Quote Originally Posted by dpzelenak View Post
ok here we go again
Reversion:
-inefficient exhaust systems allow exhaust gasses to be bottled up in the cylinder.
-the amount of air/fuel intake charge that can enter the cylinder is reduced.
-higher cylinder pressures from incomplete exhaust blowdown can force burnt gases into the inlet tract during intake valve opening.
-"mean exhaust flow velocity" is then decreased, reducing maximum engine volumetric efficiency

that seems to be what back pressure is
No, its not.