Where Does the Gas Go?

We've seen too much misinformation regarding exhaust (read: that pipe that runs under your car which gives off or "exhausts" certain things) theory.

What kind of misinformation? For starters, there are a lot of people in the "bigger is better" camp. We're talking about exhaust pipe diameters.

Of course you've seen them quasi-race cars with the biggest exhaust systems making the most thundering noises while parking at your lot. For some, this is just way irritating while for others, well, they just have to put up or shut up.

So is bigger really better? To understand and to be able to take a side on this great debate, one must know what really happens and what purpose does the exhaust pipe serve.

Let's start from the beginning. What is an exhaust system? Silly question? Not hardly. Exhaust systems carry out several important functions. First of which is getting hot, noxious exhaust gasses from your engine.

These are placed away from the engine compartment. Basically it's the waste place of the car. It also significantly soothes noise output from the engine. And in the case of modern cars, reduce exhaust emissions.

So how the heck does the exhaust system work?

Here's a point by point, step by step travel of the exhaust in your car. This will give you an idea on what happens inside your car (just the exhaust side, though)

After your air/fuel mixture (or nitrous/fuel mixture) burns, you will obviously have some leftovers consisting of a few unburned hydrocarbons (fuel), carbon monoxide, carbon dioxide, nitrogen oxides, sulfur dioxide, phosphorus, and the occasional molecule of a heavy metal, such as lead or molybdenum.

These are all in gaseous form, and will be under a lot of pressure as the piston rushes them out of the cylinder and into the exhaust manifold or header It collects the exhaust gases from multiple cylinders into one pipe.

They will also be hotter. An exhaust manifold is usually made of cast iron, and its' primary purpose is to funnel several exhaust ports into one, so you don't need four exhaust pipes sticking out the back of your Civic.

Exhaust manifolds are usually pretty restrictive to the flow of exhaust gas. So therefore, they waste a lot of power because your pistons have to push on the exhaust gasses pretty hard to get them out.

So why does virtually every new automobile sold have exhaust manifolds? Because they are cheap to produce, and easy to install. Real cheap. Real easy.

The performance alternative to the exhaust manifold is a header. What's the difference?

Where a manifold usually has several holes converging into a common chamber to route all your gases, a header has precisely formed tubes that curve gently to join your exhaust ports to your exhaust pipe.

How does this help? First of all, as with any fluid, exhaust gases must be treated gently for maximum horsepower production (that's your engine's power) You don't want to just slam-bang exhaust gas from your engine into the exhaust system.

Nextly, exhaust gases exit from your manifold or header, travel through a bit of pipe, then end up in the catalytic converter, or "cat". The cat's main job is to help clean up some of the harmful chemicals from your exhaust gas so they don't end up in your lungs.

In most cars, they also do a great job of quieting things down and giving any exhaust system a deeper, mellow tone.

From the catalytic converter, the exhaust gasses go through a bit more pipe and then into a muffler, or system consisting of several mufflers and/or resonators.

Exhaust gases leave the engine under extremely high pressure. If we allowed exhaust gasses escape to the atmosphere directly from the exhaust port, you can well imagine how loud and cop-attracting the noise would be.

For the same reason gunshots are loud, engine exhaust is loud. Sure, it might be cool to drive around on the street with that testosterone producing, chest-thumping, 150 decibel roar coming from your car... for about 5.3 seconds. Even the gentleman's gentleman has got to use a muffler, or system of mufflers, on their exhaust.