Ever since PCM came out with the new direct injection H5 and H6 engines, we have been asked what the difference is between direct and sequential injection and if PCM is the only company using direct injection. I hope to answer both questions below. Here is some basic information about injection systems.
Basically, a SFI (sequential fuel injection) system has a fuel injector for each cylinder. Each of these injectors puts fuel into the system at 30-40 PSI before the intake valve. This air/fuel mixture is pulled into the cylinder past the intake valve on the intake stroke of the piston and is then compressed and ignited. This system was way more fuel efficient and created way more power than the carburation systems it replaced. Sequential fuel injection has been used in marine engines for several years and is the system that is currently used in most new towboats [...]