In at least some implementations, a method of controlling a fuel-to-air ratio of a fuel and air mixture supplied to an engine, includes the steps of determining an engine deceleration event, determining the number of engine revolutions required for the engine speed to decrease from one speed threshold to another speed threshold, comparing the number of engine revolutions determined above against a revolution threshold, and making the fuel and air mixture richer if the number of engine revolutions determined above is greater than the revolution threshold. The method may also include determining if, before the engine stabilized at a stable engine speed (which may be an engine idle speed), the engine speed decreased below the stable engine speed as the engine decelerated to the stable engine speed from a speed above the stable engine speed, and making the fuel and air mixture leaner if the determination is affirmative.

At least some implementations of a method of distinguishing between two loads being driven by an engine, includes the steps of determining engine speed at defined intervals, comparing a second engine speed against a previously determined first engine speed, determining if the second engine speed fits an expected pattern of engine speeds, and counting either the number of incidents where the second engine speed does not fit the expected pattern, or the number of incidents where the second engine speed does fit the expected pattern, or some combination of these two. A method of determining if an engine is operating at least near a lean limit of its air to fuel ratio is also disclosed.

A combination system may include a carburetor in fluid communication with an engine intake tract and a fuel injector in fluid communication with the engine intake tract.

An engine-driven working machine according to the present invention has a controller and a muffler. The controller is operated from starting of the engine in a rotational speed limitation mode in which the engine is prevented from rotating at a rotational speed that is higher than the predetermined limitation rotational speed. The controller forces to stop the engine, after a predetermined period has passed, during which the engine operates in the rotational speed limitation mode.

The present disclosure relates to a carburetor assembly (7) comprising a control unit (17), an air channel (8), a throttle valve (9), a choke valve (10), a pulsed fuel valve (11), and a fuel supply line (12). The control unit (17) is adapted to control the fuel valve (11) to supply fuel in accordance with a certain start setting, where the choke valve (10) can be open or closed. The carburetor assembly (7) comprises a rotation angle detector assembly (20) with a choke detector part (29) that is mounted to a choke shaft (30) that is connected to the choke valve (10) such that the choke detector part (29) is arranged to rotate together with the choke valve (10). The rotation angle detector assembly (20) further comprises a choke sensor device (23, 33) that is connected to the control unit (17) and can be affected by the choke detector part (29) such that the choke sensor device (23, 33) provides different output signals to the control unit (17) in dependence of whether the choke valve (10) is open or closed.

To improve responsiveness of fuel supply control, a rotary carburetor 100 has a nozzle 8 including a fuel discharge port 8a and a needle 10 disposed coaxially with the nozzle 8 and disposed with a portion inserted into the nozzle 8. The needle 10 can be displaced relative to the nozzle 8 to change an effective area of the fuel discharge port 8a. The rotary carburetor 100 has an electric motor 14 for displacing the needle 10 along an axis, and a drive mechanism component 12 interposed between the electric motor 14 and the needle 10 and converting a rotational movement of the electric motor into a linear movement.

A control system for carburation of an internal combustion engine in use conditions comprising following activities: starting the engine with a value of equals .sub.0=.sub.T; constructing a curve c.sub.i() of the ionization current as a function of the angular position a of the crank shaft; selecting, on this curve c.sub.i(), a number of points at intervals of the rotation angle a; calculating value z, equal to integral from 0 to 360 of the curve c.sub.i(), is done by summing products c.sub.i for all preselected points; interrupting supply of fuel for some cycles in order to externally modify factor .sub.0 and take it to value .sub.1; for value .sub.1 constructing curve c.sub.i() and calculating value z.sub.1; calculating difference .sub.z=z.sub.1z.sub.0, and if the difference is >.sub.zref in absolute value, intervening on carburation by increasing the quantity of fuel injected in a case of a positive difference (lean mixture) and by reducing the quantity of fuel injected in a case of a negative difference (rich mixture).

Present embodiments provide a throttle body which may be used with a variety of engines of different manufacturers. The throttle body includes an inlet which expands to two or more bores, which extend downwardly through the throttle body. The throttle body may provide improved fuel pathways and fuel injector placement.

At least some implementations of a method of distinguishing between two loads being driven by an engine, includes the steps of determining engine speed at defined intervals, comparing a second engine speed against a previously determined first engine speed, determining if the second engine speed fits an expected pattern of engine speeds, and counting either the number of incidents where the second engine speed does not fit the expected pattern, or the number of incidents where the second engine speed does fit the expected pattern, or some combination of these two. A method of determining if an engine is operating at least near a lean limit of its air to fuel ratio is also disclosed.

At least some implementations of a method of distinguishing between two loads being driven by an engine, includes the steps of determining engine speed at defined intervals, comparing a second engine speed against a previously determined first engine speed, determining if the second engine speed fits an expected pattern of engine speeds, and counting either the number of incidents where the second engine speed does not fit the expected pattern, or the number of incidents where the second engine speed does fit the expected pattern, or some combination of these two. A method of determining if an engine is operating at least near a lean limit of its air to fuel ratio is also disclosed.