For each cylinder, one injector is needed so a four-cylinder engine will have 4 injectors. Usually, it will be present near the intake manifold. So the port of the Electronic Fuel Injection – EFI needs four injectors in the calculation of one per one cylinder.
Generally, in engines there will be one injector per cylinder. In that calculation when you have a four-cylinder engine should have 4 injectors. If four injectors are not able to keep up your engine to meet the machine performance, you can add additionally.
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