f found this as doing research and bored at work... remember I believe my inlet valves opening late and shutting late . The point that the intake valve goes closed has a large effect on cylinder pressure. When the piston is traveling back up the cylinder, it will force some of the fuel/air mixture past the still open intake valve into the intake port. If the intake valve closes later in the cycle, some of the fuel/air mixture will be forced past the intake valve into the intake port, which will reduce cylinder pressure. The point in the cycle where the intake valve opens is very important. If the intake valve opens too late in the cycle, the initial amount of fuel/air mixture draw into the combustion chamber is reduced and spent gasses will not be effectively flushed from the chamber.