User Guide

66—Dyno2000 Advanced Engine Simulation
Cam Basics
ability of the program to take multiple elements into consideration and “add up the
effects over time” is key to analyzing the effects of camshaft timing changes.
Cam Basics
In the simplest terms, the camshaft is a straight steel or iron shaft with eccentric
lobes. It is connected to the crankshaft with a chain or gear train and is usually
rotated at one-half crank speed. Lifters (or cam followers)—and in the case of in-
block cam locations, pushrods, and rockerarms—translate the rotary motion of the
cam into an up-and-down motion that opens and closes the intake and exhaust
valves. This entire assembly must function with high precision and high reliability.
Camshaft Modeling
Base Circle
Diameter
R
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t
a
t
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n
Clearance
Ramp
Lobe Centerline
Clearance
Ramp
Opening
Aeceleration
Closing
Acceleration
Nose or Toe
Foot or
Heel
Lifter
Rise
V
a
l
v
e
-
O
p
e
n
D
u
r
a
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n
The camshaft is a round shaft
incorporating cam lobes. The base
circle diameter is the smallest
diameter of the cam lobe. Clearance
ramps form the transition to the
acceleration ramps. The lifter
accelerates up the clearance ramp
and continues to rise as it ap-
proaches the nose, then begins to
slow to a stop as it reaches maxi-
mum lift at the lobe centerline.
Maximum lifter rise is determined by
the height of the toe. Valve-open
duration is the number of
crankshaft
degrees that the valve or lifter is
held above a specified height
(usually 0.006-, 0.020-, or 0.050-inch).
A symmetric lobe has the same lift
curve for opening and closing.
Valve Lift Menu
Selecting (placing a check mark next
to) Auto Calculate Valve Lift will
automatically calculate appropriate
valve lifts for camshafts listed in the
Camshaft Type drop-down menu. To
manually select valve lift from the
drop-down menu, or to directly enter
a custom value, make sure that the
Auto Calculate Valve Lift feature is
turned off (no check mark next to
Auto Calculate).