The new Caterpillar 3412 reminded me of a recent advertisement: "What it takes to turbocharge a Porsche." Through the ad, Professor Porsche asserted that changing one component can profoundly affect the performance of the others. And ultimately, the performance of the whole car. Simply bolting on a turbocharger, tweaking the engine a little, and re-naming the machine is the wrong way to go about it. The new Caterpillar 3412 also reminded me that a diesel engine has form. It has a personality. The collection of precision sand castings, sheet metal stampings, pipes, nuts, and bolts - even its paint color - does promote an image. Of and for itself, and for the company that manufactures it.
For example: the Caterpillar 3412, on the market since the mid-70s, has been known to us as a marine engine from the beginning. It was marinized at the same time it was introduced to the industrial marketplace. However, the package dimensions and weight of the 3412TA, large and heavy for an engine in its power class, have mostly relegated it to work in fishing boats where size and weight are less critical. The big, yellow beast has been denied a popular place in the poweryacht world. That is now changing. This Cat, like the emperor, has new clothes.
The basic Caterpillar 3412TA is a 1,649-cid, 60-degree V-12. The two other engines in its family have six and eight cylinders, namely the in-line 3406 and V-8 3408. All the 3400 series engines share the same 5.4-inch jugs; the stroke of the straight six is a half-inch longer than the V-8 and V-12. After two or three upratings, the previous high-performance power rating of the 3412 was 860 hp at 2100 rpm. Further development of the engine, prompted by dealer demand, began in late 1985.
Caterpillar contracted the services of one of its dealers, Pantropic Power of Miami, to build the prototype high-output 3412. Pantropic was the logical choice because they had the most interest in the project. For Caterpillar, faced with a crowded calendar of engineering activity, it was much more expedient to subcontract the engine than build it through normal development channels. The venture brought the new 3412 to market remarkably fast - 15 months from a gleam in the eye to initial delivery, a milestone for a company that once boasted that it spent 10 years bringing a new product to market. Pantropic now handles assembly and delivery - factory production, parts, and service will be brought online within the next year.
Caterpillar anticipates that the new 1,000-hp 3412 is the forerunner model in a broad "HO" (high output) product line - a lineup calculated to enlarge Caterpillar's slice of the cruiser marketplace. Similar reworking of the well-liked, bigger-cube 3500 series V-8 and V-16 is underway.
The specific method for upgrading the 3412 to create the new 3412HO was threefold: modify the size of its physical envelope, whittle its weight, and increase its power output. Combined, the modifications resulted in a formidable power-to-weight ratio. Power-to-weight ratio for the 5,400-pound standard, turbocharged, aftercooled bundle was 6.3 lb./hp. The new HO weighs 4,950 pounds, develops 1,000 horsepower at the same 2100 rpm, and boasts a power-to-weight ratio of 4.95 lb./hp. Furthermore, the physical profile of the engine was tailored to meet the space-saving requirements of pleasureboats.
The gain of 140 hp was achieved by replacing a single turbocharger with two slightly smaller turbos. No other vital changes were made in the power-producing package. This changeover increased airflow through the engine and boosted cylinder intake pressure 10 to 12 percent, which produced additional power while reducing combustion temperatures. The extra air does wonders. In addition, the smaller, lower-mass compressor wheels respond around 50 percent quicker than a single, bigger wheel. The system itself was assembled of existing parts from Caterpillar land-based generators and earth-moving machinery.
Caterpillar was able to improve power output without adding thermal strain on the same major engine components of the 860-horsepower engine. The 3412HO uses the identical gray-iron block as the 3412TA, cast by Caterpillar's own foundry. Internal components are the same, too: forged, furnace-hardened crankshaft; cast aluminum alloy pistons with three rings each (two compression rings, one oil ring); copper-bonded bearings; forged steel connecting rods; and deck plate heads. (A steel spacer fits between the block and the cylinder head, with gaskets on both sides to seal the water and oil passages.)
Caterpillar's tried-and-true direct fuel injection system has individual pumps and injectors for each cylinder. Slight recalibration of the system, opening the rack a little, allows more fuel flow. The 3400 series does not use the one-piece, cam-actuated unit injector technology found on the larger 3500 and 3600 Caterpillars.
The new 3412 sticks with a mechanical-type governor. Caterpillar's much-talked-about Programmable Electronic Engine Control (PEEC), used on the 3406B truck engine, is not available on any of its marine stock. An electronic control system can manage ·emissions, and change the characteristics of an engine to optimize fuel economy, but it won't give a diesel engine more pure performance than a mechanical system.
Continuing the metamorphosis, enterprising use of other off-the-shelf aluminum parts, and innovative re-engineering of the cooling system are the primary reasons the 3412's overall dimensions have been reduced, and why its gross weight has dropped by 500 pounds. The basic engine dimensions didn't change, however. External hardware had made the powerplant bigger. The new low-profile 3412HO is 51 inches high, 48 inches wide, and 73 inches long - or 12 inches shorter and 12 inches narrower than the 3412TA. A marine transmission such as the Reintjes WVS 532, manufactured in West Germany and supported by Caterpillar, adds 22 inches to powerplant length.
To keep air out of the coolant system on a marine engine, an expansion tank generally collects air bubbles in the coolant and vents them into the atmosphere. This expansion tank serves the same function as the top of the radiator in a motor vehicle. Should an excess of hot air or gas leak into the cooling system through hoses, connections, or seals, the coolant pump will not operate effectively. The temperature of the coolant will increase, and the hot air (being lighter than fluid) will rise instead of being discharged through the system. Diesel blocks, especially, do not enjoy entrapped air in the cooling water. It develops hot spots.
To absorb heat from the newfound power, the cooling system was reconfigured for engine-mounted heat exchanger cooling, but the expansion tank on the basic engine ate up length. Caterpillar's problem solvers engineered a brand-new and clever combined expansion tank and heat exchanger. The tank is fabricated, not cast, which again chops weight. Two innocuous-looking tubular chambers are mounted directly behind the expansion tank, connected to the tank by small hoses. These are the key clues in the Case of the Shrinking Reservoir. Perry Mason, are you listening?
These "de-airators," invented by Peterbilt for its truck radiators, trap the cooling water into a circular path, draw air bubbles from the center of the swirl, and vent the air to the expansion tank. Most importantly, the de-airators relocate the process of removing air from the water, and keep the bulk of the cooling system to a minimum. An aluminum oil pan from a 3400 series industrial generator set replaces the original steel marine oil pan. Compared to the 3412TA, the HO version uses a smaller sump, half the oil (18 gallons), and a 250-hour oil change interval. The industrial-derived work boat engine had a deep oil sump with double the oil change cycle - needed for heavy-duty applications. A smaller aluminum flywheel housing replaces the cast iron original. The engine mounting scheme is lighter, using fabricated steel. Instead of hanging behind the flywheel, the air cleaners are mounted forward of and on axis with the turbochargers, perpendicular to the crankshaft.
The high-output pleasureboat Caterpillar 3412, barely one year old, has gained immediate acceptance with big-boat buyers. Clearly, it is an impressive, long-awaited peer of the best-selling 1,080 horsepower Detroit Diesel 12V-92TA and the 965 horsepower MTU 6V396TB93. Like all engines, the 3412 is an unglamorous beast. And the configuration of a diesel engine, how those many parts, major and minor, are structured is too often taken for granted - until it's time to install it in the bowels of a boat. The theory that a whole is greater than the sum of its parts did not originate with Professor Caterpillar. But it's apparent that he, for one, wholeheartedly subscribes to it.
This review/article originally appeared in Boating Magazine, March 1988 and is written by David Speer. For more great powerboat reviews, visit their website and subscribe at: http://subscriptions.boatingmag.com/