Nauticalx

Hey Guys:

I did a check and found alot about the clicking direct injectors make but not much on what benefits direct injectors provide. Some people alluded to increased horsepower or gas mileage but if this is true can one of you techies out there explain how this is achieved and during what instances are the direct injectors working vs the port injectors or are they both working all the time.

Thanks

SteVTEC

With direct injection, the fuel is injected directly into the cylinders unlike port injection which is done through the intake ports (indirect). It's injected at very high pressures so the fuel as it expands has a cooling effect on the intake charge as it's injected. This increases the knock limit of the engine and allows for a higher compression ratio to be used which helps both with power and the overall efficiency of the engine. Naturally aspirated direct injection engines can use compression ratios in the 11-12:1 range vs 10-11:1 before. Turbocharged engines can also go a full point up in compression also, from 9:1 to the 10:1 range. BMW's new 335i engine has a 10.x:1 compression ratio thanks to the added anti-knock effects of DI.

On the 2GR-FSE engine, the "backup" port injectors are used to help increase charge tumble at various ranges on the engine map which allowed them to avoid the need for tumble valves in the ports themselves which would have decreased the top-end horsepower due to the obstruction. So yes, both are used at the same time in varying percentages.

Here's a good tech brief on the engine: http://www.sae.org/automag/techbrief...e%3Asae.org%22

I think I have an SAE white paper on the 2GR-FSE too that has additional info. If so I'll try to dig it up and see what else it says.

DaveGS4

iTrader: (2)

From Lexus... more about benefits than 'how'

Nauticalx

Dang, thats clever stuff. A pat on the back to whoever invented this. Seems so simple an idea yet so beneficial. I guess we are really pushing gas engines to the max now.

mavericck

The 1955 Mercedes-Benz 300SL, the first gasoline-powered automobile to use fuel injection, used direct injection. The Bosch fuel injectors were placed into the bores on the cylinder wall used by the spark plugs in other Mercedes-Benz six-cylinder engines (the spark plugs were relocated to the cylinder head). Later, more mainstream applications of fuel injection favoured less expensive indirect injection methods.

http://en.wikipedia.org/wiki/Gasoline_Direct_Injection

Lexmex

There is also a benefit when going up in altitude, but not quite as good as the benefit from having a turbo.

4TehNguyen

iTrader: (1)

gas burns much better when the fuel is sprayed on the piston head, evaporatng it, especially during high rpms where the window of time for gas to burn is much less, also on the head itself makes the fuel mix centralized and more even in the combustion chamber. On port injection the gas is sprayed on the cylinder wall from the intake valve before compression, not a good place to get an efficient burn when the fuel is on one side of the cylinder. DI is done during the compression cycle and the charge cools the mixture. Cleaner/quicker burn = more power, better mileage, improved emissions

as explained before the evaporation of the gas has a cooling effect and a higher resistance to knock

Ive seen some direct injection videos on the honda world website, possibly their next gen engine will have DI as well