Some details of the 2AZ-FE engine

advanced powerplant?" that's a good one.

The old 1.8T had an essentially flat torque curve over the same rev range and was only available with conventional transmissions. I wasn't aware that Audi had a CVT yet, although I have missed stuff before. I thought their new high end transmission was the dual-clutch deal?

nate

Think Diesel engine. Bigass mechanical pump driven by the engine. No, it doesn't pressurize the intake air, but the fuel has to be pressurized to significantly more than the normal 50-100 PSI because it's being sprayed into the compressed air in the chamber rather than into the intake, where it's spraying into air that's at atmospheric (or less, under part throttle - or slightly more, in a turbo/ supercharged engine on boost) pressure.

nate

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here's more reading for you to get you started:

nate

That sounds like a fun ride, even if it makes nasty blatty V-6 noises. I gotta ask, what are your other toys if that one isn't fun enough to make the cut?

nate

(gonna be driving my '55 soon, I swear... I'm going through V-8 withdrawal)

Think Diesel engine. Bigass mechanical pump driven by the engine. No, it doesn't pressurize the intake air, but the fuel has to be pressurized to significantly more than the normal 50-100 PSI because it's being sprayed into the compressed air in the chamber rather than into the intake, where it's spraying into air that's at atmospheric (or less, under part throttle - or slightly more, in a turbo/ supercharged engine on boost) pressure.

As might be expected wikkipedia has a description - see

No, it's not. Direct injection is just now starting to be used in some European cars. They're need for fuel efficiency is a lot higher.

Direct ignition is pretty much common on any car these days.

A transmission has nothing to do with torque output of an engine. A CVT is able to keep the rpms at max torque at all times while accelerating.

Max HP speed will give best acceleration.

As Nate pointed out, you appear to be confusing "injection" with "ignition." Direct injection means that the fuel is injected directly into the combustion chamber, and the cylinder head has another opening for the fuel injector instead of injecting the fuel into the intake runner (what you called the "antechamber." Injecting the fuel directly into the combustion chamber requires much higher pressure to atomize the fuel in the higher pressures within the combustion chamber.

Direct ignition has been around for over 15 years.

NEVER!!!!

Right. Correspondingly, if you have a CVT, you can get away with an engine that has high torque in a very narrow speed range, whereas with a conventional transmission the engine has to be able to provide good torque over a wider range of speeds. (ie. the torque curve has to have a much wider peak on it).

--scott

This is how I understand GDI (gasoline DIRECT injection), feel free to correct my mistake

Fuel and air mixture are injected in some kind of pressure tank where the pressure is increased, by compressing the mixture I suppose. At this stage the ratio of the fuel and air is adjusted for optimum burn.

This pressure tank sometimes called as a *common rail*? has a nozzle that will release the pressurized fuel-air mixture directly into the chamber chamber via the intake valves. This high pressure coupled with optimum ratio allows the engine to run more fuel efficiently and, of course, more powerful. The VVTi (toyota) will then adjust the opening of the valves whether to inject the mixture during the intake stroke or slightly delayed.

"EdV" wrote in message news: snipped-for-privacy@i36g2000prf.googlegroups.com...

In the direct engine engines I have researched, there is no tank that mixes the fuel and air. There is an injector in the combustion chamber instead of in the intake tract before the intake valves. Air is admitted into the combustion chamber by the valves. Fuel is injected directly into the combustion chamber, instead of being mixed with the air in the intake tract before the intake valves. By injecting the fuel directly into the combustion chamber, you can create a "stratified charge." In other words a non-uniform mixture of gasoline vapor and air. Gasoline is very difficult to ignite if you don't have the proper air/fuel mixture. By creating a stratified charge, you can have a proper A/F mixture in the area of the spark plug and a lean mixture everywhere else. The spark plug can then easily ignite the proper mixture in the area of the spark plug and this in turn will burn the leaner mixture elsewhere in the combustion chamber. This allows an overall leaner mixture to be burned, resulting in higher efficiency. Chrysler tried this years ago with carbureted engines with limited success (tried to manipulate the mixture with combustion chamber and intact tract shape). Honda tried something a little different with a three valve design in the late 70's (two "regular" valves and one smaller valve to richen the mixture near the plug). Neither worked very well. There are a lot of great claims being made for direct injection engines. However, the direct injected manual transmission Mazda 5 gets worse EPA gas mileage than the regular old 4 cylinder automatic Toyota RAV4 (which is larger and heavier...).

Ed

On Jul 18, 11:05 am, "C. E. White" wrote: There is an injector in the combustion chamber

Ahh, so the intake valves is just for the AIR and the injector for the FUEL. no pre-mixing involved. The mixing occurs directly inside the combustion chamber. The fuel is pressurized and not the air like in a turbo setup. Thanks!

Yep, you got it Edv. But the fuel is injected into the combustion chamber, not the intake manifold.

Of the three types of fuel injection, the direct injection has the capability of being the most efficient. The air/fuel mixture can be precisely adjusted for each individual cylinder and for each individual power stroke.

Throttle body injection is the least precise of the three. It is basically just a computer controlled carb that uses a injection jet instead of a metering jet. It's better than a carburetor but not by much.

Multi-port injection places one injector in the manifold runner to each cylinder. This is a better scheme that allows more precision but it is limited on how much the mixture can be leaned out before pre-ignition occurs.

Direct injection allows placing a rich fuel/air mixture around the sparkplug and a much leaner mixture in the rest of the cylinder. By the time the flame front moves out to the rest of the cylinder, the piston has moved past top dead center and the much faster burn rate of a lean mixture won't hurt the engine.

I hope this helps and if I've gotten anything wrong in this, I'm sure someone will correct me.

Jack

Great! So this means its possible not to have VVTi and Direct injection at the same time. The timing of the fuel comes from the nozzle and not from the opening of the valves, although air enters through the valves, its the fuel which is controlled and not the air.

No, I think it would still be possible to use variable valve timing and direct injection at the same time. The amount of fuel is controlled by the engine computer based on info it gets from the O2 sensor, throttle position, RPM, etc. VVTi would still be a valid way to increase engine efficiency by controlling the amount of air, that's really all it controls with multi-port injection also.

Jack

I think you misread the post. He was saying it's possible to not have both features, not that it's impossible to have both.

You are right lefty. I did misread the OP's comments. Sorry and he would be right. I guess I get in too much of a hurry sometimes.

Jack