Section 1051.615 - What are the special provisions for certifying small recreational engines?(a) You may certify ATVs with engines that have total displacement of less than 100 cc to the following exhaust emission standards instead of certifying them to the exhaust emission standards of subpart B of this part:(1) 25.0 g/kW-hr HC + NOX, with an FEL cap of 40.0 g/kW-hr HC + NOX.(b) You may certify off-highway motorcycles with engines that have total displacement of 70 cc or less to the following exhaust emission standards instead of certifying them to the exhaust emission standards of subpart B of this part: (1) 16.1 g/kW-hr HC + NOX, with an FEL cap of 32.2 g/kW-hr HC + NOX.(c) You may use the averaging, banking, and trading provisions of subpart H of this part to show compliance with this HC + NOX standards (an engine family meets emission standards even if its family emission limit is higher than the standard, as long as you show that the whole averaging set of applicable engine families meet the applicable emission standards using emission credits, and the vehicles within the family meet the family emission limit). You may not use averaging to meet the CO standards of this section.(d) Measure steady-state emissions by testing the engine on an engine dynamometer using the equipment and procedures of 40 CFR part 1065 with either discrete-mode or ramped-modal cycles. You must use the type of testing you select in your application for certification for all testing you perform for that engine family. If we test your engines to confirm that they meet emission standards, we will do testing the same way. If you submit certification test data collected with both discrete-mode and ramped-modal testing (either in your original application or in an amendment to your application), either method may be used for subsequent testing. We may also perform other testing as allowed by the Clean Air Act. Measure steady-state emissions as follows:(1) For discrete-mode testing, sample emissions separately for each mode, then calculate an average emission level for the whole cycle using the weighting factors specified for each mode. In each mode, operate the engine for at least 5 minutes, then sample emissions for at least 1 minute. Calculate cycle statistics for the sequence of modes and compare with the specified values in 40 CFR 1065.514 to confirm that the test is valid.(2) For ramped-modal testing, start sampling at the beginning of the first mode and continue sampling until the end of the last mode. Calculate emissions and cycle statistics the same as for transient testing.(3) Measure emissions by testing the engine on a dynamometer with one or more of the following sets of duty cycles to determine whether it meets applicable emission standards: (i) The following duty cycle applies for discrete-mode testing: Table 1 of § 1051.615-6 -Mode Duty Cycle for Recreational Engines
| Mode No. | Engine speed
(percent)1 | Torque
(percent)2 | Minimum time in mode
(minutes) | Weighting factors |
| 1 | 85 | 100 | 5.0 | 0.09 |
| 2 | 85 | 75 | 5.0 | 0.20 |
| 3 | 85 | 50 | 5.0 | 0.29 |
| 4 | 85 | 25 | 5.0 | 0.30 |
| 5 | 85 | 10 | 5.0 | 0.07 |
| 6 | Idle | 0 | 5.0 | 0.05 |
1 Percent speed is percent of maximum test speed.
2 Percent torque is percent of maximum torque at the commanded test speed.
(ii) The following duty cycle applies for ramped-modal testing: Table 2 of § 1051.615 -Ramped-modal Cycle for Testing Recreational Engines
| RMC mode | Time | Speed
(percent)1 2 | Torque
(percent)2 3 |
| 1a Steady-state | 41 | Warm Idle | 0. |
| 1b Transition | 20 | Linear Transition | Linear Transition. |
| 2a Steady-state | 135 | 85 | 100. |
| 2b Transition | 20 | 85 | Linear Transition. |
| 3a Steady-state | 112 | 85 | 10. |
| 3b Transition | 20 | 85 | Linear Transition. |
| 4a Steady-state | 337 | 85 | 75. |
| 4b Transition | 20 | 85 | Linear Transition. |
| 5a Steady-state | 518 | 85 | 25. |
| 5b Transition | 20 | 85 | Linear Transition. |
| 6a Steady-state | 494 | 85 | 50. |
| 6b Transition | 20 | Linear Transition | Linear Transition. |
| 7 Steady-state | 43 | Warm Idle | 0. |
1 Percent speed is percent of maximum test speed.
2 Advance from one mode to the next within a 20-second transition phase. During the transition phase, command a linear progression from the torque setting of the current mode to the torque setting of the next mode.
3 Percent torque is percent of maximum torque at the commanded test speed.
(4) During idle mode, operate the engine at its warm idle speed as described in 40 CFR 1065.510 .(5) For the full-load operating mode, operate the engine at wide-open throttle.(6) See 40 CFR part 1065 for detailed specifications of tolerances and calculations.(e) All other requirements and prohibitions of this part apply to these engines and vehicles. 67 FR 68347 , Nov. 8, 2002, as amended at 70 FR 40503 , July 13, 2005; 73 FR 59254 , Oct. 8, 2008