sentences:  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.In their challenge, EMA stated that to determine whether an engine meets a primary emission standard, engines are tested and assessed using a standardized 20-minute emissions laboratory test known as the Federal Test Procedure.The NTE, by contrast, has no specified test procedure and potentially could apply over an almost infinite number of test conditions.