Inside The Cadillac V8 That Ran 1-2 At Daytona
The engine that powered Cadillac to an overall 1-2 finish at the Rolex 24 Hours of Daytona was developed in less than a year at ECR Engines. A 6.2-liter naturally aspirated V8, the engine is based on the LT architecture found in the spirited Cadillac CTS-V but is jam-packed with custom components and technology learned in numerous racing projects.
"ECR came on board in October 2015," remembers Brian Goble, sports car engine program manager at ECR, which is located on the Richard Childress Racing compound in Welcome, North Carolina. "We started designing the engine in January 2016 and had the first test mule on the dyno by May."
Cadillac designers were charged with implementing brand styling into the Dallara chassis approved for the IMSA DPi prototype class. The engine wasn't ready for its first fitting in the chassis until later in the fall because certain design features had to be finalized that allowed the all-alloy engine to act as a semi-stressed-mounted member in the car.
IMSA gave Cadillac a target of 600 horsepower. Even though the prototype series mandates sonic air restrictors in the interest of balancing power, making 600 horsepower with a 6.2-liter V8 was achieved quickly. The emphasis for the team then shifted from performance to assuring durability.
"In endurance racing, that has to be number one," says Goble. "It's a performance balanced series. We need to make sure we're durable above all else. [The internal components are] pretty much bespoke, but everything is based around the basic production engine."
"We split the pressure stage from the scavenge system," says Goble, adding the strategy was pressured by packaging concerns. The scavenge is a 4-stage system that pulls strictly from the crankcase; there is is no scavenging from the top of the engine."The production engine works well with gravity drainback," adds Goble..
The sump is an integral member of the engine, again to help carry stress loads that come from the chassis. The front plate where the engine is bolted to the chassis is designed to handle the transfer of water and oil from the engine. It supports the water expansion tank and the dry-sump oil reservoir.
"So when the team bolts a fresh engine into the chassis, all that goes with it," says Goble. "All of the transfer is done through transfer tubes. There are no oil lines on this engine. You look at this engine from the outside and there are no flexible lines or fittings."
The cooling system is rather basic with left- and right-side radiators and a water pump drawn from the Chevy R06 NASCAR engine.
"We actually run a production thermostat," adds Goble.
"The valvetrain has a few things that are proprietary to the program," says Goble, noting that direct injection is not carried over from the production engine. Instead, the intake manifold is designed with port injection.
"We evaluated the benefits versus the cost, and it didn't warrant having [DI] initially," says Goble, adding that given the tight timeframe for development the team had to pick it's battles. "There are potential provisions for it in the future if we need to."
Kinsler helped develop the intake manifold and fuel system. From the sonic restrictors, air is plumbed to a common-plenum intake. The intake has somewhat of a modular design that keeps all the working parts, such as the shafts, seals and bearings inside the air box.
"That allows us to keep all the working working components clean and cool," explains Goble. "The service life has gone up immensely doing that."
While the intake design came together fairly easily, the exhaust tubular-header design was more dependent on packaging issues dictated by the chassis and body design.
"But they have a really nice sound on the track," says Goble. "We run it up to around 7,500 rpm and it has a really nice note to it."
Also contributing to the Cadillac racing vision are engine aesthetics and torque.
"We wanted to present an image that was in line with what Cadillac wanted to present with its cars," sums up Goble, explaining that the engine was enhanced with colors and trim tied to a Cadillac theme. "And with a bigger displacment engine you have a broad torque curve. It's also in line with what a Cadillac should achieve on the torque side."
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