In the fuel supply pipes.@Pinger I don't think fuel vapor (such as a leaking purge solenoid valve) would cause a no-start. If you watch a video about GM EVAP systems, the pressures are REALLY small, somewhere around 2 mm of mercury = 0.040 psi. Besides, the compression in the cylinders is much higher. Are you thinking like a vapor-locked engine?
With heat, the fuel can vapourise and a bubble of it be trapped at high spot and the pump not be able to shift it and it impede flow.
It's really only a thing with older low pressure supply lines to carbs as the low pressure suction pumps worsened the situation by dropping the pressure in the line and I don't suppose the intermittency of their operations helped pull a bubble through to where it could be expelled.
The purpose of a pressure accumulator in the engine bay of a high pressure fuel system though is to prevent vapour locks.
Pretty much - but it's the expansion ratio (where the piston is moving down the bore on the power strok-e) that really matters. It is - more or less - a mirror of the compression ratio hence why CR is used as the predominant term. It's not a true figure though as the closing of the inlet valve intrudes and likewise the opening of the exhaust valve on the expansion strok-e though again, they closely mirror each other. Contrast that with how CR is measured on 2-strokes - from exhaust port closing, not BDC.What does the compression ratio of an engine mean? 10:1 for example. Is that 10 atmospheres of pressure to 1 atmosphere of pressure? That's like 150 psi? I honestly had never wondered what the ratio was. I'm just a hobbyist, LOL.
'Geometrically' it is. It is the sum of the cylinder volume and the clearance (chamber) volume divided by the clearance volume.Edit: looks like compression ratio is volume of the cylinder in the "down" down position to volume of cylinder in the "up" position...