Like the Scuderi Engine, this re-imagined internal combustion rig by San Diego-based Tour Engine is a split-cycle design. But rather than capitalizing on wasted compressed air, the Tour engine manages temperatures in different parts of the engine to help the engine run optimally.
The problem: In a four-stroke engine, the first two strokes (intake and compression) take place most efficiently in a cold environment, while the second two (ignition and exhaust) work better in a hot environment. When all of that takes place in the same cylinder, engineers strike a compromise between the needs of each and the engine wastes a lot of energy (up to 40 percent) simply pulling heat away from the cylinders via the radiator.
The Tour engine, being a split cycle, can keep the intake/compression cylinder cold, then pump the compressed fuel-air mixture into a hot combustion cylinder, ensuring that both halves off the cycle occur under more optimal conditions. Further, since compression is optimized by a small cylinder and combustion happens more efficiently when there’s more space for the explosion to spread out (more energy is lost to exhaust here in a conventional design), each side of the engine can be sized to best suit its particular task.
Less energy lost to waste heat and exhaust translates into an immediate uptick in efficiency by about 20 percent, Tour Engine claims. With further improvements in design, engineers there think they could boost economy by more like 50 percent.