Sep 02 , 2024
How Can Piston Design Affect LS Engine Performance?
The Smeding 427" LS Short Block, when opting for the 1300 horsepower engine configuration, can be fitted with one of three piston options, each with a different head volume and crown shape that influence its combustion efficiency. Below, we’ll discuss how piston head volume and crown shape can impact your engine’s performance.
What Is Piston Head Volume?
Piston head volume, which accounts for the size of the piston head in cubic centimeters (cc), directly affects the combustion chamber size (the volume of the chamber in the engine’s cylinder head) and impacts the compression ratio (the ratio between the volume of the cylinder and the combustion chamber at their minimum and maximum values). High compression ratios indicate a “squeezed” air-fuel mixture, which enhances combustion and increases horsepower.
What Is Piston Crown Shape?
Performance pistons are manufactured with flat, dish, or dome-shaped crowns that can influence the dynamics involved in the movement of the ignition flame, inlet airflow quality, fuel distribution, and other factors that contribute to successful combustion. Usually, your engine’s valve clearance, compression requirements, and detonation risk will determine which piston type will work best in your build.
Flat-Top Pistons
Flat-top pistons have flat tops that support ideal combustion efficiency by offering the “best burn” of fuel and a higher compression ratio. Some flat-top pistons have a “valve relief,” which indicates that some material was removed from the top of the piston to keep it from hitting the intake and exhaust valves when they are active. This allows the piston to go further into the cylinder head and improves compression ratios.
Dish Pistons
Dish pistons have a scooped-out crown that adds volume to the combustion chamber and reduces the compression ratio. They help fuel burn fast in boosted, turbocharged, or supercharged engines and also help prevent detonation, or "spark knock.”
Dome Pistons
Dome pistons have convex crowns that reduce their combustion chamber volumes and increase their compression ratios. Dome pistons with broad, low-profile crowns can improve performance, but highly domed pistons can block flame on the piston’s power stroke and cause fuel to burn slowly, contributing to inefficient combustion.
How Does Piston Crown Shape Affect Horsepower?
A piston’s crown shape can impact the amount of horsepower your engine can produce by affecting how the fuel mixture burns inside the combustion chamber. Flat piston crowns can help a fuel mixture burn faster and more completely, which can prevent it from detonating prematurely. Since dish piston crowns tend to decrease the compression ratio, they can help boosted engines avoid detonation, but they do not typically increase horsepower or torque. Domed piston crowns tend to increase the compression ratio, horsepower, and torque. For best results, the piston crown should be matched to the cylinder head that forms the roof of the combustion chamber.
How Does Piston Volume Affect Horsepower?
A piston's volume impacts the engine's swept volume and the compression ratio, which influences combustion efficiency and power generation. Larger piston volumes and high compression ratios typically lead to more horsepower; as a rule, each whole-number increase in compression can increase power by 3 to 4%. The piston's size directly influences the volume of air the piston displaces as it moves through the cylinder, and larger swept volumes are correlated to higher air intake, which can potentially increase horsepower.
Smeding Has the Perfect Pistons for Your 1300 HP 427" LS Short Block
When you’re building out your 1300 hp 427" LS short block, the shape and volumetric differences between a 3.5 cc dome piston, a 7 cc flat top piston, and a 17 cc dish piston can affect the combustion efficiency and power production of your engine. The professionals at Smeding can help you choose the piston crown design that works best with your compression requirements and valve pocket shape, so that your car will run flawlessly and provide you with untold hours of fun. See all of LS Engine offerings.