Hi, all. I'll be experimenting with water mist injection (amongst other things) on a small single cylinder engine. Because the electrical generation capability of the engine's alternator is limited, I have to find some other way of pressurizing the water for injection (not enough juice for an electric pump)... my idea is to capture the high pressure pulse just as the exhaust valve opens (cylinder blowdown) by tapping into the exhaust pipe just outside the engine proper. I'd trap the blowdown pressure with a check valve, route it to a pressurized water tank, and use that pressure to inject the water via a modified fuel injector in the intake manifold, controlled via a reprogrammed MicroSquirt that controls both the fuel injector and water injector. It is my hope that by leaning the fuel:air ratio then injecting just enough water to keep combustion temperatures below where NOx is created, the expanding steam will add to cylinder pressure, helping to offset power loss due to burning lean, while at the same time making for very clean emissions (lean burn has low HC and CO2, but high NOx due to burning hot... cool that down and you get low HC, CO2 and NOx). A side benefit is the water acts as an octane booster to prevent lean burn knock. The intake manifold will have a piezo that breaks the water and fuel into a fine mist, for more complete combustion and to force the water to flash to steam quicker. The injected fuel will be heated to 250 F, the intake air will be heated to approximately 150 F, and the injected water will be preheated to just below boiling point using exhaust heat, so we get the most expansion in-cylinder with as little heat input as possible (ie: it uses more water to cool combustion temperatures, giving as big a boost to cylinder pressure as possible). The engine is 174.5 cc. Compression ratio is 11.2:1. Compression pressure is 227.2 psi. Exhaust valve opens at 28 degrees BBDC. Exhaust valve closes at 8 degrees ATDC. Maximum RPM is 9200 (rev limiter) Redline RPM is 8000. The cylinder sits at approximately a 45 degree angle from vertical. Exhaust pipe is 1.2" in diameter. There is a 90 degree downward bend in the exhaust pipe about 2 inches after where it attaches to the engine, then a 90 degree bend to the right about 4 inches after that, then a third 90 degree bend at the right side of the bike before it goes to the muffler. Not sure if any of the above info helps. Is there any way to calculate what peak blowdown pressure would be present in the exhaust pipe just outside the engine proper? What shape and orientation of pipe (that will be grafted to the exhaust pipe) would be most beneficial (prior to the check valve) for capturing the pressure pulse? Directly in line with the exhaust port, at an angle? Expanding bell shape, straight pipe, reducing bell shape? Would spacing of the check valve from the exhaust port be a consideration (ie: is closer better or farther away)? Thanks.