What's so great about direct injection?

[Thai]

Link to article: What's so great about direct injection? (ABCs of Car Tech) | The Car Tech blog - CNET Reviews

"Toyota has offered its D-4S fuel injection system for a number of years with certain models of its 3.5-liter V-6 engine. The D-4S uses a combination of both direct and port injection to blend the best traits of both systems. As it's explained in this article from Wards Auto, the port injection system handles clean startup, the direct injection handles full load acceleration, and the two systems work in tandem to balance everything in between. This D4-S system is also used on the 2.0-liter boxer four-cylinder that powers the Scion FR-S and Subaru BRZ."

 

[BlackWorksInc]

The D-4S system is pretty good, but it still has its issues. GDI is a great technology and really comes into its own when combined with a comprehensive dual VVT system and a turbo/supercharger.

The positives are far better control of the vehicle's burn characteristics, better fuel mixing, 5 additional types of combustion (i.e. one involves swirling a donut of EGR gases and using a small pocket of air/fuel in the center of the piston to reduce fuel consumption and maintain momentum when cruising).

The negatives are pretty obvious, cost, complexity, newer technology (has only been in play for about less than a decade, mainly by the Europeans.) There is also the carbon issue that plauges these engines due to the design (Toyota attempted to use a second set of injectors to clean the backs of the intake manifolds and create a comprise between the flaws and benefits of a GDI and MPI, but it still has some bugs in it. Not a bad system but not perfect) of the intake systems and lack of fuel to wash off the valves. They get so carboned up sometimes they block off the port completely and we're not talking lik 80k down the road, try more like 20~30k. Look up VW/Audi, BMW, Mercedes GDI Carboning to really understand it. This technology is also severely limited in its potentional because of emissions regulations. The government is so hard on manufactuerers to styme CO2 emissions it actually hurts the performance of these vehicles and in a way is counter productive. To get these engines to run so much "Cleaner" CO2 wise, the engines punch out a TON of NOX and limit the amount of phase timing and fuel manipulation they could use to make some serious power out of itty bitty engines.

All in all, GDI is a great technology and it shows real promise when combines with VVT & Forced Induction (hence why so many are making GDI engines in this "trifecta" configuration), but it is still a relatively young technology in practice and needs to have a few bugs worked out of it first.

 

[Jeff Kleb]

Gdi


The technology really is not new - as compression-ignition (diesel) engines have been set up this way for years; but it is revolutionary for spark-ignition (gasoline) engines. I drive big rigs at work and they all operate like that, be they equipped with Cummins, Navistar or Hino engines. Fuel is injected directly into the cylinder's combustion chamber rather than just into the intake manifold.

I can only imagine the high pressure at which these things operate. Wow! If they get the bugs worked out, I see more and more cars utilizing GDI.

:artist: