TURBO INTER-COOLER

TURBO INTER-COOLER

Abstract

Most people know that engines make more power when the inlet air is cooler. Let’s take a look at why this is true at least in most applications. We’ll also tell you right up front that this article might leave you with more questions than answers. Then again, you might be the one that provides the additional answers and takes the world to the next generation of internal combustion engines.
To understand what goes on during both the intake cycle and the power cycle when inlet air temperature is reduced, we need to consider both normally aspirated and supercharged gasoline engines, as well as turbocharged diesels. We’ll also limit this discussion to four-cycle engines.
Before we go any further, let’s define a couple of terms. For this article, we’ll say that supercharging is anything that increases the amount of oxygen available in the cylinder to support combustion of fuel above what could be expected from cylinder filling due to atmospheric pressure only. We’ll assume atmospheric pressure at sea level to be 14.7 PSI and that “normal” air contains approximately 21 percent oxygen. We’ll also exclude oxygen-bearing fuels, such as nitro methane, as a form of supercharging. This means that any form of mechanical compressor that pumps more air into an engine, such a belt- or gear-driven “supercharger”, or an exhaust- or turbine-driven “turbocharger” is included, as well as the injection of nitrous oxide, or even oxygen itself.