High Speed

At high engine speeds the balance valve remains open and the six power valves are opened. This allows the engine to breathe from the short tract plenum via the short primary tract lengths. These lengths and diameters are tuned to produce a spread of torque from 4000 rev/min upwards, with maximum power produced at 6250 rev/min.

The manifold also gives an improvement in part load fuel consumption. At part load, the manifold operates as at high speed. The pressure dynamics significantly reduce the pump losses below 4000 rev/min resulting in improved fuel consumption.

The following chart shows the status of both of the valves with respect to engine speed and throttle position:

Fig 1: Engine Speed And Throttle Position Chart

Courtesy of LAND ROVER NORTH AMERICA, INC.

There are two variable intake manifold system diagnostic checks: -

1. An electrical continuity check while the system is active. A short to battery positive, ground or an open circuit condition can be detected.
2. A rationality check where an always closed or always open valve can be detected. A fault is present if the valve is commanded open and the feedback signal is inactive and vice versa.

If the above table does not include details of the following enabling conditions: - IAT, ECT, vehicle speed range, and time after engine start-up then the state of these parameters has no influence upon the execution of the monitor.