Exhaust System: Description and Operation

Introduction M56 2.5L SULEV Engine

The 6-Cylinder M56 SULEV (Super Ultra Low Emission Vehicle) is available on a limited (by state) basis in the E46/2, E46/3 and E46/4.

SULEV models (E46 sedan, coupe and sportwagon all with automatic only) will be sold in
California, New York and Massachusetts as 2003 models and in Vermont starting in 2004
model year. In addition these vehicles are certified as PZEV (Partial Zero Emissions Vehicles).

PZEV regulations include:
- Vehicles must meet SULEV tailpipe emissions standard (approx. 1/5 of ULEV standards)
- Vehicles conform to Zero Evaporative Emissions
- Vehicles subject to extended OBD regulations.
- Emission relevant components warrantied for 15 years or 150,000 miles M56 Engine.

The following components are used to achieve SULEV and Zero Evaporative Emission
requirements:
- Pistons Revised to change spark travel path.
- Catalytic Converters Ceramic carriers with high cell density for better Warm Up Control.
- Oxygen Sensors Planar wide band O2 sensors in front of the cats
- Vanos Positioning changed during start up for improved start up and emissions
- Fuel Pump Control Revised with raised pressure and more accurate flow control
- Fuel Injectors New design for improved fuel flow and higher working pressure
- Fuel System All metal fuel system components made of stainless steel
- Air Intake System Revised to block HC escape
- Crankcase Ventilation Revised
- Secondary Air System Mass air flow sensor to monitor secondary air flow
- Cooling System Revised to reduce Ozone levels.

Catalytic Converters
The catalysts attached in direct proximity to the engine and are equipped with ceramic(s) carriers in high cell density technology. These converters reach operating temperature faster and offer quicker control of exhaust emissions.
Vehicles are also equipped with dual downstream converters.


Oxygen Sensors
The M56 engine uses four Oxygen sensors, two planar broadband sensors upstream of the converter and two sensors downstream.
The planar broadband sensor reach operating temperature very fast and are able to effect fuel mixtures in approximately 5 seconds.

Fuel Pump System
Fuel system operating pressure is increased to 5 Bar.
The fuel pump is controlled by the Fuel pump control unit, based on engine demand as received from the DME over the Lo-CAN. The fuel pump control unit additionally receives information over the K-Bus, specifically crash information from the MRS.

Fuel Injectors
Nozzle diameter of the fuel injectors has been reduced and the installation angle has been changed. The injectors were also adapted to perform at the higher system operating pressure. Injectors screw into the rail and a tap to test pressure readings is NOT provided.

Secondary Air
The secondary air pump has been revised to improve its response time in cold weather starting situations. A HFM (Hot Film Air Mass Meter) has been added to the secondary air system to monitor air volume pumped into the exhaust for more accurate control of the NOx emissions.

Fuel System Components
1. DMTL
2. Pressure Pipe
3. Charcoal canister
4. Breather Pipe
5. Evaporation Line
6. Fuel Fill Line
7. Fuel Tank
8. Fuel Tank Vent Line

In order to meet the Zero Evaporative Emission requirement, the fuel system was completely revised. The fuel tank, tank filler neck, charcoal canister, fuel rail and tank ventilation valve are all made of stainless steel. When perform repairs on the fuel system, it is imperative that all fitting's remain clean and that the proper tightening torques are observed. The fuel tank is manufactured of high grade steel and completely coated to meet the requirements of a minimum durability of 15 years.

The fuel tank can be exchanged only as a complete unit.

Cooling System
The radiator of the E46 SULEV looks similiar to the standard E46 radiator. The surface of the cooling fins are coated with a special "PremAir" coating. The coating consists of multiple porous layers of a catalytic surface. The task of the catalyst coating is to convert Ozone into Oxygen.

Transmission
New 6 speed manual transmissions will soon be available for all E46 models except the xi. The 6 speed will be available as the H-SMG as well. Refer to the E85 Training Manual for more information.