Cadillac’s new twin-turbo V-8 is a 550-hp bombshell
V-8s are yestertech according to Tesla and other soothsayers. That begs the question, who will be the last to launch a new V-8 capable of meeting today’s expectations for poise, vitality, and efficiency? Bucking the electrification tide, Cadillac is tapping more than a century of V-8 expertise to introduce the clean-sheet design depicted here.
More than four years in the making, Cadillac’s hero V-8 embodies practically every known modern design feature.
At 4.2 liters, it’s modestly sized in the interests of fuel efficiency, though EPA ratings are as yet unspecified.
Chain-driven dual-overhead cams, four valves per cylinder, and variable intake- and exhaust-valve timing provide exemplary volumetric efficiency.
Roller finger cam followers with hydraulic lash adjusters minimize friction and disable four cylinders (two per bank) during light loads to save fuel.
The combination of a relatively small 86.0 mm (3.39-inch) bore and long 90.2 mm (3.55-inch) stroke provides a compact combustion chamber while minimizing overall engine length.
Aluminum block, head, cam carrier, and oil pan castings save weight while pressed-in cast-iron cylinder liners foster durability.
Connecting rods and the crankshaft are forged steel to handle their dynamic loads. Each main bearing cap is secured by two horizontal and four vertical fasteners to maximize lower end rigidity.
Two Mitsubishi Heavy Industries variable-nozzle turbochargers are positioned between the cylinder heads—a configuration called “hot V”—to recycle energy that leaves the combustion chambers. Titanium aluminide turbine wheels spin up to 170,000 rpm generating the maximum 20 psi (1.4 bar) boost pressure.
Exhaust manifolds are cast integrally with the turbine housings. Twin catalytic converters are located just behind the turbos. Two liquid-to-air intercoolers mounted atop the cylinder heads lower the intake charge temperature by up to 130 degrees F.
Ultra-high pressure (over 5000 psi) injection delivers highly atomized gasoline directly to each cylinder for complete combustion from idle to the 6000-rpm redline. Premium fuel is required.
GM engineers devoted 10,000 hours to development and validation testing including 80 hours with the engine running on a fixture that tipped this powerhouse every which way. According to chief engineer Jordan Lee, a daunting development issue was managing residual turbo and exhaust system heat following shut down. The solution is a pump circulating coolant through the turbochargers’ bearing housings and a large fan to flush trapped heat from the engine compartment after the ignition is switched off.
Cadillac CT6 customers will be able to order this engine in the first half of 2019. The top version will produce a competitive 550 horsepower at 5700 rpm and 627 lb-ft of torque from 3200 to 4000 rpm in the CT6 V-Sport. A second edition with the same basic hardware but milder calibrations will provide 500 horsepower at 5200 rpm and 553 lb-ft of torque from 2600 to 4600 rpm in regular CT6 sedans. Since development will continue for another year, these ratings are subject to change.
GM’s 10-speed Hydramatic transmission and all-wheel drive will be standard. The front differential is supported by the new V-8’s structural oil sump.
Each twin-turbo V-8 will be hand assembled at GM’s Bowling Green, Kentucky, Performance Build Center, located within the confines of the Corvette assembly plant. Per tradition, each assembler will autograph an ID plaque attached to the engine.
While GM insists this engine is exclusive to Cadillac for the time being, it’s easy to speculate on how additional dividends will accrue from its use. Slipping the twin-turbo 4.2 under the Escalade’s hood would add power and prestige to Cadillac’s SUV starship. The new XT6 crossover will surely take advantage of the engine when it arrives and a naturally aspirated version generating 400 or so horsepower could add gusto to the XT5 crossover’s soul, although that is the least likely eventuality to pan out.
Don’t forget about GM’s other needy children—Chevrolet, Buick, and GMC. All have crossovers capable of putting versions of this new V-8 to good use.
While the current Corvette is endowed with up to 755 rampant stallions, the next generation of Chevy’s sports car poses fresh powertrain opportunities. Given what we know about the eighth-generation (C8) Corvette and the convenience of a prestigious engine shop adjacent to its assembly line, it’s likely that a 600-horsepower version of this new twin-turbo V-8 will reside just behind the 2020 Corvette’s driver.
So, when and if Tesla rolls forth its new $200,000 Roadster, a Corvette should be ready and able to defend the hallowed piston’s honor.