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The development of technology suitable for meeting the CARB Ultra-low- emission-vehicle (ULEV) legislation has now become a main focus for vehicle manufacturers worldwide. This proliferation of interest is mainly a result of the increasing number of eastern US-states currently considering the adoption of CARB legislation and the indication that emission legislation in Europe and Japan for the turn of the century is likely to be of the same severity as CARB ULEV legislation. Current three way catalyst (TWC) emissions control technology suffers from low catalytic conversion efficiency of HC, CO and NOx pollutants during cold operation i.e. before catalyst light off. Cold start emissions generally contribute up to 70% of HC and CO tailpipe emissions during an FTP test. However, in some cases even early light-off of the catalyst, similar to hot operation is not sufficient to achieve catalytic conversion over a test cycle to reach ULEV emissions levels.

A project has been carried out to develop a practical G-DI vehicle with very low emissions; primarily assessed over the European EUDC cycle, but with emissions consistent with ULEV, Euro Stage IV and Japan 2000 legislation whilst maintaining acceptable driveability. A combined test bed and vehicle programme was conducted. Vehicle benchmarking established target emissions reduction areas and testbed work characterised the combustion system. The programme was based on a Mitsubishi Carisma GDI™ vehicle. The vehicle used a prototype Lean NOx Trap (LNT) based aftertreatment system. The Ricardo Vehicle Engine Management Prototyping System (VEMPS) Control System replaced the OEM ECU giving control of drive components and strategies to regenerate LNT of stored NOx were developed. Constant torque during regeneration spikes was achieved. The fuel economy penalty of different regeneration strategies was investigated.