There are companies, divisions of companies, sister companies, and manufacturing associations who make engines.
Daihatsu is a sister company of Toyota. Engines in some Toyotas are Daihatsu engines with different valve covers, injectors, and ECUs. Daihatsu makes Kei class, Japanese home market cars and trucks, and engines for world wide distribution. Some of their engines say Daihatsu, some say Toyota, some say Briggs and Stratton, some say Cat, and are in Cat skid loaders, and MiniExs.
There is an Italian company, which makes vehicles with the same body, and trim packages, but a larger displacement engine, built on the same engine block, as Daihatsu Kei class JDM vehicles, for the EU market.
Engineers, can redesign all kinds of things to work together. An engine doesn’t care what bell housing, bolted to what transmission, generator, etc., is bolted on the back of it. If you want to change the torque curve, and make more or less horsepower, you change the cam, injectors, and ECM. You can change the crankshaft to make more torque on the low end, or more horsepower on the high end.
I know that the Mitsubishi engine in my TYM, is also in Cat skid steers, and MiniExcavators, and in gensets, and water pumps, and a couple of versions of other small diesel powered whatevers, made by whoever. I also know that if I look for the TYM, part number for engine component, and only use the last eight numbers, the injection line I’m looking for will come up under other equipment manufacturers parts numbers and systems, and work. I know that the engine was made for thirty plus years, and I can find complete rebuild kits on eBay for the engine in the displacement installed in my TYM T233HST, or I can buy a rebuild kit for $30 more with the cylinder liners, and pistons, to turn my tractor into a T273HST. And, if I ever need to rebuild the engine I probably will. I also know that, I can install a belt drive Aisan Roots pattern supercharger, and larger injectors on the engine, set it up with 10-lbs of boost, and increase the torque.
It is important to know what engine, you have and who designed it. Because if you know that, you can frequently, step outside the box, and save money on parts, or even get parts to work on orphaned equipment, and keep it running.
I’m constantly bemused by the guys on the minitruck forum I post on.. They can’t seem to grasp that the generators and alternators, are standard Denso parts, and if they know how to ask, they can replace them inexpensively at NAPA. Or save even more by rebuilding them. They insist on ordering them out of Japan for three and four times as much..