![]() ![]() By fitting a larger turbo we will lose some low down torque but we will get it back at higher RPM, which give us more power, without necessarily increasing stress on the engine. On a test drive they may feel fast but when you get used to the low down torque, exploring the upper reaches of the rpm range will reveal there is nothing less to give, the engine is being choked due to the small turbo. Generally turbos supplied by the car manufacturer are hopelessly undersized. Garrett has an excellent resource on their website detailing the technical aspects of a modern turbocharger OE Turbos Video can’t be loaded because JavaScript is disabled: Turbo Size Calculator – How It Works () Too big an AR ratio will feel sluggish, too small engine can be difficult to drive smoothly. The Formula: Turbo Output Starting HP x ( (PSI/14. This is usually a trial and error process. This line absolutely lie to the right of the surge line on the compressor map.Ī steep surge line on a compressor map shows that a turbo will produce high boost pressure at low CFM flow rates.Ī shallow surge line on a compressor maps shows that a turbo will not produce high boost at low CFM flow rates. Vd engine displacement in cubic inches (convert liters to CI by multiplying 61.02. ![]() Then draw a line from this point down to Pressure Ratio of 1 and a CFM of 20% of the maximum. ![]() Plot the CFM number onto the compressor map graph. Select what to solve for and enter values for the other fields. Surge LineĬhoose the RPM where you want to achieve full boost. A guide on volumetric efficiency values is provided below. Displacement (Liters) (122.04 CID) Ambient Air Temp (deg F) Altitude (ft above sea level) (14.502 psi barometric pressure) Fuel Type. Generally speaking erring on the larger size of turbo is better than smaller. This calculator gives the baseline horsepower and cubic feet per minute (cfm) that an engine will develop at its maximum rpm given the volumetric efficiency of the engine. The following two calculators can be used to estimate the engine horsepower of a vehicle based on the weight of the vehicle. We are looking for the line to be in the highest efficiency areas of the map for as long as possible. Plot multiple points to see where the turbo performs versus your requirements. FuelTech also offers the option to determine the maximum horsepower rating of fuel injectors by working backwards, using fuel injector sizing and other parameters. Compressor Chartsīolt the pressure ratio number and the CFM (or lbs/min) number into a compressor map graph for various RPMs. The selector allows the user to pick the number of fuel injectors, input estimated horsepower, and the type of induction. When we obtain the pressure ratio and CFM and lbs/min numbers we can now look at turbo compressor maps to see which turbo will be most suitable for our application and goals. *Horsepower is measured at the crankshaft.Turbo Size Calculator – Using the numbers The chart below lists some general guidelines for gasoline engines (with 8 injectors): Injector Flow Rate ![]() However, you can Fine-Tune Flow Rate by adjusting fuel pressure. Wallace Racing BACK to Calculators Todays date is These equations are for recreation only. You might not find a fuel injector rated for your exact needs. of fuel per injector at an 80% (0.8) duty cycle. This calculator gives the baseline horsepower and cubic feet per minute (cfm) that an engine will develop at its maximum rpm given the volumetric efficiency of the engine. (Horsepower X BSFC) ÷ (number of injectors X injector duty cycle)įor example, a naturally aspirated, 300 hp engine (BSFC 0.5), with 8 injectors will need 23.4 lbs./hr. To calculate your required flow rate, use this formula: An injector this size can also provide an accurate amount of fuel at low rpm. This lets the injector close 20% of the time at WOT which keeps it from overheating. The right size injector can supply enough fuel under full load conditions at an 80% duty cycle. It is listed in pounds per hour (lbs./hr.) or cubic centimeters per minute (cc/min.). Flow rate is a measurement of how much fuel can be delivered over time. Use our automatic points calculator to determine your BIMMER CHALLENGE Competition. Fuel Injectors are sized by their flow rate. ![]()
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