This project involved re-powering four (4) Terex TS 24B dual-engine scrapers with Tier 2 certified engines. The existing engines predated the first emission standards for off-road engines and were uncertified two-stroke diesel engines. The replacement of old, uncertified diesel engines with new, certified lower-emission diesel engines in off-road construction equipment is a very cost effective strategy for reducing ozone precursor emissions as well as toxic air contaminants.
MSRC Clean Transportation Funds were used to offset the cost of engine replacement. Caufield also contributed to the project in the amount they would have spent had the engines gone through a traditional rebuild. MSRC Clean Transportation Funds in the amount of $478,000 were appropriated to this project.
Valley Power Systems, a licensed Detroit Diesel Corporation distributor, was selected to perform the vehicle re-powers. The major elements of the re-power project included removal of two diesel engines for each scraper. Originally, each scraper was configured with a DDC 12V71T twelve cylnder front engine and a DDC 6V71T six cylnder rear engine. These engines were removed and replaced with the DDC Series 60 six cylinder engine in front and DDC Series 50 four-cylinder rear engine. The new engines are four cycle engines as opposed to the original two cycle engines. As the new engines are dimensionally different as compared to the original engines, installing the new engines requires fabrication of new engine mounts and adapter plates.
In addition to the engine replacement, Valley Power Systems installed a charge air cooler. Reducing the inlet air temperature is an effective means of reducing NOx production in the combustion chamber. The charge air cooler is similar to a separate radiator system installed on the vehicle. However, since the dimensions of the radiator with the charge air cooler is different than the original radiator, installation required fabrication and installation of new mounting brackets and the relocation of coolant lines.
Finally, wiring harnesses and displays were installed to control the new engines. In the original engines, the fuel injection was controlled by the mechanical action of the engine. The new engines are electronically controlled by an onboard computer. There is no mechanical connection between the foot throttle pedal and the engine fuel system. In an electronically controlled engine, depressing the throttle pedal sends an electric signal to the computer and the computer determines how much fuel to inject based on inputs from multiple engine sensors. Re-powering a vehicle originally equipped with a mechanical injection engine with a electronic control engine thus requires installation of wiring harnesses, throttle controls, and driver display unit.
The objective of this project was to re-power four existing pieces of off-road construction equipment. "Re-powering" consists of removing the orignal engine and replacing it with a new engine. In this project, four (4) Terex TS 24B dual engine scrapers were selected for engine re-powering. The vehicles were originally equipped with uncertified Detroit Diesel Corporation (DDC)non-emission certified two stroke engines.
Re-powering existing off-road construction equipment with new lower-emission diesel engines is an extremely cost-effective air pollution reduction strategy, specifically as it relates to NOx emissions and particulate matter. Funding programs such as the MSRC's Clean Transportation Funding Program and the AQMD Carl Moyer Program make vehicle re-powering a viable and attractive option to engine rebuilding.
Each piece of equipment has accrued approximately 800 hours since completion of re-powering. Only one issue was encountered; one unit experienced a compressor failure that resulted in engine damage. The engine was repaired under warranty and the scraper is was returned to operation.
Each re-power was completed within approximately three weeks after vehicle delivery to Valley Power Systems. All four scraper re-powers are are complete. Performance of the units in construction operation has been excellent.