US Transient Cycle Versus ECE R.49 13-Mode Cycle

The potential of what is applicable today to measure the exhaust emissions of Heavy-Duty Diesel engines has been examined through extensive testing of the US Transient cycle and the ECE R.49 European 13-mode cycle. A careful analysis of the US Transient cycle demonstrates that only 15% of it represents true transient operation, for the majority of transients are relatively modest and thus their influence on gaseous as well as on particulate emissions is of little significance. Furthermore the US Transient cycle does not reflect the most common traffic situations. On the contrary, the 13-modes ECE R49 is representative of the driving conditions on European roads, particularly by correctly weighting of the peak torque speed. Compared to the Transient cycle, the ECE R.49 procedure is simpler and does not require expensive facilities. Tests carried out on 35 different engine configurations show that a correlation exists between particulates measured over the US Transient cycle and the ECE R.49.