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Off-Road Insider - Vortec I-5 Engines

0301 OFRP 02 Z  010 14  Insider
Posted January 1, 2003

Inline Fever: GM Introduces Two New Inline Truck EnginesFollowing the lead of the successful Vortec inline-six engine that powers Chevrolet's TrailBlazer, General Motors has developed two additional engines based on the six-in-a-row Vortec. The Vortec 3500 inline five and the Vortec 2800 inline four are, in essence, scaled-down versions of the Vortec I-6 and are slated to power the new Chevrolet Colorado and GMC Canyon midsize trucks, which will be introduced later this year as '04 models.

The new Vortec I-5 and I-4 engines share common design elements, such as all-aluminum construction, dual overhead camshafts, and four valves per cylinder. The smaller siblings share the big VortecI-6's 10:1 compression ratio, electronic throttle control, coil-on-plug ignition, and adjustable exhaust cam phasing.

GM was able to rapidly develop the new four- and five-cylinder engines by employing 75 percent of the parts used to build the Vortec I-6 engine, with obvious savings in development costs. Similar to the big I-6, the I-4 and I-5 are stout performers: the 3500 I-5 is targeted to produce 215 hp and 225 lb-ft of torque, and the I-4 will be tuned to deliver 170 hp and 175 ft-lb of torque.

While the I-6 design effectively cancels out engine vibrations through its crankshaft layout and ignition firing order, the I-5 and I-4 engines must be balanced via add-on balancing shafts. Both new engines were designed to operate with dual balance shafts that are incorporated into housings on each side of the engine block. The balance shafts rotate at twice the engine speed and in opposite directions, thereby counteracting the natural rotational vibrations created by the I-4 and I-5 design.

To keep the exhaust of the Vortec I-4 and I-5 engines as clean as possible using today's technology, each engine's exhaust manifold uses an integral three-way catalytic converter. Making the cat a part of the manifold results in a quicker light-off time, which rapidly oxidizes hydrocarbons and carbon monoxide. Any pollutants that get past the initial catalytic converter are burned off inside a secondary cat mounted in the traditional location. The results are impressive: both new Vortec engines are able to meet California's Low Emission Vehicle standards.

As with the I-6, the I-4 and I-5 engines boast variable valve timing. Simply stated, the valve timing of the exhaust cam is electronically regulated (advanced and retarded) through a sophisticated program designed to enhance torque and overall drivability, deliver a smooth idle, and reduce emissions. Retarding the exhaust cam increases the overlap of the intake and exhaust valves, which increases the amount of exhaust gas recirculation within the combustion chambers, and thus creates the aforementioned performance benefits. A high-energy ignition spark is delivered by the coil-on-plug ignition system, which is electronically controlled, has no moving parts, never requires timing adjustments, and eliminates the need for spark plug wires.

Although these new GM engines are only now reaching the market, GM has looked far ahead to future development. In the works are full variable valve timing (adjustable intake and exhaust camshafts), turbo charging, direct-injection fuel systems, and models with larger-displacement. With the Vortec I-6, I-5, I-4 and V-8, GM certainly has an enviable lineup of powerplants for its midsize trucks and SUVs.

V-8 TrailBlazer A RealityOne of the worst kept secrets last year was the existence - in prototype form - of a V-8-powered TrailBlazer. Now, those test mules that were spied undergoing testing from Detroit to the deserts of the Southwest have finally sired a production V-8 TrailBlazer, and it's available at GM dealerships.

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