E53 M54 Exhaust Headers

[Bdc101]

You are confusing stress (force per unit area) and work (energy).

You are right that the E53 has more kinetic energy at a given speed than an E46, and requires more work (fuel) to get it up to that speed. But if the motor is the same, then the force on the transmission and drivetrain is the same. It has to be applied longer, but the force is the same.

You are right that there will be more heat added to the transmission, differential, u-joints, etc. But heat is not stress, and those things typically don't get so hot that they break. They absorb a very small portion of the work transmitter through them.

Stress is a force divided by an area (it has the same units as pressure, such as pounds per square inch). Heat is not stress, heat is heat.

Think of it this way: let's say you tie a rope to your X5, which weighs 4,600 lbs, and try to pull it. Let's say you can pull with a force of 100 lbs. You pull until your car is traveling at 10 mph. You are completely exhausted, but the rope has experienced no more than 100 lbs of force.

Now tie the rope to your neighbor's sweet Lotus Elise, which weighs 1,980lbs. You pull on it with a force of 100 lbs. The Lotus accelerates to 10 mph a lot faster, and you are not very worn out. But the rope never experiences more than 100 lbs of force. The transmission is the rope. It is exactly the same.