User Guide

Dyno2000 Advanced Engine Simulation—77
Camshaft Modeling
relative to the crankshaft. Why is this done? It is just about the only valve-timing
change available to the engine builder after the camshaft has been purchased.
While it’s possible to “tune” the cam using offset keys, special bushings, or multi-
indexed sprockets, let’s investigate what happens when all the valve events are
advanced or retarded from the cam manufacturer’s recommended timing.
It is generally accepted that advancing the cam improves low-speed power while
retarding the cam improves high-speed power. When the cam is advanced, IVC and
EVC occur earlier and that tends to improve low-speed performance; however, EVO
and IVO also occur earlier, and these changes tend to improve power at higher
engine speeds. The net result of these conflicting changes is a slight boost in low-
speed power. The same goes for retarding the cam. Two events (later IVC and EVC)
boost high-speed power and two (later EVO and IVO) boost low-speed performance.
The net result is a slight boost in high-speed power.
Advancing or retarding a camshaft has the overall affect of reducing valve-timing
efficiency in exchange for slight gains in low- or high-speed power. Consequently,
most cam grinders recommend avoiding this tuning technique. If advancing or re-
tarding allows the engine to perform better in a specific rpm range, the cam profile
was probably not optimum in the first place. More power can be found at both ends
of the rpm range by installing the right cam rather than advancing or retarding the
wrong cam. However, if you already own a specific camshaft, slightly advanced or
retarded timing may “fine tune” engine output to better suit your needs.
SAVING CAM SPECS MENU
The Dyno2000 can save and retrieve cam file specifications. Simply select the
Cam File field in the CAMSHAFT category. Choose Save from the drop-down menu.
Enter a filename then click OK. A “.cam” is automatically added to the filename and
the file will be saved in the selected directory.
Note 1: If you change any of the on-screen cam specs after saving or retrieving cam
files, the cam file will not be automatically updated (if desired, choose the Save
function again to update the cam files on disk).
Installing offset cam
bushings in the cam
gear is a common
method of advancing or
retarding cam timing.
While this method can
improve power, it can
hurt almost as much as
it helps. Camshafts that
show power gains using
this method have the
wrong event timing for
the engine.
Changing Camshaft Advance/Retard