6-SPEED MANUAL TRANSMISSION (CL TYPE-S)
To enhance the 3.2 CL's already impressive credentials as a high
performance luxury coupe, Acura offers the '03 CL Type-S with an
optional close-ratio 6-speed manual transmission. This all-new
transmission was designed to take advantage of the high power and
torque of the CL engine and enable driving enthusiasts to select the
perfectly matched gear ratio through a precise, short-throw shifter
using a light and progressive clutch. Additionally, the transmission
was designed to be lightweight to avoid weight-related performance
loss and to ensure that the transmission would fit into the CL's
existing engine compartment.
To meet these goals, CL engineers employed a variety of innovations:
- The lightweight transmission housing is constructed entirely of high-pressure-cast aluminum alloy. Gears are narrow and made from high strength steel. The result is a compact transmission that is about the same size as a comparable 5-speed manual and is 60 pounds lighter than the CL's Sequential SportShift automatic transmission.
- A close-ratio 6-speed helps provide quicker acceleration by keeping engine revs up and in the center of the CL engine's powerband.
- To reduce shift load and help ensure smooth, precise, effortless shifting, brass multi-cone synchronizers are used on first through fourth gear with a single-cone synchronizer for reverse. A large gear teeth contact area helps to reduce gear noise.
- The leather-covered shift lever operates a short-throw shift linkage via large diameter cable to provide quick action and precise shift feel.
- A reverse lock-out feature prevents the transmission from accidentally being shifted into reverse while the car is moving forward.
LIMITED SLIP DIFFERENTIAL
To help enhance traction during acceleration and reduce understeer in
high cornering load situations, the CL Type-S with 6-speed manual
transmission features a helical gear limited slip differential. This
limited slip differential is specifically designed for the CL Type-S
and is lighter, more compact and more durable than traditional
clutch-type limited slip differentials.
Mounted within the ring gear, a set of helical gears continually monitors traction in each wheel, detects slippage and directs torque away from the slipping wheel and to the wheel with the surest footing. This allows enhanced traction not only when cornering, but also when negotiating slippery surfaces or surfaces where traction is uneven.
CLUTCH
The CL Type-S 6-speed manual transmission comes with a self-adjusting
clutch to ensure consistent pedal height and feel throughout the
service life of the clutch. This innovative clutch system
automatically takes up the slack between the pressure plate and
clutch disc and lowers release loads while maintaining consistent
pressure for the diaphragm spring. The clutch disc is made of an
all-new friction material that improves engagement feel as well as
clutch longevity.
To reduce noise, cut down the transmission of engine vibration into the cabin and provide increased comfort during shifting, the CL Type-S model's 6-speed manual transmission has been equipped with a dual-mass flywheel. Rather than having a single conventional flywheel, this unit is divided into two flywheels with a torsion spring and viscous damper sandwiched between the two. This design reduces vibration and gear rattle, enhances the durability of the synchronizers and reduces the shift load.
The clutch includes a one-way delay orifice (check valve) located in the slave cylinder that restricts return fluid flow during rapid clutch engagement. This restriction of fluid reduces drive train shock and limits the torque load on transmission components. The result is a less abrupt engagement of the clutch during overly aggressive release.
5-SPEED SEQUENTIAL SPORTSHIFT™ AUTOMATIC TRANSMISSION
To maximize the performance capabilities of both the CL and CL
Type-S, an advanced 5-speed Sequential SportShift automatic
transmission was developed. This transmission was designed to enhance
the sporty character of the CL while also providing smooth and
effortless shifting.
The CL's Sequential SportShift transmission operates as a traditional automatic or puts gear selection in the hands of the driver, much like a manual transmission. By moving the console-mounted transmission selector handle to the left of the "D5" position into the Sequential SportShift gate, upshifts and downshifts can be commanded with a quick fore or aft motion. Gear selection is indicated by an LED display located in the tachometer face.
To foster the immediate feel of a manual transmission, in Sequential SportShift mode the transmission logic commands firmer shifts that are approximately 10 percent quicker than shifts in automatic mode. Additionally, the system is engineered to deliver a quicker response time to shift commands than other semi-manual automatic transmissions.
Typically, the CL's transmission responds to a shift command in just 0.35 seconds, with the total shift completed in just over 0.9 seconds from the time of the initial lever movement. These figures are quicker than those of semi-manual automatic transmissions of sports cars costing twice as much as the CL.
The Sequential SportShift system includes built-in safety override features to prevent downshifting that would cause the engine to over-rev. When decelerating, the transmission will stay in the selected gear until the vehicle approaches a complete stop and then will shift into first automatically. During acceleration, except for shifting between first and second gear, the transmission will not up-shift automatically in Sequential SportShift mode. However, should the driver fail to upshift in time, the engine ECU will cut off the fuel flow to prevent the engine from over revving.
The gear ratios were carefully chosen to match the engine's power characteristics. The wide ratio transmission's lower gears provide quick acceleration while the tall top gear ratio results in low cruising rpm's for reduced engine noise and better fuel economy.
The CL's transmission downshifts quickly with little shift shock, and is optimally tuned to take advantage of the abundant power generated by the CL's engine.
By sharing the idler and third gear clutches, the transmission provides a total of five ratios without a significant increase in size or weight over typical 4-speed automatic transmissions. Other features include a first gear one-way clutch for smoother shifts and a heat exchanger design that moderates transmission operating temperature. A large torque converter lockup area provides a direct driveline feel, similar to that of a manual transmission.
The CL's transmission uses a 16-bit, 20 MHz ECU operating in concert with the engine management system to apply Direct Control shift technology. Linear solenoids provide precise, real-time control of the clutch on/off pressure in the CL's transmission. With superior clutch-engagement accuracy, the sophisticated control logic operates smoothly under all conditions. To reduce noise, a bearing supports the idler shaft, and the gear-mesh contact ratio was optimized.
Multiple safety and control strategies use interaction between engine and transmission controllers to manage overall powertrain operation. By limiting engine output torque and/or transmission clutch pressure during shifts, sharp driveline shocks are eliminated. The engine is also prevented from exceeding 5000 rpm in neutral and park.
GRADE LOGIC CONTROL
By monitoring throttle position, vehicle speed and
acceleration/deceleration, then comparing these inputs with a map
stored in the transmission computer, the Grade Logic Control System,
found in CL models with an automatic transmission, determines when
the car is on a hill. The shift schedule is then adjusted
automatically to hold the engine in a lower gear for better climbing
power, increased downhill engine braking and reduced shift frequency.