The small block carburetor combines several systems (idle, transitional, main metering) and devices (accelerator pump, economizer, economizer, starting), the purpose of which is to create combustible mixtures corresponding to a particular engine operating mode. There are many modes - engine start, idle, medium loads, full loads - and each of the listed modes requires its own combustible mixture.
It should be remembered: running the engine on a lean mixture is undesirable, since the engine power drops. If the mixture is leaned even more, the power will decrease significantly, the engine will overheat and, despite the fact that the mixture is lean, gasoline will be consumed more than normal. When running on a lean mixture, flashes occur in the carburetor and it begins to "sneeze". The engine also runs poorly with an over-rich mixture. "Shots" are heard, clouds of smoke burst from the muffler. And inside the cylinders at this time the following occurs: unburned fuel particles create carbon deposits, coked oil particles and varnish deposits together with carbon deposits contribute to overheating of engine parts.
Unburned fuel, flowing down the cylinder surface, washes away the oil film, and this, in turn, increases the wear of rubbing parts.
What mixture provides optimal conditions for engine operation? Experience suggests that for normal operating conditions, a slightly lean mixture will be the most advantageous (the most economical).
In difficult road conditions where excess power is needed, the mixture should be enriched slightly.
VAZ cars are equipped with two-chamber carburetors (Fig. 22) with sequential opening of the throttle valves. The Ozone carburetor has a pneumatic drive of 1 throttle valve of the secondary chamber and can be equipped with either an autonomous idle system (abbreviated as AXX), or a set of ASKH and EPHKH, i.e. forced idle economizer. The set of these devices was called "Cascade".
Most experienced drivers use the engine as a brake. On long descents and in tight traffic flow, this method of braking is quite justified. One bad thing is that gasoline flies into the wind.
In idle mode (forced idle) — this is the name for elementary engine braking, the latter does not need gasoline. In order to interrupt the fuel supply at the right moment, a forced idle economizer was developed. The automation is controlled by special sensors that respond to the position of the throttle valve and the speed of rotation of the crankshaft.
The Ozone carburetor is significantly more economical than its predecessors due to the adjustment of the primary chamber metering systems. The Cascade system allows for even more economical fuel consumption, and the overall reduction in consumption can be 1-3 liters per 100 km.
Although the Ozone carburetors were designed specifically for installation on cars VAZ-2105 and VAZ-2107, they can be installed on VAZs of all models and any year of manufacture without any modifications. DVAZ-2105 (this is another name for a carburetor produced by the Dimitrovograd Aggregate Plant) designed for VAZ-2101, VAZ-2102, VAZ-21011, VAZ-2105 vehicles, and DAZ-2107 for VAZ-2103 vehicles, VAZ-2106, VAZ-2107 and VAZ-2121.
In connection with the appearance of the new carburetor, a new vacuum ignition distributor was also developed, which automatically changes the ignition timing depending on the engine load.
However, there are cars with old carburetors and distributors in operation and, naturally, some car enthusiasts want to equip the engine with modern devices. The designers took this into account. Here are the combinations that can be used:
- vacuum distributor and carburetor designed to work with it;
- ozone carburetor and old model distributor;
- new distributor and old carburetor. In this case, to avoid increased fuel consumption, it is necessary to reduce the performance of the main metering system jet.
If on the carburetors of the generation preceding the "Ozone" any car enthusiast could adjust the engine crankshaft speed at idle, as long as he considered it necessary, then on the "Ozones" the plant sharply limited this necessity and possibility. Thus, the car enthusiast is given only a field of activity for control. Intervention is permissible only in case of obvious excess fuel consumption.
If adjustment is necessary, unscrew screws 1 and 2 (Fig. 23), break their heads, remove bushings 4 and 5 and tighten new screws; warm up the engine (the coolant temperature should be at least 80-90°C); check if the ignition timing angle and valve clearances are set correctly. For objective adjustment, it is necessary to use a gas analyzer.
Screw 2 should be used to set the maximum crankshaft speed, screw 1 should be used to bring the crankshaft speed to 850–900 rpm. In this position of screw 1, screw 2 should be used again to ensure the CO content in the exhaust gases is up to 1–1.5%. During the adjustment, the crankshaft speed may change, in connection with which screw 1 should be used to restore the speed to 850–900.
After completing the adjustment work, you should press the limiting bushings onto the screws (these red bushings, unlike the blue factory ones, are available at service stations) so that the stop of sleeve 4 is to the right of stop 3 at a distance of no more than 1.5 mm, and the stop on sleeve 5 is at an equal distance to the left and right of stop 6.
It is known that the main advantage of the new generation of carburetors is their efficiency, which is achieved mainly by using a pneumatic drive of the secondary chamber throttle valve.
It should be remembered that the pneumatic drive is activated when the loads are high. Thus, it has been experimentally established that on a VAZ-2103 car with two passengers on board and 100-120 kg of cargo in the trunk, the throttle valve in the secondary chamber opens in 3rd gear at a speed of 90 km/h, and in 4th gear in the speed range from 100 to 120 km/h.
The text is taken from the online resource [www.VAZbook.ru]
It is clear that such a speed cannot be developed when driving in the city, the secondary chamber does not come into operation, and fuel consumption must be optimal. If excessive fuel consumption is detected, then the conclusion suggests itself: there are malfunctions in the secondary chamber drive.
The most probable cause of excessive fuel consumption is loose closing of the secondary chamber throttle valve at low loads. In this case, the automatic system is often "to blame", or rather its vulnerability. Automatic system and dirt are incompatible concepts. It is the dust and dirt settling on the drive parts that distort the "precision" of the automatic system. Dirt makes it difficult for the throttle valve axis to rotate in the housing. Sand and dust settling on the springs between the levers make it difficult for them to move relative to each other.
It happens that small and precise drive parts are deformed by careless movements of the assembler or repairman. As a result, the secondary chamber flap hangs and there is a clear deterioration in engine performance with a significant increase in fuel consumption.
Recently, devices have appeared on the market that can be used to adjust the carburetor's operation quite accurately. Some car enthusiasts, for example, speak well of the IKS-1 quality indicator. The indicator is screwed in place of one of the spark plugs. The indicator's mirror shows whether the mixture is burning well. A bright blue flame indicates that the carburetor is producing a good mixture. An orange flame indicates that adjustment is needed.
The carburetors of "Zhiguli" really "don't like" when the fuel level in the float chamber rises above the norm. It is necessary to check and, if necessary, adjust this level. It makes sense to perform this operation also because when the level increases, fuel consumption increases significantly. "Ozon" carburetors are especially "sensitive" to the increase in the fuel level. Even minor deviations from the norm can cause unstable engine operation at idle due to the ejection of fuel droplets from the sprayer into the diffuser of the primary chamber.
Carburetors of VAZ cars can be disassembled step by step, in parts. Thus, to check and adjust the fuel level in the float chamber, it is necessary to remove only the carburetor cover. Before the cover, it is necessary to remove the air cleaner, disconnect the drive of the starting device, disconnect the throttle drive by removing the plastic joint from the ball pin of the primary chamber throttle drive lever, disconnect the fuel line and the crankcase ventilation pipe.
To remove the carburetor cover, you need to prepare a clean table and good light. Then remove the spring 8 (see fig. 22) the secondary chamber throttle actuator lever, disconnect the rod 7 of the pneumatic actuator. Compress the spring of the telescopic rod 2, separate it from the lever 6'. Having completed these operations, you can remove the carburetor cover, having first unscrewed the screws.
Wash the removed cover 1 (Fig. 24) of the carburetor in gasoline, blow it with compressed air, check the condition of the filter 3. Clean it from dirt, oil and check the condition of the cover, all parts and units located on it.
After finishing the work, inquire about the condition of the mating surfaces, gasket 10, which should not have any damage or hardening; float 9, which must be sealed, without dents or cracks. Before installing the carburetor cover, it is necessary to check whether the float moves freely on the axis.
The fuel level in the float chamber depends mainly on the condition of the float 9 and the distance between the float body and the carburetor cover 1. The float operates normally if the distance between it and the edge of the carburetor cover is within 6.5±0.25 mm. The easiest way to control this size is with a gauge. When taking measurements, the carburetor body cover must be held vertically. At this time, the tongue 8 of the float must touch the spherical surface 6 of the needle valve 5. The specified size is ensured by bending the tongue. In this case, it is desirable to maintain the perpendicularity of the needle valve axis and the tongue support area. The full stroke of the float should be within 7.75-8.25 mm, and this is achieved by bending the stop 4.
After making the adjustment, it is a good idea to make sure that the valve needle pull-off fork 7 does not interfere with the free movement of the float. When adjusting the fuel level in the float chamber, be consistent to the end: check the needle valve itself. It is considered to be in good working order if it meets two conditions: it moves easily (without jamming) in its nest upward under the influence of the float and downward according to natural laws; does not pass fuel when closed. To replace a faulty needle valve, you need to remove the float shaft, remove the float, the needle valve and at the same time replace the seat 2 valves, using a 10 mm wrench for this purpose. While the cover is removed, blow out all the carburetor jets, channels and cavities with compressed air. Having done all this, put the carburetor cover back in place and tighten the screws.
While working on the carburetor, check how it is secured to the engine; and if necessary, tighten the nuts, and use a screwdriver to fasten the cover (see fig. 22) carburetor starter, automatic starter and warm-up cover. Install the damper drive rods and air cleaner in their places.
Usually, when the jets are blown out with compressed air, the fuel pump filter is also treated. To do this, use a 10 mm wrench to unscrew the bolt securing the fuel pump cover, remove the cover together with the washer and filter. The filter and the cavity underneath are blown out with compressed air, and everything is installed in place. To prevent an air lock from forming, after disassembling the fuel pump, it is imperative to pump up the fuel using the manual drive.