Comment by PunchyHamster
5 hours ago
They have no driving electronics, electronic throttle, ECU controlled injection etc, so you are limited, you can't for example easily make it go constant set speed, because the throttle isn't electronic.
It went a bit too far, optimum would be modern enough to have drive by wire but with open ECU and documentation
You can still control a completely mechanical engine to work with set speeds. There are mechanical governors that can do this, or you can get an electronic component that moves the throttle for you. Fixed speed engines with variable load are much older than the transistor.
It is no harder than doing it with an ECU, except that you need to install a servo or speed governor with hand tools, instead of fiddling with ECU code.
It has a governor.. The P pump 12 valves (and many other multi-application diesels) come with either one of two different governors, an automotive one which has a high idle and low idle, but unrestricted fueling in between. This is what you want in a car or truck where you're controlling road speed with your foot. There's also the "industrial" governor that essentially maps lever input linearly to engine RPM, and endeavors to maintain its set RPM independent of load. This is the kind you find in tractors, generators, boats, etc.
These governors are basically mechanical analog computers which use the inertia of flyweights, springs, and some very clever linkages to do their thing.