The Science of Intakes

So What’s the Difference Between Aluminum, Steel and Plastic?

Our competitors say it’s heat absorption. While the issue of heat absorption with an intake system has a degree of validity, we have found that too much emphasis is placed on material selection, instead of the real issues of tuning the system, and the rate of airflow not allowing adequate time for heat absorption under throttle regardless of the pipe material.

• We use aluminum to eliminate any chance of the system rusting, and it's lighter than steel
• We limit our use of plastic because this material absorbs some of the sound energy we work to create in the inlet duct
• Whether or not an inlet system is made from aluminum, steel or plastic, the thermal conductivity of the duct material has little effect on engine power
• The rate at which air travels through the inlet path under open throttle, when one is asking the engine for maximum power, negates the effect of material heat soak, regardless of the material

We use aluminum—or a combination of aluminum and plastic plenums for throttle-body-injected applications that require a special plenum—for every intake we produce. This eliminates any chance of rust occurring on the inside of the inlet pipe. We also choose aluminum because of its lightweight properties. Heavier components place higher loads on the brackets they are attached to—or even worse, to the pipes they are attached to. We limit our use of plastic because this material absorbs some of the sound energy we work to create in the inlet duct.

Whether or not an inlet system is made from aluminum, steel, or plastic, the thermal conductivity of the duct material has little effect on engine power. The tuning of the pipe, in addition to providing the coolest inlet air source, are the keys to making useable power, and this is what we do best.

At light throttle opening, air speed and airflow at the inlet are relatively low. The high residence time of air in the inlet while at low-throttle settings will increase inlet charge temps when materials with high thermal conductivity are used. Typically, when someone is at light throttle they are not asking the engine to make power though. Most likely, fuel economy is the issue.

When the throttle is fully opened however, air speed and airflow increase considerably. Typically, the inlet air speed of a 5.7L engine with a four-inch duct at full throttle is 34 feet-per-second, based on a volumetric efficiency of 70% and an engine speed of 3,000 rpm. Most inlet systems for every intake manufacturer for this engine are 30 inches or less. This means that the air in the duct of a 30-inch inlet length on this engine at the given rpm is 1/10th of a second—hardly enough time to transfer an appreciable amount of heat into the air stream on any system.

So what does this add up to?  ALL INTAKE SYSTEM MATERIALS ABSORB HEAT, REGARDLESS OF THE MANUFACTURER. Basically, the rate at which air travels through the inlet path under open throttle, when one is asking the engine for maximum power, negates the effect of material heat soak, regardless of the material. Plastic is no better than steel, which is no better than aluminum, when discussing heat absorption. If you want the best performance, filtration and dust trapping, your only choice is a BRUTE FORCE intake system.