Step By Step
Variable-Valve Exhaust Timing
One of the most interesting aspects of the Vortec 4200 I6 is whats called variable-valve exhaust timing. This feature adjusts the exhaust camshaft timing within a range of 25 degrees as engine operating conditions change. To do that, an onboard computer first collects several points of data including throttle position, engine load, and vehicle speed. From there, a control valve adds or removes oil from a cavity and piston chamber (see cutaway photo) at the front of the camshaft. Thus, advancing or retarding the exhaust camshaft not only enhances the torque curve, but also improves idle quality and reduces emissions. With the ability to change timing, a more aggressive camshaft profile can also be used.
To increase casting accuracy and minimize engine weight, the aluminum block and cylinder head of the Vortec 4200 I6 are made using a lost foam process. This casting technology provides both improved control of the manufacturing process and allows direct-mounted accessories that reduce vibration and weight. With the exception of the power-steering pump bracket, all engine accessories bolt directly to the engine.
The 4200 I6 ignition system employs an electronic spark-control system that uses no moving parts and does not necessitate timing adjustments. This coil-on-plug system delivers a high-energy spark for a cleaner and more consistent combustion. This contributes to increased engine efficiency, improved fuel economy, and better performance, and eliminates the use of spark-plug wires. The ignition system also utilizes a crank and camshaft-position sensor for accurate engine-condition monitoring and added reliability. If one sensor fails, the engine can continue to operate, but the computer will activate the check engine light to alert the driver of a component failure.
Advanced Powertrain Control
The Vortec 4200 uses an engine-mounted electronic Powertrain Control Module that records hundreds of measurements per second and makes immediate adjustments of air, fuel, spark control, and valve timing to provide optimal engine operation.
Electronic Throttle Control
To eliminate the mechanical link between the accelerator pedal and throttle, the Vortec 4200 uses an electronic throttle control (ETC). The ETC sends a series of signals from an accelerator-pedal module using a sensor that relays acceleration-intent data to the powertrain control module (PCM). The PCM then signals an electric motor to position the throttle to match the drivers intent.
The Vortec 4200 has a 10:1 compression ratio that helps it achieve impressive power levels. The engine produces 90 percent of its torque from 1,600 to 5,600 rpm running on unleaded fuel. This is due in part to good combustion-chamber design and the cylinder heads ability to efficiently transfer heat.
More than 1 hp per cubic inch. Mention that phrase to Chevrolet enthusiasts and youll probably hear about early Z/28 engines, fuel-injected 327s, and a few big-blocks. But Chevrolet has a completely new engine that not only delivers that kind of power, but also does it with fuel-efficient performance and unmatched smoothness. The engine is called the Vortec 4200 I6 and was initially created for General Motors midsize sport utility vehicles. Chevrolet engineers created a 24-valve, dual overhead cam, all-aluminum straight-six that produces 270 hp from 256 cubic inches, with 90 percent of its torque coming in from 1,600 to 5,600 rpm. Lets take a closer look at this amazing new engine.