Horses for Courses – GM’s Small Block V8 Versus Ford and Ram

A lot of time was spent in the wind tunnel understanding  turbulence, with new mirrors, triple-sealed inlaid doors, as well as roof and tailgate tweaks that all help air flow smoothly, which also improves the fuel economy of the Sierra and Silverado.

The pickup truck business is based on capability that derives from the chassis and powertrain, with owners balancing a combination of power, useful load and fuel efficiency. In a different approach than the one currently used at Ford or Ram, GM will offer a new engine family for Silverado and Sierra pickups starting this spring with pushrod engines that include a 4.3-liter V6, as well as 5.3-liter or 6.2-liter V8s. Significant technology has been added to what is a post WW2 design with direct injection and cylinder deactivation added, a fuel saving technique GM pioneered in trucks.

These so-called GM EcoTec3 engines have other modern technologies – aluminum blocks and heads, 11:1 or higher compression ratios,  but they run on regular gasoline. Moreover, adding cylinder deactivation under lighter loads seems a good combination to make the most power, torque and efficiency across a broad range of operating conditions, at least that’s GM’s view.

This debatable engineering philosophy gained some credibility today when GM revealed that the 2014 Silverado and Sierra pickups with the 5.3-liter V8 engine – the most popular engine – will be rated at an EPA estimated 23 mpg highway. The trucks also have better fuel economy and higher load capacity at a maximum of 11,500 pounds than the 2013 model Ford EcoBoost V6, an expensive approach that uses two turbochargers and intercooling, among other tweaks. Ram is using a 5.7-liter double overhead camshaft multi-valve V8 linked in its best version to an 8-speed automatic, and is rated at 20 mpg. 

All three of the new GM Ecotec3 engines will come with a six-speed automatic transmission (Dodge has 6- and 8-speeds, Ford 6-speeds) with gear ratios and shift schedules optimized for performance and efficiency. The transmissions will have ‘Auto Grade Braking,’ which downshifts on downgrades to help reduce brake wear, a now common technology. Because of the added torque of the heavily revised V8 engines, new 9.5- or 9.76-inch rear axles are used.

The Silverado and Sierra pickups will prompt a real debate between GM’s naturally aspirated engines and Ford’s forced fed, turbocharger approach, which has been criticized for its overly optimistic fuel economy ratings that evaporate when you work the turbo hard. There are also potential durability and maintenance concerns. Judging by sales, though, Ford had a distinct marketing advantage here, at least for the moment.

Toyota has shown a heavily revised Tundra pickup truck that will debut later this year, but the engines are carried over with its three powertrains –  a 4-liter V6 with a five-speed, yes five-speed automatic, and two V8 engines, 4.6-liter and 5.7-liter, both with 6-speed automatic transmissions. All the engines are 4-valves per-cylinder, but Toyota is lagging on transmission speeds, direct injection and cylinder cut-out technology compared to GM. No fuel economy ratings yet. Tundra is selling in small volumes far below what Toyota originally thought probable at 102,000 during 2012 compared to F-Series at 645,000, Silverado 418,000, Ram 293,000, and Sierra 157,000.

GM powertrain is committed to an aggressive cylinder-deactivation approach. The new Silverado and Sierra have improved engine mounts, electronic throttle control, adaptive exhaust systems, improved aerodynamics, low-rolling resistance tires, and other technologies that help the V8 engines operate in four-cylinder mode for longer periods of time, further increasing efficiency. It’s all going to come down to how the owner loads, and to a lesser extent drives the pickup. The inherent torque of the V8 if it keeps engine running as a V4 could be a real breakthrough. Now all GM needs is an 8-speeded or nine-speed automatic transmission.