• Outside/steam lap (OL) = 0.5
• Inside/exhaust lap (IL) = 0
• Lead angle (LA) = 20^o
• Exhaust relief (ER) = 0
• Link-up (LU) = 0

Steam Lap means the slide valve faces are wider than the steam ports therefore the valve is fully closed for longer than in the basic configuration.  After the admission port closes, the steam in the cylinder expands to push the piston to the end of the stroke (shown as grey in the cylinder) - this improves fuel economy.

The valve eccentric (magenta pointer) is 90^o plus the Lead Angle ahead of the piston crank (green pointer) so the admission occurs just before top and bottom dead centre.  This provides cushioning  at the end of the stroke.

The eccentric throw is increased to allow the steam port to fully open however the exhaust port is open longer.

The red and blue ray plots indicate the amount the upper steam port is open to steam and exhaust respectively.  Notice how the blue rays show that the exhaust port is fully open for a significant proportion of the revolution to minimise back pressure.  The radius of the green cardioid plot indicates the volume of the cylinder above the piston (relative to the eccentric pointer).

• See Basic Valve Configuration
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