ENGINE OIL CONTROL [SKYACTIV-G 2.0]

2016 – MX-5 – Engine

To reduce the oil pump load applied to the engine, the PCM controls the engine hydraulic pressure to the appropriate pressure according to the engine operation conditions.
The engine hydraulic pressure switches in two steps. When hydraulic pressure is not needed, the oil pump discharge amount is reduced by the operation of the engine oil solenoid valve.

The PCM switches the engine oil pressure (which lubricates the engine) in two steps. It does this by driving the engine oil solenoid valve according to the engine operation conditions.

The PCM controls the operational voltage energized to the engine oil solenoid according to the duty signal. After opening the engine oil solenoid valve at the output duty ratio of 100 %, load applied to the parts is reduced by lowering the duty value to the output duty value at which the open valve condition can be maintained. The output duty value for maintaining the opening value changes according to the battery voltage.

The operation conditions for the engine hydraulic pressure switching control vary according to the vehicle conditions.

Normal control

The PCM operates the engine oil solenoid valve when all of the following conditions are met:

Engine speed: Less than 4,000 rpm
Engine coolant temperature: Less than 98 °C {208 °F}
Charging efficiency: Less than specification (varies according to engine speed.)

Air bleeding control

If all of the following conditions are met, the PCM operates the engine oil solenoid valve several times to bleed air from inside the hydraulic circuit. (Engine oil solenoid operation amount varies depending on engine speed and engine coolant temperature.)

For details on the engine oil solenoid valve, refer to the “LUBRICATION SYSTEM”. (See ENGINE OIL SOLENOID VALVE [SKYACTIV-G 2.0].)

When the engine oil solenoid valve operates, the hydraulic circuit changes according to the following. The engine oil supply amount is controlled by changing the hydraulic circuit.

Engine oil flow during low hydraulic pressure setting (engine oil solenoid valve ON)

When the engine oil solenoid valve turns on, the oil passage flows through the pilot valve from the oil pump discharge outlet.
Hydraulic pressure (A) is applied to the upper part of the pilot valve. At this time, because the hydraulic pressure (B + D) applied to the pilot valve to the top and the hydraulic pressure (A + C) applied to the bottom is nearly equal, the spring valve is pressed down by the spring force (a), engine oil flows to the upper part of the relief valve, and hydraulic pressure (E) is applied to the upper part of the relief valve.

NOTE:
- During low hydraulic pressure setting (engine oil solenoid valve ON), the pilot valve presses downward by spring force because the hydraulic pressure applied to the top and bottom directions of the pilot valve is nearly equal.
Hydraulic pressure is higher than pressure setting

The relief valve is pressed down by hydraulic pressure because the hydraulic pressure (E + G – F) applied to the bottom of the relief valve is stronger than the spring force (b).
Hydraulic pressure decreases when part of the engine oil fed by the rotor returns to the engine oil intake of the oil pump.

The relief valve is pressed down due to spring force because the hydraulic pressure (H + K – J) applied to the bottom of the relief valve is weaker than the spring force (b).
Hydraulic pressure increases when all of the engine oil fed by the rotor flows into the engine.

Steps 3 to 4 are performed repeatedly to maintain a low hydraulic pressure setting.

Engine oil flow during high hydraulic pressure setting (engine oil solenoid valve OFF)

When the engine oil solenoid valve turns off, the oil passage to the pilot valve from the oil pump discharge outlet closes and the oil passage flows through the top of the pilot valve to the oil pan.
Hydraulic pressure applied to the top of the pilot valve is eliminated.

NOTE:
- During high hydraulic pressure setting (engine oil solenoid valve OFF), the hydraulic pressure applied to the top and bottom of the pilot valve changes according to the oil pump discharge outlet and the pilot valve opens/closes.
Hydraulic pressure is higher than pressure setting

The pilot valve is pressed down by hydraulic pressure because the hydraulic pressure (A + C – B) applied to the top of the pilot valve is stronger than the spring force (a).
Engine oil flows through the upper part of the relief valve via the pilot valve.
The relief valve is pressed down by hydraulic pressure because the hydraulic pressure (D + F – E) applied to the bottom of the relief valve is stronger than the spring force (b).
Hydraulic pressure decreases when part of the engine oil fed by the rotor returns to the engine oil intake of the oil pump.

The pilot valve is pressed down by spring force because the hydraulic pressure (G + J – H) applied to the top of the pilot valve is weaker than the spring force (a).
Engine oil via the pilot valve does not flow through the upper part of the relief valve.
The relief valve is pressed down by spring force (d) because the hydraulic pressure (K) applied to the top and the hydraulic pressure (L) applied to the bottom is nearly equal.
Hydraulic pressure increases when all of the engine oil fed by the rotor flows into the engine.

Steps 3 to 4 are performed repeatedly to maintain a high hydraulic pressure setting.