Gasoline direct injection

A layer of charge is a method of the technology gasoline engine, wherein the fuel (e.g., gasoline) is prepared in such that in the region of the spark plug, there is an ignitable mixture (lambda λ = 0.5 to 1.0 ) while the rest of the combustion chamber, a has very lean, hard ignitable mixture ( λ = 1.5 to 3.0 ). The total air ratio is about four-stroke engines from 1.2 to 1.6. Only after the ignition of the fat part of the mixture to conditions that could ignite and result in the remaining mixture. Stratified charge engines have the hybrid motors (not to be confused with hybrid drives ) are considered, as they combine the feature -ignition of the gasoline engine with the inhomogeneity of the fuel-air mixture of the diesel engine.

Today's method

In the stratified method is used today primarily the direct injection and a quality control (similar to the diesel engine). This scheme results in the partial load and the lower speed range consumption advantages, since no throttling losses caused by the throttle valve. Development goal is the design of the combustion process in terms of improvement of the efficiency and the reduction of the regulated pollutants ( hydrocarbons, nitrogen oxides, carbon monoxide ).

Honda introduced in 1974 with the CVCC method ( Compound Vortex Controlled Combustion ) a system based on a carburetor and Fackeldüse layer charging process in series.

Likewise, the stratified charge in the slot -controlled two-stroke engines, in particular reverse -flushed, be implemented to reduce the fresh charge losses. Also known as the scavenging ( SpV ) known principle has been known since the 1920s and is increasingly being used there due to increasingly stringent emission regulations in series where valve-controlled motors are too heavy or prone to errors. The layer charge is based on vorzulagern the mixture either in the fresh air transfer ports or old gas ( temporal stratification ) or shield the outlet throughout the charge cycle by means of a fresh air curtain ( spatial stratification ). In the temporal layering the fresh air passes through pockets in the piston skirt of the fresh-air channels in the transfer ports. Also, by check valves at the transfer ports, the fresh air supply can be controlled. The total air ratio is much richer than in four-stroke engines (lambda approximately 0.8 to 0.9 ) in mixture-lubricated engines.

Technology

The development of stratified charge engines began with the proposed tightening of emissions legislation in the early 1970s in all major car manufacturers and various research institutes. The main objective was to comply with the laws as possible without catalyst; these were then still in the early stages of development.

The principle of a three-valve stratified charge concept was first mentioned in 1918 in the literature and patent applications.

It crystallized two different stratified charge method out ( which of course overlaps were possible, as the Newhall process, for example).

Version A

Gemischverdichtendes method with a subdivided combustion chamber ( secondary chamber and the main combustion chamber ). Advantages of this method were defined separation of the supplied with a rich mixture side of the chamber and supplied with a lean mixture main combustion chamber and thereby a reliable operation over the entire operating range. The disadvantage, however, were the jagged combustion chamber with an unfavorable ratio of surface to volume, higher hydrocarbon emissions, increased fuel consumption and reduced performance.

Porsche SKS ( stratified charge chamber system ) and the PCI procedure of Volkswagen (both with direct injection into the secondary chamber ) and the Honda CVCC method ( Compound Vortex Controlled Combustion ) were known, which only made ​​the CVCC briefly as standard and in U.S. and Japan has been sold. In addition there exist some other methods which, however, only by detailed solutions mainly in the secondary chamber area distinguished (eg Ricardo, Nilov, Gussak, Nissan, Mercedes -Benz, General Motors).

Prior to the introduction of direct injection with standard passenger car diesel engines in the 1990s, this principle has been used almost exclusively in the form of pre-combustion chamber and swirl chamber engines in such.

Version B

Luftverdichtendes method with modified combustion chamber and fuel injection. Advantages of this method were the undivided combustion chamber, the performance-enhancing direct injection and the opportunity to drive higher air ratios, and thus to operate the engine in a large operating range exclusively with quality control and thereby throttling losses largely to avoid. The disadvantage, however, was that it was not possible to achieve a stable stratification and thus a reliable engine operation in the entire operating range of the engine.

The Hesselmann methods were known and the

• MAN FM,
• Deutz AD ( AllStoff direct )
• Ford PROCO ( Programmed Combustion ) and
• Texaco TCCS method ( Texaco Controlled Combustion System )

But none of which got beyond the experimental stage and was produced as standard.

Since a few years, this process has become topical again with modern injection technology. Are known about the GDI method (Gasoline Direct Injection) from Mitsubishi and the FSI method ( Fuel Stratified Injection) of Volkswagen, with the latter a mixture stratification but realized only in a small part of the operating range and with increasing load and engine speed again with a homogeneous stoichiometric mixture is conducted. VW but this procedure abandoned due to technical and principle -related problems. All current FSI models are only used in homogeneous operation (as of 2009).