Important: Get us to test your injectors in good time!
As well as the fuel injector calculator, we also recommend our fuel injector service – for both new and used injectors. It’s always very important to know whether the injectors are functioning correctly and are all injecting precisely the same quantity. Only our injector tester can tell you this. You can’t tell once they’re installed in the engine!
- 1. NB: The injector calculator uses a turbo as the basis for calculation
- 2. How to use our fuel injector calculator
- 3. How fuel injection works
- 4. Advantages of fuel injection over a carburettor
- 5. Why should I calculate the injected fuel quantity?
- 6. What does the injected fuel quantity mean for turbocharged engines?
- 7. What is the duty cycle?
NB: The injector calculator uses a turbo as the basis for calculation
The injector calculator uses a turbo as the basis for calculation. So, we assume that your project is a turbocharged engine with multi-point fuel injection, and the fuel is just normal petrol from the pump. For naturally aspirated engines, the calculation would be different. As well as the right injectors, the entire fuel supply system is important, i.e. pumps, filters, fuel pressure regulators, etc. If you’re not entirely sure, simply get in touch with us via chat or give us a call.
We cannot provide any guarantee for the accuracy of the calculator’s results. If in doubt, please ask your tuner or us. We’ll be happy to help you with your project.
How to use our fuel injector calculator
Our calculator lets you work out which fuel injectors are ideal for your project. Here’s how to do it:
- Desired performance: Simply enter your desired engine power here. The greater the power, the more fuel has to be injected, of course.
- Number of cylinders: Our fuel injector calculator needs this figure, too. We have entered 4 cylinders as a guide here, because most engines in the VW Group have 4 cylinders.
- Duty cycle in %: This figure tells us how long the fuel injector is open. It shouldn’t exceed 90%, because each injector also has to close briefly again after opening. An injector is nothing more than a magnetic coil that heats up during operation. The continuous opening and closing puts the coil under stress due to friction. Therefore, give the coil at least 10% of ‘peace and quiet’. If you want to play it safe, select a figure between 60 and 70% in our calculator. This will also give you room to spare for boosting the engine performance in future.
- Flow rate: This is the result of the fuel injector calculator, and is therefore the injector you need. If the result here is 590 ccm, for example, we recommend 660 ccm injectors. Then, you still have some room for manoeuvre and your tuner can lower the duty cycle a bit. This will protect your injectors and ensure you enjoy your engine for a long time to come. Go straight to our in-store selection of fuel injectors here.
Number of cylinders:
How fuel injection works
Unlike in older engines with a carburettor, these days the engine is supplied with petrol by fuel injection. This is controlled electronically. When the pistons are in a certain position, a fixed amount of fuel is injected (this is the flow rate).
Advantages of fuel injection over a carburettor
- Reduced fuel consumption (the dosage and supply of petrol is better).
- Higher performance density (thanks to optimum cylinder filling).
- Fewer harmful emissions.
- More account is taken of the engine state (warm-up, fuel cut-off).
Why should I calculate the injected fuel quantity?
When a car is designed, the injected fuel quantity is calculated so that the injection pump and its control parameters can be designed appropriately. Injection is controlled by the engine control unit, to ensure your engine can always have the optimum fuel supply. The ECU’s software can even take account of the properties of different types of fuel. This way, you always get roughly the same performance – regardless of the fuel.
What does the injected fuel quantity mean for turbocharged engines?
Engines with a turbocharger or compressor need more fuel than naturally aspirated engines. This is because they have a higher internal pressure (boost pressure) and also higher temperatures. What’s more, the high oxygen content in the combustion chamber can be used to burn more fuel. Therefore, naturally aspirated engines can also manage with leaner mixtures, while engines with a turbocharger or compressor need richer mixtures. With the right injected fuel quantity, the engine’s efficiency improves and you get more power. And ultimately, that’s what we want to achieve with tuning.
What is the duty cycle?
The duty cycle indicates the working cycle of an injection valve, i.e. the relative time that an injection valve is switched on and supplies fuel during an engine cycle (intake, compression, combustion and exhaust). For example, a duty cycle of 80% means that the injection valve is kept open 80% of the time and is closed 20% of the time. If the engine needs more fuel, the duty cycle increases so that more fuel gets into the engine. A working cycle of 100% is referred to as a static duty cycle. In this case, the injection valve can no longer control the fuel supply, which may indicate that the valve is too small.