Thread: Question for the mechanically minded

Yes possible.
big marine diesel two strokes will not run (or extremely poorly)without a supercharger or turbo as they have no bottom end pressure (being common bottom end)to push charge air into the cylinders.
usually a hydraulic supercharger is run on start and idle and is switched off as load comes on and the turbo winds up and provides boost off its own accord.

Spanners will correct me if I am wrong on any points here I am sure its been well over ten years since i had anything to do with a wartsilla and it wasn't my dept.

Your common "crosser" single cylinder two stroke uses bottom end pressure to push charge air into the cylinder and reed valves to contain the pressure, "tuned" exhaust expansion chambers are designed to work in a rpm range.

As exhaust bursts out of the cylinder the velocity and mass of the gases(mass/velocity effect think leaning into a strong wind and any loose clothing being pulled behind you) it pulls fresh charge air into the cylinder and exhaust and the exhaust charge air is thrust back into the cylinder by a pressure wave returning from the big to small taper of the exhaust, so charging the cylinder with more than its share.
all this works on resonance/harmonics.

As a very very general rule.

Stiffer reed valves more top end, dual or light more bottom and mid at the expense of top.

exhaust. once again very generally, long skinny tapers top end short fat taper bottom mid.

turbo or super charger is really something that would have to be designed into the port timing, intake and exhaust, or even run an exhaust valve to have any real benefit.
not impossible but for any real gains the engine would have to be designed around forced induction.

nitros oxide on the other hand :thumbup:


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