Engine - M42 Production Changes: Overview
9230bmw01
Group 11
Engine
Bulletin Number
11 01 92 (2123)
Woodcliff Lake, NJ
March 1992
Product Engineering
SUBJECT:
1.8 Liter Four Cylinder Engine (M42) Changes
MODEL:
318i and 318iS E36
With the introduction of the M42 powered E36 models, the successful and proven M42 four cylinder engine has been revised.
The new M42 Engine includes a two-section "Differential Air Intake System" (D.I.S.A.) and an adaptive-selective knock control system as well as other design changes.
With these changes the revised M42 engine develops 137hp (103 Kw) at 6000 rpm and a maximum torque of 175 N-m (129 lb.ft.) at 4600 rpm. The increased torque in the medium speed range (5% increase) makes the engine considerably more flexible as compared to the E30 (M42) version.
The differential air intake system (DISA) offers the advantages of both short and long intake pipes, which contributes to improved power, torque and fuel efficiency.
The intake manifold is produced using a new low pressure chill casting process. This process permits thinner walls, reducing the weight of the intake system assembly. The system consists of four ram air pipes, branch pipes (with connecting flap valve), primary intake pipes and a plenum chamber.
In order to obtain more power at higher engine speeds (above approx. 4800/ min), the connecting flap valve between the intake air pipe assemblies for the two cylinder groups is opened. This largely eliminates the dynamic effect of the air in the primary intake pipes. The shorter ram air pipes now take over and yield greater power at the upper end of the engine-speed range.
The DISA connecting flap valve is actuated electro-pneumatically in response to a signal from the engine control module. The flap valve begins to open as engine speeds rise above 4840/min, and closes when the speed drops below 4760/min.
The action of the valve is deliberately delayed (hysteresis) to prevent it from opening and closing repeatedly within a short time.
The flap valve control system incorporates:
- a vacuum can with pneumatic actuator
- a vacuum reservoir
- a solenoid (electromagnetic) valve
- a non-return (check) valve
- various connecting hoses
In the part-load engine operating mode, the vacuum reservoir is evacuated by intake manifold vacuum. The connecting flap valve is kept closed by the vacuum can and pneumatic actuator.
If the engine speed of 4840/min is exceeded, the engine control module de-energizes (switches off) the solenoid valve. This vents the vacuum can, so that the flap valve can open.
As soon as the solenoid valve switches over again (when engine speed drops to 4760/min), the vacuum reservoir and the vacuum can are connected together again and the flap valve closes.
This form of control ensures that the connecting flap always remains open if there is any malfunction of the electro-pneumatic actuating mechanism, and therefore that full power output is guaranteed in the upper engine-speed range.
In other words, the flap valve's basic setting is "open".
The flap is held open or returned to the open position by two springs:
- 1 spiral spring on the flap shaft
- 1 helical spring in the vacuum (diaphragm) chamber
The solenoid valve is actuated directly by a high-power output stage in the engine control module. This output stage can accept a maximum electrical load of approx. 1 Amp.