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Volvo Penta D9 Marine Diesel Engine

Volvo Penta D9 Marine Diesel

Recently I traveled to Sweden to test the Volvo Penta D9, a brute force marine diesel inboard available in both 500 and 575 hp ratings. It's an appropriate choice for powering fly bridge boats, sport cruisers and sport fishing boats ranging from 40 to 50 feet. Dockside at Volvo's Krossholmen, Sweden, Marine Test Center, I took the helm of a 50-footer rigged with two of the 575 hp version of the Volvo Penta D9.

Even before we started the twin marine diesel engines I knew they would be powerful and quiet. No, I'm not a psychic, or privy to special information. It's just that marine engines have evolved so wildly that Rudolf Diesel probably wouldn't even recognize today's breed. After all, his first engines burned coal dust.

These days most contemporary marine diesels are so well mannered they could masquerade as gas engines. They've given up smoking, they don't clatter like there's something loose inside and instead of slow poking their way to cruising speed, they slam full speed ahead. Suffice it to say that during testing on the North Sea, the Volvo Penta D9 acceleration proved to be quite impressive. Throttling up the big boat from idle to ten knots took just 6.5 seconds. Getting up to 30 knots only took 24 seconds. Remember, this was a 50 footer, not a little 18-foot speedboat.

Obviously the Volvo Penta D9's high degree of performance is due its large swing of the crank. True to the timeworn axiom, there's no substitute for cubic inches. But the heart and soul of the new machine's efficiency is its electronic control system, one the Scandinavian engineers have affectionately dubbed EMS 2.

To hear the guys in the white lab coats tell the story, genesis for EMS 2 was the need to meet future exhaust emission requirements that will begin to took effect back in 2006. A long, boring, technical story made short, EMS 2 relies on a fast microprocessor and a few lines of elegant firmware coding that precisely calculates how much fuel the engine needs.

EMS 2 performs this computation up to 100 times a second. That net result: Lag time between the instant the helmsman bumps the throttle lever forward and when the extra fuel shoots into the combustion chamber, is virtually zero. Besides eliminating lag time, EMS 2 significantly reduces fuel consumption and minimizes exhaust emissions. So not only is the ride infinitely more pleasurably, range is extended and operating costs are lower.

But to my way of thinking the real eyebrow raiser is the way EMS 2 monitors the engine's vital signs. Predictably, things like oil pressure and coolant level are monitored. But so too is piston ring condition monitored. The payoff is greater reliability and longer engine life. Should some component or system ever show a red flag you can schedule diagnosis and repair before any real damage is done.

There's more to the D9 performance story that you ought to know. Volvo engineers specified a completely new, center-mounted, twin-entry turbocharger. With this configuration, individual exhaust pulses quickly pump up intake pressure. When the boost comes on stronger and sooner, you feel it in the seat of your pants, right now, even when bumping waves in a big, heavy offshore boat.

Like other marine engine builders Volvo Penta cools intake air temperature. Cooler air is denser, which means more oxygen molecules are drawn in with every breath the engine takes. Cooler, denser air builds more horsepower and reduces emission. Working hand in hand with the charge-cooled turbo are electronically controlled fuel injectors that flow fuel as per split second instructions provided by EMS 2.

Tim Banse in Sweden

During the on the water testing at I noticed how quietly the Volvo Penta D9 was running on a variety of different boats. Some of that soft-spoken nature is due to common sense foundry work. The grey iron engine block is fitted with a one-piece cylinder head. A ladder frame bolts full length to the crankcase below.

This top and bottom reinforcement scenario dramatically reduces vibrations that might otherwise cross over to the stringers and rattle the hull. Also, with a rock steady block, the marine diesel reciprocating mass doesn't bounce around. Pistons, rings, crankshaft journals and rod bearings last longer. Volvo Penta D9's inline six-cylinder configuration allows room for a substantial crankshaft that's machined with wide bearing journals. The big crank, locked hard to the block with its big bearings, minimizes vibrations. Remember, every crash of a wave is trying to plunge the crankshaft through the oil pan and on out through bottom of the boat. I also noticed how the engine mounts are generously proportioned, about the size of a paving brick. Over-sizing better maintains engine alignment and effectively isolates engine vibration from the boat.

While not very exciting, it's also important to know the D9 marine diesel is built in Volvo Penta's engine plant located in Skovde, Sweden. At this state of the art facility the company builds land-based D9s as well as marinized D9s. Automated assembly lends high and consistent quality to their work. That consistency spells greater reliability and longer life. The already good news gets even better yet. Building commercial and marine engines side by size blossoms the economy of scale. The more engines Volvo Penta builds, the lower the unit cost. The bottom line, purchase price for marine engines is reduced.

Crawling around in one boat's engine compartment, I also took note of the D9's compact dimensions. In comparison, its footprint is about the same as Volvo's existing 7.0 liter (TAMD75). Yet the 9.4 liter D9 builds 100 more hp. Relatively small in stature, this new diesel can be squeezed into some very tight spaces. And because there are no service points on the front of the engine, it can be mounted nearly flush with the forward bulkhead. Short fore and aft installation length means the D9 can fit in compartments more typically associated with a V-8. Rest assured, service points are easily accessed. The de rigueur preflight took me about two minutes.

Volvo Penta D9 includes an electronically controlled transmission. That means no stiff, hard to shift mechanical cables. Different ratio transmission gears are offered, as well as a conventional inboard or V-drive. An important part of the package is Volvo Penta's Electronic Vessel Control that's based on CAN bus technology. Essentially it means the typical maze of wiring is replaced by a single serial data cable. Finally, Volvo Penta build leisure and commercial marine engines and boasts 5,000 dealers in 130 countries.

ENGINE SPECIFICATIONS D9-500 D9-575
Displacement 9.4 L 9.4 L
Configuration Inline 6-cylinder Inline 6-cylinder
Horsepower 500 @ 2600 rpm 575 @ 2500 rpm
Alternator output 115 amps 115 amps
Engine Weight 1075 kilos 1075 kilos
Transmission Electronically controlled V-drive Electronically controlled V-drive