On 6/26/05, Al Gietzen <ALVentures@cox.net> wrote:
Al, all I can tell you is that the pressure would go immediately (within 2 seconds) to 21-24 psi. Then as the engine warmed up the pressure would drop to a nominal 8 psi or so
It makes sense to me Ed. Heat the coolant just a little, and it needs to expand just a little. In order for any of the coolant to flow out past the cap (even just a little coolant), it must reach the pressure rating of the cap.
How much can the coolant heat up in 2 seconds after start? Just about zero. The only thing that is heated a little in that time is the rotor housing walls. Maybe that reduces coolant volume. In any case, if you have any radiator hose in the system, it will expand enough to keep the pressure from increasing that much. There is some weird science in here somewhere.
Al
Do you mean "just about zero", or absolutely zero?
Just about zero would imply something slightly larger than zero. Which means that the coolant expands something just a little more than zero. If you truly have no air in the system, an expansion of just about zero still has to open the pressure cap, which requires opening pressure. If you sealed water in a steel box with no air, heating the water a fraction of a degree would raise the pressure hundreds of psi. Just a few degrees will deform the steel box. Its not weird science, its just weird freaks of nature.
If you mean absolutely zero heating of the coolant a few seconds after starting I will take exception. That flame is well over 2000 deg F and the rotor housing water jacket is not very thick. Some (although small) heating of the coolant easily occurs within one second after starting the engine.
Someone mentioned radiator hose expansion. I don't know about your system, but my steel braided hose is going to take a lot more than 25 psi before it allows any expansion. 25 PSI is nothing. Not going to harm any part of anyone's cooling system except maybe with multiple cycles. That said, I also believe in having an air spring/absorber. The main part of my cooling system I keep full, but have a 1 qt pressurized overflow can that is empty at engine start.
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