b'GAS PRESSURE GAS PRESSUREKEY HEAD VALVE PRESSURE HEAD VALVE PRESSUREGAS PRESSURE COMPRESSION PRESSURE COMPRESSION PRESSURE COMPRESSION PRESSUREHEAD VALVE PRESSURE REBOUND PRESSUREREBOUND PRESSURE REBOUND PRESSURETypical Pressure Balance Scenarios COMPRESSION REBOUNDSTROKE STROKE1. (Ideal) Balanced Damper: 2. Cavitating Damper:This set-up creates a symmet- Thisset-upmayberic damper curve with the somewhat symmetric butrebound pressures above 0 psi. the rebound pressuresPRESSURE (PSI) PRESSURE (PSI)The curve shape is parabolic COMPRESSION approach0psi.The COMPRESSIONand smooth. Hysteresis is at a STROKE damper will cavitate and STROKEminimum. 125 is not optimized. 125Example: On the compression + 50 PSI Example: On the compres- + 50 PSIstroke, compression pressure in- BUILD sion stroke, compression BUILDGAS pressure increases to 125 GAScreases to 125 psi from 75 psi PRESSURE PRESSUREwhilethereboundpressure - 50 PSI psi from 75 psi while the - 85 PSIdecreases to 25 psi. A total 25 REBOUND STROKE reboundpressurede- REBOUND STROKEpressure change across the piston 0 creases to -10 psi. A total 0TIME pressure change across the - 10 TIMEis 100 psi. Rebound and compres- (S) piston is 135 psi. Rebound (S)sion pressures change by the same and compression pressures change by different amounts and the rebound pres-amount of 50 psi which is symmetric and maintains a low pressure which will keephysteresis low and response time up. sure drops below zero which causes cavitation.Remedy: Add gas pressure/Stiffen Head Valve/Add High-Speed Compression3. Excessive Head Valve Damper: 4. Unstable Excessive Head Valve Damper:This set-up creates rebound This damper is verypressures that are above the COMPRESSIONSTROKE similar to the Ex-static gas pressure and is not cessive Head ValvePRESSURE (PSI)symmetric because head valve 250 Damper but has anPRESSURE (PSI)stack is too stiff or compres- COMPRESSIONunstable compres- STROKEsion adjuster setting is high. +175 sion pressure curve.This damper will not be in 150Usually, this can bemuch danger of cavitating butattributed to a stiffwill have considerable hyster- BUILD +75 BUILDGAS head valve stackesis. May be an option for very PRESSURE GASand a non-standard PRESSUREsmooth tracks and stiff springs stack(allshimswith little damper displace- REBOUND STROKE same diameter) or REBOUND STROKEment as low gas pressure can 0 TIME not sufficient bleed. 0be run for reduced friction. (S) TIMEExample: On the compression stroke, compression pressure increases to 250 psi from 75 psi (S)while the rebound pressure increases to 150 psi. A total pressure change across the piston is Remedy: Reduce Head Valve Stack/Soften High-Speed Compression100 psi. Rebound and compression pressures change by different amounts. Although the Adjuster/Add Bleedpressure differential across the piston is 100 psi as in the ideal damper, the pressures aremuch higher and they are not symmetric which will add hysteresis and slow response.Remedy: Reduce Head Valve Stack/Soften High-Speed Compression AdjusterOther tips: Advantages of Pressure Balancing:Curve Shape COMPRESSION 1.) Optimized Damper ResponsePRESSURE (PSI)Study the profile of the rebound pres- STROKE 2.) Reduced Hysteresissure curve on the compression stroke.It is ideal to have a smooth, parabolic 3.) Increased Mechanical Gripshape which indicates steady change in BUILD 4.) Reduced FrictionLower Static Rod Pressurepressures. Abrupt, sharp slopes and cor- GASners or flat curve shapes indicate a harsh PRESSURE IDEAL (in most cases)transition between pressures. Add bleed NOT 5.) Increased Oil Lifeto adjust slope and shape. IDEALFor more details, contact:Penske Racing ShocksEngineering Group or Aaron LambertReading, PA Open Wheel and Sports Car Manager (610) 375-6180 ajl@penskeshocks.com'