Auto Service World
Feature   October 1, 2009   by Andrew Ross

GM’s 3.0 Litre V6 LF1

An Engine Worth Knowing:

The current climate of the engine building business continues to require much from its proponents in the way of diversification, but the automotive segment remains an important part of the business.

And into this changed market has emerged a changed General Motors– at least if you believe the hype. Despite any suggestions to the contrary, the venerable automaker continues to be a significant player and it continues to increase the repertoire of engines that shop staff have to be familiar with.

One that seems destined for the workbenches of the future is the 3.0L DOHC High Feature V6 (LF1), found in several Cadillac models such as the SRX (GM is also dropping it into the CTS sedan, CTS wagon, and Buick Lacrosse; for those who are curious, it will also be found in the 2011 Saab 9-4.)

The direct-injection, variable-valve timing unit features four valves per cylinder and a reasonable output of 265 hp @6950 rpm. The 3.0L direct-injection V-6 is a smaller-displacement version of the 3.6L direct-injection engine featured in the CTS sport sedan and named one of the World’s 10 Best Engines for 2009 by Ward’s Automotive.

It is paired with a Hydra-Matic 6T70 six-speed automatic transmission with manual shift control.

The engine is part of GM’s global family of V6 engines that employ the most advanced automotive engine technology available, from state-of-the-art casting processes, to full four-cam phasing, to ultra-fast data processing and torque-based engine management.

The 3.0 litre LF1 is one of GM’s Global Engines.

On the LF1 engine, fuel is introduced directly to the combustion chamber during the intake stroke. The fuel injectors are located beneath the intake ports.

Direct injection requires higher fuel pressure than conventional fuel-injected engines produce, so an engine-driven high-pressure fuel pump is used to supply up to 1740 psi (120 bar) of pressure. The system regulates lower fuel pressure at idle, approximately 508 psi (35 bar) and higher at wide-open throttle. The cam-driven high-pressure pump works in conjunction with a conventional fuel tank-mounted supply pump.

The V6 VVT’s engine block and cylinder heads are cast from A319 aluminum alloy. The sand mould cast block features strong cast-in iron bore liners, six-bolt main caps, and inter-bay breather vents.

A four-valves-per-cylinder inverted tooth chain cam drive contributes to the smoothness and high output. The inverted tooth chain uses a design that spreads out the period of engagement between the sprocket and chain. This reduces the force of the initial impact between the two components because it is spread out over a longer time period, reducing noise.

The V6 VVT’s nerve network is a new torque-based engine management system, which improves upon previous throttle-based management systems that rely exclusively on the throttle position sensor to govern throttle operation for the electronic throttle control (ETC).

The torque-based strategy calculates optimal throttle position, the position of the intake plenum plate, cam phasing positions, and other operational parameters, and translates that data into an ideal throttle position and engine output, based on the driver’s positioning of the gas pedal.


3.0 L V6 LF1 At a Glance

3.0L DOHC V-6 direct injection, variable valve timing, four valves per cylinder

Displacement (cu in / cc): 183 / 2994

Bore x stroke (in / mm): 3.50 x 3.16 in / 89 x 80.3

Block material: A319 aluminum with cast iron liners

Cylinder head material: A319 aluminum

Valvetrain: DOHC, four valves per cylinder

Ignition system: coil-on-plug

Fuel delivery: high-pressure direct injection

Compression ratio: 11.7:1

Horsepower (hp / kW @ rpm): 265 / 198 @ 6950

Torque (lb-ft / Nm @ rpm): 223 / 302 @ 5100

Recommended fuel: regular unleaded

Max engine speed (fuel cut-off): 7000 rpm

Emissions controls: dual close-coupled catalysts and single underfloor catalyst; variable valve timing, evaporative system

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