Evolving engine technology

Motor, Aug 1998 by Nash, Tom

Don't look now, but the engine under your hood is changing. That's right, it's going through a metamorphosis. lust as a caterpillar "morphs" into a butterfly, your engine is going to improve during the process of evolution. It's becoming more sophisticated, to catch up with the technology of the accessories and components engineers have been hanging on it.

For years, Detroit and the import manufacturers have created high-tech gadgets and gizmos for better performance and lower emissions, and incorporated them into old-engine designs with old-engine technology. Yes, there were some bold steps forward over the years, but the general architecture of the engine stayed about the same.

In more recent times, the demand to meet even stricter emissions standards has fueled a frantic effort bv engineers to modify engines to pass these tougher specs. While many devices and systems were quickly developed to overcome or rectify emissions problems created by engines, little time and effort was spent to eliminate the problems at the engine itself. Until now.

Every auto manufacturer today is advancing the technological design of its engines by leaps and bounds. Let's take a look at some of the more recent examples of modem engine architecture.

New Olds V6

Oldsmobile has developed a new 3.5liter twin-cam 90 deg V6 engine for the 1999 Intrigue GLS, replacing the 3800 V6 currently used. It will be standard in all Intrigue models by the end of '99. This latest engine, a derivative of the 4.0-liter Aurora V8, is a showcase of GM's technology and foreshadows future trends of engine development.

The new DOHC 24-valve V6 employs three single-row roller chains and eight sprockets to keep the valve timing synchronized, with no maintenance for the life of the engine.

A single primary chain drives the two intake cams and the balance shaft directly from the crank sprocket. Two separate shorter loops connect the exhaust cams to the intake cams. Three guides help restrain the primary chain along taut runs, while a hydraulically activated tensioner arm eliminates slack. Oil pressure-fed tensioners complete the maintenance-free design.

The two-piece aluminum engine block, split at the crankshaft midline, uses iron cylinder liners to house aluminum pistons. Aluminum cylinder heads sit atop the block to reduce weight while improving heat dissipation. A counterrotating balance shaft is located in the vee of the block for smoother, quieter operation. Powdered metal is used in the connecting rods, cam drive sprockets, camshaft bearing caps, valve guides and valve seats, providing more consistent parts that require less machining.

Smaller, top-feed SFI fuel injectors are fed by an advanced-design composite fuel rail, which attaches to the tuned, thermoplastic intake manifold without bolts. The engine's 3.52x3.62inch (89.5x92mm) bore/stroke and a 9.3:1 compression ratio produce 215 horses at 5500 rpm and 230 ft-lb of torque at 4400 revs, all on regular fuel.

A caseless oil filter is located in the bottom of cast-aluminum oil pan, which is designed for complete oil drainage. The 512-kilobyte Powertrain Control Module (PCM) continuously monitors engine operation and calculates when maximum useful oil life has been reached, then notifies the driver to change the oil. The PCM, which monitors more than 29 sensors, is located in the air cleaner, where airflow provides cooling. It also oversees the coil-on-plug ignition.

DexCool engine coolant, purported to be good for 150,000 miles, is used in the low-volume, high-flow-rate cooling system, which includes an internal bypass for faster warmup and reduced caold-start emissions. In the event of sudden coolant loss, a "limp-home" mode allows the engine to run at lower revs.

The new 3.5-liter V6 has lower NVH (noise, vibration and harshness) levels than its predecessor and meets California's Low Emission Vehicle (LEV) standards.

New Corvette Small-Block

When Chevrolet was developing its fifth-generation Corvette, they convinced the GM powertrain folks to build them a new engine. And what an engine it is!

The new 5.7-liter V8, dubbed the LS1, has all the latest technical toys while still retaining the muscle. The third generation of the legendary smallblock still retains "440" bore centers, but has a 10.1:1 compression ratio, a slightly smaller bore at 3.90 inches (99mm) and a longer stroke at 3.62 inches (92mm). The result is 345 hp at 5600 rpm and 350 ft-lb of torque at 4400 rpm.

The lightweight aluminum engine block features cast-in iron liners and a "deep skirt" design that extends down past the bearing caps. The powdered metal caps are secured to the block with two horizontally mounted and two vertically mounted bolts, along with two studs, for strength and lower NVH. A very lightweight aluminum cylinder head optimizes airflow and features a four-bolt design, with long bolts that anchor deeply into the block for added strength and torsional rigidity. The tuned intake manifold is made of composite material, while the dualwall exhaust manifold is constructed from stainless steel. An air gap between the walls reduces noise and lowers cold-start emissions.