The FTP (Federal Test Procedure) heavy-duty transient cycle is currently used for emission testing of heavy-duty on-road engines in the USA [CFR Title 40, Part 86.1333]. The transient test was developed to take into account the variety of heavy-duty truck and buses in American cities, including traffic in and around the cities on roads and expressways. The FTP transient test is based on the UDDS chassis dynamometer driving cycle. The cycle includes “motoring” segments and, therefore, requires a DC or AC electric dynamometer capable of both absorbing and supplying power.
The transient cycle consists of four phases: the first is a NYNF (New York Non Freeway) phase typical of light urban traffic with frequent stops and starts, the second is LANF (Los Angeles Non Freeway) phase typical of crowded urban traffic with few stops, the third is a LAFY (Los Angeles Freeway) phase simulating crowded expressway traffic in Los Angeles, and the fourth phase repeats the first NYNF phase. It comprises a cold start after a parking overnight, followed by idling, acceleration and deceleration phases, and a wide variety of different speeds and loads sequenced to simulate the running of the vehicle that corresponds to the engine being tested. There are few stabilized running conditions, and the average load factor is about 20 to 25% of the maximum horsepower available at a given speed.
The cycle is carried out twice and the second repetition is made with a warm start after a stop of 1200 s (20 min) on completion of the first cycle. The equivalent average speed is about 30 km/h and the equivalent distance traveled is 10.3 km for a running time of 1200 s. The variation of normalized speed and torque with time is shown in Figure 1.
Figure 1. FTP Transient Cycle
The average load factor of the FTP cycle is roughly 20-25% of the maximum engine horsepower available at a given engine speed. Heavy duty diesel engines tested on the FTP cycle produce medium to high exhaust gas temperatures. Generally, the temperature is at a medium level between 250 and 350°C, but there are some hot sections with temperatures reaching as high as 450°C.