How To Choose A Turbo It’s no longer necessary to use black magic or cast a voodoo spell to choose the right turbocharger. Turbonetics makes it easy! Each family of turbochargers features Turbonetics Top Performers based on the displacement and power. While there are many other variables to consider, these will certainly get you started. We have over 125 years of forced induction sales and engineering expertise in our building to help you select the best possible combination of turbochargers and intercoolers. Feel free to contact Turbonetics and or any of our distributors, if you have questions. The dealer locator feature is available online at the top right hand corner of the site. HERE ARE SOME THINGS TO CONSIDER: POWER: • Think in horsepower not boost. • Boost is just a number that you will have to run on your engine to make a certain horsepower. • How much power do you want to make? Be realistic, the more accurate that you are, the better tuned your forced induction system will be. • Can your vehicle (not just the engine, but the entire setup) handle such power? • Remember the turbocharger is generally not the weakest link. •Forged pistons, connecting rods, head studs, etc. • “As much as possible” is not a goal. INTENDED USAGE: • What are you using the vehicle for? • Race or street use? • The way that you will be using the vehicle dramatically changes the sizing of the turbocharger and intercooler needs. • Your choice of transmission type and gearing will greatly affect the performance and characteristics of the turbocharger, keep this in mind. PACKAGING: • Will the turbocharger(s) fit in your vehicles space constraints? Consider using differently sized compressor housings to more easily fit a given location. REMEMBER TO CHOOSE WISELY: Most street/autocross/drift enthusiasts will prefer a smaller turbocharger due to its fast response. A turbo system equipped with a smaller turbocharger is generally considered more fun to drive. The tradeoff is the final power output of the setup. On another note, dedicated track cars are aimed for peak power over boost response. There’s no doubt track cars spend more time in the upper RPM than average street cars. So, a small sacrifice in boost response is offset by the huge power potential. Larger frame turbochargers are preferred by track car owners due to their maximum power capacity. For most street applications the best solution for selecting turbine wheels and turbine housings, is to choose the smallest wheel diameter available that meets the horsepower level wanted. It is also important to remember that response/spool-up time is greatly affected by turbine wheel diameter and turbine housing A/R. The A/R sizing can be used as a tool to fine tune the response range in the RPM band. The smaller the A/R, the faster the turbocharger will be able to spool up from the increase in exhaust gas velocity entering the turbine housing. Backpressure has become a major tuning issue associated with high performance turbocharged engines and the turbine wheel and turbine housing A/R are both critical to maximizing the performance of the turbo system. Backpressure is the pressure that the exhaust gas generates trying to enter into the turbine housing inlet. If backpressure becomes too great (a 2:1 ratio), the exhaust gases can not escape the cylinder head and can possibly cause major tuning, performance and durability issues. It is important to try to keep the backpressure to boost pressure ratio as low as possible and should be no greater than 1.5:1 for best performance (Example: 15 psi of boost to 22.5 psi of backpressure). http://www.turboneticsinc.com/sites/default/files/HowToChooseATurbo.pdf http://www.turboneticsinc.com/sites/default/files/Turbo Matrix .pdf Compressor Maps Turbocharger systems are a complex combination of many different parts. From the turbo itself and intercooler to the fuel management system and the quality of the engine’s internal components, a vehicle must have many different things just in the right order to run properly. One of the most important aspects to a well designed turbo system is choosing the right compressor and turbine wheel correctly the first time. When the right wheels are selected you can be confident that the turbocharger is going to perform exactly as it should without complications from surging, excessive lag, or overspeeding. There are a few key mathematical formulas and general information points that you should be familiar with before choosing your wheels. This section is intended to provide general turbocharger sizing information, not specific turbocharger-vehicle-engine solutions. Typical turbocharger matches are the result of engine dynamometer testing and installed vehicle performance evaluation. Often, compromises must be made to arrive at a match that yields satisfactory response and power. Actual power produced by any gasoline-fueled engine is a function of how much air flows through the cylinder head and engine itself, regardless of whether it is naturally aspirated, supercharged or turbocharged. The best rule to gauge how much airflow an engine will need to make a certain amount of power is to use a factor of 10. This is based upon the rule that it generally takes 1 lb. of air to make 10 HP. Thus, if an engine makes 500 HP then it flows 50 lbs. of air per minute. It is also important to note that cubic feet per minute or cfm, is not a valid value to use in measuring air for turbochargers. Once a turbocharger has compressed air, the air has density. This density gives the air weight and must be measured in lbs./minute. The conversion formula from cfm to lbs./min. is to multiply or divide by 0.0691 depending upon the conversion direction. For example 500 HP or 50 lbs./min equals 723.59 cfm (50 / 0.0691) and 723.59 cfm equals 50 lbs./min. (723.59 x 0.0691). Keep this conversion in mind when selecting a compressor wheel, as this is a key point in selecting a compressor wheel for a turbocharger. After the HP is converted to airflow in lbs./min., a compressor wheel selection can be made by matching the air flow plotted on the compressor map,with the associated pressure ratio. Pressure ratio is defined as absolute compressor discharge pressure P2, divided by the absolute inlet (ambient) pressure. For example: (boost pressure in psi + ambient pressure in psi; ie. 15 psi of boost + 14.7 psi (1 atmosphere) / 14.7 (1 atmosphere) = 2.02 pressure ratio. The pressure ratio, shown as P2/P1, is located on the left hand vertical axis of the compressor map. Select a compressor map where the air flow and the pressure ratio intersect at a flow rate where the plotted efficiency is no less than 65%-70% for a street application. There will probably be more than one compressor which will satisfy your requirements – in this case, pick the compressor which has the LOWEST surge air flow limit at the selected pressure ratio – this will provide the widest range of performance at the boost pressure your vehicle will be operating at. Turbine selection must also be considered for a successful turbocharger match. Most turbochargers described in this catalog are designed for use with an external wastegate or other device to bleed off excess exhaust energy when a desired boost is attained. TURBONETICS Inc. offers four different external gates matched for various HP outputs. Turbine selection is a variable based on intended use, weight, and desired response. Turbine power available to drive the compressor wheel can vary 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 affect an increase or decrease in turbine pressure for a given turbine housing A/R (see A/R Ratios & How To Choose A Turbocharger for determining the proper A/R ratios). Attachment Size Attachment Size HowToReadCompressorMap.pdf 345.25 KB 60-1.gif 10 KB 62-1.gif 7.42 KB HP_76.gif 4.14 KB T3Super60.gif 8.87 KB T04BH-3.gif 10.16 KB T04BS-3.gif 9.19 KB T04BV1_V2.gif 10.11 KB T04E40.gif 8.76 KB T04E46.gif 9.6 KB T04E50.gif 9.94 KB T04E54.gif 8.02 KB T04E57.gif 8.49 KB T04E60.gif 9.84 KB t58.gif 7.87 KB T61.gif 9.36 KB T64.gif 10.97 KB T66.gif 11.44 KB T70.gif 9.17 KB T72.gif 8.71 KB T340.gif 6.91 KB T345.gif 6.91 KB T350.gif 8.33 KB T360.gif 9.42 KB . ---------- Post added at 07:20 PM ---------- Previous post was at 07:18 PM ---------- A/R Ratios What you need to know: As the volume decreases in the volute of the housing, the exhaust gas is able to maintain velocity and a high energy level thus increasing turbine wheel speed. A small turbine housing A/R can also be a choke point with too small a size limiting the efficiency of the system by increasing backpressure and preventing total horsepower capability. If the boost pressure to backpressure remains equal (1:1) the engine essentially thinks it is naturally aspirated. The boost pressure can continue to be turned up higher and higher until the backpressure climbs too high (above 1.75-2.0:1) or the strength limitations of the engines components are reached. Some backpressure can be a good thing for street/driving use as the pressure differential helps with turbine wheel speed and transient boost response. For racing applications it is critical to maximize the turbine housing as much as possible to keep backpressure low and efficiency high while still providing the necessary response time. There are no written rules to sizing turbine housings and as such professional recommendations and testing are often the best way to start.