HATZ 4L41C and 4M41 multi-cylinder engines with drastically reduced nitrogen oxide content
As from 2008, EPA Tier 3 will apply to engines with power ratings from 37 kW onwards, and that will include the four-cylinder models from the HATZ L + M range. This is a multi-cylinder format in a modular system, which as the 4L41C is used in the fully encapsulated SilentPack version for the most widely differing applications. And to make sure that first-time users can be absolutely confident of planning reliability, development work was completed last year.
These regulations from the US Environmental Protection Agency (EPA) mean that, for the first time, HATZ has been obliged to work with an exhaust gas recirculation system. Integrating this module into the SilentPack capsule of the 4L41C, in every cubic centimetre is already used, was a major challenge for everyone concerned.
Dipl.-Ing. Erich Eder and his staff had to break a really vicious circle:
“First of all, we had to deal with the particulate value, which had to be brought down from 0.4 to 0.3 g/kWh. At first glance, that might seem like a small step – except that the previous value was already at this extremely low level.”

Nitrous oxides had to be reduced by 37 percent

When it comes to nitrous oxides, the NOx value, the regulations take on a whole new dimension. The requirement was to bring the value down from 7.5 g to 4.7 g/kWh, a massive jump of 37 percent, which could only be achieved by the exhaust gas recycling system (AGR) already referred to. “In practice, what that meant was our having to be disproportionately better with regard to particulate values, because the recycling system required for the NOx limit means that the particulate values start to rise again,” explains Dipl.-Ing. Erich Eder. “In order to be able to maintain the required value of 0.3 g/kWh, the engine without recycling may achieve limit values of maximum 0.2 g/kWh, and better still 0.1 g/kWh, so that in the final analysis the 0.3 g/kWh required will not be exceeded due to the exhaust gas recycling.”
As well as this, both versions are to be fitted with a recycling valve, which is actuated electronically by an ignition map. The reason for this is that under full load the engines have a low recycling rate (some 5 percent), while at part load a high rate of 35 to 40 percent is needed.