The Most Common Bolt On Power Adders

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.

Forced Induction
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.

Tips
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.