Technical Information – North American Performance

Our Competitors are Great at Marketing, We’re Great at Engineering

Why Our Experience Counts

Many of our competitors have been selling aftermarket parts for years and can claim a wealth of experience in the development of their products. What makes us different is that we started out as engineers working in the OEM auto industry developing and manufacturing components, cars and trucks for the big 3 American auto companies. After more than a decade of working for the OEM, our founder having an entrepreneurial spirit formed a company as a tier 1 supplying directly to the big 3. Our parent company was a key supplier of high performance Mopar, Chevrolet Performance and Ford Performance systems. That’s what makes us different. We know the business inside and out, we know the specifications, validation, quality and processes of the OEMs as well as the supply base. We know the constraints and the compromises that need to be made to meet the OEM requirements for high volume manufacturing. This allows us to take the best of the OEM requirements and improve on the constraints/compromises to provide our customers with the best of both worlds – OEM quality and Aftermarket performance.

Let’s cite some examples illustrating what we mean.

Installation and fitment into the vehicle

Our system installs in 30 minutes or less!

The OEMs have cycle time requirements for assembling components in order to meet their line rate. Each operation is allotted a strict amount of time so that at the end of the assembly line a vehicle is completed and exits the line at what is called line rate. Each operation has a cycle time, and this time is usually in the 30 second range, it can vary based on complexity and length of line associated with the operation, but we are not talking minutes but rather seconds. In addition to that, there are ergonomic requirements for worker health and safety to prevent injury and health issues. The parts must be assembled easily and quickly. The effects of this are parts must be designed with ample clearances, size, weight and operator access. We have personally bought aftermarket systems for personal use as well as for competitive analysis and these systems would violate the OEM requirements. They are difficult to install, do not provide ample clearance for assembly or account for vehicle-to-vehicle variations. Our systems consider what we have learned from OEM requirements but knowing that the time constraint can be reconsidered. It is reasonable to allow an assembly time of 30 minutes. However, with that said, we pride ourselves in having the easiest system to assemble on the market, that inexperienced installers can assemble our system in 30 minutes or less. We also preassemble many of the components to save you time. The most difficult part of installing our system is the disassembly of the OEM parts

How Cold Air Makes a Difference – 1% HP for every 10°F

Hp vs Temperature (SAE correct HP), rise over ambient, heat soak, thermal conductivity.

There are many factors that affect an engine’s torque/horsepower but a simplified relationship between inlet air temperature and horsepower is that for every 10°F of air temperature relative to a baseline measurement you gain or lose horsepower approximately equal to 1%. This can be supported by the mathematical relationships below. The correction factor was derived by SAE to compare dynamometer results for engine certifications from region to region where atmospheric conditions would vary. The correction factor considers the differences in atmospheric pressure and temperature. So, this illustrates mathematically the effects of pressure and temperature on engine power output.

PER SAE J1349 ATMOSPHERIC CORRECTION FACTOR

AND THE SAME BASIC RELATIONSHIP

Both formulas show the square root of the inverse temperature ratios. So, for an engine that was SAE Certified per J1349 @ 400 hp @ standard conditions, you’d gain 4hp for a 10°F decrease of temperature over the standard conditions. This was a “rule of thumb” that has been circulating for some time and can be supported by this calculation. The Chart below shows the relationship plotted.

Restriction and Horsepower

If we use the SAE J1349 correction factor (CA) to assess the effects of pressure on horsepower, we derive the chart below. Restriction is nothing more than a pressure drop across the filter. Atmospheric pressure at sea level is approximately 14.7psi. Less restriction means the pressure drop approaches atmospheric pressure. Pressure that exceeds atmospheric pressure is force induction (superchargers, turbo chargers, or “Ram Air”).

Applying the SAE J1349 Correction Factor (CA) to our flow bench comparison between the GM OEM System and the North American Performance Classic Air Induction, we find that the improvement in restriction alone (not considering temperature affects) results in a theoretical horsepower improvement of 8hp alone. Our flow improvement on the Super Flow bench was 46.67% @ 600 CFM. The “rule of thumb” derived from this is that 1.07 hp per 1 in H₂O restriction improvement. Note a competitor advertises 51.69% flow (5% better than our system) which sounds great but provides virtually no improvement in horsepower (0.05hp) with potential damaging trade-offs for filtration efficiency. Also, they have an opening to draw in hot under hood air to accomplish this restriction number that will actually hurt performance. See our thoughts on filtration efficiency.

“Ram” Tuning

Based on the speed of sound, the length and diameter of the induction system can be used to tune the resonant characteristics of the system. Most hot-rodders are familiar with the types of intake manifolds they bolt on their engines to obtain a performance goal. Long runner dual plane manifolds produce more torque at the sacrifice of high-end horsepower and conversely, short runner single plane manifolds are used for higher RPM applications. Each is “tuned” for the application. With an air induction system, the same principle applies. The difference is that the intake manifold and the pressure impulses are affected by the manifold plenum and the signal to the air induction is controlled by the throttle body. So, the throttle body affects the air induction system like the intake valve & piston does to the intake manifold. The theory on “Ram tuning” and pressure pulse still applies. In fact, the Helmholtz resonators on the OEM systems illustrate that they are trying to tune the acoustic output from the induction system through pulse acoustic phasing. The long runner OEM systems with the long series of tubing is not tuned for a “ram” effect.

The length of this system and any system using the long air inlet tubing puts the acoustic resonance at about 1700 RPM. As a result, pressure pulses above this RPM will interfere with each other causing restriction. Our system with the short runner is tuned to the peak horsepower of the 5.3 & 6.2 L engines and the 9L of plenum area act as a “reservoir” of clean fresh air reducing restriction. 9L volume would support 3 revolutions the 6.2/5.3 90° V8. The pressure pulses at lower RPM do not interfere with the air flow due to the high resonant frequency and large plenum volume and thus do not create more restriction. This is as close to an ideal inlet drawing from atmospheric air as possible.

Filtration Efficiency – ISO fine vs Coarse

We develop air induction systems for the OEM auto manufacturers (See our Parent Company website: http://www.naassembly.com). It is required to meet all the OEM specifications on our products. When it comes to filtration efficiency, the requirements have been getting more and more stringent. The trade-off with filtration efficiency is air flow or restriction. ISO-5011 is the specification used for testing the efficiency and capacity (how much dust the filter holds before it should be changed/cleaned) but the OEMs specify the acceptance criteria. Within ISO 5011 there are options for the type of dust that can be used. Some manufacturers will claim certain efficiencies, but they are using ISO coarse dust. There is an overlap but basically, they are choosing a larger particle size which is easier to filter out of the air stream. The most stringent OEMs use only A2 fine dust or at a minimum a mixture of A2 and A4. So, keep this in mind when comparing advertised filtration efficiencies. Our Walker Performance Filters have a 99+% ISO Fine Dust Filtration Efficiency.

Rise over Ambient (Air Inlet Temperatures) “Cold” Air

Rise over ambient is a term used by our OEM customers to characterize the Rise over Ambient (Air Inlet Temperatures) “Cold” Air.

Operating air inlet temperature increases over the outside ambient air temperature. We have shown theoretically that for every 10°F of air temperature increase over the engine power rated standard, a loss of 1% of the rated horsepower can be expected due to the temperature alone. That’s why it’s important to draw air into the air intake from an outside ambient air source. We see fantastic restriction numbers from reputable manufacturers, but they have an opening to unshroud their system that draws in hot under hood air. So be aware of this when making a purchasing decision. Our system draws from a high-pressure zone when moving and the cooling fan draws in cooler outside air into the cavity that we access for our system. Our data has shown that we run at ambient air temperature when moving down the road. However, when stationary the temperature will rise in time. ALL systems will do this unless there is some type of active cooling. Based on heat transfer principles, all under hood items will trend towards equilibrium no matter if you insulate, coat or whatever passive countermeasures you take to prevent heat transfer to the intake. Insulation and coating only help postpone the heat transfer (and can delay the cooling as well – holding in heat). It’s the same if you turn off the heat in your house when it’s cold out or AC when hot out. Eventually, you trend towards heat moving from hot to cold – your house gets cold in winter and hot in the summer. In the same manner, hot under hood temperatures will saturate the intake system with continued energy input. Time is a big factor as well in the heat transfer process. When you are drawing in large amounts of air at part to full throttle, there is no time for the heat to significantly transfer to your airstream. The size of the system can also help or hurt. If you had a mile of hot pipe then by the time the air exited the pipe, it had time to be exposed to the heat transfer from the pipe. So, we designed a short runner system with cool ambient air source and used thermoplastic materials that tend to delay the heat transfer from the engine compartment.

Fuel Economy

Measuring fuel economy is a difficult task due to all the variables and environmental factors that can affect the measurement. For example, the aerodynamic drag from cold denser air in the winter is more dominant than the gains from the cold dense air provided to the engine. Just compare the real-world fuel economy you get to EPA rated fuel economy listed on your vehicle window sticker (Monroney Label). That’s why you will see general claims from manufacturers of cold air intake systems rather than specific claims. Theoretically you should improve your fuel economy IF you can fight the temptation to hear the awesome sound generated from your cold air intake. This is the reason OEMs have specifications for Rise Over Ambient (see Rise over Ambient (Air Inlet Temperatures) “Cold” Air section) – to meet fuel economy targets and improve their CAFE (Corporate Average Fuel Economy) rating.

Acoustics

Sound is a very subjective thing when asking someone what sound is pleasing to them. There will be a distribution of opinions. When the OEMs develop a vehicle, they must design it to satisfy a large group of customers and typically the choice is to decrease the acoustics associated with air induction. They integrate resonators to cancel both “bad” noise and reduce the amplitude of the induction acoustic for a quiet cabin. That’s why you see these “bubbles” and various shapes attached to the clean air duct on the OEM systems. For the performance enthusiast, we want to hear the induction noise because it enhances the driving experience. From an acoustics standpoint, to provide the loudest system would be to not block the path to the passenger’s compartment or have the air intake open but this is bad for intaking hot air and hurting performance. Some of the systems available do just that though. They have a very loud system, but suck in hot air as well. So be aware of the trade-offs when making a purchasing decision. On some OEM systems, they plumb a tube to the dash area to “pipe” sound to the passenger’s compartment. Our system provides a much better acoustic performance than the OEM while also improving engine performance by being completely enclosed and blocking hot air from entering the airstream.