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Eugenio,77
The principles of LeanBurn system operation (Carina E (AT19#) for European market as an example). It should be noted that 4A-FE and 7A-FE LeanBurn engines for domestic and overseas markets are significant different.
Implementation of Lean Burn technology reduced maximum power output by 8% and maximum torque by 4%. Fuel consumption decreased by 3% (at highway) or 11% (in the city). Thus, there was no sense of innovations, especially in view of higher complexity and reduced reliability.
Design Notable distinctions of 4A-FE LB are in the cylinder head design. There are projections at four of eight intake ports, forming the air turbulence in cylinders.
The fuel injectors are mounted directly in the cylinder head and fuel is injected close to the intake valves. The injection is carried out by each injector in turn ("sequential").
1 - IACV valve, 2 - from throttle position sensor, 3 - from crankshaft position sensor, 4 - ECU, 5 - actuator, 6 - vacuum tank.
Most LB engines at second half of 1990s was equipped with DIS-2 (Direct Ignition System), with two ignition coils. At European LeanBurn engines a new type of oxygen sensor was installed (Lean Mixture Sensor 89463-), much more expensive beside to the traditional sensor and without non-genuine counterparts. At Japanese LeanBurn conventional oxygen sensor applied (89465). Between the intake manifold and the cylinder head the set of valves with pneumatic control was installed (IACV - intake air control valve). Flaps are driven by vacuum actuator, via vacuum switching valve by signal if engine control module depending on the throttle opening angle and engine speed. When the valve is closed, air flows through one of the ports, creating a swirl in cylinder. It contributes to better fuel evaporation and mixture turbulence, allows to lean mixture combustion.
Vacuum tank with built-in check valve supplies vacuum to the actuator and, accordingly, provides the valve closed state even with low vacuum in the manifold. When driving in LeanBurn mode, the "Econo" indicator light up at combination meter. Indicator should be extinguished (for Euro-versions) in the following cases: Operation
Fuel supply is performed in two modes - the stoichiometric (S) and the lean combustion mode (LB) depending on driving conditions. 1. Lean combustion mode (LB). 2. Low to medium load operation VSV is OFF and the vacuum from tank is applied to actuator via VSV, IACV flaps are closed. Air passes through the "helical" port, forming a vortex in the cylinder. At the same time, some air passes through the bypass hole in "straight" port. It allows to improve the evaporation of the fuel and use lean mixture.
3. High load operation At high load ECU turned VSV ON and air is supplied to the actuator. As a result, the both intake ports are opened, the intake resistance is reduced and power output is increased.
4. Stoichiometric mixture combustion mode applied under the following conditions:
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