Small Commercial Vehicle (SCV) is an emerging Commercial Vehicle (CV) segment both in India and throughout the world. Vehicles in this segment have diesel engine of capacity less than 1 l and GVW of less than 3.5 t. Normally for the CV, engines are tested on engine dynamometer for emission test, but SCV are tested on chassis dynamometer as they are classified as N1.1 class vehicles. Hence SCV have to follow same emission regulations as diesel passenger cars. The main challenge is to meet BS-IV NOx and PM emission target together with high torque optimization along with required durability targets.
This paper addresses this challenge and reports the work carried out on an Indian SCV with 0.7 l naturally aspirated indirect injection diesel engine. The existing vehicle's aftertreatment system, which consists of a DOC and a partial flow particulate filter in close coupled plus under-body positions was replaced by a close coupled only solution by using advanced EnviCat® DOC and PM Metalit® (partial-flow deep-bed particulate filter). EnviCat® DOC has lower light-off temperature for CO, high NO to NO2 conversion and necessary HC storage required for cold start driving cycle. This change, which was applied to make the system more compact and light-weight, also offers benefit in terms of potential cost savings compared to the previous system. Highly efficient DOC substrates with suitable precious metal loading and improved PM Metalit® structures were evaluated.
The experiments also include coated PM Metalit® options for better SOF / Soot conversion and improved regeneration characteristics. High temperatures available at the close coupled location have benefitted in getting higher conversion efficiencies of CO and HC oxidation, and in addition have led to passive regeneration of particulate matter in the PM Metalit®, thereby facilitating in achieving BS-IV emission legislations without using any additional under-body after-treatment system.
Principles of PM Metalit® and its passive soot regeneration characteristics are also explained, in addition to reporting detailed profiles of temperatures, emissions and conversion efficiencies on BS-IV cycle for this application.