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Cat’s 3500E engine adds power and trims fuel consumption while retaining existing form factors.


Enhanced Cat 3500 engine boosts power 20%, trims fuel usage by 10%

The 3500E, the latest iteration of Caterpillar’s venerable 3500 engine family, provides up to 20% greater power density, 10% greater fuel efficiency, enhanced durability and longer life before overhauls. The upgraded engine maintains existing form factors, so rebuilds and replacements can be utilized with minimal infrastructure changes.

The 3500E outputs 188 kW (252 hp) per cylinder, more than double the 75 kW (101 hp)/cylinder output of the first 3500, which went into production in 1981. Overall, the engine offers up to 4040 hp (3015 kW). Engine displacement ranges from 34 L for the eight-cylinder model to 78 L for the 16-cylinder version.

While improved performance was the primary goal for developers, maintaining backwards compatibility was also a key parameter. The 3500 has been in production for 35 years, with more than 190,000 engines in the field. Those engines are operating primarily in mining, rail, electric power, oil & gas and marine applications, as well as in Cat machines.

Joe Markun, Cat’s General Manager of Large Engine Manufacturing, highlighted the engine’s legacy by noting that one of the first 3500Es is being shipped to a company that bought a very early 3500 engine.

Redesigned but backwards compatible

The revamped engine series achieves its power increases from the enhanced cast-iron engine block and cylinder heads. A redesign for the block and crankshaft increases durability.

“We redesigned the crankshaft, though it remains backward compatible with existing engines,” said Ronald Smith, Engineering Manager for the 3500 platform. “We added material to the cylinder head and block in some places. We also altered the processes, but we didn’t change the steel. We also increased the pressure in the cylinder.”

Cat has remanufactured more than 13,000 model 3500 engines at the Lafayette, IN, facility where the engine is manufactured. Rebuilds in Indiana and a second engine manufacturing plant in China augment rebuilds done by dealers and others. The factory has several ongoing programs designed to ensure quality while meeting demanding specifications. Though the 3500E is huge, it’s manufactured with extreme precision.

“The crankshaft tolerances go down to five microns,” Smith said. “Every fourth crankshaft is validated to maintain those tolerances. The whole factory is temperature controlled so all our measurements are precise.”

The engine has two fuel system options: mechanical electronic unit injector or common rail. Various fuels can be used. Gas, diesel, biofuels and any mixture of these options can be burned efficiently, letting users in different markets pick the best solutions for their operating environment, gaining fuel efficiency improvements of up to 10%.

Aftertreatment options are also available. The 3500E uses either a selective catalytic reduction (SCR) or an exhaust gas recirculation (EGR) aftertreatment system to meet U.S. EPA Tier 4 Final and EU Stage IIIB emissions standards.

“Some engines will use SCR, using urea,” Smith said. “In applications like fracking, they don’t want another fluid, getting it to a remote site is difficult. EGR is an alternative to urea. The cost of ownership is also different.”

Those are just a few of the available options for the engine line, which is designed for customization so variants can be produced in small volumes for specific markets. In many applications, orders are for only one or two engines. Even versions built for data centers, a higher volume application where five to 10 similar units will be produced at one time, will have differences such as right- or left-hand servicing.

“We make as many as 900 variations,” Smith said. “We build everything to order, 44% of our engines are unique.”

Telematics for predictive diagnostics

The 3500E is also getting upgraded electronics. Cat’s A5 engine control module provides enhanced I/O capabilities along with a faster processor and more memory. One of its key roles is to drive the injectors.

The additional processing capabilities also help provide more diagnostics and predictive diagnostics, or prognostics. Monitoring engines so maintenance can be performed before breakdowns occur is becoming simpler. Technicians can more easily monitor usage from remote sites so they can determine the optimal time for servicing.

“We’re putting telematic modules on the engine,” Smith said. “Users can interrogate any sensor, getting readings and doing things like comparisons of the sensor compared to 30 days ago. Product Link uses cellular or satellite connections to operate anywhere.”

Cat isn’t limiting its focus on reducing energy consumption to the hours that the engine is operating in the field. When engines are being validated at the factory, they’re used to generate up to 6.5 kW of electrical energy. That’s roughly half the consumption of the 1.3 million square foot Lafayette facility, Markun noted.

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