Forged Crank, Forged Rods, Cast Pistons — Wait, WHAT?
As you start to dig into the parts that make up the rotating assembly, you see that there is a lot of “forged” material there. The crank and connecting rods are all forged, but, what about the pistons? Well, they are cast.
Before you scream out about how Ford went cheap on the Coyote, let’s take you through what the pistons actually are. You may just be surprised to find out what “forged” actually means in the rods.
The pistons in the Coyote are a hypereutectic cast piston, meaning the metal that the pistons are made of is an aluminum alloy that contains silicon beyond the eutectic point of the aluminum. The eutectic point is the homogeneous solid mix of atomic and/or chemical species, to form a joint super-lattice, by striking a unique atomic percentage ratio between the components.
This type of piston actually doesn’t expand as much as normal aluminum does and it allows Ford to create a piston that fits into the bores of the block with tighter tolerances. They are also far stronger than standard cast aluminum pistons yet weigh about the same or lighter, without the cost and noise of forged pistons.
Yet, the other parts of the rotating assembly are “forged” and far stronger than the pistons will ever be, right? Well, not exactly. Anything that is forged is typically stronger, but the forging process that your Coyote’s rods went through is not the hammer forging you’d normally think of. Instead, they are a powder metal material that was sinter forged.
The powder metal fills a mold of the rods and is heated until they bond together without melting the metals. This heating process is done by heat or by pressure. After heating them up to 1,500 degrees for final forging with a machine press, they are known as pre-forms. From there, the near-net-shape rods are then sent to be machined into their final shape.
Make sense?
You must be logged in to post a comment.