Slam Valve Motor, supplying efficient steam engines for homeowners and professional solar installers
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Slam valve performance ported

Porting a motor means to machine a hole in the side of the cylinder wall which connects to the radiator. Porting reduces displacement of the block by 10-20%. Porting allows two additional modes of operation that allow increased torque. The first mode which provides high efficiency at lower torque is still available. Unported motors can stall, ported motors are very difficult to stall. At low RPM, a ported motor puts out maximum torque and can do so at arbitrarily low speed. The low speed high torque mode is effectively the same cycle as the James Watt steam engine.

Ported motors are suitable as automotive power plants.  The high torque mode provides for rapid acceleration of the vehicle. The lower torque mode has the efficiency to be competitive with the gasoline engine.  Generally an automobile requires about 20 horsepower on the average to maintain freeway speeds.  See the 'guess my MPG' spreadsheet to see how much power this is for any given car.  For a 2 liter motor running at 2000 RPM, the maximum efficiency is met at 24 horsepower or below with 350 deg F boiler and no vacuum pump,  or 37 horsepower or below with a 450 deg F boiler.  Maximum power at 2000 rpm (at lower efficiency) is 80 horsepower at 350 deg F boiler, or 260 horsepower at 450 deg F boiler.  Compare to a gasoline engine which produces only 40 peak horsepower at 2000 RPM.

Ported and unported slam valve motors feature a smooth accelerator control which has no time lag from actuating it to change in torque out.  The accelerator is a simple mechanical linkage on each cylinder, easily tied to the throttle cable from a vehicle.  Unlike the gasoline engine, the slam valve motor efficiency does not drop as the accelerator is changed.  There is a wide range of torque and RPM over which the motor will achieve its maximum efficiency.  Reducing torque reduces the steam consumption of the motor proportionately.
efficiency graph
This efficiency applies to ported motors as well at low torque
ported power graph
Ported motors feature extremely high peak torque
unported power graph
This is the power to stay below to get optimal efficiency.
converted gasoline generator
This gasoline powered generator was converted to a ported steam motor