The Constant-Speed Variable-Load Cycle (CSVL) is a transient test developed by the US EPA for constant-speed engines. The test was a part of the US EPA Tier 4 proposal signed on April 15, 2003, but was not included in the final Tier 4 rule adopted in May 2004. The test has never been used for regulatory testing and has only historical significance.
The cycle is an engine dynamometer schedule of total duration of about 1200 seconds. The speed and torque during the CSVL test are shown in the following chart.
Figure 1. CSVL Cycle For Constant Speed Engines