The Air Filter
What Does It Do?
The air filter plays a vital role, especially for those of us who like to play in the dirt. It filters out dust, dirt and debris while still allowing air into the engine. Without a filter, the life of your engine would be a short one. Dirt and other foreign objects are your engine's enemies because they rapidly accelerate wear.
How To Get More Power:
Getting more power from an air filter is simple. Like the majority of factory parts, most stock air filters are manufactured with cost being the overriding concern-and they tend to be fairly restrictive in nature-which means that they don't flow as much air as we might like them to. Luckily for us, the aftermarket has come to our rescue with high-performance filters for pretty much every vehicle you can think of. These are much less restrictive than the standard items, and they still do a great job of filtering. Even a bone-stock engine can benefit from a better-breathing filter, and they are mandatory for a modified engine.
Tips For The Trail
When you get a new filter, make sure to get one that is washable and reusable. This makes a big difference because air filters get dirty rather quickly on the trail. Once they're dirty, they lose their efficiency and rob the engine of horsepower. A washable and reusable air filter can always be kept clean and it beats running out and buying new air filters all the time.
Fuel Delivery
What Does It Do?
The fuel delivery system's job is self-explanatory: It delivers fuel to the engine and mixes it with air. On late-model vehicles, fuel injection is used, and on earlier vehicles, a carburetor is used. Whole books have been written on fuel-injection systems and carbs, so we won't go into much detail here. To keep things simple, you can just think of their main job as supplying the right amount of fuel, at the right mixture of fuel and air, into the engine.
How To Get More Power:
Getting more power from a fuel system is where things start to get tricky. This is because if your engine is stock, your factory carburetor or fuel-injection system already does a pretty good job of metering the air and fuel mixture-those systems already are more or less optimized to your engine by the factory. But when you modify your engine, it requires more air and fuel. So simply slapping on a bigger carb-"bigger" means that it flows more CFM, or cubic feet of air per minute-or a set of larger injectors onto an otherwise stock engine does not increase power output. To the contrary, doing so would hurt performance by sending too much mixture to the engine. What you do want to do, however, especially with carbureted engines, is to make sure that your intake system is properly adjusted to send the right mixture of air and fuel down to those combustion chambers. Remember that 14 to 1 ratio-said to be the stoichimetric ratio. Too much fuel, and you waste gas and lose power because your mixture is too rich. Too little fuel, and you also lose power, and your engine might run hotter than it should because your mixture is too lean.
Tips For The Trail:
Carbs can be pretty picky animals. Just by the nature of their design, they are not the best setup for hillclimbs or off-camber terrain. That's because they like a constant, consistent level of fuel in their float bowls, which is where raw gas is stored immediately before it is mixed with air and shot into the engine's combustion chambers. Fuel sloshing around in the float bowls of the carb when your rig achieves weird angles tends to produce stalling. If you have been on the trail in a carbureted rig, you probably already have noticed this. So what is the solution? For most carbs, you will want to run the float level as low as possible to avoid stalling. We have also found Quadrajets to work well on the trail, and the new Holley Truck Avenger carb also does a good job. The ultimate, but more expensive solution, is fuel injection. By the nature of its design it eliminates float bowls and injects the fuel either directly into the cylinder or into a throttle body, giving your engine the ability to run at any angle.
Intake Maniifold
What Does It Do?
On a carbureted engine, the job of the intake manifold is to channel the fuel/air mixture from the carb to the engine's combustion chambers. With fuel-injection systems using a throttle body, the job of the intake manifold is the same. For later and more modern fuel-injection systems, however, the job of the intake manifold is to deliver just air, as the injectors squirt fuel directly into the cylinder, or into its intake port. While the intake manifold performs a basic duty, it is not a part that should be overlooked in the quest for more power because it has a direct influence upon how much air flows into the combustion chambers, and upon how quickly and smoothly it flows there.
How To Get More Power:
Most factory manifolds are built with cost and emissions, not performance, as primary considerations. Therefore it is fairly easy to improve upon their performance. The main difference between a stock manifold and an aftermarket unit is that an aftermarket manifold features smoother, and sometimes larger, passages-or runners, as they are called-and is designed to improve the flow of air and fuel. Using runners of differing lengths and diameters, an aftermarket manifold can also deliver the majority of its power in different areas of the engine's rpm band.
Tips For The Trail:
Probably the most important thing to consider when making a decision on purchasing an intake manifold involves determining where you want your power: Do you want high-rpm horsepower, do you want a strong midrange, or do you want low-rpm torque? Manifolds can be chosen to deliver the majority of their power in certain areas of the rpm band, so choose wisely and match it to the type of off-roading you do.