boiling point of water...cooling systems

Ah Ha, didn't know that.

 

I don't know if this was clear in prior posts but...

There are two scales for pressure PSIA (absolute) and PSIG (gauge).

PSIA = PSIG - 14.7 PSI (at sea level and 70 degrees F).

The relief valve in the cap is rated in PSIG. When reading a steam table to determine the boiling point of water or any other value it is reading PSIA, you must convert.

 

Yep, just like most pressure gauges it is above atmosphere, other wise a guage would read 14.7 just lying on a shelf. I believe there is psig and psia

 

Some old dusty book I had somewhere years ago rated the average increase in boiling point temperture at 3 degrees F per pound of pressure. If 1 bar = 14.7 lbs atmospheric, you should be able to raise the boiling point to 256 F at sea level, or there abouts.

Scott, the reason the caps holding pressure is effected by outside ambiant air pressure is that the cap has an inside, the seal, and the outside with the spring is vented to outside ambiant air pressure. Thus the pressure rating is the internal pressure rating of the system against standard conditions atmospheric pressure. So its the internal system pressure, in addition to atmospheric that the cap will release at. so a .9 bar will break at .9 bar internal pressure above whatever ambiant air pressure exists at the moment. At high altitude they can blow off at a much lower temp/pressure. Antifreeze such as Prestone supposedly raises boiling point, but I dont think its really very much.

 

The boiling point of water is real close to the breaking point of your Ferrari engine.