How CDA compares to LIVC in terms of net CO2 and thermal management effect? Eaton study of the two technologies on 11L commercial engine.

Diesel engines for commercial vehicles are called to deal with a big challenge as in the near future and in all the regions of the world new vehicles sold must meet more stringent limits for nitrogen oxides (NOx) emissions and simultaneously must reduce fuel consumptionand carbon dioxide (CO₂) emissions. The full engine is under scrutiny and the Variable Valve Actuation system is a building block of the strategy to meet the new emission limits. Several studies can be found on this topic where cylinder deactivation (CDA) and/or or late intake valve closing (LIVC) are measured in combination with new engine calibration, new aftertreatment systems, additional thermal management methods. But what is the net contribution of CDA vs LIVC? To answer this question Eaton, in collaboration with FEV, a leader in the design and development of advanced powertrains, has launched an investigation on a commercial engine with its aftertreatment system, by replacing standard valve train with Eaton switchable rockers capable of delivering either CDA or LIVC.

A commercial 11-liter diesel commercial engine DOHC (Figure 2) has been equipped with Eaton VVA system capable of switchable LIVC on all the cylinders and CDA on 3 over 6 cylinders. The engine was installed on a dyno at FEV, and the investigation has run through three different phases:

Focusing on thermal management effect and fuel saving (Figure 4), the CDA is showing a much higher temperature increase of exhaust gases vs LIVC (up to 175°C vs 20°C) while maintaining fuel consumption low (peak of 10% reduction). But thanks to the higher exhaust.

 

Mass flow in LIVC mode, and to the wider range of usage of LIVC vs CDA, the Miller lift strategy can still provide interesting advantages depending on the engine application and usage.

The test indicated NOx and CO2 benefits for CDA and LIVC compared to base engine mode calibration and measured for three different homologation cycles. (Figure 5) Overall, the CDA shows a reduction of NOx up to 38% vs 13% of LIVC, thanks to exhaust gasses temperature increase. And this is delivered while simultaneously reducing CO2 emission (-2,7% for CDA vs -0,6% for LIVC), on the 3 homologation cycles investigated.