Acura TSX / Honda Accord CL. Manual — part 564

Fig. 46: VTEC/VTC Operation Chart

Fig. 47: VTEC/VTC Description

VTC system

The VTC system makes continuous intake valve timing changes based on operating conditions. Intake valve
timing is optimized to allow the engine to produce maximum power.

Cam angle is advanced to obtain the EGR effect and reduce pumping loss. The intake valve is closed quickly to
reduce the entry of the air/fuel mixture into the intake port and improve the charging effect.

The system reduces the cam advance at idle, stabilizes combustion, and reduces engine speed.

2004 Acura TSX

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX

If a malfunction occurs, the VTC system control is disabled and the valve timing is fixed at the fully retarded
position.

Fig. 48: VTC System Intake Valve Timing Chart

2004 Acura TSX

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX

Fig. 49: VTC System Intake Valve Timing

VTEC system

The VTEC system changes the cam profile to correspond to the engine speed. It maximizes torque at low
engine speed and output at high engine speed.

The low lift cam is used at low engine speeds, and the high lift cam is used at high engine speeds.

2004 Acura TSX

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX

Fig. 50: Low Speed Valve Timing

2004 Acura TSX

2004 ENGINE PERFORMANCE Fuel & Emissions Systems - TSX