System Description: VTEC/VTC: Notes

2008 Acura CSX Base, K20Z1SECTION Notes
  • The i-VTEC has a variable valve timing control (VTC) mechanism on the intake camshaft in addition to the usual VTEC.

    This mechanism improves fuel efficiency and reduces exhaust emissions at all levels of engine speed, vehicle speed, and engine load.

  • The VTEC mechanism changes the valve lift and timing by using more than one cam profile.
  • The VTC changes the phase of the intake camshaft via oil pressure. It changes the intake valve timing continuously.
Fig 1: Engine Speed Graph (High And Low)
G06265769
VTC CONTROL DESCRIPTION

Driving Condition VTC Control Description
(1) Light-load Base Position For stable combustion the cam angle is retarded, and if reduces the entry of exhaust gas into the cylinder.
(2) Medium/high-load Advance Control Cam phase angle is controlled to optimize valve timing, improving fuel efficiency and reducing emissions.
(3) High speed Advance-Base Position To reduce pumping loss, the intake valve is closed quickly. This gives a charging effect to the air/fuel mixture, maximizing engine power.
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.