We are sometimes asked about
cylinder firing pressures in S.I. gasoline engines.
In the 60's and 70-s it was pretty common to see peak
firing pressures of 600/650 p.s.i. in naturally aspirated
Since the 80's many changes have
occurred in passenger car engines. Computer controlled
engines, turbocharged, supercharged, and fuel injection
to name a few. All of these changes have resulted in
more efficient engines. The result of a more efficient
engine is higher peak cylinder firing pressures and
higher engine temperatures.
It is common in today's engines
to encounter cylinder pressures of 900/1000 p.s.i.
The above figures and statements
should be considered general. Many other factors affect
cylinder pressures such as fuel injection position,
piston top design, valve over lap, etc.
Norman W. Pugh
Manager-Piston Ring Engineering
Hastings Manufacturing Company