Differential Air Intake System (DISA)

Vehicle: E36 - M42/M1.7, M44/M5.2

DISA allows the dynamics of the incoming air charge to take advantage of a long pipe at mid-range RPM. This produces a ram air effect that increases engine torque at mid range. At high speed the change over valve switches allowing the engines breathing dynamics to switch to the short air pipes.







This change enables additional power output at the upper RPM range. The change over valve is held normally open by spring pressure and closed by vacuum. Control of the DISA solenoid is an output function of the ECM. DISA is the intake manifold arrangement on the M42 and M44 that provides the advantages of both long and short intake pipes.







- The M42 intake manifold incorporates a non replaceable brass change over valve. The components of the system (vacuum motor; solenoid, reservoir and check valve) are available separately.







- The M44 intake system uses a unitized replaceable DISA assembly.

The components of this system perform the same function as the M42 system but are encapsulated into one housing which must be replaced as a unit if necessary.

Programming







M42: The M1.7 Engine Control Module is programmed to activate the change over solenoid below 4,840 RPM. When activated the solenoid applies vacuum to the change over valve and the valve closes, providing the long pipe effect.

Above this RPM, the solenoid is switched off and the change over valve opens, providing the short pipe effect.







On decel, the solenoid will not be activated until 4,760 RPM. This overlap prevents repeated opening and closing of the valve while driving at a constant engine speed of 4800 RPM.







M44: The engine speed at which the DISA changeover flap is opened has changed. The M5.2 control module opens the flap to provide the "short pipe" intake manifold characteristics within a range of 3300 to 4520 RPM. The range is varied depending on engine load.

These new parameters provide a greater utilization of the intake manifold's cylinder filling characteristics to further enhance the torque curve of the M44 engine.