Variable Induction System: Description and Operation

IMT System Description










The IMT system varies the effective intake pipe length by opening and closing the IMT valve in order to improve air volumetric efficiency.

As the intake valve in the cylinder head is opened and closed repeatedly, intake air pulsation occurs. If the intake valve is opened when air pressure is momentarily at the maximum level, the intake air volumetric efficiency increases. This momentary maximum air pressure depends on the effective intake pipe length.

When IMT valve is totally closed [A]:

The effective intake pipe length is longer. Engine torque in the high engine speed range drops, while it improves in the middle range.

When IMT valve is fully open [B]:

The effective intake pipe length is shorter. Engine torque in the high engine speed range improves, while it drops in the middle engine speed range.

IMT system utilizes this characteristic of engine. IMT valve is closed in middle engine speed range, and opened in high engine speed range.

In this way, engine torque is improved in whole engine speed range.