Nissan-Mitsubishi (through NMKV joint venture) are currently the only mass-production manufacturers of kei cars. Mazda sells rebadged Suzuki models, Toyota and Subaru sell badge-engineered Daihatsu models, while Nissan-Mitsubishi sourced their commercial kei models from Suzuki.