RLE alpha prototype operating under 7 bar IMEP (~6 bar BMEP) and 1280 rpm at engines lab - University of Texas at Austin (opens in a new tab)

We keep on increasing the speed. The cylinder rotates at the same speed as the vertical shaft. The very high rate of pressure rises (up to 25 bar / degree) makes the whole ground shake. But you can see how steady the cylinder pressure is on the screen. After about 5 minutes we started the engine (preheated by the heaters some), the 90 dg. gearbox was about 16°F above ambient. After the high speed and high load runs (fraction seen here), it actually cooled down to about 6°F above ambient (3.5°C). That indicates that all the liner parasitic losses were a lot less under load (despite higher speed), because the cylinder and piston are hot.