CONNECTING ROD

Connecting Rod



Connecting Rod

The materials requirements for a connecting rod in a car engine includes various grades of steel, aluminum, and titanium. Steel rods are the most widely produced and used type of connecting rods. Their applications are best used for daily drivers and endurance racing due to their high strength and long fatigue life. The only problem with using steel rods is that the material is extremely heavy, which consumes more power and adds stress to the rotating assembly. Performance steel rods can be made from 4340 and even 300M grade steel. The tensile strength, yield strength, and hardness of 4340 steel depends on the temperature at which the steel is forged, and how the steel is heat treated. Variations in the tempering temperature and quenching procedure can produce extremely different results with tensile strength and yield strength. This is why it is important to buy your rods from a reputable manufacturer. 300M steel alloy is stronger than 4340 and can be used to manufacture steel rods that are lighter than their 4340 counter parts by using less material. 300M rods rated at the same strength level as 4340 rods can be 10% to 25% lighter. Aluminum rods are used widely in high horsepower, high revving drag engines. Aluminum rods can be manufactured to the same strength level as a steel rod due to large amount of material that makes up the rod but still be 40% lighter than a steel connecting rod. Reducing the weight of the rods reduces the mass of the rotating and reciprocating parts and allows the engine to rev faster and rev higher safely. In addition to better throttle response than steel, aluminum's lighter weight can reduce vibration and stress on the crankshaft. This reduced stress from inertia loading results in connecting rod journal bearings looking "good as new" after thousands of miles. The rods can stretch, and they may fatigue and fail, but unlike the aluminum rods from the 70's modern aluminum rods are much stronger and can be used in daily drive engines. Depending on the use and power levels aluminum rods can last 50,000 miles on an engine that is street and strip, the secret to making aluminum rods last long is to not constantly be over revving the engine when you drive to work. (Ritti 2007: 138-163)

Titanium rods are both lighter and stronger than steel. Unfortunately titanium is extremely ...