The objective of the Tier System is to deliver higher performance engine while reaching Near-Zero emission. In Tier 4, emission has to decrease 25x of Tier 1 while key differences from Tier 4 is as follow. Particle Matter(PM) is to decrease from 0.4 g/bhp.hr to .09 g/bhp.hr (175 bhp to 300 bhp) while NMHC+NOx(Non Methane Hydrocarbon plus Nitrogen Mono or DiOxide) is to decrease from 6.9 g/bhp.hr to 3.0 g/bhp.hr. While key Tier 3 is only at 0.15g for PM and 3.0g for NMHC+NOx. Advance Technologies have to be installed to archive high performance and low emission engine.
To archive this, it require both Pre and Post Exhaust treatment. In Pre Exhaust Treatment, Four key enablement include high-precision and high-pressure injection, high-efficiency combustion, cooled-EGR, and advance turbo. First, high-precision and high-pressure injection is to atomize fuel and result in better efficiency. Caterpillar focuses on Unit Injection(UI), which combine high pressure pump into individual injector. This can create final pressure up to 2,500 Bar. On another side, Cummins utilizes common rail design to archive such high pressure. This system requires combination of high and low pressure pump, with very small nozzle. Without proper maintenance, it may result in severe failure. For example, clogged fuel filter causes adequate fuel in high-pressure pump and permanently damage the pump, which is expensive. Secondly, high efficiency combustion archived by previous injector with higher tolerance parts such as piston ring, shaped piston, computer simulated combustion chamber and multi-stage cooling. This requires unprecedented properly maintenance by the books, without this it will fail. Thirdly, cooled-EGR recirculate hot exhaust gases, cool it and combine with intake air no only to lower combustion temperature but also to lowering NOx. Clogged EGR part or damage valve may result in high exhaust temperate and may damage related parts such as turbo or even the whole engine in the long run. Finally, advance turbo technology such as multi-stage turbo and Variable Turbine Geometry. Objective is to deliver efficient air flow at every RPMs by using computer controlled. This again is complex any small issue may damage the whole system. For example, fail EGR cause higher combustion temperature and damage the turbine, later its will start to damage the housing, and final is low or no power engine. These above technology is reliable but proper care and experienced technicians is unavoidable.
In Post Exhaust treatment, Selective Catalytic Reduction(SCR) uses for converting NOx in exhaust gas to Nitrogen Gas up to 90% Efficiency. It works by injecting Urea (Approx 5% of Diesel used)ahead of catalyst, This process convert Ammonia in exhaust stream with temperature above 392 Deg F(200 Deg C). The Ammonia reacts with Oxide of Nitrogen (NOx) over the SCR catalyst to form harmless Nitrogen and water. However, this system add complexity by adding Urea tank, leveling, injector and controller with diagnostic.
Diesel Particulate Filer(DPF) traps and incinerate Particulate Matter(PM) or Soot particle in diesel exhaust system with efficiency around 90-95%. The system made of porous ceramic in honeycomb structure which collects carbon soot. In passive Regeneration, when temperature reach 572 Deg F(300 Deg C), NO2, generated during combustion in this temperature, oxidizes carbon soot into Ash. In active regeneration, when soot trap inside is full and it causes back pressure, the engine inject added diesel during exhaust blow down cycle to increase heat to 1022 Deg F(550 Deg C) to rapidly oxidize soot into ash. Some design add precious metal for enhancing oxidation of hydrocarbons to achieve lower temperature in generating NO2. However, the system itself is extremely complex in active regeneration. For example, when certain part fails and active cycle stop to prevent excessive damage. In this case, the filter will be clog fast. As a result, added complexity, requires specialize skill and process to properly maintain the engine.
Here at S.Suvit Trading Ltd., Parts, we are working closely with top tier partners in above technologies, all official service papers must be trained to our technician. In addition, we research and develop extra maintenance and quality control process to make sure longevity of our product with highest possible standard. All key possible weakness must be checked thoroughly. For example, CAT HEUI Injection system use both both hydraulics and mechanic to create adequate pressure. If contamination is spotted in the part, all injectors must be removed and send it to our partner in the US for overhaul, while local Injector shop is not capable of overhauling this type. All parts related to the common failure must be replace to ensure long-life and lowest TCOs.
For further details, please contact our representative.