Posted by TBR (IP: 205.188.200.23) on July 02, 1999 at 20:33:28:
In Reply to: (TBR) the compression stuff posted by scully on July 02, 1999 at 20:09:50:
...That is where the power is going to come from. I don't believe calculating CR from a compression test is going to give an accurate number. As an extreme example: high performance camshafts have enough overlap that some pressure is lost on the compression stroke due to the slow closing of the exhaust valves. A compression test would give misleading info. This overlap is why you can get away with 12:1 CR in those engines. A short duration cam would cause havoc with those engines - read grenade:) Another example is turbocharging. Those engines have low CR (7.5:1) but put out huge horsepower numbers because the blower raises the effective cylinder pressure.
: ok ,lets see if i can make us both right
: your version of compression would be using water displacement,
: to get mechanical compression,(as listed by the factory specs)
: my version is using air ,which is effected by altitude,and temprature,
: but this is the only one u can get with a compression guage,i think
: i think tht if u calculate in all the varibles (temp ,alt,and maby even humidity) they will be equil to each other at some point.
: does this sound better???? ( i think u made a good point !)