RE: Some engine help please.
Hugh,
This drawing you posted does not portray much, I must say...
First of all, it is a five-port engine; not a Schnürle ported engine.
Also, the flow within the cylinder is three dimensional; not flat...
Let's call the exhaust side of the cylinder 'the front' and the opposite side will be 'the rear' of the cylinder...
If the drawing is as viewed from above; and the two ports nearer to the exhaust are the Schnürle ports, they seem to flow up and then then to the rear and then down, eventually flowing toward the exhaust under where the flow begins...
This cannot be. The drawn loop is reversed the the actual flow.
Schnürle ports flow to the rear, in and up, toward the rear of the combustion chamber and then the flow loops back through the combustion chamber, toward the front and down along the exhaust side of the cylinder.
The flow does not cross the place where it begins and flows over its beginning; not under.