CNH Selective Catalytic Reduction (SCR) – Tier 4a Emission Strategy

Technical Highlights

• Manufacturer: CNH Industrial (Case & New Holland)

• Engine Family: FPT NEF Tier 4a Diesel Engines

• Document Type: Factory Emission System Presentation

• Date: September 2013

• Slides: 46

• System Type: Selective Catalytic Reduction (SCR) using Diesel Exhaust Fluid (DEF / AdBlue)

• Emission Compliance: Tier 4a (Interim) and Tier 4b (Final) for off-road diesel engines

Coverage

• Introduction to Tier 4 Regulations

  • EPA emission standards and phasing (Tier 1–4b)

  • 90% reduction in PM and NOx required for Tier 4b

  • Comparison of CO, HC, NOx, and PM limits across engine power ranges

• Pollutant Formation and Control

  • Chemistry of NOx and PM generation during diesel combustion

  • Relationship between temperature and NOx emissions

  • Acid rain and health effects from PM inhalation

• Emission Solutions for Tier 4

  • Comparison: SCR vs CEGR/DPF (Exhaust Gas Recirculation with Diesel Particulate Filter)

  • Advantages of SCR on 850M–2050M dozers (fuel efficiency, less maintenance)

• Selective Catalytic Reduction (SCR) Overview

  • 5% fuel savings through high-efficiency combustion

  • Conversion of NOx to nitrogen (N₂) and water (H₂O) by DEF injection

  • Core components: DEF tank, supply module, injector, mixing baffle, and catalyst

• Component Layout and Hydraulic Scheme

  • Diagram showing DEF flow circuit between DCU (Dosing Control Unit), Supply Module, and Injector

  • Pressure range: 5 bar at dosing module (Bosch SM)

  • Sensors: NOx, temperature (upstream/downstream), DEF level, and humidity

• DEF (AdBlue) System and WEMA Tank Module

  • 32.5% urea / 67.5% distilled water composition

  • Freezing point −11°C; includes coolant-heated WEMA probe

  • Magnetic fill neck prevents misfuelling and ensures expansion space

• DEF Injector and Mixer Assembly

  • Bosch dosing valve (200 g/h to 9 kg/h)

  • Active cooling and 54° spray angle

  • Mixer ensures proper DEF vaporization before catalyst

• Filtration and Maintenance Intervals

  • Inline pre-filter (100 µm Voss) – clean/replace every 600–1200 hrs

  • Main filter – replace every 1200 hrs

  • Injector filter – no maintenance required

• System Logic and DNOx Function Sequence

  • Pressure build-up → Reverting valve check → Normal dosing → Afterrun purge

  • Afterrun (90 seconds): reverses flow to clear DEF lines

• Electronics and Diagnostics

  • ECU & DCU control with 5 sensors and 2 actuators

  • EST (Electronic Service Tool) and EASY software integration

  • Urea Dosing System Test (UDST) for performance validation

• Faults, Inducements & Tamper Protection

  • DEF low level, poor quality, SCR failure triggers performance limits

  • Anti-tamper algorithm prevents software downgrades

  • Severe inducement = 50% torque reduction + RPM limitation

Delivery

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