There are two types of cylinders as for gasoline engine, saying, iron casting engine and aluminum casting engine. Today, we’ll talk about the strengths and defects of the two cylidners. Most of the cylinder head is aluminum, so it is exluded here. 1) Weight Since iron is weighty than aluminu, with the same required strength, aluiminum cyliner will be much more lighter than iron cylinde. A light engine will make the vehicle lighter and play a positive role to the vehicle weight distribution. Thus, aluminum wins in this point. 2) Size With the same reason, as aluminum is lighter, the aluminum structural strength in unit volumn is less than that of iron. So generally, aluminum cylinder is bigger in volumn. 3) Corrosion Resistance and Strength Aluminum can easily reacts with the water produced from combustion, so its corrosion resistance is not as good as iron cylinder, especially for the engine of high temperature and pressure. Therefore, iron casting cylinder is selected for supercharged engine. 4) Cost Obviously, aluminum cylinder is more expensive than iron cylinder, so iron cylinder is better. 5) Antiknock and Heat Dissipation Property Aluminum conducts heat faster and cool down quickly, which can help engine reduce the occurrence of abnormal combustion. With same reduction ratio, aluminum cylinder can bear lower grade gasoline. 6) Friction Coefficient To decrease the inertia from reciprocating motion of component and improve revolution and response speed, aluminium alloy is generally adopted as the material of piston. If the cylinder is also aluminum, the friction coefficient between two aluminum materials will become bigger, which can affect performance of the engine. If iron cylinder is used, this problem will be neglected. Conclusion: Strength of aluminum cylinder: not weighty, excellent dissipation property Strength of iron cylinder: low cost, duable.