Usually, the engines we cover here on EngineLabs have an even number of cylinders, with the notable exception of the contested V5 engine layout we recently spoke about. While a majority of radial engines have an odd number of cylinders, we generally don’t feature radial engines in our day-to-day operation, so odd-numbers of cylinders really don’t come across our plate all that often, and catch our attention when they do.
While most inline-seven-cylinder engines are meant for marine use, there are a few notable exceptions to the world’s I7 lineup, like the Kawasaki KH606 built by the Hertfordshire Superbike Centre, in which several two-stroke Kawasaki engines were grafted together to make an inline-seven. The contraption was then mounted laterally into a Kawasaki Triple motorcycle frame, a unique four-tube exhaust was built, and then driven around the English countryside.
Known for making the largest diesel engine in the world (14 cylinders, 109,000 horsepower, 110,450 cubic-inches), Wärtsilä makes a version of the RTA96-C with half the cylinders, making it an inline-seven-cylinder engine. To further solidify the seven-cylinder lineup, they also make the 46F and X82 inline-seven-cylinder marine engines, which are smaller, higher-revving (relatively speaking) models.
However, before you start thinking that the inline-seven-cylinder engine is only a ship engine or crazy, one-off, motorcycle engine, there is a production inline-seven-cylinder engine designed for land use: The AGCO HD 98 (formerly known as the SISU). Designed for agricultural use, the 598 cubic-inch I7 engine makes about 470 horsepower at 2,100 rpm and 1327 lb-ft of torque at 1,500 rpm. Featuring a compound turbocharger arrangement, the latest generation of the AGCO seven-cylinder engine has been modernized to meet today’s performance and emissions requirements.
These are only three of the eight engines covered in the video, so make sure to watch the video for all eight of the fascinating inline-seven-cylinder designs. While not particularly applicable to the automotive market, they are definitely an interesting engine configuration.
Here, you can see the operating order of an inline-seven-cylinder engine in this animation of the AGCO SISU 598ci diesel engine.