John Baxter | January 01, 2012

Powering 2012

After years of emissions hurdles and technology evolutions the current 2010 compliant engines deliver better fuel economy, will likely last longer, and, in some cases, offer longer oil change intervals than past engines. The following is a quick guide to what is being offered today from the major engine manufacturers in the Class 8 market.


Cummins’ ISX15 was introduced in 1998. Design of its block was optimized through new electronic tools to minimize noise and weight. The engine also had an integrated engine brake.

The cylinder liners got an improved hardening process in 2002 because exhaust gas recirculation can cause corrosion of the wear surface. Also, the piston pin was supplied with lube oil under pressure to allow the piston to carry the additional cylinder pressure of EGR. The harder liners actually extended life. Other features include a combination full-flow and bypass oil filter from Cummins Filtration.


horsepower: 400-600

torque: 1,450-2,050 lb.-ft.

Bore and stroke: 5.4 in. by 6.7 in.

Displacement: 15 liters

Lube Oil capacity: 14 gallons

In 2007, a new combustion chamber was introduced. It stirs up the air around the fuel sprays to allow increased EGR levels with less air. The result was little or no increase in cylinder pressure while other engines were forced to handle more pressure in their cylinders.


2010 brought a new injection system, the XPI common rail design. The original, simple ISX fuel system was not able to split each injection cycle into separate shots of fuel. The XPI system allows a “pilot” shot of fuel early in compression to produce much quieter and faster ignition, and enables each main shot of fuel to be split up, to reduce nitrogen oxide (NOx) and soot. It provides fuel pressure independent of rpm to a large pipe, or common-rail. Maximum injection pressure even below the torque peak means a better torque curve, improved fuel economy, less soot for the DPF to handle, and faster, quieter cold starts.

Equipping 2010 and 2011 models with Cummins Filtration’s own integrated DPF and SCR system with a copper-zeolite catalyst means less EGR and more favorable engine tuning. This gives 3 to 5 percent better fuel economy, depending on the application.

Cummins also offers the ISX 11.9-liter engine, which has the XPI fuel system and a rear-driven camshaft. It offers maximum ratings of 425 horsepower and 1650 lb.-ft. of torque.

Detroit Diesel

Detroit Diesel, which will be rebranded as Detroit later this spring, and its parent company, Daimler AG, developed the DD13, DD15 and DD16. The DD16 is an owner-operator/heavy-haul version of the platform displacing 15.6 liters.


The 15- and 16-liter versions have a turbo-compounding system, says Admir Kreso, senior engineering manager at Detroit. The turbo-compounding turbine sits behind the regular turbo, but instead of driving a compressor for the intake air, it drives the crankshaft through hydraulics and a geartrain. It recovers energy that would otherwise be lost, so, in addition to saving fuel, it increases power output.

The turbo-compounding system also provides the exhaust backpressure necessary to make the EGR system work without a variable geometry turbo. So the DD16 also uses a simple, non-wastegate turbo, which is claimed to provide quick throttle response.

Says Kreso, “There are many design elements of the Detroit DD16 that enable it to deliver outstanding power, torque response and fuel economy.” The engine includes an integrated Jacobs engine brake, integrated coolant passages (to reduce leak points), a webbed engine block, patterned cylinder liners, the amplified common rail fuel system (ACRS), and Detroit BlueTec emissions technology. Webbing on the block increases its strength and rigidity without adding much weight; and patterned liners do a superior job of retaining oil in their bores to lubricate the pistons and rings. Detroit’s proprietary 1-Box emission package forces exhaust through two identical diesel oxidation catalysts, diesel particulate filters, and selective catalytic reduction catalysts rather than one, which the company claims reduces backpressure and helps conserve fuel.


Horsepower: 475-600

Torque: 1,750-2,050 lb.-ft.

Bore and stroke: 5.47 in. by 6.73 in.

Displacement:15.6 liters

Lube Oil capacity: 47 quarts

The ACRS system provides injection pressures well over 30,000 psi, yet the external piping needs to carry only about 13,000 psi. This pressure is hydraulically amplified inside each injector as it delivers fuel. It’s a common-rail design, with an external pump that supplies fuel pressure independently of rpm, so full injection pressure is available even below the torque peak. This optimizes the torque curve and reduces emissions. Each injection cycle has rate shaping, delivering fuel more slowly at first to keep emissions low, but speeding up later to give good fuel economy. strives to maintain an open forum for reader opinions. Click here to read our comment policy.