2009 Acura ARX-02a
Images copyright  Michael J. Fuller
Text copyright Michael J. Fuller
Acura ARX-02a, Sebring WDWT 2009Precious little of the front suspension is visible being either closed up within the shrouds or enclosed within the monocoque.  The hatch on top of the monocoque allows access to the dampers, 3rd spring, anti-roll, and torsion bars.  Here we can simply see the reservoir for the clutch and brake master cylinders as well as the actuator for the hydraulic power steering.  The use of hydraulic power steering is bucking the recent trend of electric power steering (EPS) units and Wirth indicates that the choice of a hydraulic power steering was for a singular reason, "Packaging rules here, end of story..."  An EPS needs to be mounted to the front of the monocoque in order to engage the steering rack and this puts the weight up high, especially so given the raised tub nature of contemporary monocoques.  With a hydraulic unit, the pump itself is back with the engine and only the actuator unit is mounted to the front of the tub.  The actuator unit itself weighs much less than the EPS and helps remove weight from up high though the hydraulic pump and actuator all told weigh about the same as the EPS.  So it's a matter of reducing CG as it is always better to place weight low.
Acura ARX-02a, Sebring WDWT 2009There's an upright in there some where we're told.
Acura ARX-02a, Sebring WDWT 2009At the rear the pushrod engages the torsion bar (1) via the bellcrank which in turn actuates the dampers (2) and the third spring (3).  The length of the torsion bar is driven by the desire to keep them from breaking.  The front torsion bars are similarly long.  Note the A-arms are tube cross section.
Acura ARX-02a, Sebring WDWT 2009The third damper is a through-shaft type.  Adjustments are made via the knobs on the forward face of the damper.  The bump rubber helps maintain minimum ride height when under maximum aero loading.
Acura ARX-02a, Sebring WDWT 2009The drive shaft angle measures to approximately 10 degrees from centerline and is further indication that mass has been shifted forward.  The gearbox is a thin-wall aluminum casting and designed and manufactured by Wirth Research.  According to Nick Wirth, gear changes are made electrically as on the Zytek system (of which Acura utilized last year on the LMP2), though this year Acura has developed their own.
Acura ARX-02a, Sebring 2009The 4.0 liter Acura LM-AR7 V8.  The aluminum oil reservoir mounts to the front of the engine and is recessed into the back of the monocoque.  This helps move weight forward.

An interesting detail is that the LM-AR7 had two water pumps.  The pumps were controlled by the ECU and designed to maintain constant engine temperatures semi independently between each cylinder bank.  This became particularly important during caution periods when engine temps would typically drop; the twin pumps allowed the AR7 to go to back to green already up to temperature.
Acura ARX-02a, Sebring 2009HPD/Wirth Research designed thin-wall cast aluminum gearbox/bellhousing (note that it is upside down).

ęCopyright 2009, Michael J. Fuller