GDI may be getting Gasoline Particulate Filter (GP

[leeharvey418]

There's not really anything about direct injection that inherently makes more power. In Mazda's case, it allows them to run an Atkinson cycle without having to manage fuel in the intake tract. In cases where it's used with forced induction, it helps cut pre-ignition.

It used to be that you set up an engine to run at stoichiometric in the interest of the catalytic converter being able to do its job, and to continue to do it for years. Direct injection (theoretically) gave engine designers an alternate method to cut NOx emissions by getting lower peak temperatures in the combustion chamber. The problem is that cats still don't like dealing with an excess of oxygen flowing through them.

 

[440Magnum]

You don't have to be "rolling coal" to have too much particulate emission. Just look at the rear bumper of any older white-painted Nissan. Well, maybe not every one, but for whatever reason Nissan has been prone to tunings that cause a lot more soot than other gasoline engines, all the way back to the early 1990s and that definitely pre-dates GDI!

I really think the manufacturers will resolve it with changes to injectors, fuel pressures, piston dish and combustion chamber shape design to reduce droplet impingement and improve vaporization.

 

[440Magnum]

Originally Posted By: supton
I don't get it. How is it that the engine is supposedly more efficent with DI yet has larger particulate emissions? Poor swirl / poor atomization, seems to me like its the same as not getting a good burn.

I don't get why DI makes more power. More responsive I get. Well, sorta, since port injection isn't exactly TBI (in terms of distance from injector to valve).

It must hold some edge else it wouldn't be put forth.


Detonation resistance. Since the fuel is introduced into the engine at the last possible moment and at the point of combustion rather than upstream in the intake manifold where it is then heated as it moves into the cylinder, the fuel is cooler and less likely to pre-ignite, even at the same octane rating of the fuel itself. So that in turn allows higher static compression or higher boost pressure, either of which results in more available power form a given size engine.

 

[MCompact]

Originally Posted By: 440Magnum
Detonation resistance. Since the fuel is introduced into the engine at the last possible moment and at the point of combustion rather than upstream in the intake manifold where it is then heated as it moves into the cylinder, the fuel is cooler and less likely to pre-ignite, even at the same octane rating of the fuel itself. So that in turn allows higher static compression or higher boost pressure, either of which results in more available power form a given size engine.


Bingo!!!

 

[SteveSRT8]

Originally Posted By: 440Magnum
I really think the manufacturers will resolve it with changes to injectors, fuel pressures, piston dish and combustion chamber shape design to reduce droplet impingement and improve vaporization.



There is a very real cylinder filling issue at part throttle. It is challenging some mfgrs and seemingly solved by others.

Seems there are varying degrees of expertise when it comes to DI...

 

[BMWTurboDzl]

My $.02

Due to the fact that the US does not require ULSG a more efficient catalyst along with lean burn cannot be utilized to reduce NOX. As a result US cars are tuned to run richer to keep exhaust temps down and thereby reduce NOX.


A richer tune causes elevated particle emissions.