Penske Racing Shocks 8900 Series - Manual (Page 9)

9
8981 Series Compression Adjuster
The 8981 compression adjuster is located in the remote reservoir
assembly. The remote reservoir serves as an extension of the shock
absorbers vital elements: oil and nitrogen. The remote reservoir theory
allows for the use of increased volumes of oil and nitrogen while
allowing for smaller shock packaging. Increased nitrogen volume is
essential for consistent damping forces throughout a long race and
extreme conditions.
In the compression mode of the shock absorber, fluid is forced into the
remote reservoir in direct proportion to the area of the shaft entering the
shock body. As fluid enters the reservoir, it must pass through the
compression adjuster. Inside the compression adjuster is the CD drum.
The CD drum has (6) settings, numbered (1-6), with number one setting
(the largest hole) being full soft and number six (the smallest hole)
being full firm. As fluid is forced through the CD drum (Figure 1), it is
metered through one of the preassigned orifices in the drum; it then
enters the reservoir body, moving the floating piston. The floating piston
is designed to separate the fluid and nitrogen, eliminating any chance
of aeration.
In the event of high speed shaft velocities, fluid passing through the
hole in the CD drum could pack-up, causing an increase in damping
forces, due to the fact that fluid can no longer pass through the hole.
In this event, the fluid forces open the blow-off valve (Figure 2). The
blow-off valve makes a more linear damping curve.
Note: The remote compression adjuster is a fine tuning device for the
main valving located inside the shock absorber.
Figure 1
Figure 2
Low Speed High Speed