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Cat cuts out camshafts

19th November 1992
Page 12
Page 12, 19th November 1992 — Cat cuts out camshafts
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Which of the following most accurately describes the problem?

• Caterpillar is developing a "no-camshaft" heavy diesel engine which should be ready in time to help meet the 1998 US emission regs.

The no-cam engine uses computer-driven electrical solenoids and hydraulic amplifiers to control conventional inlet and exhaust valves. Eliminating the conventional valvetrain is said to reduce mechanical complexity and boost performance: valve timing can be tailored to match the engine's demands, controlling timing, duration and the valve opening and closing speed.

The no-cam valvetrain should enable Caterpillar to move the fuel map around to match the operating point of the engine in line with power demand and throttle position. Currently the most fuel efficient operating point of the fuel map is close to the power curve lug line". But few of the latest high-torque engines operate at this point for much of the time.

While the no-cam engine may be a few years off, the latest 14-litre straight-six 3406E is on schedule for a launch by the end of next year. It is based on the 3406C bottom end, which was revised and beefed up last year to the level introduced on the 343kW (460hp) model.

The block will be changed, however, because the 3406E will be fitted with an overhead cam

shaft. This will leave the block ready for the no-camshaft engine.

Injection will be by electronic unit injectors (EUI). Caterpillar has EUI experience with the 3176 electronically controlled engine that is doing well on the European truck racing circuit.

The 3176 suffered from early injector problems, but is now claimed to be Caterpillar's most reliable engine.

The EUIs for the 3406E are currently under evaluation in fleet trials, as is the second-generation Advanced Diesel Engine Management (ADEM II) which will replace the Caterpillar's PEEC electronic fuel control system, currently used on the 3406C.

Power ratings for the 3406E have not been released, but it is expected to match upcoming 373kW (500hp) ratings from competitive engines such as the latest Cummins N14, recently unveiled at the Scottish IRTE show.

Caterpillar's engine research indicates that seven and 10-litre engines will be the common LGV power units of the future. Analyses of two-stage turbocharged and turbo-compounding shows that an engine based on the 3176 could reach Caterpillar's target specific fuel consumption of 152g/kWh with outputs as high as 522kW (700hp).

Craig Kroege, project engineer for engine research, believes that engines will be producing around 45kW (60hp)/litre within 10 years, opening up the possibility of up to 671kW (900hp) 3406 engines with 298kW (400hp) from a seven-litre model.

Ceramics are likely to be used for valves, piston crowns and a liner for the cylinder head. Articulated pistons with an air-gap thermal barrier are also under development. According to Kroeger, such engines will achieve 55% fuel efficiency compared with the current 43%.

The 10-litre concept is running as a single-cylinder development engine and achieving 161g/kWh. This shows Cat's targets are achievable, says Kraeger.

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