MPI vs GDI

[Auto-9]

After reading about GDI on Mitsu's website I still don't quite understand how it differs from regular fuel injection...don't our cars inject directly into the cylinders? I so confused...

[Fishboy55]

Here to ease your confusion, Chip to the rescue!

The GDI engine has upright straight intake ports (USIP) rather than horizontal intake ports used in conventional MPI engines. In a GDI engine, the fuel tumble is anti-clockwise as opposed to clockwise in a MPI engine. This is because the fuel is injected directly into the cylinder in a GDI engine. In an MPI engine, the fuel goes into a port first then is pulled into the cylinder on the intake stroke of the piston. Also, GDI engines have a curved top piston, which results in better compression, and the injectors shoot the fuel into the cylinder in a curved pattern rather than a straight spray in MPI systems.

Now go write your book report Peter.

Chip

[Auto-9]

It's always you :twisted: Makes me wonder thought why not adopt this technology on all models...

[TJC]

Basically, the technology there helps swirl the A/F mixture resulting in better atomization..... which leads to more thorough combustions.

[~TaranTula~]

I've got a GDI 4G93 1834c.c. and I get good power from that engine. I get a minimum of 30mpg so the technology does seem to offer fuel economy........thats with a/c.

[TJC]

Unfortunately the latest and greatest technologies with cars takes forever to come here to the U.S.A. from overseas. <sigh>

[Auto-9]

Cars, cell phones, anything except the latest politics

[mitsuaddict]

The reason why we don't have it here is because the gas here has a higher sulfur content than in Japan. Supposedly Mitsubishi is working on an engine that can operate using gasoline here. 8)

[manybrews]

heres the skinny.
the GDI has HUGE advantages over normal MPI for several reasons.
first is that the mixture can be stratified right at the spark plug.. its blasted directly at it, and the design of the piston and intake makes for a vertical tumble, which concentrates the air at it also.
compression ratios can be bumped substantially due the the evaporative effect of the fuel. as it evaporates in the cylinder (instead of the intake manifold), it removes heat. this allows the higher compression ratio without detonation.
As the design allows for nearly total combustion, the fuel mixture runs at a lean 40 to 1 for normal operation. (compared to 14.7 to one for our normal cars). At its leanest, it attains a 63 to 1 mixture ratio, and is still usable due to the incredibly efficient design. at its richest (as when accelerating) it does go to 14.7 to one, but our cars actually goto about 12 to one under the same conditions.

so basically, youre talking about an increase in performance, an increase in mileage, and a massive decrease in most emissions.
why dont we have it here? well, it IS due to the fuel, but not directly. the high sulfer fuel can be used, but the catalytic converters cant deal with it at that extreem lean condition. And government mandate says that all cars in america MUST have a catalytic converter on them, no matter what. Its unfortunate, as these cars are cleaner without the cat than most are with it.
they ARE working on it. there is low sulfer gas in most of california, but not nationwide. and mitsu is working on a cat. technology that will work with our shitty gas.
Its an incredible tech, and mitsu pioneered it about 5 years ago. Honda and toyota also are using it now.

[Auto-9]

Further proof that Mitsu leads the tech pack...but fails miserably at applying it to the market

[manybrews]

<div class='quotetop'>QUOTE(Rallifan)</div><div class='quotemain'>Further proof that Mitsu leads the tech pack...but fails miserably at applying it to the market </div>
cant blame mitsu for the idiocy of our government.

they have the tech in damn near every other developed country..

[TJC]

That's fascinating manybrews. I didn't know there was that much more to the Mitsubishi GDI design. Very impressive indeed.