Читать книгу Turbo: Real World High-Performance Turbocharger Systems - Jay K Miller - Страница 18

The word “turbo” has been widely used to describe everything from computer software to shoes. Marketers use the word “turbo” to convey power, speed, and a superior level of performance. Those of us who work in the turbo industry see humor when somebody flips a switch labeled “turbo” and a sudden power surge is produced. It doesn’t work that way. While the term has been glamorized by this over use, there is good reason for it. The turbocharger has successfully worked itself into just about every engine application, with the exception of NHRA Top-Fuel Dragsters and Funny Cars, where they are banned outright.

The turbocharger’s development was accelerated due to the need that aircraft had to achieve high horsepower levels in the thinner air seen at high altitude. Turbine speed increases about 2 percent per 1,000-foot increase in altitude. Both aircraft and commercial engine equipment benefit from this natural altitude compensation characteristic in turbochargers. The jet engine made the piston engine obsolete for most commercial passenger planes today, but turbos are still applied to lower-cost small aircraft that use piston engines.

Today’s diesel engine, whether a large commercial diesel truck, earth-mover, or consumer diesel pickup, is turbocharged. The reasons are both for power and emissions. As Gale Banks says, “A diesel engine is just not complete until it is turbocharged.” The high-BTU (British thermal unit) property of diesel fuel makes it virtually impossible for a naturally aspirated diesel engine to breathe enough air on its own to burn all of the fuel completely. Gasoline contains about 125,000 BTU per gallon, while diesel contains about 138,000. I don’t believe there has been an on-highway commercial diesel engine (class 4 through 8 trucks) produced without a turbocharger for nearly 30 years.

This 1999 Case-IH MX150 uses a fixed-geometry, or free-float type turbine housing, which means no wastegate or other type of variable turbine geometry. This type of turbo system is the most commonly found type in use today. The engine is rated at 130 hp, with 5.9 liters of displacement and a Holset brand H1 model turbocharger. Most agricultural tractors, from brands such as John Deere, Case-IH, Massey Ferguson, etc., rated over 100 hp use a turbocharger. All of today’s on-highway diesels use a turbocharger because they have to in order to meet emissions regulations.

The racing community discovered turbos many years ago. There has been a steady evolution of more and more classes of racing that accept turbochargers. The sport compact class in NHRA is one of the most recent examples of this movement. For many years turbos were seen almost exclusively in the Indy car circuit, where high budgets were the norm. For most other classes of racing the sportsman populated the ranks, and turbos were exotic and expensive and viewed as an unfair advantage by most average racers. That is now changing. While turbos are still expensive, the real expense of the pioneers was in trial and error to obtain the correct and optimized match in a world of minimal hardware options. That’s no longer the case, as turbos are widely available in a variety of sizes to match virtually any engine design.

Today the sport and pleasure market is completely covered by turbos. Whether it’s a sport car, recreational vehicle, or a boat, turbos add driving pleasure. The turbocharger will return to several more automobiles than are currently available very soon, and for one simple reason—efficiency won’t be denied. Higher fuel prices are probably here to stay, as is the increasing demand for fuel economy. It’s cheaper for the automakers to manufacture a 6-cylinder turbocharged engine than a comparably powered naturally aspirated V-8. The smaller engines fit into smaller vehicles and fuel economy gains are seen from both the smaller engines, as well as the smaller and lighter vehicles where they are used.