Not-To-Exceed

by the United States Environmental Protection Agency (EPA) ensures that heavy-duty truck engine emissions are controlled over the full range of speed and load combinations commonly experienced in use.

[2] As part of the resulting consent decree settlement with the EPA, these manufacturers were assessed heavy fines and were subjected to new emissions standards which included NTE.

The fourth boundary is 30% of maximum power [4] A controversial issue is the applicability of the NTE limits to the real-world driving.

Concerns arose that performing this action could prove to be difficult, as each time the driver removes the foot from the accelerator pedal, or shifts gears on vehicles with manual transmission, the engine leaves the NTE zone.

In urban or suburban driving, this happens relatively often, to the point that NTE standards are applicable only a very small portion of the operation [5] or, in some cases, not at all.

Their preliminary findings echo those of WVU as they found that the time of engine operation in the NTE zone is rather low.

Controlling PM in this range of operation presents fundamental technical challenges which we believe can not be overcome in the 2004 time frame.

Specifically, the cylinder pressures created under these high speed and low load conditions are often insufficient to prevent lube oil from being ingested into the combustion chamber.

Each of those lawsuits challenged the legality and technological feasibility of certain engine emission control standards in EPA regulations now referred to as NTE requirements.

This, in the manufacturers' view, made it virtually impossible to ensure total compliance with the NTE—since there is no real or practical way to test an engine under all conceivable conditions—and so made the NTE both unlawful (the CAA authorizes EPA to adopt engine standards AND accompanying test procedures) and technically infeasible.

The parties agreed upon a detailed outline for a future regulation that would require a manufacturer-run heavy-duty in-use NTE testing ("HDIUT") program for diesel-fueled engines and vehicles.