User Guide

110—Dyno2000 Advanced Engine Simulation
Mini Glossary
the length of the measurement arm: Torque = Force x Torque Arm , where Force is
the applied or the generated force and
Torque Arm is the length through which that
force is applied. Typical torque values are ounce-inches, pound-feet, etc.
Valve Head and Valve Diameter—The large end of an intake or exhaust valve that
determines the working diameter. Valve head temperature can exceed 1200
degrees(F) during engine operation and a great deal of that heat is transferred to the
cylinderhead through the contact surface between the valve face and valve seat.
Valve Lift—The distance the valve head raises off of the valve seat as it is actuated
through the valvetrain by the camshaft. Maximum valve lift is the greatest height the
valve head moves off of the valve seat; it is the lift of the cam (lobe height minus
base-circle diameter) multiplied by the rockerarm ratio (in engines equipped with
rockerarms).
Valve Motion Curve or Valve Displacement Curve—The movement (or lift) of the
valve relative to the position of the crankshaft. Different cam styles (i.e., flat, mush-
room, or roller) typically have different displacement curve acceleration rates. Engine
simulation programs calculate a valve motion curve from valve event timing, maxi-
mum valve lift, and other cam timing specifications.
Volumetric Efficiency—An engine measurement calculated by dividing the mass of
air inducted into the cylinder between IVO and IVC by the mass of air that would fill
the cylinder at atmospheric pressure (with the piston at BDC). Typical values range
from 0.6 to 1.2, or 60% to 120%. Peak torque always occurs at the engine speed
that produced the highest volumetric efficiency.