Every time you mash the accelerator to the floor and ride the burst of speed down the road or around the track—you are putting your car’s pistons through Hell—literally!
Fortunately, manufacturer’s like CP Pistons
, which joined forces with rod and performance parts builder Carrillo in 2010, are cranking out some of the tightest most technologically advanced ever built.
If you’ve ever crawled inside a performance engine, you can clearly attest to the fact that the pistons are arguably the most abused parts within the engine. Imagine accelerating from a dead stop up to an average velocity approaching 5000 feet per minute and back down to a dead stop 125 times every single second. Now, imagine doing this in an environment filled with combustion gases in excess of 1400 degrees Fahrenheit. Sounds like Hell, and that's exactly what each piston in your engine must endure when you find yourself pushing 8000 rpms along a straightaway.
For over a decade CP Pistons
has been manufacturing high-performance pistons and ring kits for virtually every vehicle make and model you can imagine (and a few you can’t). They’re known in auto-sports circles for their fully machined, lightweight, precision pistons. CP Pistons
are engineered using sophisticated computer modeling for optimum designs, while their 5-axis machining capability enables them to create any piston for any application—from a Chevy big block, to a Mazda sport compact.
Keeping Silicone Out of Your Jugs
Aftermarket pistons generally come in two flavors, 2618 and 4032 alloys. CP Pistons lean to the low end of the silicone spectrum and are forged and made from a special alloy of aluminum.
Custom engine builders prefer the use of forged pistons because time and experience have proven them to be more durable and easily customized to any configuration, which is essential in engine tuning. Even in cases that require modifications to the piston crown to assist in valve relief this can be easily achieved with a forged piston.
Forged pistons undergo a more involved manufacturing process than cast pistons (which tends to make them more expensive). The molten metal is first formed into bars by a continuous casting or extrusion process. The bars are then cut into 3" to 4" long slugs, which are then heated and fed into a forging press that shapes the slugs into raw pistons. The forging process increases the density of the metal, which significantly improves its strength, ductility and thermal characteristics.
One of the key characteristics that make forged pistons excel in high performance applications is strength and durability. The high silicon content of cast pistons makes them brittle compared to forged pistons. Silicon gives the metal lubricity and is mixed in the alloy to limit heat expansion. This is primarily the reason why cast pistons require careful handling. Mild shock applied to it may cause the material to break. The process of forging compresses the molecules inside the alloy, which results in a denser surface area compared to a cast piston.
It’s true that forged pistons are heavier than cast pistons, but this minor negative aspect is far outweighed by the ability to provide a high compression ratio inside the engine, enabling the engine to rev higher and produce more power. Most turbocharged and high performance car models use forged pistons because they're more tolerant to the abuses of extreme heat, detonation and pressure inherent in performance-oriented engines.
An engine modification tweaked toward producing more power will benefit from a forged piston, as the high tolerance to abuse enables the tuner or engine builder to make incremental adjustments to enhance engine performance. Forged pistons are also readily available compared to cast pistons which are only available in OEM sizes, hampered by the expensive casting process.
Picking the Perfect Pistons
With so many pistons to choose from, it's kind of tough to narrow down the choices and decide on an appropriate piece.
Really, the two factors to consider are application versus dollar. Given a choice, we can't think of a reason, other than price, anyone would prefer a cast replacement piston to a modern forged model. But again, it's important to consider the whole picture. If the goal is an economical rebuild in a low-rpm, low-compression, low-output engine, cheaper, cast pistons may work for you.
On the other hand, if you're looking to build horsepower and performance, then it only makes sense to check out CP Piston’s
constantly growing line of performance, forged pistons that will add some to the cost, but could save you hours of frustration and regret.