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title: Calculate injector and fuel pump size!
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# Calculate injector and fuel pump size

Use our injector calculator to easily find out which size injectors your car needs, and check out which fuel pump setup fits your needs. There is also more in-depth information about injectors and all the different values the calculator uses.

Advanced mode 

Injectors

Power target (crankshaft)

Number of injectors Click for more information.

Keep in mind this is not the same as the number of cylinders; sometimes there can be two injectors per cylinder.

Engine type Click for more information.

Choose whether the engine is naturally aspirated or forced induction. The choice affects the fuel consumption calculation.

Turbocharged Naturally Aspirated Supercharged

Fuel Click for more information.

Which fuel the fuel system will be built for. E85 and Methanol require a higher flow than petrol for the same power.

Petrol E85 Methanol

BSFC Click for more information.

Stands for *Brake Specific Fuel Consumption*. Indicates how much fuel the engine consumes per horsepower per hour. Calculated automatically but can be manually overridden.

Duty Cycle Click for more information.

Leave this at 80% unless you have a specific reason to change it. 80% means the injectors are open a maximum of 80% of the time to ensure a good safety margin.

 Changing this value is not recommended. Only do this for specific applications if you understand the consequences.

Recommendation

**Minimum injector size:** cc/min

**Recommended injector:**

Advanced mode 

Fuel pump

Base fuel pressure Click for more information.

The pressure the fuel pressure regulator (FPR) is set to when the vacuum hose is disconnected. 3 bar is the most common standard.

Max boost pressure Click for more information.

The maximum overpressure (boost) the turbo or supercharger is expected to deliver at max power. For naturally aspirated engines, this is 0.

Number of pumps

Recommendation

**Minimum flow the pump must handle:**

L/h

**At total operating pressure:**

 bar /  psi

**Recommended fuel pumps:**

## How do you maintain fuel injector performance?

Regularly servicing your fuel injectors is a must to maintain optimal flow and performance.  It is especially important to submitt your injectors for regular service if you run on ethanol (E85), as this fuel causes corrosion inside the injectors, which negatively affects the spray pattern, flow, and more. The injector filter may also need to be replaced periodically, because ethanol often carries more dirt that gets trapped in the filter, risking a clogged system that can result in severe engine damage.  **EU Customers: We offer professional fuel injector servicing using the best technology available on the market.** 

[Service your injectors!](https://www.speedingparts.eu/p/fuel-system-an-fittings/fuel-system/injectors/injector-service/injector-service.html)

## How do you know which fuel injector to choose?

Like many things in motorsport, this comes down to relatively simple mathematics. Fortunately, you don't have to do the math yourself – just use the calculator above and we will solve it for you! 

But for those who are interested, it is good to know what the different values mean and how they affect the fuel system and ultimately the car's performance. 

#### BSFC (Brake Specific Fuel Consumption)

Simply means how much fuel is needed per hour to generate one horsepower. The formula is fuel consumption in pounds (lbs) divided by the number of horsepower. 

**BSFC**  =

Fuel flow (lb/hr) Horsepower

There are generic values for BSFC if you do not have specific data from your engine, but the calculator will figure it out for you. 

#### Injector flow rate

How much fuel flows through the injector. In Europe, this is usually measured in cc/min (cubic centimeters per minute), but it is also very common to measure this in lbs/hr (pounds per hour). To calculate the flow rate, you need the BSFC, horsepower, number of injectors, and something called the *duty cycle*. 

**Injector flow rate** =

Horsepower X BSFC Number of injectors X Duty Cycle

Duty cycle is the percentage of time the injector is open versus closed, so a value of 80%, or 0.8, means the injector is open 80% of the time. We recommend leaving this at 80%, as it provides a good safety margin if conditions should change elsewhere that might require more fuel. You do not want the injector capacity to become a bottleneck. 

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