Ultra Low NOx

Ultra Low NOx



The Ultra-Low NOx for Diesel project aimed to develop a base engine independent technology pathway demonstrating the CARB optional 90% reduction in tail-pipe NOx (compared to current legislation of 0.2g/bhp-h for on-highway trucks).  Ricardo quantified system cost, fuel penalty, pollutant, and other criteria trade-offs at the three lower optional legislation levels of 50%, 75% and 90%. The project also developed and demonstrated necessary know-how from controls and after-treatment technology to achieve 90% NOx reduction.

Customer Benefit

The primary benefit was the development of the base engine methodology to achieve the 90% reduction in tailpipe NOx compared to 2010+ on-highway truck levels whilst minimizing the fuel penalty to achieve that reduction. Additionally, the project aimed to understand the system cost and fuel penalty trade-offs for each of the optional lower NOx levels. This research enabled Ricardo to apply the solution synergistically with parallel research efforts to develop low CO2 technologies to create a complete engine and after-treatment solution for addressing future greenhouse gas and low NOx legislations our customers will need to meet.


The following technologies were explored throughout this project in relation to different sub systems of the related to NOx production:

  • After-treatment:
    • Cold NOx storage catalyst
    • SCR on filter
    • Close-coupled solutions
  • Thermal Management:
    • Heaters
    • Burners
    • Traditional throttle based systems
  • Advanced dosing:
    • Heated urea
    • Gaseous ammonia
    • Efficient mixing dosing
  • Controls:
    • Advanced NH3 sensor based storage models
    • Reference governor based dosing models


Please get in touch at [email protected] for more information about this project.