Crankcase vacuum pump installed on Willys Super Hurricane Engine

Crankcase Evacuation System (CES)

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Overview

The Crankcase Evacuation System (CES) was developed to address engine blow-by gases, which can cause crankcase overpressure, oil leaks, and decreased engine efficiency. Traditional systems, such as the Draft Tube and Positive Crankcase Ventilation (PCV) systems, have limitations for high-performance engines. This project explores mechanical and electrical CES configurations to maintain a crankcase vacuum of 5 in·Hg at 10 CFM flow, ensuring optimal engine performance and environmental compliance.

Traditional Systems and Limitations

  1. Draft Tube System:
    • Uses Bernoulli’s principle to create a low-pressure zone for ventilation but is ineffective at low speeds.
    • Provides negligible crankcase vacuum at typical operating conditions.
  2. PCV System:
    • Relies on intake manifold vacuum to pull air through the crankcase, directing blow-by gases into the combustion process.
    • High-performance engines face challenges with PCV systems due to contamination and air-fuel ratio disruption, necessitating additional enhancements like oil separators.

CES Development and Testing

The project consisted of six test series focusing on various pump and motor configurations. Tests evaluated free flow, dead-head performance, and simulated blow-by scenarios under real-world conditions.

Key Findings

  1. Electric Drive Challenges:
    • Electrically driven pumps were tested extensively using 12V and 24V DC motors.
    • Motors at 14.2 VDC (standard automotive voltage) proved insufficient due to high power demands, inefficiency, and heat dissipation issues.
    • Tests revealed the impracticality of electric drives for sustained operation, especially at the required performance levels.
  2. Mechanical Drive Solution:
    • The project pivoted to a mechanically driven pump powered by the engine’s crankshaft.
    • This approach provided a more reliable power source and resolved issues with power limitations and heat generation.

Test Series Overview

Series I–III: Early Electric Drive Testing

  • Motors: Initial tests used underpowered DC motors, leading to overheating and poor performance.
  • Pumps: Moroso and Star Mini rotary vane pumps were evaluated.
  • Results showed the need for improved motor-pump compatibility and highlighted inefficiencies in free-flow and dead-head scenarios.

Series IV: Improved Electric Pump Testing

  • Used a more efficient Star Mini pump paired with a DC motor.
  • Demonstrated that smaller pumps with reduced displacement offered better performance at lower power levels.
  • Simulated blow-by tests showed 3–5 in·Hg vacuum at 6–8 CFM flow but highlighted overheating as a persistent issue.

Series V: Integration of a Speed Reducer

  • A 1.2:1.0 speed reducer was introduced, optimizing motor performance and reducing waste heat.
  • Tests demonstrated improved flow and vacuum consistency, but the electric motor still struggled to maintain performance under sustained loads.

Series VI: Transition to Mechanical Drive

  • Recognized the impracticality of electric systems in standard automotive voltage environments.
  • Focus shifted to crankshaft-driven pumps, ensuring reliable power delivery and better alignment with engine dynamics.

Lessons Learned

  1. Electric Drive Limitations:
    • Electrically driven CES is not viable at 14.2 VDC due to power and heat constraints.
    • Operating efficiency significantly drops with temperature increases, especially in high-temperature engine compartments.
  2. Mechanical Drive Benefits:
    • Mechanically driven systems eliminate reliance on the vehicle’s electrical system.
    • Crankshaft-driven pumps provide stable power and improved efficiency.
  3. Pump Performance:
    • The Star Mini pump outperformed the Moroso pump in terms of efficiency at lower flow rates.
    • Displacement and design differences between pumps greatly influence system performance.
  4. System Design Optimization:
    • Integration of speed reducers allows better matching of motor torque and speed to pump requirements.
    • Heat rise testing revealed waste heat as a critical limiting factor for motor longevity and efficiency.

Final Conclusions

  1. Electric CES:
    • While initial tests highlighted potential for electric pumps, the practical constraints of automotive electrical systems (14.2 VDC) rendered this solution impractical.
    • Further advancements in motor technology would be required to revisit this approach.
  2. Mechanical CES:
    • A crankshaft-driven pump proved to be the optimal solution, offering reliable performance without the limitations of electric motors.
    • This system achieved the desired 5 in·Hg vacuum at 10 CFM flow.
  3. Future Recommendations:
    • Custom pump designs tailored to specific engine requirements could further improve system efficiency.
    • Enhanced motor cooling and alternative drive configurations (e.g., hybrid systems) may address remaining challenges.

Summary

The CES project provides a comprehensive roadmap for developing robust crankcase evacuation systems where the goal is to eliminate road draft tubes used with older engine designs. While electric solutions were found impractical in the current automotive context, the mechanical drive approach demonstrated superior performance and reliability. This report serves as a valuable reference for engineers aiming to optimize crankcase ventilation for high-performance engines.

Click hear for the detailed engineering report.

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