Theory

If you are reading this chances are you are interested in increasing the horsepower output of your engine. In order for you to successfully modify your engine to produce more power it is necessary to have a basic understanding of how an engine works and how modifications do what they do to increase your power output. For starters, think of an engine as a giant air pump. It gobbles up air from the atmosphere and dumps it into six cylinders. Inside each cylinder, the air is mixed with fuel that is sprayed in by the fuel injectors. The spark plug ignites, causing a small but powerful explosion. This explosion rapidly expands the air that is inside the cylinder, forcing the piston upwards. The piston is connected to the connecting rod which turns the crankshaft. The crankshaft spins and is connected to the transmission, driveshaft, rear differential, and finally, the rear axle and wheels.

The general idea behind making your engine stronger is the more air and fuel you can dump into each cylinder, the more powerful the explosion will be. If the explosion is more powerful, the piston will be forced upwards faster, resulting in more power turning the crankshaft and propelling the car.

From the factory, most cars are not designed for raw performance. They are designed to be reliable, quiet, fuel-efficient, and environmentally friendly. The hotrod owner, however, is willing to sacrifice some of these qualities in order to increase the power output. The first step in doing this, understandably, is to upgrade the intake and exhaust. A free-flowing intake and exhaust setup will allow your engine to breathe better, giving it the ability to effectively burn more fuel and produce more power.
 

Complete 3" Exhaust System for 3.8, including Headers

Because the engine of the V6 F-Body is not designed out of the box for all-out performance, upgrades can work wonders. The factory air intake system is highly restrictive, allowing only a trickle of air to enter the combusion cylinders. The exhaust is restrictive, resulting in backpressure that robs your engine of performance. Why does GM design the cars like this? One major reason is noise. Free-flowing intakes are loud, as you can hear the air wooshing in. Another is emissions. During each stroke, not all of the fuel molecules in the combusion cylinder are burned. Let us say for the sake of this example that only 80% of the fuel molecules in a cylinder burn during the first cycle. If your car is equipped with a free-flowing exhaust system, 100% (theoretically) of that gas will leave the cylinder in time, allowing fresh fuel and air to enter (good power output). However, that 20% of gases that remains to be burned leaves your engine unburned--and results in exhaust pollution. OEM exhaust systems are designed restrictive so that an incomplete amount of burned gases leaves the cylinder in time. This means that some of that gas will be burned again, reducing the amount of unburned gas leaving the engine. Although this results in lower emissions, it means that not all of the gases in the cylinder are fresh, new, unburned fuel and air molecules. The end result of all this is a less powerful explosion within the cylinder--and less horsepower.

To a certain extent, your engine needs backpressure. However, the amount that it needs is very low compared to the backpressure that is present in stock configuration. A good idea when upgrading your intake and exhaust is to reduce your backpressure as much as possible while retaining all components that were originally present. If your engine did not need any backpressure then running open headers would result in the highest power gain, since open header setups have virtually no backpressure. Going this extreme, however, results in a sharp loss of torque. (Similar results are seen with cutouts in the open position.) Your engine needs a little, but not a lot. So, exactly how much does it need? This question, while it may sound simple, is impossible to answer on an internet guide. Exact numbers cannot be attained, as they vary by ambient air pressure, density, temperature, elevation, driving style, other modifications present, and thousands of other variables that are different for every car and driver. But if you upgrade every component of the intake/exhaust system with a high-performance one, the chances of you hitting that "happy, very little but not too little backpressure" point is high.

The components that people upgrade include the intake, the exhaust manifolds (by replacing them with headers), the Y-pipe, the catalytic converter, the intermediate pipe, the muffler, and the tips. We will discuss each part in turn.