About: Whether you're pushing 500 horsepower to the rear wheels or targeting 1000 horsepower at the crank, getting the right fuel injectors is critical. With CPR Racing’s advanced flow calculator, you can determine exactly what size injectors you need by entering just a few key specs. We’ve built this tool using the same airflow and fueling expertise we’ve honed since the 1990s. Scroll down and input your setup — and if you’re curious about any field, check the explanations below for guidance.