HOW TO CHOOSE A TURBOCHARGER

• How to Use a Turbocharger
• Turbo Notes and Recommendations

"Which turbo?"

That's the question we get right, the first time, every working day as we consult with performance enthusiasts and racers. Here's the short answer.

The selection of the best turbocharger for the job boils down to three questions.

• What's the horsepower target? (be realistic.)
• What are the engine's specifications? (displacement, number of cylinders, number of valves, compression ratio, volumetric efficiency, etc.)
• What are the vehicle's specifications? (weight, operating RPM, max RPM, street car or RACE car.)

Give us realistic, accurate answers to the above and we'll put you where you want to be. We'll ensure the best results, save you time and money if you think through certain decisions and criteria. In other words, to build a faster car you need a plan. First you must decide on the intended use of the car: mainly street driving or racing only?

A race car is highly specialized. The goal is the ultimate horsepower within a narrow RPM range. But the trade-off is lousy power at low engine speeds. A street car, on the other hand, needs low-end response. If you're honest, you'll see that a street car can spend 90% to 95% of its time at 4000 rpm or less. This means a well-designed "driver" must pull strongly from idle.

What's very often missed by beginners who wake up and declare, "I'm going to build a fast car!" is that a properly engineered 300 hp street car will outperform a 600-hp race car on public streets and highways under normal driving conditions.

Other issues that need to be addressed include:

• ECU capability
• Injectors
• Fuel quality, pressure and volume
• Knock sensing
• Available space in engine compartment

Just remember that our specialty is providing the air. Fuel, ignition, exhaust, cooling, electronic engine control mapping, etc. are the responsibilities of the vehicle builder. What you get when you select a Turbonetics turbocharger and accessories is our knowledge and expertise in providing more airflow to the engine. In the vast majority of cases, we know what works for any given application. Our tech and sales department have highly specialized computer programs and flow maps to aid in the selection of your turbocharger. We don't buy into the one-size-fits-all mindset. That's why we don't have any completed turbochargers on shelves. Virtually every unit we sell is customized and blueprinted for your specific vehicle and application.

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TURBO NOTES

Note: This section is intended to provide general turbocharger sizing information, not solutions to specific turbocharger- engine-vehicle combinations. Typically, an optimized turbocharger match is the result of combined engine dynamometer testing and installed vehicle performance evaluation. Often compromises must be made to arrive at a match yielding satisfactory response, power, and fuel economy in a retrofit or special application. Estimated engine air flow requirements at varying RPM are plotted in Figure 1 for typical 5 psi and 10 psi boost levels, and in figure 2 for 10 psi and 15 psi (Intercooled, typical modern 4 valve/cyl. engine, or race “ported” 2 valve engine.) To determine air flow for a given size engine at maximum engine speed, read upward in Figure 1 or figure 2, to the appropriate boost and speed line. Engine air flow requirement is read directly by projecting the boost-speed point horizontally to the left.

Engine air flow requirements can be used directly in establishing an operating line on an appropriate compressor map. Refer to pages 18 - 23. Compressor pressure ratios corresponding to boost levels of 5 psi and 10 psi are 1.34 and 1.68, (1.68 and 2.02 in figure 2) respectively. Select a compressor such that the engine torque peak operating point is near to the compressor peak efficiency island as possible while maintaining the engine rated speed point in the compressor 60% or higher efficiency region. In the case of larger displacement engines with high RPM capability, it will usually be necessary to use two turbochargers to provide adequate air for the desired airflow / boost conditions. To determine operating points on a compressor map for a twin turbocharger arrangement, divide the total air flow found in Figure 2 in half, and select a map that will satisfy those conditions.

Do not attempt to establish an operating point in an area on a compressor map to the left of the surge line. This is an area characterized by unstable operation and violent flow reversal, potentially resulting in turbocharger failure. Turbine selection and a method of boost control for spark ignited engines must also be considered for a successful turbocharger match. Most turbochargers described in this catalog are not equipped with a wastegate or other device to bleed off excess exhaust energy when a desired boost is attained. Turbonetics, Inc. offers the DELTAGATE Mark II and the RACEGATE wastegate in several configurations to satisfy most applications.

Turbine selection is a variable based on intended use, weight, and desired response. Turbine power available to drive the compressor can be varied in two ways: 1) the Area to Radius (A/R) ratio of the turbine housing can be changed to alter turbine inlet pressure; and 2) the turbine wheel trim can be specified to effect an increase or decrease in turbine pressure for a given turbine housing A/R. (See data sheets for available turbine trim and housing information.) Initial recommendations for normal single turbocharger applications (assuming a controlled boost of 10 psi or less) may be selected as shown in the following table:

High speed engines, heavy vehicle loading, special purpose vehicles, and applications requiring multiple turbochargers will require turbine configurations based on specific requirements and may vary considerably from above recommendations. Contact a Toysport turbo specialist for specific recommendations.

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