Page 13
Lotus Service Notes Section JL
6. Remove the 4 remaining fixings securing the pedal shaft bracket to the pedal box, and manoeuvre the
pedal assembly from the car.
7. Release the three Torx head screws securing the pedal shaft and withdraw the shaft and pedals
8. Refit the pedals in reverse order to removal, noting that the pivot bushes of the brake and clutch pedals
should be lubricated with Syntheso GLK1 or equivalent.
Torque Settings Nm
Brake servo to alloy spacer 25
Pedal shaft bracket to pedal box 16
Throttle pedal mounting bracket to pedal box - M6 16
- M8 25
JL.11 - ABS THEORY OF OPERATION
The Bosch antilock brake system is an ‘add on’ type used to supplement the dual circuit, tandem master
cylinder, vacuum servo assisted brakes fitted to the Evora. A single electro-hydraulic unit comprising a hydraulic
modulator, hydraulic pump, microprocessor and solenoid valve bank, is flexibly mounted on the forward side of
the driver's toebox, and plumbed into the front and rear brake circuit lines from the tandem master cylinder.
The microprocessor receives signals from magnetic wheel speed sensors integrated into each of the four
road wheel hubs, and interprets the individual wheel acceleration, deceleration, and comparative wheel speeds.
From this data, the processor is able to determine if any wheel is tending to lock up, and if imminent lock up
is sensed, the unit commands the relevant solenoid valves firstly to reduce pressure in that particular brake
circuit in order to restore wheel speed, and then to modulate pressure to that providing the maximum braking
force consistent with continued wheel rotation. The system is able to monitor and independently control each
of the four wheel brakes, and is referred to a 4-channel system.
In order to achieve the required pressure modulation, three basic modes are used:
- Pressure hold;
- Pressure reduction;
- Pressure increase;
In order to maintain the safety provision of two entirely independent hydraulic circuits, one for the front
brakes, and one for the rear, the hydraulic elements of the control unit are doubled up, with no part of the sys-
tem shared between the two circuits. For the pressure hold function, four isolation solenoid valves are used,
one in the hydraulic circuit for each wheel brake. The pressure reduction function is achieved by a separate
dump solenoid valve in each of the four wheel brake circuits, and the pressure increase provided for by a single
electric motor operating two hydraulic pumps, one serving the front, and on the rear brake circuit. Separate
low pressure accumulators are used for the front and rear circuits.
Electro-Hydraulic Control Unit
The electro-hydaulic control unit comprises an alloy valve block containing the four isolation valves, four
dump valves, two hydraulic pumps and two accumulators, with the single pump motor screwed to the housing,
and with a solenoid block and ECM unit attached. The complete assembly is flexibly mounted via a bottom
spigot and two threaded studs, each of which engage with a rubber grommet in a mounting bracket secured by
4 bolts to the front side of the driver's toebox. A protective alloy shield is secured by two nuts.
The isolation and dump valves share a similar construction, but the spring loaded isolation valves are
normally open, and the dump valves normally closed.
To Next Page
Loading...
