Penske Racing Shocks 7800 Series - Manual (Page 10)

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Dyno Graph Overview
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OVAL (Force / Displacement)
QUADRANT #1
This is the beginning of the compression stroke. Where
the graph crosses the zero line (pounds) in quadrant #1
begins the compression stroke. Approximately the first 1/
2" of displacement is formed with relation to the low
speed bleed bypass. When the shaft reaches a certain
velocity, the low speed bleed holes choke off and the
compression valve stack begins to react.
QUADRANT #2
This quadrant begins with the compression valve stack
open. Where the graph crosses the zero line (inches) in
quadrant #2 is the maximum force produced by the
compression valving. As the shock approaches the full
compression point, the compression valve stack begins
to close as it approaches the rebound movement.
QUADRANT #3
This quadrant begins with the shock at full compression
and the compression valve stack closed. Where the
graph crosses the zero line (pounds) in quadrant #3
begins the rebound stroke. Approximately the first 1/2" of
displacement is formed with relation to the rebound
bleed through the piston. When the shaft reaches a
certain velocity, the bleed chokes off and the rebound
valve stack begins to react.
QUADRANT #4
This quadrant begins with the rebound valve stack open.
Where the graph crosses the zero line (inches) in
quadrant #4 is the maximum force produced by the
rebound valving. As the shock approaches the full
extension point, the rebound valve stack begins to close
as it approaches the compression movement. At this
point the cycle starts over again in quadrant #1.
Force / Velocity Average
This graph shows the averages of the
accelerating and decelerating compression and
rebound forces. It is a good quick, general
review of the shock curve, but is the least
accurate of the options displayed.
Force / Velocity
This graph displays the accelerating and decel-
erating compression and rebound forces. Think
of this graph as the Force / Displacement graph
(below) folded in half.
* Hysteresis is the gap between accelerating and
decelerating compression and rebound damp-
ing. It is affected by the type of piston and the
shims used. The bleed hole(s) will close the gap
or soften the low speed forces.
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Penske Racing Shocks uses SPA or Roehrig Dynamometers because of their versatility and
low speed metering and sample rates. Penske Shocks primarily uses the Force Average
display, but SPA and Roehrig both offer Decelerating CD/Accelerating RD and Accelerating
CD/Decelerating RD viewing options for all their graph displays.
Hysteresis
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