This has potential. Very similar to the torpedo engines from the WWII era. Although the "Technical Data" they provide is very lacking in detail, I estimate it is likely in the 1.2 to 1.5 liter range, so the performance is respectable if true. A big advantage for this approach is small frontal area and light weight for the power. The challenge is in lubrication strategy and cooling. I will interested to see how this progresses.