I was just reading about AchatesPower's opposed Liston two stroke diesel and was einder and if it needed some sort of one way valve to operate. I figure that the constant pressure from supercharging not only provides enough air for adequate compression from compression ignition but also keeps the flow going the right direction. I've never given this much thought but now it's bothering me because I am not entirely sure. I figure that only has two strokes that pull fuel air mixture up through the crank case so this as uniflow is more controlled in this regard but I still have to get this confirmed. I am a big engine nerd and the EMD 710 series is a uniflow two stroke as well. I never gave much thought to that but *I am almost confident it doesn't have any sort of reed valves." The 710 outside of being two stroke, has more in common with conventional four strokes as it has a sealed crank case with a lossless oiling system, direct fuel injection, and even valves on the exhaust ports. It does however have a geared turbo-supercharger that unsurprisingly provides constant pressure to keep the engine running properly. So I suppose that's just it, without forces induction, two stroke (especially uniflow) diesels can't keep flow in the right direction and thus couldn't run without something like reed or check valves? Or is there some other reason / am I completely wrong and two stroke diesels do indeed have reed valves or otherwise? Thanks for any and all replies!