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When More is Less: Toyota’s new 3.5-liter V-6 for the Avalon

When Toyota redesigned its 2005 Avalon (shown last month at NAIAS), it used a new gasoline engine with 15% larger displacement that delivers 33% more horsepower—and decreases fuel consumption by 5%, while dropping emissions from LEV to ULEV status.

The new all-aluminum V-6 is the most powerful V-6 Toyota has yet to put in one of its cars. Toyota developed a number of technological improvements specifically for this engine, including the introduction of a unique new roller rocker concave cam profile that provides faster opening and later closing of the valves which is a key contributor to the power increase. In addition, the dual VVT-i system optimizes intake and exhaust valve timing to increase high-speed torque and ultimately improving fuel economy.

The conceptual schematic for the control and implementation of VVT-i in the new engine (named the 2GR-FE) provides some insight into the growing complexity of intelligent engine control. The diagram below and to the left shows the number and location of the required sensors and their input into the engine control module (ECM). The diagram below and to the right provides a rough idea of the data and control flow. 

Avalon_v61 Avalon_v62

By using the engine speed, intake air volume, throttle position and engine coolant temperature, the ECM calculates optimal valve timing for each driving condition and controls the camshaft timing oil control valve. In addition, the ECM uses signals from the camshaft position sensor and the crankshaft position sensor to detect the actual valve timing, thus providing feedback control to achieve the target valve timing.

This is a good example of the potential ongoing incremental improvements in engine efficiency enabled by new materials, manufacturing processes and increasingly sophisticated computer control of the combustion system.

From a sustainability point of view, however, it would be better to use the engineering enhancements to apply a smaller engine yielding even greater savings in fuel consumption and emissions, rather than using the larger engine with the even greater output.

But with a relatively slow-selling sedan (Toyota sold some 36,000 Avalons in 2004), Toyota is currently opting to deliver much greater performance while delivering small improvements in efficiency and emissions.

Avalon Engines
 Model Year 2004Model Year 2005
Displacement (cc) 2,995 3,456
Output (kW/hp) 157/210 209/280
Torque (Nm/lb-ft) 298/220 352/260
Combined EPA Mileage (mpg US) 24 25.3
Combined fuel consumption (l/100km) 9.81 9.29
Emissions LEV ULEV

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