Better breathing means more power and torque. That's the lesson magazines and the automotive aftermarket have been preaching for years. Whether gas or diesel, the power principle remains the same: More air in and more air out equals improved horsepower and torque. To understand this philosophy, you have to get down to basics.
First and foremost, an engine, whether it be gas or diesel, is essentially a giant air pump. The up-and-down motion of the pistons moves specific volumes of air through the engine. The quantity of air depends on many factors, including engine displacement, the size of the intake system, the camshaft configuration, and the efficiency of the exhaust side of the powerplant.
On a typical four-cycle engine, the atomized fuel mixture is drawn into the cylinder, past the open intake valve by the downward motion of the piston. As the piston moves upward, the air/fuel mixture is compressed and ignited. The force of the explosion pushes the piston downward. This is considered the power stroke. On the piston's return upward, the burnt gases are pushed out through the open exhaust valve, and the process begins again.
Sounds simple enough, right? But where's the "hidden" horsepower in this equation? By improving the efficiency of the engine in any of the critical areas (intake, valve timing (camshaft), ignition, or exhaust), you can make more power. For the purpose of this discussion, we'll focus on the intake side of the engine.
Most manufacturers face quite a challenge when it comes to designing intake systems for today's trucks. First off, the systems have to fit the platform (model). Secondly, they have to thoroughly filter the incoming air to the engine. Finally, these intake systems have to be somewhat quiet to reduce the vehicle's overall NHV (noise, harshness, and vibration). What's left is what you get on your new truck. Does it work? Yes. Is there room for improvement? Most definitely.
On the stock intake system, the main airflow restrictions are usually the design of the intake box itself. This is the actual air inlet, where the box meets either the inner fender or radiator bulkhead, with the factory paper-style filter inside the box. The easiest upgrade to any intake system is to simply change the filter from a paper-style element to a high-flow filter. The most common performance air filter is an oiled cotton-gauze style, which is capable of flowing more air while dirty than the stock filter flows while clean. Airaid Filter Company has taken the standard cotton-gauze filter to the next level by adding a synthetic layer of filter material, which improves filtration (down to 2 microns) without affecting airflow. The company's patented SynthaFlow layer is now standard on its line of direct-replacement filters as well as all intake system filters.
The next step to better breathing is to change out the complete airbox for an aftermarket intake system. Since the stock airbox and airbox lid on most trucks are major restrictions, removing them and replacing the assembly with a high-flow air intake usually generates a big improvement in not only horsepower and torque, but also throttle response. Sometimes just changing out the lid yields substantial results, as this flow bench data from Airaid indicates.
A typical airbox on an '04 Chevrolet Colorado pickup equipped with the 3.5L inline-five powerplant flows approximately 397.88 cfm of air at 20 inches of water. The Airaid QuickFit air intake, which retains the lower-half of the stock airbox but replaces the lid with a high-flow filter and cool-air dam, flows 615.98 cfm at 20 inches of water. That's a 54.8 percent increase compared with stock.
On the Power Stroke diesel found in many of today's Ford Super Duty pickups, the flow bench results also yielded gains when the entire intake was swapped out. The factory Ford intake system on the Power Stroke-equipped Super Duty is one of the best factory systems on the market. It uses a fresh air snorkel through the radiator core and a large commercial-style air filter in front of the turbo inlet.
On the flow bench, the stock system flowed a whopping 766.15 cfm. By comparison, the new '05 Airaid Power Stroke intake system flowed nearly 1,000 cfm (997.39 cfm) at 20 inches of water. That's a 30 percent gain compared with stock, which can be felt at the drop of the throttle without sacrificing filtration. On the dyno, with the Airaid intake installed on an '05 Ford Super Duty, the system yielded 21.2 rear-wheel horsepower and 35 lb-ft of torque with no other changes.
No discussion of improved airflow would be complete without touching on the exhaust part of the performance equation. With improved breathing on the intake side, it makes no sense to leave the stock exhaust system in place. The OE muffler, which features multiple internal baffles that restrict flow, was originally designed to reduce noise, not make maximum horsepower and torque. An aftermarket exhaust system with a free-flowing muffler goes a long way toward building additional horsepower and torque. Also, most aftermarket exhaust systems use larger-than-stock mandrel-bent exhaust tubing for smoother transitions and better airflow than the stock crimp-bent tubing.
When it comes to better breathing for your truck, the bottom line is the need to improve the pumping efficiency of the engine. Whether it be with an aftermarket air filter, exhaust system, or headers, improved efficiency mean more usable horsepower and torque when you mash the throttle, and oftentimes, improved fuel economy as a byproduct.
Installing Airaid's Power Stroke Diesel Intake
There's no debating that Ford's 6.0L Power Stroke is one of the strongest diesel powerplants on the road today. With nearly 600 lb-ft of torque on tap and a super-sized tow rating of nearly 17,000 pounds, the new '05 Ford Super Duty has already earned bragging rights with the towing crowd.
As is the case with most stock vehicles, however, manufacturers have left something more on the table in terms of power. Unlocking this hidden power is what Airaid Filter Company is all about, and the '05 Power Stroke Ford Super Duty is no exception.
The new Airaid Power Stroke Intake System replaces the restrictive and expensive factory-inline air filter with a high-flow high-filtration SynthaFlow filter. The SynthaFlow filter is located in a heat-resistant housing, which draws in cool air from the factory location while providing additional airflow through the cool-air dam on top.
The end result is dramatically improved throttle response, a 21.2 rear-wheel horsepower gain compared with stock, and an additional 35 lb-ft of torque. The Airaid Power Stroke Intake System fits Super Duty pickups as well as '05 Power Stroke-equipped Excursions. Installation can be accomplished with ordinary handtools in less than an hour. The following photos highlight a typical install.
The Hunt For Pulling Power and More mpg
True off-road enthusiasts are always looking for more off-idle torque and throttle response to get those big tires rolling. The never-ending hunt for grunt just got easier, thanks to the folks at Airaid. The company's Helix-Bore PowerAid throttle-body spacers are famous for enhancing an engine's low-end torque and midrange powerband while helping in the fuel-economy department as well.
How do they work? The patented Helix-Bore design actually spins the incoming air charge, boosting velocity and improving atomization into the intake and combustion chamber. The result is a boost in torque from approximately 800 to 3,000 rpm. Also, with improved efficiency in filling the combustion chamber, it's not uncommon to also see a boost in fuel economy.
PowerAid throttle-body spacers simply install between the throttle body and intake manifold. Each PowerAid comes complete with all the necessary mounting hardware and detailed installation instructions. PowerAids are available for a variety of gas and diesel applications.