At this stage in the horsepower and size wars among full-size trucks, every little advantage is worth pursuing. Case in point: Ford’s “cobra head” turbo exhaust downpipe that helps the 6.7-liter Powerstroke diesel make best-in-class horsepower and torque.
A press release from Ford said the unique shape of the downpipe, which the release compared to the shape of a cobra snake’s head, helps the Powerstroke engine breathe easier. The new, second-generation 6.7-liter Powerstroke diesel engine reportedly is rated at 440 horsepower (up from 400 horsepower in the first generation) and 860 ft-lbs (up from 800 ft-lbs) across all Super Duty models, from the F-250 all the way up to the F-450.
Some may remember Ford’s designing the first-generation 6.7-liter Powerstroke V8 diesel engine in a “hot-V” layout, where the exhaust ports are on the inside of the cylinder banks while the intake ports are on the outside. This is the opposite of the usual engine layout. Ford said the seemingly backward design was used for its thermal efficiency — it shortens airflow from the exhaust system to the turbo sitting between the cylinder banks, which improves turbo responsiveness, and it helps the engine efficiently use hot temperatures, which improves performance and efficiency, according to Ford. An added benefit for those who may not like their diesel truck sounding like a clattering Peterbilt semi: Ford says the layout also reduces noise, vibration, and harshness.
But getting all those hot exhaust gases out of the turbocharger inside the engine’s “V” is the job of the so-called “cobra head” downpipe, the press release said. Ford offered this explanation of how it all works:
Any sharp turn or kink in an exhaust system can disrupt the flow and increase the pumping work an engine must do, reducing efficiency. The Cobra head acts like a widened, banked turn, allowing exhaust gases to flow smoothly through the 90-degree turn from the engine to the aftertreatment system and reduce backpressure. By reducing pumping losses, the design improves efficiency and allows greater torque production.
By applying hundreds of hours of advanced fluid dynamics computer modeling simulations to the design, Ford engineers were able to optimize the shape of the pipe bend.
Ford Powerstroke Engine Air Path Technical Leader Robert Wade said, “Fluid dynamics allowed us to precisely tune the curvature and width of the pipe to optimize exhaust gas flow. It turns out that a downpipe shaped like a cobra head is the ideal design for air flow and breathability, which we validated through thousands of miles of durability testing.”