Why does an exhaust system have to move a little?

Question

what would happen if it is solid for example bolted in to the frame of the vehicle ?

Answer 1

The movement of the engine would cause stress cracks in the exhaust . Also , if you bolt it solidly to the frame , the vibration , heat and noise transfer would be atrocious .

Answer 2

There's a few of reasons. Most important is because the engine moves. If the exhaust system didn't move with the engine, something would crack, like the exhaust pipe, exhaust manifolds, or exhaust system mounting brackets. Cracks in the system cause leaks, and exhaust can get into the inside of the car, causing carbon monoxide poisoning. Second, on a vehicle with a frame, the entire frame of the car can flex, especially trucks and big cars, so the exhaust system needs to be able to move a little so it doesn't break. Third, because some exhaust systems are quite long, as they heat up they expand in length a bit, and if they are bolted to the frame with no "wiggle room", they can buckle or bend.

Answer 3

The engine... motor sits on engine mounts fo that the vibrations and movements of the engine are not transmitted to the car body or chassis. If it was solidly fixed the car would vibrate like crazy and belive me it wouldnt be comfortable...
So the exhaust has to be able move with the movements of the engine.. If it was directly bolted to the chassis or frame of the veh it would flex and flex at the point where it is connected until it snaps at that point. The contstant strain against the fixing bolt would lead to many small cracks in the system. Also .. again the exhaust fixed to the frame would transfer the noise it is is also trying to cancel out ( the muffler or silencer ans it is called in the uk) to the body of the car effectively amplfing it and again making the inside of the car noisy and uncomfortable.

Answer 4

Exhaust systems are secured to the underside of cars by rubber bushings to prevent them from cracking.

When you rev your engine up, the torque it produces makes the engine move (or flex). If your engine was on stock (or even some aftermarket polyurethane) motor mounts, and your exhaust was solidly welded to the frame, your exhaust would develop a weak spot because the engine would be able to move, but the exhaust would have no where to go. The weak spot would probably be the first solid mount point on the exhaust pipe. Once that happens it would just keep on finding weak points in your solid exhaust (or maybe even the manifold) until the torque the engine produces isn't enough to break it anymore.

Answer 5

because your engine moves on the engine mounts. You don't see it, because you're driving. IF you had it solidly mounted, it would eventually crack and break, as there's no "play" or give to allow the pipes to move with the engine. Or, you can have a flex section from the engine to the system, some cars, like VW Scirocco's, had that, so the rest of the system COULD be solidly bolted in. But that is one EXPENSIVE piece of exhaust piping.
- The Gremlin Guy -

Answer 6

The only reason is the torque of the motor moving the exhaust has to be free in the front only, you could bolt the rest of it solid if you wanted.

Answer 7

It would resonate so badly in that car that you couldn't stand it. The exhaust is mounted with rubber bushings so it wont resonate through the metal and so that it wont transfer heat into the body panels.

Answer 8

torque of the motor, the twisting of the body .,to keep heat from conducting into the car. Prevent paint and insulation from burning.