Turbo System Basics

Turbo System Basics
» The Science of Forced Induction


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Text and Photos by DSPORT Staff
Excerpted from DSPORT Magazine # 13




Double, triple or even quadruple you naturally-aspirated engines horsepower with modern turbocharging. While it may sound too good to be true, the fact is that most applications fitted with an aftermarket performance turbocharger kit will see power increases in the 40-to-50 percent range on the low side. Increases up to 100 percent (double the original output) can even be seen on some specific applications with some turbocharger kits. Higher order increases (that triple or quadruple the engine's original output) are generally the result of combining an upgraded engine foundation with a high-performance custom turbocharger system.

The bottom line is that there is no better solution for a substantial power increase than a well-designed and well-matched turbocharger system. In addition to generating additional power, a turbocharger system will change the character of the engine. Ultimately, it's the tuner's decision in establishing the character of the engine. A tuner may choose one particular turbocharger system configuration for maximum quarter-mile performance. A different turbocharger system configuration might be selected if a responsive street rocket is the goal. Still another turbocharger configuration might be selected if lap times are to be quicker than ever on a road course. While a turbocharger system may seem magical, there are performance limits. As such, there is not one turbocharger system configuration that will do it all.

Taking the Steps

If you have decided that turbocharging is in your future, you have taken the first step. Your next step is deciding what goals you wish to reach with your turbocharging system. Ask yourself questions: How much horsepower do I need the engine to make? Will I be modifying the engine or running the stock block? Is response more important than ultimate power? Or, is power the primary goal? What is my budget? How long can I car be inoperable during the turbo system transition? Do you need a smog-legal system because you are putting the system on your daily driver? Are you planning to race the vehicle in competition? Are you going to be happy with the horsepower the system delivers or do you know you are going to want more power in the future? Don't be intimidated by the questions, just be honest with your desires. Depending on what type of vehicle you are modifying you may have a limited or an endless amount of forced induction solutions. Answering these questions and establishing the final goals at the first stage will make your quest much simpler.

Understanding how a turbo system works will help you get the most from these power adders when you lay down the big bucks for the big power gains. The purpose of this chapter will be to explain the basic elements in a modern turbocharger system. First, we will outline the basics of horsepower production in the engine. Second, we will see how the turbocharger system generates additional horsepower. Finally, we will investigate the individual components (exhaust manifold, turbo, wastegate, intercooler & I/C pipes, fuel enrichment circuit) of the turbo system and explain their basic function.

Engine Power Basics

An automotive engine is designed to convert the chemical energy stored in the fuel (gasoline, methanol or ethanol) into kinetic energy (motion energy) to perform work over time (measured as horsepower). The input and output relationship is simple. When a greater amount (mass) of fuel can be combusted in an engine, more horsepower will be generated at the flywheel.

Unfortunately, just adding extra fuel to an engine doesn't make more power. When a greater amount of fuel is added, a greater amount of air must also be added to supply the additional oxygen needed for combustion.

So to make more power, it's obvious we need to add more fuel and force more air into the engine. A modern turbocharger system accomplishes both.

 

Forced Induction Advantage

Old-time performance enthusiasts can often be found telling others that "there's no replacement for displacement." That statement is a lie. The truth is that increasing an engine's displacement is a way to increase the power and torque. However, there ARE replacements for displacement that can provide even more power and torque than adding cubic inches. In most cases, increasing the bore and stoke of an engine can increase the displacement on the order of 10 to 20 percent in extreme cases. The torque increase is generally directly proportional to the increase in displacement. With a modern turbocharger system, power gains can be in the order of 40 to 300 percent. What does this mean? Quite simply, turbocharging is the ultimate replacement for displacement.

 

For more on this article and everything else in Issue 13, get your DSPORT Magazine Back Issues online here!







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