Direct Injection

[Deuce]

What is it, how is it mechanically different from traditional fuel injection, and why isn't it stateside yet?

[fredk]

direct injection has the injector in the combustion chamber instead of somewhere ahead of the intake valve, I have heard of a couple cars that have it here

[Squidward]

VW has sold DI cars here in the 'States since '95. AKA VW's TDI. Turbodiesel Direct Injection.

BMW has had DI in a gasser here in the 'States for a few years, now.

The main difference between a conventional FI system and a DI system is that the injection pressures have to be a lot higher to be able to spray into a highly compressed air mixture. The DI system sprays fuel directly into the combustion chamber as opposed to spraying it into the intake tract, which is mixed with the air in the combustion chamber where it is compressed then burned.

The advantage of this system is that the fuel is much more precisely controlled, which means more power, less emissions (theoretically), and a longer lasting engine, since the raw fuel never gets a chance to touch the cylinder walls, which are coated in motor oil. On a conventional system the gasoline thins the motor oil on the cylinder walls.

[gcs118]

Originally Posted by Squidward

The advantage of this system is that the fuel is much more precisely controlled, which means more power, less emissions (theoretically), and a longer lasting engine, since the raw fuel never gets a chance to touch the cylinder walls, which are coated in motor oil. On a conventional system the gasoline thins the motor oil on the cylinder walls.

How in a DI system does the fuel not touch the cylinder walls? Also, would the fuel injectors have locations more like the spark plugs in DI rather than the traditional fuel rail/intake manifold location?

[Squidward]

In a conventional setup the fuel is mixed with the air as it enters the combustion chamber and this allows the fuel to make contact with all surfaces that it can come into contact with. With a DI system the fuel is sprayed in just before the spark plug fires so the piston is approaching TDC when it starts to spray and the spark plug fires almost right after that, burning the fuel before it even has had a chance to hit the top of the piston.

[ShawnM]

not much but there is a little pic of the setup.

http://www.boschusa.com/AutoOrigEqui...rectInjection/

Vw is using this setup in europe right now. Not being used here in the US as far as I know.

[b1gb3n]

in reality, DI uses less fuel when idling. other than that, it doesnt produce more power or fuel efficient when car is running.

that is y not all cars use DI system.

[4Aaron GE]

Honda's explanation is nice. Long though.

http://world.honda.com/HDTV/news/2003-4031127a/