The concept of the Selespeed transmission system for Alfa Romeo 147 follows the aim already developed on the Alfa Romeo 156 from which it originates. The aim is to improve performance of the manual gearbox transmission components. To avoid that the driver has to check the clutch pedal and the gear control lever but at the same time ensuring the driving pleasure that comes from direct control of transmission. To improve driving safety by a direct control that foresees the errors of the driver and prevents an incorrect control of the transmission system. Offer the driver a more advanced car interface? It should be remembered that the system essentially consists of a mechanical transmission, with dry monodisk clutch and synchronised mechanical gear, moved by hydraulic power steering. As previously with the Alfa Romeo 156, neither the clutch nor the gearbox is changed to install the hydraulic actuators that control the stroke of the clutch and the gear engagement and selection.
An electronic control unit manages a complex functioning logic that permits the use of the gearbox:
- in “semi-automatic” conditions, where the driver controls the gear engagement by the lever on the tunnel or with two push-buttons.
- In “automatic” mode, called “City” that assigns the decision to change gear to the electronic system. The clutch pedal has been eliminated , the traditional “H” gear lever of manual transmission has been replaced by a specific “Joystick” lever and two “UP-DOWN” buttons on the steering wheel.
General overview with the main components of the Selespeed system
- Control unit
- Electro-hydraulic group with electric pump
- Engine control unit (Bosch M7.3.1)
- Motorised throttle case (D.V.E.)
- Gear selection display
- Down-gear button (Down)
- Up-gear button (Up)
- “City” mode button
- Gear control selection lever
- Switch on brake pedal
Power steering system
Essentially consists of an electro-hydraulic group (2) mounted directly onto the gearbox. By means of two pistons it manages the gear selection and engagement. The two pistons are controlled by a group of solenoid valves, to which an electric pump and an accumulator supply the required hydraulic power.
An electronic control unit (1) having identified the requirements of the driver from the lever (9) or from buttons (6) and (7) autonomously manages the gear change, directly controlling clutch, gearbox and engine torque. During the gear shift the engine control is subordinated to the gear control.
The gear – engine interface
Considerably improves the system performance and relieves the driver of any need to synchronise the clutch-accelerator movements during the gear change, that can be effected with the accelerator always fully pressed down. Furthermore, the system inhibits incorrect requests to change gear and avoids engine stalling. In terms of aid to driving it also ensures: immediate availability of first gear when the vehicle stops; automatic downward gear change n the case of a strong deceleration. The gear engaged is shown on a display built into the panel on board (central display), whereas indications of faults or driving conditions critical for the vehicle or for transmission components are indicated directly on the display highlighting the text: Selespeed system fault, and, on the right of the panel the gearbox fault symbol is shown.
Selespeed system components
- Gear selection lever
- “City” button
- Selespeed control unit (assembled in passenger compartment under the dashboard, passenger side)
- Gear selection buttons on steering wheel
- Electro-hydraulic group
- Electric pump
- Hydraulic oil pump
- Speed sensor on gearbox
- Gear selection display
- Fault warning light