MPI and EFI Engines

The Highlander offers MPI (3.3 hybrid) and EFI(3.5) engines. What's the difference and why isn't the 3.5 EFI engine used for the hybrid since it seems to have more power?

-- Ron

Reply to
Ron Peterson
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As Hachiroku mentioned, MPI is multi-port fuel injection, while EFI is electronic fuel injection. MPI is a type of EFI. The hybrid drive system doesn't necessarily need an internal combustion (IC) engine with more power since the electric motors take up the slack, or in some cases, the combination of the IC and electric motors develops more power than the IC drivetrain by itself.

Reply to
Ray O

Did he buy the store back? Tell him I said hi!

Reply to
Ray O

Thanks, I am starting to get it straight. I was confusing MPI with direct injection. Apparently, EFI means that the fuel is injected into the throttle instead of directly in front of the intake valves as in MPI or MPFI. One article indicated that all the new MPI engines use sequential MPI.

Other articles have indicated that the 3.3 engine is lighter and more fuel efficient which makes sense for the hybrid.

I suppose that direct fuel injection will take over, but some engines use both.

-- Ron

Reply to
Ron Peterson

EFI means that the fuel injectors are controlled electronically instead of mechanically as early fuel injection systems were.

Multi-port or multi-point injection means that the injectors spray fuel near the valves instead of in the throttle body like throttle body injection. Throttle body injection, or TBI, uses just one injector instead of one for each cylinder. As far as I know, all multi-port injection systems are sequential, where fuel is injected in the same sequence as the firing order.

Direct fuel injection sprays the fuel directly into the combustion chamber (cylinder). This system is more expensive to implement because higher fuel pressure is needed and the injector has to be able to withstand the higher pressures and temperatures in the combustion chamber than is would if located outside of the valves. Direction injection is more efficient because all of the fuel goes into the combustion chamber and the fuel is mixed with air more consistently so it burns more completely.

You will start to see direct injection become more common as implementation costs come down and new engines are designed.

Reply to
Ray O

Some MPI systems are batch injection instead of sequential. Case in point is this snippet from allpar.com referring to the 3.0l Mitsubishi V6 as used in some front wheel drive Chryslers: "Multiple-port fuel injection was used, with 36 psi of fuel pressure in 1987 and 48 psi in 1988; it ran on regular gas. Two injectors fired together, with the same controller, one against a closed valve and one against an open valve. Sequential injection with single injectors firing one at a time would be used starting in 1992." Also a GM 3800 (3.8l) V6 series 1 (the original) will revert from sequential to batch injection and still run if the cam angle sensor signal is lost.

Reply to
Daniel Who Wants to Know

Multi-port fuel injection (MPI) means that injectors are pulsed in pairs/groups. Therefore fuel can collect at the intake valve area. A more advanced form is the sequential fuel injectin (SFI) where individual injectors are pulsed at precise moments in the crank cycle. EFI, as others mentioned, is just a generic term.

Most modern cars today use gasoline direct injection (GDI). On many European cars these are combined with Stratified Charge combustion, where a rich mixture is sprayed around the spark plug and mostly air elsewhere in the cylinder. Acceleration is controlled by Continuously Variable Valve Lift -- not by a throttle plate. These engines can burn at up to 65:1 air:fuel ratio!!

Reply to
johngdole

"Daniel Who Wants to Know" wrote in message news:5X7ml.518483$TT4.159609@attbi_s22...

Thanks for the correction. I had assumed incorrectly that since all Toyota MPI systems were sequential and a sequential system is the logical way to go, all automakers would follow suit.

Reply to
Ray O

FYI, cutting edge technology in fuel injection:

Bosch fast switching piezo-electric injectors for Gasoline Direct Injection:

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Reply to
johngdole

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