To obtain approval for single-cylinder testing the manufacturer must rely on the provision for special test procedures (40 CFR 94.207). This requires a demonstration "that it is equivalent to the specified procedures." We will address the concern that single-cylinder testing may not be appropriate in some cases by evaluation of the individual situations under §94.27.
2. In-Use Testing
Before manufacturers produce engines, they certify that their engines will meet all the standards that apply, including the standards based on testing with the specified duty cycles and based on the broader Not-to-Exceed standards, throughout the useful life of the engines. We are interested in testing in-use engines to confirm that they are emitting within these standards. For any in-use testing for purposes of section 207(c), we would depend on receiving the permission of the owner to conduct the testing on that vessel. We could do this testing one of two ways. First, we could remove the engine from the vessel and test it on a laboratory dynamometer, much like the manufacturer's certification testing. This would be the most direct way to determine if an engine continues to meet the certification standards after the engine has been installed on a vessel. However, the cost of removing and testing engines this way would be extremely high and a ship operator may be unwilling to allow us to remove the engine from service for emission testing.
Onboard testing is a second type of in-use emission measurement. Being able to conduct emission testing onboard the vessel can make in-use testing more accessible since onboard testing eliminates the need for engine removal and minimizes the disruption of normal vessel operations. The goal is for us to accurately assess the emission performance of these engines when they are in service. We may use onboard emission testing to identify and hold manufacturers responsible for noncompliance with the emission standards (including the Not-to-Exceed limits). The Clean Air Act authorizes us to pursue an emission-related recall if we determine that a substantial number of engines, when properly maintained and used, do not conform to the regulations throughout their useful life. Noncompliance relates to meeting the emissions levels under the associated test procedures, as defined in the regulations. For example, the test procedure for the NTE emission standard calls for nominally steady-state operation within a specified zone of engine operation. In-use testing results may provide credible and probative information relevant to making a determination of compliance. We also recognize that the level of accuracy and precision of in-use testing is one of the key factors to take into account when making any such evaluation or determination of compliance. We believe such systems and procedures would provide a significant benefit to both the agency and the industry.
For marine diesel engines that expel exhaust gases underwater or mix exhaust gases with water, we require that manufacturers equip the engines with an exhaust sample port, where a probe can be inserted for in-use emission tests. It is important that the location of this port allows a well mixed and representative sample of the exhaust. The purpose of this provision is to simplify in-use testing.
3. Test Fuel
The test procedure, including the test fuel, must adequately represent in-use operation to ensure achievement of emission reductions in use. To facilitate the testing process, we generally define a range of specifications for a test fuel that is intended to represent in-use fuels. Marine diesel engines need to comply with emission standards on any fuel falling within the range of the test fuel specifications, with one modification described below. This section describes the test fuel we are specifying for Category 1 and Category 2 engines (see also 40 CFR 94.108). This test fuel is for all testing associated with the standards in this final rule, including certification, production-line, in-use, and NTE testing.
We are applying the recently finalized test fuel specifications for land-based nonroad diesel engines to marine diesel engine testing, with a modification to the sulfur specification as described below. We believe that largely adopting the nonroad fuel will simplify development and certification burdens for marine engines that are developed from land-based counterparts. The test fuel for marine diesel engine testing has a sulfur specification range of 0.03 to 0.80 weight-percent (wt%), which covers the range of sulfur levels observed for most in-use fuels. Manufacturers are generally responsible for ensuring compliance with the emission standards using any fuel within this range. Thus, they will be able to harmonize their marine test fuel with U.S. highway (&glt;0.05 wt%), nonroad (0.03 to 0.40 wt%), locomotive (0.2 to 0.4 wt%) and European testing (0.1 to 0.2 wt%). The full range of test fuel specifications are presented in Chapter 3 of the Final RIA.
We are setting a higher upper limit for the marine diesel engine sulfur specification (0.8 wt%) than was recently finalized for land-based nonroad engines (0.4 wt%), because there is some information available suggesting that marine fuels may have higher sulfur contents than land-based diesel fuels.4 Using ASTM specification D 2069 as a guide, we considered choosing an upper limit of 1.5 wt% sulfur. However, we are setting an upper limit on sulfur content of 0.8 wt%, because the available data show that most in-use marine fuels have sulfur levels lower than this. Moreover, it is not clear that PM emission could accurately be measured using the specified testing procedures, or if the correction factor would be accurate, if fuels with a sulfur content higher than 0.8 wt% are used.5
4 "In-Use Marine Diesel Fuel," Final Report by ICF Consulting Group for EPA, August 1999 (Docket A-97-50, document IV-A-4).
5 "Exhaust Gas Emission Measurements: A Contribution to a Realistic Approach," D. Bastenhof, dieselMAC, May, 1995.
We determined that the new PM standards are feasible based largely on the feasibility of the corresponding standards for land-based nonroad and locomotive applications, which have a 0.4 wt% sulfur upper limit for the test fuel. Since PM emissions are somewhat fuel sulfur-dependent, we do not believe it is appropriate to require compliance with the PM standards using fuel with a sulfur content above 0.4 wt%. We are therefore allowing a correction of PM emissions for testing with a fuel sulfur content greater than 0.4 wt%. Thus, the measured PM emissions for any test performed using fuel with a sulfur content of greater than 0.4 wt% may be corrected to the level that would have been measured if the fuel had a sulfur content of 0.4 wt%. This does not apply to systems using aftertreatment technologies, since the correction equation is not valid for those engines. This correction method is the same as that used for land-based nonroad engine testing to Tier 1 emission standards. Moreover, in the nonroad rulemaking, for engines rated over 37 kW certified to Tier 2 standards, we agreed to use only fuel with sulfur levels up to 0.2 wt% for our testing. Because Category 1 marine engines are mostly derived from land-based nonroad engines, we believe it is appropriate to extend this provision to Category 1 marine engines for the period during which they rely on land-based engines operating at Tier 2 emission levels.
