The settlement between the engine makers and the U.S. Environmental Protection Agency last fall resulted in a rewriting of the EPA test procedure. The old test cycle included a so-called transient test, which was designed to simulate urban driving conditions (a combination of driving cycles from New York and Los Angeles freeways).

EPA-certified diesel engines met the requirements of this cycle, but also had programmed into them different fuel maps for steady-state (highway) driving conditions. This optimized the engines for fuel economy during over-the-road use, but created higher NOx emissions.

In the wake of the settlement and the controversy over the old test procedures, the EPA revised its test cycle to include 12 steady-state test points. EPA also has reserved the right to test at undisclosed throttle and load values as additional audit points. And engine makers are required to recalibrate engines that come in for overhaul.

But what about performance in the real world, right now? The tougher NOx limits imposed on 1999 engines haven’t been a big deal for most manufacturers. Initially, many believed there would be a fuel economy penalty, but most now say that if there is a fuel penalty, it will hardly be measurable.

Caterpillar was already in compliance with the new 1999 regulation when it became effective at the beginning of the year, and fully expects to meet the 2002 emissions targets. While the company has made revisions to engine timing, the fuel economy penalty is negligible and less than most users will be able to measure. Cat is developing kits to be used at normal rebuild or overhaul to bring engines built between 1993 and 1998 into compliance with the rebuild emissions levels.

Cummins takes an identical position. It says it has no problem meeting the new NOx requirement and that as far as the customer is concerned, fuel economy will change either very little or, in some cases, actually improve.

Detroit Diesel has been quiet about the impact of the new steady-state tests on its engines, but vice-chairman Lud Koci has said that the company’s engines meet the regulations and guidelines. However, DDC engines have been fuel economy leaders and potentially have the most to lose under the new EPA testing procedures.

Mack says the move to the new 1999 levels has been seamless. Since a large proportion of its production has continued to be mechanical engines, operators moving to electronically controlled engines can expect significant fuel economy gains whatever the strategy employed in the electronics. According to chief engineer Steve Homcha, Mack has been building the 1999-level engines since September last year and there have been no problems.

Navistar International says drivers shouldn’t notice any difference in its 1999 engines. The engines go forward with no performance changes, though the company hints there are some big things coming mid-year, unrelated to the emissions agreements. Navistar has boasted about its clean engines in the past and notes that it even dropped exhaust catalysts in California back in October.

Volvo says there will be some ratings changes through the year, but they are more in response to market pressures than the EPA agreement. Drivers will see no changes, and president Marc Gustafson says the customer will not see any added costs passed on, either.