Ford’s Other Cobra: The 6.7L Power Stroke Downpipe
When it comes to turbocharging, get the exhaust out as quickly as possible with little back pressure is the name of the game in gain. So, to increase the power of the second generation 6.7L Power Stroke many different parts of the exhaust system were looked and none more so than the downpipe off of the turbo. So, how does this “Cobra Head” shape make more power?
The exhaust system of any turbocharged engine, be it EcoBoost or Power Stroke, has to be efficient in its flow to minimize back pressure. Back pressure will slow the turbo down and spool time will increase leading to less power.
Through the use of fluid dynamics, Ford’s engineers were able to produce a shape that would act much like a banked 90-degree turn rather than a sharp, flat bend and it came out to look much like a Cobra head.
“Fluid dynamics allowed us to precisely tune the curvature and width of the pipe to optimize exhaust gas flow,” said Robert Wade, engine air path technical leader. “It turns out that a downpipe shaped like a cobra head is the ideal design for air flow and breath-ability, which we validated through thousands of miles of durability testing.”
This and the decision to go with the “hot-V” design to put the turbo in the engine valley have not only increased the response of the turbo, but have also allowed the new 6.7L to produce 440-horsepower and 860-lb/feet of torque.
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