CAT 15 ACERT

Strokes of genius

The C15 ACERT is the current development of an engine that started life as the mechanically-injected, straight-six 3406C, which developed 580hp (based on 1hp equalling 746W) at 2100rpm.

This engine was upgraded to 800hp at 2300rpm when released as the electronically-managed 3406E, culminating in the C15 ACERT which develops 800 or 853hp; both outputs at 2300rpm. All of these outputs are based on Caterpillar’s ‘E’ rating, where full load is allowed for 30 minutes in every six hours with a yearly usage of 250 to 1000 hours, enabling the C15 ACERT to be used not only in pleasure craft but also in some patrol boats. Caterpillar says that power produced at the flywheel will be within standard tolerances to 49 degrees, unlike some manufacturers, which rate performance at only 25 degrees.

The C15 ACERT displaces 14.64lt, has a cylinder bore of 137mm and a piston stroke of 165mm.

Torque delivery between the two versions is substantially different. The 800hp model produces a peak torque output of 3566Nm at 1500 to 1600rpm, with 1890Nm available at just 1000rpm, and 2000Nm at 1200rpm, tapering off to 2533Nm at 2300rpm. At the maximum cruising revs of 2100, this model produces 2700Nm.

However, the 853hp model produces 1731Nm at 1000rpm, 2248 at 1200rpm, and peaks at 3282Nm from 1600 to 1800rpm, tapering off to 2900Nm at 2100rpm and 2700Nm at 2300rpm.

Therefore, the higher-output model is better suited to lightweight planing hulls, while the lower-output model suits charter gameboat operations.

In comparison, the 12lt C12 produces 2942Nm at 1600rpm, while the 18.1lt C18 produces 4115Nm at 1600rpm. As of July 2006, torque figures were not available for the C12 ACERT, but the maximum output is 705hp, while the C18 develops 1001hp, both at 2300rpm.

Based on a standard prop power curve and using distillate at 838.9 grams per litre (the same density as fuel sold in Australia), in both versions the C15 ACERT’s fuel flow is reasonable for output. At 1000rpm, where the prop absorbs 65.8hp, the 800hp model uses 13.7lt/h, rising to 22.5lt/h at 1200rpm and absorbing 113.7hp. In the peak torque range, with the prop absorbing 222 to 269.3hp, the flow rate is 42.4 to 50.6lt/h. At 2100rpm the fuel flow is 109.4lt/h, with 609hp absorbed by the prop.

In the 853hp version, at 1000rpm, where the prop absorbs 70.1hp, the flow rate is 14.4lt/h.

In the peak torque range the fuel flow is 53.8 to 74lt/h for 287 to 408.7hp absorbed by the prop, while at 2100rpm and 648.9hp at the prop the flow rate is 116.6lt/h, rising to 163.8lt/h at 2300rpm and full load. For a seven per cent greater full load output, the 853hp model uses seven per cent more fuel; unusual in that many diesels up-rated from their base counterparts use significantly more fuel to achieve the additional horsepower.

The C12 has a full load fuel flow of 136.6lt/h, whereas the ACERT version uses 138.1 but should produce significantly better torque. In the peak torque range the C12 uses 43.6lt/h. Cruising at 2100rpm, it uses 70.2lt/h. The C18 has a full load flow rate of 195.7lt/h, with 59.2lt/h used in the peak torque range.

DIMENSIONS AND ENGINEERING
In bobtail form, the C15 ACERT measures 1527mm long, 942mm wide, and 1171mm high and has a dry weight of 1463kg – 0.5 per cent less than the 3406C and a massive eight per cent under the 3406E. The C12 measures 1875 x 969 x 1005mm and weighs 1177kg, while the C18 is 1845 x 1058 x 1159mm and weighs 1718kg.

The C15 ACERT has the same basic features as the C12 and C18, such as a cast iron cylinder head and block with pushrod valve actuation from a gear-driven camshaft. The compact titanium-plate heat exchanger is far more efficient than a conventional tubular system due to the surface area of the plates effectively transferring heat out of the freshwater cooling system. The jacket water pump is gear driven and the oil cooler, filter, and dipstick may be fitted to the port or starboard side for handed engines in twin installations. Provision for a power takeoff is made at the forward end of the engine and the electrical system is 12 or 24V.

All C15 ACERT engines undergo a rigorous testing procedure before being shipped to the worldwide dealer networks. During my time at Caterpillar’s Mossville, Illinois production and research and development facilities in July, I saw an engine being run to 600rpm in a ‘cold’ test to check for harmonic vibration, followed by dyno testing to ensure it met CAT’s usual high standards. This attention to detail ensures consistent engine reliability.

Both versions of the C15 ACERT meet US EPA Tier 2 pleasure craft marine diesel compliance, scheduled for implementation in 2007, without resorting to the full ACERT treatment, developed originally for ‘on highway’ engines. The ACERT program covers ‘microburst’ fuel spray technology, sophisticated ‘ADEM’ electronic engine management, variable valve timing, and series turbocharging. But through the use of careful fuel mapping, the C15 ACERT has Tier 2 compliance with just microburst fuel spray via high pressure unit injectors.

For more details on the C15 ACERT, contact Garry Dann at Energy Power Systems on (07) 3722 1400, or email Garry.Dann@energypower.com.au.