More of this Feature • Part 1: Volvo Penta D-12 • Part 2: Volvo Penta D-12 continued • D-12 Specs
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Horsepower is a measure of power. Torque, which is mathematically related to horsepower, is a measure of twisting force. Torque is what turns the propeller; the more torque delivered to a propeller (assuming an efficient hull and the correct-size propeller), the faster and more efficiently the boat will go.

A key characteristic of the torque produced by diesel engines is that compared to a gasoline engine, it increases more quickly as rpm increases and peaks earlier. As you can see in the graph at the top of this page, the D-12 series is a particularly good example of these characteristics, even compared to other diesels. By programming the engine’s onboard computer to optimize injection timing and metering and selecting the right turbocharger, Larsson and his team were able to create a torque profile that increases very quickly, producing rapid acceleration, and stays relatively flat for most of the engine’s operating range, which yields good fuel efficiency.

I was able to experience the fruits of this labor at the helm of a Princess 55 equipped with a pair of 700-hp D-12s during a visit to Volvo Penta’s headquarters in Goteburg, Sweden. The outcome of that sea trial can be seen in the test results box at right on this page. I noticed excellent acceleration out of the hole and virtually no smoke throughout the entire test run.

At the heart of such performance is the latest version of Volvo Penta’s Electronic Diesel Control (EDC). Not only does it control the electronic unit injectors by analyzing data from an array of sensors, it constantly monitors the engine for problems and, if it detects one, notifies the operator via a series of fault codes and in some cases protects the engine by reducing rpm. It also maintains the engine’s operating history for retrieval by a service technician. This information can be used not only to identify and diagnose a problem but also to establish an operational profile that can be used to help the operator maximize engine efficiency and longevity and to assess warranty claims.

EDC has been around for a few years, but Volvo Penta improved it for the D-12 by incorporating more data points to give it better control over the engine. In addition, a single serial data cable enables the engine computer to be connected to multiple control station. The new EDC is also faster than previous models, a feature that allows it to monitor and control cylinders individually and adjust each unit injector accordingly. Finally, the new EDC can be updated with new functions by adding new software. Little wonder that the new D-12 not only is a performer, but also complies with all proposed European and American emission regulations for pleasure and commercial vessels.

Volvo Penta’s new D-12 is so modern and up to date, it seems to have little, if anything, in common with that first rudimentary paraffin-fired engine the company created nearly a quarter-century ago. But the present-day company does share one important characteristic with the old one: a commitment to build the most advanced marine engines available.
   
Volvo Penta of the America (757) 436-2800. Fax: (757) 436-5150. www.volvo.com.

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