The aviation world has been clamoring for new engines for a long time. Owners want EFI and EI, or they want diesel. But they think that since General Motors can develop this stuff and sell it in a new car for $30K or whatever that Lycoming and Continental can build it for the same price as the legacy gasoline engines.
But it doesn't work. New technology (in aviation, almost anything is new) has to be designed to be safe and reliable, and it has to be tested for thousands of hours, and then it has to be certified, which is when the lawyers and the FAA and insurance companies get involved and costs really go up. Lycoming built the iE2, an EFI/EI engine, but it cost more than owners would pay. SMA and Thielert built diesels, but they weren't cheap either and they had considerable teething problems. I worked on an SMA about eight years ago, fixing some of those issues, and SMA told us that they had spent a billion (with a "b") dollars so far and had, at that time, 50 engines flying. Total. Worldwide. Things like that make a lot of CEOs say "no way" to new developments.
Aviation is expensive. Aviation with neat new technologies is prohibitively expensive. Even in the uncertified homebuilt world that new stuff isn't cheap. If someone is selling it they have to cover themselves against litigation when some guy flies into a mountain in the clouds and the jury blames the ignition system or something.
Diesel? Noisy. Smoky. Smelly. Oily. I'd rather smell avgas. The old 80/87 has a lot of nostalgia to it. Old airplanes smell like it. And diesels are hard to start in the cold. IIRC, SMA had a lower starting temp limit of about -10°C. Works in Africa. Not so good here.
