The FSI engine is equipped with an intake manifold with a variable cross-section of the channels. The cross-section is reduced, when the engine is running at part load, and increased as the torque requirement increases. The cross-section size is regulated by a vacuum actuator, changing the position of additional dampers (tumble).
The problem, which the designers had to deal with, there was, however, the regulation of exhaust gas composition. When burning lean mixtures, the classic triple-action catalytic converter turns out to be insufficient, when it comes to limiting the content of nitrogen oxides in the exhaust gas, eliminating them only in 70%. These harmful substances react with hemoglobin, causing, among others. pulmonary oedema, degeneration of the heart muscle, nervous system damage, and even death in high concentrations. Therefore, an additional device was introduced in the exhaust system to trap nitrogen oxides in the form of nitrates. However, this "tank" converter requires periodic regeneration. It follows what 60 s and consists in automatic switching to the engine operation with full mixing of fuel and air (lambda = 0,8) on a draft 2 s. During this time, the nitrates are converted into oxygen, azote, water and carbon dioxide, then released into the atmosphere. In addition to the lambda probe, the exhaust system also has a temperature sensor and a nitrogen oxide concentration sensor. During the combustion of stoichiometric mixtures, the operation of both reactors is added together.
The engine is more flexible thanks to the laminated mixture combustion system with variable lambda coefficient, more economical and more dynamic. The torque increases by approx. 5% due to the higher compression ratio and optimization of the blending process. Fuel consumption is reduced by an average of 15-5-20%, compared to conventional engines with multi-point fuel injection into the intake manifold, a during partial load operation (especially when idling), savings can be as high as 40%. Tests show, That 70% measurement cycle according to the new European test (directive 93/116 / EC) falls within the lean mix range.
According to the factory data, Lupo FSI is satisfactory on average 5-5,5 dm3 of gasoline for 100 km, its maximum speed is 199 km/h, a acceleration from 0 do 100 km / h followed by 10,5 s. The car already meets the Euro toxicity standards 4, which will apply from 2005 r. Two years later, as predicted by experts, every second gasoline engine produced in Europe will be equipped with a direct fuel injection system.
Full use of the advantages of this solution will be possible after the sale of gasoline with a low sulfur content, at the level 10 ppm, against those present 300 ppm. Sulfur oxidation products hinder the processes taking place in the catalytic reactor, and their removal requires keeping it at a very high temperature for a long time (ok. 650°C), which can only be achieved in practice when driving at maximum speed.
The lambda excess air factor.
Until complete combustion 1 kg of gasoline is needed 14,7 kg of air. This ratio, resulting from the course of a chemical reaction, is called stoichiometric. This relation was assumed to be described by the so-called. lambda excess air ratio, which is the quotient of the mass of air actually consumed in specific conditions to the mass of air theoretically needed to burn a given amount of fuel. With stoichiometric combustion, the lambda has a value of 1. The gasoline / air mixture is flammable in the lambda range 0,7-5-1,25. The highest torque is achieved by spark ignition engines at a lambda of 0.9-M. If there is excess air in the cylinder, the mixture is defined as lean, and lambda is then greater than one, otherwise the mixture is said to be rich, and lambda is less than one.