Emissions Management M54B25 / M54B30 Ultra Low Emission Vehicle II (Ulev II)
Emissions Management M54B25 / M54B30 Ultra Low Emission Vehicle II (ULEV II)LEV II Amendments to Low Emission Vehicle regulations
At its November 1998 meeting, the Air Resources Board (ARB) amended California Low Emission Vehicle (LEV) regulations. The new amendments, known as LEV II, will advance the states clean air goals through improved emission reduction standards for automobiles. The ARE first adopted LEV standards in 1990.These first LEV standards run from 1994 through 2003.
LEV II regulations, running from 2004 through 2010, represent continuing progress in emission reductions. As the states passenger vehicle fleet continues to grow and more sport utility vehicles and pickup trucks are used as passenger cars rather than work vehicles, the new, more stringent LEV II standards are necessary for California to meet federally mandated clean air goals outlined in the 1994 State Implementation Plan (SIP).
LEV II brings the advanced emission controls of passenger cars to light trucks and sport utility vehicles;
^ Near-zero evaporative emissions
^ Advanced electronic engine management and on-board diagnostic systems
^ More efficient catalysts
^ Increased engine durability
The SIP is the states road map to attain federal clean air standards by 2010 and includes among its measures strategies to further reduce air pollution from automobiles and other mobile sources. When LEV II is fully implemented in 2010, it is estimated that smog forming emissions in the Los Angeles area will be reduced by 57 tons per day, while the statewide reduction will be 155 tons per day.
The U.S. EPA has proposed the adoption of more stringent Tier 2 (II) exhaust emission standards to start with the 2004 model year. The current federal evaporative emission standards are very similar to the current California standards. The more stringent California LEV I and LEV II programs are necessary to attain the national and state ambient ozone standards, and to fulfill the requirements of state and federal law.
Evaporative Emissions Standards
Evaporative emissions from motor vehicles account for approximately half of the reactive organic gas (ROG) motor vehicle emission inventory in the state, and are classified into three types running loss, hot soak and diurnal emissions.
^ Running loss emissions occur when the vehicle is driven.
^ Hot soak emissions occur immediately after a fully warmed up vehicle is stationary with the engine turned off.
^ Diurnal (daily, happening every day) emissions occur when a vehicle is parked and are caused by daily ambient temperature changes. Most of these emissions result during increasing ambient temperatures which cause an expansion of the vapor in the fuel tank.
Exhaust Emission Reductions
The LEV II amendments include three major interrelated elements designed to reduce to exhaust emissions:
^ Restructuring the light duty truck category so that most SUVs, minivans and pickup trucks are subject to the same low emission vehicle standards as passenger cars
^ Strengthening the NOx standard for passenger car and light duty truck LEVs and ULEVs, and changing other emission standards
^ Establishing more stringent 2004 and subsequent model year phase in requirements for passenger cars, light trucks and medium duty vehicles. They also contain various other changes, including elimination of the TLEV standard after the 2003 model year.
The LEV II Amendments
The LEV II amendments affect passenger cars, light duty trucks, and medium duty vehicles. The main elements are:
^ Extension of passenger car emission standards to heavier sport utility vehicles and pick up trucks (with gross vehicle weight up to 8,500 pounds) which formerly had been regulated under less stringent emission standards.
^ Extension and tightening of the fleet average emission standards during 20042010 (a fleet includes all new vehicles from an auto manufacturer)
^ Creation of a new super ultra low emission vehicle (SULEV) category for light duty vehicles (SULEVes will only emit a single pound of hydrocarbons during 100,000 miles of driving about the same as spilling a pint of gasoline)
^ Significantly lower oxides of nitrogen emission standards for the low and ultra low emission vehicle categories, a reduction of 75% from the current LEV standards
^ Increased emission control durability standards from 100,000 miles to 120,000 miles for passenger cars and light trucks
^ Further reduction of evaporative emissions
^ Creation of partial zero emission vehicle (ZEV) credits for vehicles that achieve near zero emissions. The credits would include full ZEV credit for a stored hydrogen fuel cell vehicle, 0.7 credit for methanol reformer fuel cell vehicles, 0.4 credit for a compressed natural gas SULEV and 0.2 for a gasoline fueled SULEV
^ Changes in how the smog index is calculated
^ Amendments to the zero emission and hybrid electric vehicle test procedures
^ Removal of a less stringent emission standard that would have resulted in increased sales of new diesel cars, pickups, and SUVs.
E60 Evaporative Emissions
The control of the evaporative fuel vapors (Hydrocarbons) from the fuel tank is important for the overall reduction in vehicle emissions. The evaporative system has been combined with the ventilation of the fuel tank, which allows the tank to breath (equalization). The overall operation provides:
^ An inlet vent, to an otherwise "sealed" fuel tank, for the entry of air to replace the fuel consumed during engine operation.
^ An outlet vent with a storage canister to "trap and hold" fuel vapors that are produced by the expansion/aporation of the fuel in the tank, when the vehicle is stationary.
The canister is then "purged" using the engine vacuum to draw the fuel vapors into the combustion chamber. This "cleans" the canister allowing for additional storage. Like any other form of combustible fuel, the introduction of these vapors on a running engine must be controlled.
The ECM controls the Evaporative Emission Valve which regulates purging of evaporative vapors. The evaporative system must be monitored for correct purge operation and Leak Detection.
The E60 fuel tank design reduces the potential evaporative emissions. This design reduces the number of external connections and openings by increasing the amount of "in tank" or integral components including molding the filler pipe to the tank. In addition, the plastic walls of the fuel tank are made up of several layers.
Note: The distinction between the following vent gases:
^ Service vent gases service vent gases are created at high ambient temperatures by heating of the fuel.
^ Filler vent gases filler vent gases are created by the air displaced by fuel during refuelling.
Service Venting System
The service venting system is integrated in the tank system and ensures pressure compensation in the tank for the following situations:
Reduction of Excess Pressure
Excess pressure is generated by heating of fuel. The gases rising from the tank flow through the service vent valves and the vent lines to the activated carbon filter.
Compensation of Negative Pressure
Negative pressure is generated by the fuel pump pumping off the fuel. The air is routed in the opposite direction for pressure compensation. Fresh air is routed to the fuel tank via the DMTL fresh air filter on the activated carbon filter.
Valves for Ventilation and Venting
Service Vent Valves
The fuel tank incorporates 2 service vent valves with a rollover function: if the car is inclined at an angle exceeding 45° (impending or actual rollover situation), the floats in the service vent valves close off the vent apertures. This prevents any fuel from escaping through the activated carbon filter.
A compensating volume is required in the fuel tank for the service venting function. This compensating volume is the space above the fuel level when the fuel tank is completely full (approximately 6 liters). The compensating volume remains unfilled when automatic cutout of the fuel pump nozzle is triggered.
Pressure Relief Valve
Any damage to the vent lines or the activated carbon filter may result in a pressure increase in the fuel tank. To prevent such a pressure increase, the filler cap incorporates a 300 mbar pressure relief valve.
Filler Venting System
Refueling
The following safety requirements are met when the tank is filled:
^ Grounding The filler neck is provided with a metal bayonet collar which accommodates the filler cap or the fuel pump nozzle. The filler neck is grounded by the cap or fuel nozzle insertion.
^ Prevention of fuel sloshing back A slosh baffle is fitted where the filler neck enters the tank. This prevents the fuel from sloshing back into the filler pipe.
On-Board Refueling Vapor Recovery (ORVR - DM TL Equipped Vehicles)
The ORVR system recovers and stores hydrocarbon fuel vapor during refueling. When refueling the E60, the pressure of the fuel entering the tank forces the hydrocarbon vapors through the Filling Vent Valve (14) and the large tank ventilation line into the Carbon Canister (17). The HCs are stored in the Carbon Canister and the system can then "breathe" through the DM TL and the fresh air filter.
Note: A small diameter connection to the filler neck is provided and is necessary for checking the filler cap/neck during Evaporative Leak Testing.
The ventilation continues until the rising fuel level lifts the float in the Filling Vent Valve (14) and closes the outlet. When the ventilation outlet is closed, a pressure cushion (vapor area) is created in the fuel tank. This creates a backup of fuel into the filler neck and the tank is full.
This leaves a vapor area of approximately 6 liters above the fuel level. This area provides integral liquid/vapor separation. The vapor condensates separate and drain back into the fuel. The remaining vapors exit the fuel tank (when sufficient pressure is present) through the Service Vent Valves (15 & 16) to the Carbon Canister.
Note: The Service Vent Valves are also equipped with protection floats in the event of an "overfill" situation.
E60 Exhaust Emissions
The combustion process of a gasoline powered engine produces Carbon Monoxide (CO), Hydrocarbons (HO) and Oxides of Nitrogen (NOx).
^ Carbon Monoxide is a product of incomplete combustion under conditions of air deficiency. CO emissions are dependent on the air/fuel ratio.
^ Hydrocarbon are also a product of incomplete combustion which results in unburned fuel. HO emissions are dependent on air/fuel ratio and the ignition of the mixture.
^ Oxides of Nitrogen are a product of peak combustion temperature (and temperature duration). NOx emissions are dependent on internal cylinder temperature affected by the air/fuel ratio and ignition of the mixture.
Control of exhaust emissions is accomplished by the engine and engine management design as well as after treatment.
^ The ECM manages exhaust emissions by controlling the air/fuel ratio and ignition.
^ The ECM controlled Secondary Air Injection further dilutes exhaust emissions leaving the engine and reduce the catalyst warm up time.
^ The Catalytic Converter further reduces exhaust emissions leaving the engine.
Secondary Air Injection
Injecting ambient air into the exhaust stream after a cold engine start reduces the warm up time of the catalysts and reduces HO and CO emissions. The ECM controls and monitors the Secondary Air Injection.
An Electric Secondary Air Pump and Air Injection Valve direct fresh air through an internal channel in the cylinder head into the exhaust ports.
The Air Injection Valve is opened by air pressure (from the pump) and is closed by an internal spring.
The secondary air pump is equipped with an additional intake hose (4) to accommodate a secondary air filter with the mini HFM (3). The mini HFM is secured in the secondary air cleaner with two screws.
Mini Hot Film Air Mass Sensor (HFM)
A compact mini hot film air mass sensor (HFM manufactured by Siemens) is used in the secondary air system for the M54 in the E60 (US market).
The mini HFM detects the air mass supplied by the secondary air pump. This function monitors the secondary air system for OBD compliance.
When the mini HFM detects no air mass or insufficient air mass, a fault is stored in the ECM and the Malfunction Indicator Light (MIL) is activated.
The mini HFM has a compact pipe shaped design with O-ring connections.
The Malfunction Indicator Light ( MIL) will be illuminated under the following conditions:
^ Upon the completion of the next consecutive driving cycle where the previously faulted system is monitored again and the emissions relevant fault is again present.
^ Immediately if a Catalyst Damaging fault occurs.
The illumination of the light is performed in accordance with the Federal Test Procedure (FTP) which requires the lamp to be illuminated when:
^ A malfunction of a component that can affect the emission performance of the vehicle occurs and causes emissions to exceed the standards required by the (FTP).
^ Manufacturer-defined specifications are exceeded.
^ An implausible input signal is generated.
^ Catalyst deterioration causes HC emissions to exceed the standard (FTP) limit.
^ Misfire faults occur.
^ A leak is detected in the evaporative system, or purging is defective.
^ ECM fails to enter closed loop oxygen sensor control operation within a specified time interval.
^ Engine control or automatic transmission control enters a limp home operating mode.
^ Ignition is on (KL15) position before cranking = Bulb Check Function.
Within the BMW system the illumination of the Malfunction Indicator Light is performed in accordance with the regulations set forth in CARE and as demonstrated via the Federal Test Procedure (FTP).
The Malfunction Indicator Light can be diagnosed with an aftermarket Scan Tool that allows Technicians without BMW Special Tools or Equipment to Diagnose an emission system failure.
With the use of a universal scan tool, connected to the OBD DLC Located in the drivers side lower a pillar area) an SAE standardized DTC can be obtained, along with the condition associated with the illumination of the Malfunction Indicator Light.
Using the DlSplus or GT1, a fault code and the conditions associated with its setting can be obtained prior to the illumination of the "Malfunction Indicator Light".
There is no direct connection to the OBD diagnostic connector. The ECM is connected to the SGM via the PTCAN Bus. The OBD diagnostic connector is connected to the SGM via the Diagnosis Bus.
The hhard wire shown above between the CAS2 and the PTCAN control modules is the KL15 (w up) signal.