TPI, SFI, MPFI, TBI, and CPI Variations

Q: What is the difference between TPI, SFI, MPFI, TBI, and CPI injection?

A: TPI (Tuned Port Injection) is a "batch" fire system (from the factory) which means that each bank of injectors will fire all at the same time. SFI (Sequential Fuel Injection) is sequential in that only the injector that needs to fire does so. Both TPI and SFI have injectors located in every runner of the intake manifold. MPFI (Muti-Port Fuel Injection) has one injector per cylinder for more power and precise amounts of air and fuel delivered directly to each cylinder via fuel rails. However, there are more parts to wear or break. TBI (Throttle Body Injection) has two injectors placed over the throttle body (carb bowl type unit) indirectly injecting through the intake manifold. This result in less power and imprecise amounts of air and fuel delivered to the cylinders, but there are less parts to wear or break. CPI (Central Point Injection) is a hybrid of MPFI and TBI in that there are two injectors placed over throttle body sending more precise amount of air and fuel to the cylinders through a direct injection via a plastic tube and poppit valve at each cylinder. There are less parts to wear or break this way.