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Questions and Answers

Sequential Fuel Injection (SFI)

Q. Hello, Let me introduce myself, I'm engineering student in Brazil and I am looking for information about Sequential Fuel Injection (SFI) and Semi-Sequential Fuel Injection. I found in internet your site with very interesting information about vehicles parts. Please, could you send me more information about SFI and Semi-SFI?

Thanks and Best Regards...

Sequential Fuel Injection (SFI)

A. You can get some basic information here: Electronic Fuel Injection

TBI: Throttle Body Injection
Usually a single point injector placed before the throttle plate; looks much like a carburetor. One injector feeds all the cylinders. In some applications, two injectors may be used side by side. Usually TBI systems run low pressure (15 psi) fuel systems.

EFI: Electronic Fuel Injection
Generic name for electronically fired injectors versus continuous mechanical injection (older Bosch). This does not refer to any more specific injection set up than that as far as I know.

MPFI: Multi point Fuel Injection
Where an injector is mounted in the intake plenum pointed more or less at each cylinder's intake valve. 6 cylinders = 6 injectors. There are two firing circuits in the ECM, one for the front bank of 3 cylinders and one for the rear bank of 3 cylinders. Example: when fired, the front three injectors simultaneously spray fuel toward their respective intake valves. Fuel Pressure is approximately 45 psi. An additional injector for added fuel during cold starts is often present.

SFI: Sequential Fuel Injection
One injector per cylinder with a firing circuit for each injector individually. Results in better emissions and more power. Same fuel pressure as the MPFI.

TPI: Tuned Port Injection
Is the same system as MPFI, just for more cylinders and a fancier name.

Each basic system has one or more sub systems and that can get confusing.

Additional Information provided courtesy of ALLDATA

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