Posted by: Mike Clark
I just fitted a pressure gauge to the main steam pipe to the engine of my H (tee fitting to oil feed pipe). Very interesting and remarkable how little steam pressure is actually needed to move the car.
Typically when running with a light throttle on the flat at 35-40mph the gauge shows no more than 100psi, even 50 psi keeps it moving well. Accelerating or a modest hill takes it up to 200psi and it needs a stiff hill (10%) to bring it up to 300psi. The highest seen has been 400 psi when pulling with plenty of throttle on a 25% hill. This is with 600psi boiler pressure.
It is also very obvious how the driver can ease the load on the engine as only a very small closure of the throttle which has little effect on performance can bring the pressure down by 50 psi or more. Moving slowly up a steep hill which gives the impression of being hard work is not necessarily so if the pressure is only 200psi. and it is probably better to let the car find its own speed rather than be tempted to give it more throttle to get going.
Interestingly, but obvious when you think about it, the pressure rises by 50psi or so when hook up is engaged because less steam is being used by the engine but the same amount is coming through throttle thus building up more pressure in the steam pipe.