ToolFusion
📋 Case Study

John Deere S700 Series Combine Harvester — Repeated Parked Regen Failures in Cold Climates

Parked regen aborting at 35% completion due to urea crystallization and low exhaust temp ramp rate

🏗️ Project Overview

Large-scale grain operation in Manitoba, Canada

🎯 Challenge

Parked regen aborting at 35% completion due to urea crystallization and low exhaust temp ramp rate

🔧 Design Approach

Revised thermal management strategy: pre-heating via engine coolant bypass + extended idle warm-up protocol + DEF heater circuit voltage drop audit

📐 Design Diagram

John Deere S700 — Parked Regen Thermal Redesign Challenge: Parked regen aborts at 35% → Urea crystallization & slow ΔT_exh t_crystal = 18.2 min @ −22°C Q_deficit = 42.7 kW Design Approach: • Coolant bypass pre-heat • Extended idle warm-up • DEF heater voltage audit Engine Pre-heat DEF Heater Exh SCR ΔT ramp ↑ Challenge Solution Active component Heated subsystem

AI-generated project design illustration

📐 Key Calculations

Crystallization Threshold Time

t = (T_ambient − T_crystal) / k × R_th
Result: 18.2 min @ −22°C
Defines safe purge window before line blockage

Exhaust Energy Deficit

Q_deficit = m_dot_exh × Cp × (T_target − T_actual)
Result: 42.7 kW
Drives need for coolant-assisted heating

📊 Results

98% parked regen success rate restored; 0 unplanned shutdowns over 1,200 operating hours

💡 Lessons Learned

  • •DEF heater circuit resistance must be < 0.8 Ω at all connectors
  • •Idle warm-up must exceed 8 min before regen start in sub-zero conditions

✅ Key Takeaways

  • 1DEF heater circuit resistance must be < 0.8 Ω at all connectors
  • 2Idle warm-up must exceed 8 min before regen start in sub-zero conditions