There are two types of cylinders as for gasoline engine, saying, austempered ductile iron casting engine and aluminum casting engine. Today, we’ll talk about the strengths and defects of the two cylinders. Most of the cylinder head is aluminum, so it is excluded here.
1) Weight
Since austempered ductile iron is weighty than aluminum, with the same required strength, aluminum cylinder will be much more lighter than austempered ductile iron cylinder. 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 volume is less than that of austempered ductile iron. So generally, aluminum cylinder is bigger in volume.
3) Corrosion Resistance and Strength
Aluminum can easily reacts with the water produced from combustion, so its corrosion resistance is not as good as austempered ductile iron cylinder, especially for the engine of high temperature and pressure. Therefore, austempered ductile iron casting cylinder is selected for supercharged engine.
4) Cost
Obviously, aluminum cylinder is more expensive than austempered ductile iron cylinder, so austempered ductile 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, aluminum 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 austempered ductile iron cylinder is used, this problem will be neglected.
Conclusion:
Strength of aluminum cylinder: not weighty, excellent dissipation property
Strength of austempered ductile iron cylinder: low cost, duable