As truck guys, it is a fact that we need our horsepower and torque, and no time is it more apparent than when we add big, heavy tires, weighty armor and accessories, and lifts that make our rigs less aerodynamic. Short of tearing into the engine, what can you do to increase your engine’s output and make it more efficient? There are a huge number of companies making performance-increasing bolt-on parts, so here is a general overview of the most popular power improvers.?>
How Bolt-on Power Works
Many people wonder if bolt-on power is just snake oil. The rationale being that if my car could really make that power, it would have come that way from the factory. Well yes, and no. Unlike aftermarket performance companies, the OEs need to serve a number of masters and the tuning of a product reflects a compromise of fuel economy, fuel octane, costs, noise levels, sound, emissions, and other factors. This leaves some performance on the table for the aftermarket to extract with the power-adding products you’ll read about here.
Performance air filters can increase horsepower and improve throttle response. Filters come in several types of media, some being dry and some being oiled. Direct replacement filters have the same shape as an OE filter, but improve flow by increasing surface area through the use of deeper and more numerous pleats. This greater surface area allows the filter to flow more freely than stock, even when dirty. Direct replacement filters are an easy way to open up your factory intake and require no modifications. Other benefits of drop-in filters are an improvement in efficiency, a small increase in horsepower (1hp-4hp), and the ability to be cleaned and reused. Generally speaking, a properly installed direct-replacement performance filter doesn’t have any real drawbacks.
Intakes are one of the most popular add-ons because they deliver the most bang for the buck and are often easy to install and relatively inexpensive to buy. An intake essentially pairs a new, high-flow intake tract with a performance air filter, which allows the engine to take in a larger volume of air.
The biggest gains are usually seen by “cold air” versions, which typically protect the air filter and draw cooler air from outside the engine compartment, providing the engine with a denser air charge. These intakes are often more expensive and are more complicated to install than a standard aftermarket intake.
Quality intakes can provide 6-20 horsepower, depending on engine size, and owners often report a small increase in fuel economy. Drawbacks of performance intakes can be an increase in noise level and, depending on the application, power that doesn’t manifest until high RPM levels. It is also important to note your aftermarket intake’s location, as it could be lower than stock or less protected, limiting water fording capability.
Some of the most popular power-enhancing products are programmers. While the main goal of a programmer is to increase power, some offer the benefit of increasing fuel economy, while others come packed full of ancillary features, such as the ability to calibrate the speedo, adjust for a re-gear, or adjust transmission shift points. Most programmers are highly engineered and considered safe upgrades.
Gas engine programmers typically achieve their gains by adjusting engine timing and requiring the user to use premium fuel, although some programmers promise gains from regular fuel. Turbodiesel and other forced induction applications can see incredible gains by adjusting the amount of boost, among other parameters. With a typical gas engine programmer, gains of 5-8 percent are realistic.
Programmer pros are increased power, the ability to maximize gains when used in conjunction from other bolt-ons, and increased efficiency. Cons can include the expense of premium fuel, power gains that are only available at wide-open throttle on some models, and the sensitivity of some diesel engines to excessive boost or power.
Exhaust and Headers
Just as filters and intakes open up the intake side of the engine, aftermarket exhaust systems uncork the back end, lowering backpressure and resistance, allowing the gas to exit faster. Exhaust upgrades can usually be broken down in to three categories: headers, mufflers, and systems.
Performance exhaust manifolds, or headers, are much less restrictive than stock manifolds and can increase horsepower and torque, as well as move the powerband, depending on design. Performance mufflers keep the stock exhaust tubing, but replace the factory mufflers. Full exhaust systems use larger diameter tubing, mandrel bends, and stainless or aluminized construction for greater durability. Full systems are the most popular exhaust modification and typically replace all of the factory exhaust after the catalytic converter system, which allow for performance enhancements while maintaining smog compliance. Exhaust systems can add up to 20hp, more if you combine a matched-set of headers and an exhaust system together.
Benefits of exhaust upgrades are better sound, more power, crisper throttle response, and improved fuel economy. Drawbacks can include increased noise level, exhaust leaks, and a higher price, which makes them less cost effective than intakes. We have also seen some complete systems that don’t provide any gains on an otherwise stock vehicle, so our rule of thumb is to choose an exhaust on looks, function, and sound, rather than on sheer performance.
If cost is no object, the biggest bolt-on power adder is forced induction. Forced induction works by compressing the intake air charge to force more air into an engine. With proper tuning, this denser air charge maximizes the amount of energy that a unit of fuel can provide. In other words, forced induction increases power and efficiency.
The two types of engine compressors are superchargers and turbos and both are available in the aftermarket for your 4x4. Superchargers are engine-driven compressors that provide additional power throughout the entire RPM range and have little to no power lag. Turbo systems rely on exhaust gases to spin a turbine, which pressurizes the intake charge and depending on the size of the turbo, it can also have little to no lag in performance.
Whether it is a supercharger or a turbo, a realistic gain for a “safe” bolt-on system is about 40 percent at 5-8psi. This might not sound like much when you consider there are OE systems that run higher boost pressures, but a typical normally aspirated engine doesn’t have the robustness that the OEs have built in to engines coming from the factory with forced induction.
Out of all the available performance parts out there, superchargers and turbos allow for the greatest gains, achieving big power from smaller displacement engines. On the downside, too much power can stress drivetrain components that were never meant to have that much power flowing through them. Also, not every engine is a good candidate for boost, and a bad tune can make an expensive bolt-on become a really expensive new engine faster than your new 0-60 time.
When choosing which products to use, it is best to go with ones that have California Air Resources Board (CARB) certification, whether you are in California or not. The CARB certification not only ensures your vehicle will pass smog, but makes sure the part works without throwing any engine codes. We also recommend going with companies that back up advertised gains with real dyno sheets.
Another important consideration to note is that just because two parts are advertised to make 10hp each, you aren’t necessarily going to see 20hp when those two products are used together. There is only so much more efficiency gains you can get from stacking bolt-on parts before you will reach a point of diminishing returns.
From a perspective of power per cost, the cold air intake is clearly the winner, but if you want the maximum power a bolt-on can provide, there is no doubt that forced induction is the way to go.