Camshaft Control (CVVT)
Both camshafts can be adjusted by the Engine Control Module (ECM) individually using their separate camshaft reset valve.
The induction camshaft is located in the engine's leading edge (in the travel direction) and the exhaust camshaft in the trailing edge (towards the passenger compartment).
The camshafts are driven by the crankshaft via a gear housing located on the engine's top side.
When each camshaft is adjusted in the factory, its position is aligned with the crankshaft's position. The camshaft's position at alignment against the crankshaft is called the camshaft's 0-position (basic setting).
At camshaft control (CVVT), the camshaft's 0-position is displaced so that the camshaft's angle position is changed. Thus, opening and closing of the exhaust and inlet valves changes relative to the crankshaft.
By controlling the camshaft's angle position, the engine's performance can be increased, idle quality can be improved, and emissions can be reduced.
The Engine Control Module (ECM) detects the position of the camshafts by comparing the signals from the engine speed (rpm) sensor (1) (crankshaft position) and the camshaft position (CMP) sensors (2) (camshaft positions). The Engine Control Module (ECM) then controls the angle of the camshaft by controlling the oil flow to the CVVT unit using the reset valve camshaft (3).
There are diagnostics for this function. See also: DIAGNOSTIC FUNCTIONS
, Camshaft diagnostics (CVVT)
Controlling, reset valve camshaft
- Oil filter reset valve camshaft.
- Oil channel (pressure, inlet).
- Channel connected with CVVT-unit's chamber (triggering).
- Channel connected with CVVT-unit's chamber (re-triggering).
The camshaft reset valve controls the oil flow to the continuous variable valve timing (CVVT) unit. The Engine Control Module (ECM) uses a pulse width modulation (PWM) signal to control the valve. See also: DESIGN
Camshaft reset valve
The continuous variable valve timing (CVVT) unit allows the position of the camshaft to be adjusted relative to the crankshaft.
The camshaft is secured to the CVVT-unit's rotor. The rotor (and thus, the camshaft) can rotate in relation to the timing belt pulley by the oil pressure building up on one or the other side of the rotor's vanes in the CVVT-unit.
Control occurs according to the following during deployment/return of the camshaft.
A: Inlet camshaft
- Oil pressure from the lubrication system (1) of the engine.
- The oil passes the filter for the camshaft reset valve (2) and then on to the reset valve (3).
- The Engine Control Module (ECM) controls the oil flow to one of the CVVT unit chambers (4) depending on whether it is to be deployed/returned by the camshaft.
The reset valve is controlled by the Engine Control Module (ECM) by high frequency, switching for deployment and return. This results in rapid and precise control. The camshafts can be triggered up to approx. 40 crankshaft degrees.