For the past several years, the MSRC Clean Transportation Funding program has offered incentives for the re-power of existing, unregulated off-road construction equipment operated with the jurisdication of the South Coast Air Quality Management District with new, CARB-certified lower emission diesel engines. This air pollution reduction strategy has been demonstrated to yield significant reductions in ozone precursor emissions, including hydrocarbon and oxide of nitrogen emissions, as well as reductions in fine diesel exhaust particulate, which has been designated as a Toxic Air Contaminant by CARB. In addition, the replacement of exisiting diesel off-road equipment engines with new CARB certified engines is very cost-effective; that is, a significant reduction in exhaust emissions is realized for each dollar of MSRC Clean Transportation Funding invested.
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The engine re-power work was performed on behalf of Larry Jacinto Construction by Johnson Machinery, a licensed regional Caterpillar distributor. Major elements of the engine re-power include the following:
Addition of Charge Air Cooler - A cost-effective strategy for reducing oxide of nitrogen (NOx) emissions is to reduce the inlet air temperature. This was accomplished by installing a separate inlet air cooling system on each vehicle;
Engines - The Caterpillar 631 was equipped with the 3408 Caterpillar engine with mechanical fuel injectors. The new engine installed in the 631 is a CAT 3408 with computer controlled fuel injection. The Caterpillar 651B scrapers were originally equipped with the mechanical CAT D349 engine; the CAT 3456 engine was used for the re-power in these vehicles. These engines have very different physical dimensions, however, necessitating the fabrication of new engine mounting hardware as well as modifying the length of the drivetrain;
Engine Wiring - The new Tier 2 engines are electronic engines where fuel injection is controlled by computer rather than by the mechanical action of the engine. Thus, rather than having a mechanical linkage from the throttle to the engine, the foot throttle is connected to a computer that relays instructions to the engine on when and how much fuel to inject into each cylinder. Re-powering with an electronically-controlled engine therefore requires the addition of the electronic engine control system, including the computer and associated wiring harnesses.
Larry Jacinto Construction was awarded MSRC Clean Transporation Funding for the re-power of one Caterpillar 631 diesel scraper and five Caterpillar 651B diesel scrapers. The existing engines in these vehicles were non-certified and unregulated; that is, their manufacture predated the first emission standards for off-road engines. The objective of this project was to remove these unregulated, high-emitting engines and replace them with new engines certified by CARB as Tier 2 diesel engines.
Each scraper re-power was completed over a 2-3 week period by Johnson Machinery. Overall, the performance of the re-powered equipment has been excellent. Only two minor reliability issues were encountered: 1) a fan hub bolt on the first Model 651 scraper became loose and damaged the radiator. The installer immediately replaced the radiator and checked the bolts on the other vehicles; 2) a hose clamp on the Caterpillar 631 scraper became loose, resulting in a loss of engine coolant, subsequent overheating, and a cracked cylinder head. The machine was repaired and is currently back in service.
Over the first four months of operation following engine re-powering, the six project vehicles have accumulated over 2,900 hours of operation.
All vehicle re-powers were completed as of May, 2005. While the first re-power of an older piece of construction equipment is always the most difficult, once the required changes are confirmed subsequent re-powers become routine. In this case, Johnson Machinery had previously performed Caterpillar 631 and 651B engine re-powers under earlier MSRC Clean Transportion Funding programs; this project benefited direcly from the MSRCs prior investment.