Cranking pressure calculator

[techinspector1]

Here's a dandy calculator to determine cylinder cranking pressure when other values are known. The originator of this calculator uses cam duration for one of the values, when it actually should have been intake closing point. If you know the actual intake closing point at zero tappet lift, add that figure to 210 and enter the result into the duration slot. Most all cam grinders will give the intake closing point at 0.006" tappet lift but won't give it at zero lift, so add 2 degrees to the 0.006" figure and add the result to 210 to enter into the cam duration slot on the calculator. Example: The grinder shows an intake closing point of 37 degrees ABDC @ 0.006" tappet lift. Adding 2 gives 39 degrees. Adding 39 to your constant of 210 gives 249. Also, you will need to adjust your elevation where you live to meters if you live in the U.S. Dividing your feet of elevation by 3 will get you close.
http://www.not2fast.com/turbo/compre...pressure.shtml

[southerner]

You getting bored Tech ?



Had a look at the site, takes a bit of working out, as I want to figure out the cylinder pressure for a supercharged engine I punched in an altitude of minus -1000 meters, only trouble is, is that I have to figure out what the air pressure is 1000 meters down ?

I figure it like this atmospheric pressure at sea level is 14.7 lbs/inch squared or 1 atmosphere so if we had a boost of 7 lbs it would be approx 1.5 atmospheres. But there must be a formula lying around somewhere to figure increases of air pressure below sea level so that I can get a reasonably accurate boost pressure and air temp in the cylinders