lead to irregularities in idling and fuel distribution problems. Then, when installing the manifold, make sure that the mating surfaces of the manifold and the duct flange are flat and machined.

with correct angles. Use only high quality pads and clean surfaces methodically. In many cases, it is not necessary to use a sealant on the gaskets to ensure a quality seal. Some designers use a thin coat of white grease to prevent gaskets from sticking when disassembled. However, if you use gasket sealant, do not use silicone sealant around the mix passages as the gasoline will soften the sealant pretty soon.

Generally, a smooth transition from the bottom of the manifold to the mixture channels will improve power. Some collectors can show significant improvements in this area over others, but modification often helps. However, avoid over-grinding that changes the shape of the chamber or channel, especially if the test cannot be performed on the bench or in motion. Blind modifications can reduce power, often due to fuel distribution problems or flow dynamics. Keep in mind that most shaped tunnel manifolds benefit less from internal modifications than from single 4-barrel designs, so work carefully.

V In conclusion, the use of carburetor spacers (spacers) on the tunnel manifold is an inexpensive and reversible way to fine tune the intake system. Some professional mechanics have found that protruding carburetor holes (chambers) (described earlier in this chapter) can improve engine start-up performance

with places. They believe that by directing the accelerator pump jet into the mixture passages, the engine's response to throttle movement can be improved. Deepening the carburetor holes can also help reduce fuel consumption at high revs.

Carburetor dimensions

Matching the carburetor to the engine is very important to engine performance and economy. Many engine designers often fall for the wrong opinion and install carburettors on their engines on a "more is better" basis.

If the engine is equipped with a too large carburetor, it will stall and run intermittently at low rpm and will not perform well until it reaches very high rpm. Naturally, the efficiency and composition of the exhaust gases deteriorate.

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Large displacement engines and engines operating at high rpm require larger carburetors than small displacement engines operating at low rpm.

Many carburetors are combined for their potential air flow capacity, measured in m3 / min. Most, but not all, manufacturers test their carburetors at 38mmHg. Art. When comparing carburetors of different models, check if the measurements are taken in the same way.

The most important factors in sizing carburetor are engine displacement, maximum engine speed and volumetric efficiency.

Volumetric efficiency is a measure of the ability of an engine to fill its cylinders completely and is indicated as a percentage (%). For example, a 1639 cc engine that receives 1311 cc of air / fuel mixture into its combustion chamber at each intake stroke has a volumetric efficiency of 80%.

For simplicity, a volumetric efficiency of about 80% is assumed, which is the average for an uprated engine. For day-to-day use with a 4-barrel carburetor, you need to determine which RPM range the engine will run in most often. Be realistic - you can hurt yourself if you overestimate. Round off the results to the nearest suitable carburetor size. The table below is a guide to determining the flow capacity of the carburetor.

Typically, small displacement boost engines require carburettors with an upstream capacity of 14,200 to 17,040 m3 / min, depending on actual displacement and modification level. High displacement boost engines work well with carburetors downstream of 18 to 23 m3 / min again depending on displacement and boost level.

Carburetor capacity by flow m3 / min depending on the working volume and

engine speed
		Number about engine speed, rpm

engine,
cm3

Comment. This table is for standard motors. For boosted engines, the downstream capacity should be increased by about 10%.

There are special air filters for most 4-barrel carburettors. Some of them are low in height to be able to install such a filter under the hood without any problems.

Choose a carburetor that can be fitted to your engine's intake manifold and to which your old throttle rods can be adapted. If the carburetor has a vacuum drive for the secondary throttle valves, do not attempt to change it to mechanical. Also, the old air filter (air cleaner) may not always be installed on other carburetors. Purchase a high flow air filter for installation on a new carburetor.

If your car is equipped with an exhaust gas control system, then after replacing the carburetor and air filter, reconnect all devices of this system. Finally, adjust the entire system with a gas analyzer for the most effective performance.

Most carbureted engines have mechanical fuel pumps. If you are seriously boosting the engine, install a high-performance fuel pump, or install a high-performance mechanical pump, or install an electric fuel pump next to the gas tank. Follow the instructions supplied with the fuel pump for safe installation and subsequent operation of the pump.

The jets of the Solex 21083 carburetor are presented in the form of two types: fuel and air.

Air and fuel jets are opposite in their interaction to the composition and quality of the combustible mixture. In the process of increasing the cross-sectional area of the fuel jet, enrichment of the combustible mixture will be observed, and in the case of an air jet, depletion.

It should be noted that the degree of their impact is not the same under different operating modes. If you change the cross section of the main jet, the fuel mixture will begin to change in direct proportion for all modes of throttling from low loads to full throttle opening.

Also, the effect of the air jet is more felt in the process of increasing the throttle valve opening angle.

Thus, if it is necessary to change the composition of the fuel mixture over the entire range of characteristics, it will be necessary to change the performance of the fuel main jet. To change the characteristics of the curve of the composition of the combustible mixture, it is necessary to use an air jet.

From the shown economic characteristics of a car with different performance of the air and fuel jets of the main system of the carburetor, it follows that in the case of an increase in the performance of the fuel main jet, the fuel consumption will accordingly increase at all speed modes of the car.

Changing the performance of the air jet allows you to increase fuel consumption only at high speed auto modes. When choosing the most suitable performance of the air and fuel jets, it is important to select the optimal composition of the supplied fuel mixture for a particular mode of engine operation.

The correct selection of the required characteristics of the metering main system will further determine the smoothness and stability of the engine, this will be especially noticeable at partial loads. A car in the process of driving around the city 65% of the time works with a slightly closed throttle valve at the time of discharge of the intake pipe above 450 mm Hg, and also consumes up to 35% of the total amount of fuel.

Solex 21083 carburetor fuel jets table

In the process of throttling the carburetor, it is possible to observe an unstable composition of the fuel mixture over time in the working charges, there is no identity of the cycles. This has a significant effect on the composition of the exhaust gases.
Also, three factors can affect the inhomogeneous composition of the combustible mixture in cycles:

the nature of the distribution of the mixture over the cross section of the flow;
dispersion of fuel;
the nature of the distribution of the mixture along the flow.

The flow pattern of the mixture emulsion from the channel of the main spray system can have a significant effect on the flow structure. Depending on the ratio of the performance in the metering system of the nozzles and the speed of the emulsion outflow, the following types of flow can be obtained: laminar, slug, coarse emulsion, axisymmetric and wave.

Thus, depending on the change in the type of flow from the atomizer of the main emulsion system, the homogeneity of the composition of the fuel mixture in the operating cycles of the car engine will largely change. Axisymmetric mode is the most optimal for the stable operation of the car engine. This is achieved through a uniform fuel supply.

The air jets of the Solex 21083 carburetor allow you to adjust, together with the fuel jets, the optimal operation of the carburetor. It should be remembered that the location of the air jet of the main system inside the fuel-air main path is undesirable due to the possibility of clogging or gumming of the jet, which can lead to.

This is often observed when engine crankcase gases pass through the carburetor. It is most correct to place the air jets in special pockets that will protect them from direct air flow.

Due to the large volume, a lot of air will pass through the diffuser per unit of time, and as a result, much more fuel will be consumed. Of course, if you are not going to pump your car for fast driving, then it will not be so important for you. Otherwise, it is better to install jets with a smaller cross-section.

It is most correct to start the selection of the nozzle with the fuel one, and then go to the selection of the air one. It should also be noted that you first need to select the jets for the first chamber, and after the jets are installed on it, you should go to the second carburetor chamber. Only in this way is the most correct installation or replacement of the jets considered.

Every car owner should have at least a general idea of its structure. Not a single repair is complete without such knowledge, and if it comes to tuning the performance of a car, then it is imperative to know its device.

An important part of an internal combustion engine is a carburetor - a device in which air and fuel are mixed. The result is a combustible mixture of the consistency necessary for the operation of the power unit.

If we are talking about domestic carburetors, then we cannot fail to mention the Solex 21083 - one of the best devices in its class, with excellent performance and high reliability. This model has one indisputable advantage in its arsenal - it can be modified in a variety of ways, thereby "adjusting" the carburetor to specific working conditions.

What are jets

As a rule, the modification of the carburetor consists of replacing the jets. Nozzles are small metering elements with holes with a certain cross-sectional size through which the components of the combustible mixture pass. This article will focus on the Solex 21083 carburetor jets.

Types and classification of jets

To create a good lean mixture, fuel jets with a small orifice section should be installed in the carburetor, and air jets with an increased one. The use of such a scheme allows the engine to operate stably even with a sharp change in the driving mode.

There are two types of jets installed in the Solex 21083 carburetor:

Fuel. Provides a uniform flow of fuel into the carburetor chamber.
Air. Metering the air supply to the carburetor.

It is important to understand that an increase in the inner diameter of the fuel jet will lead to a significant increase in fuel consumption, and this choice will be justified only if you want to increase engine power. In turn, the large cross-section of the air jet also causes increased fuel consumption, but only with active and fast driving.

Most car owners prefer to reduce the appetite of the power unit, so the best solution would be to install a combination of jets that reduce fuel consumption (sometimes it turns out to improve this indicator by a third). To choose the right jets, you need to understand their labeling, which is not as complicated as it might seem at first glance.

Jet marking

When choosing carburetor jets, inexperienced motorists are often confused by the presence of several numbers in the jet marking. The decoding of these symbols is as follows:

The Solex 21083 carburetor in the basic configuration is equipped with jets marked 21 (for the first chamber) and 23 (for the second chamber). The numbers represent the diameter of the metering elements.
On the bottom of the "native" fuel jets there are numbers 95 and 97.5 (the first and second chambers, respectively). This data represents the throughput of the jets.
In the same way as in the previous example, air jets are labeled, only in this case they will be labeled 155 and 125, indicating the performance of the parts. Naturally, these numbers on jets with different flow rates will change.

The marking of carburetor nozzles is quite simple, but simple recognition of numerical values is not enough - you still need to understand how and what these indicators affect.

See how to independently adjust the beam of your car's headlights. More details -

An important parameter affecting the operation of the jets is the ratio of the amount of air and fuel in the chamber. A ratio of 14.9: 1 is considered normal, in which fuel consumption and power are in balance. To determine the combination suitable for a particular driving style, it is enough to figure out what the ratio of air to fuel in the combustible mixture will be.

The factory fuel jets of the Solex 21083 carburetor are designed for economical driving and have a fairly small cross section. Native jets can not be changed if there is no particular need to increase engine power. In addition, as a result of replacing the jets, the mixture may turn out to be too lean, and the engine will simply not have enough combustible mixture for normal operation.

If the engine is “not pulling,” and the problem is clearly in the fuel mixture, you might want to consider options: different fuel and air jet configurations make it possible to select the most efficient circuit and use it in your vehicle to achieve the best results.

Choice of jets

When choosing a set of new jets for modifying the carburetor, it is worthwhile to comprehensively study this issue: Solex 21083 is being modified very often, and a couple of additional tips from experienced drivers will not hurt. Selection recommendations most often sound like this:

it is very important to take into account the volume of the engine: with a large working volume, it is better to choose air jets with a small cross-section in order to improve the combustible mixture;
first of all, it is worth choosing exactly fuel jets, and only then look for air ones;
the sequence is also important when installing the jets: first they are installed in the first chamber, and only then in the second - such a step-by-step approach will allow you to choose the most suitable scheme.

As an example of the selection of jets for a 1.5-liter engine, consider the following combination:

a fuel jet 102.5 is installed in the first chamber, and the air jet has a section of 155;
for the second chamber, the fuel jet 110 is selected, and the air jet is marked 125 or 135.

It is worth paying attention to the fact that Solex 21083 was originally designed for 1.5-liter engines, and its installation on a power unit with a large displacement is not recommended: due to the design features of this carburetor, too "bulky" engine will not receive a sufficiently high-quality fuel mixture.

It is also worth remembering that all Solex carburetors have a similar structure, due to which the interchangeability of their elements is ensured. This rule also applies to jets: if necessary, you can select jets from a different carburetor with a different section for your version.

From the aspects and features of Solex carburetors described above, a simple conclusion can be drawn: for different engine volumes, an appropriate configuration must be selected to ensure high-quality creation of a combustible mixture.

And the last recommendation: when selecting jets with a large cross-section, sometimes there is a desire to squander them yourself. It is not worth doing this, since the correct ratio is required for the operation of the jets, which cannot be achieved in "garage" conditions even with the availability of suitable equipment.

Video jets for the carburetor VAZ 21083 Solex

The video will tell you about the Solex carburetor 21083

Conclusion

The Solex 21083 carburetor is famous for its reliability and simplicity, not because of the modification possibilities, but because of its good basic configuration, designed for a calm and measured driving style. Of course, replacing the fuel and air jets of the carburetor can increase the power of the power unit or reduce fuel consumption, but if these indicators are already good, then they should not be changed.

The selection and refinement of jets on Solex carburetors is carried out in two cases: if it is necessary to increase the power indicators of the car engine (quick start, throttle response, increase in speed) or to reduce engine fuel consumption from the passport indicators.

In the case of an increase in power, they usually select and increase the throughput of the GDS fuel nozzles (enrich the fuel mixture). If necessary, improve fuel efficiency - increase the throughput of the GDS air jets (deplete the fuel mixture). In any case, it is necessary to install on the carburetor nozzles with a modified orifice section and a capacity different from the nominal (the marking on the nozzles means the diameter of the hole and corresponds to their certain throughput).

Before starting work, make sure that both the carburetor and the engine are working normally on standard jets. It is also recommended to bring the power supply system and the ignition system of the car into proper condition before carrying out the modification of the carburetor. If the car engine eats gasoline in buckets or even doubles, it makes sense to carry out a full diagnostics of the engine systems, bring everything back to normal, and only then take on the revision.

It should be remembered that when working with the carburetor, it is necessary to adhere to a certain pattern: an engine of a certain volume corresponds to a carburetor with a certain section of diffusers, fuel and air jets of the main dosing systems. A change in one or more of the components of this chain leads to a clear change in the operation of the engine. The increase or decrease in the throughput of the nozzles should be small and gradual - within hundredths of a millimeter. Therefore, for revision, it is better to purchase an additional set of GDS fuel and air jets and perform all manipulations on them. We put the native jets back in case of failure of the experiment.

Options for the refinement and selection of jets on Solex carburetors

- Install air or fuel jets from a different carburetor, from a different engine

You can choose from the lists below.

Table of sizes and applicability of GDS fuel jets for Solex carburetors

Carburetor models	1st camera	2nd camera
2108-1107010	97,5	97,5
21081-1107010	95	97,5
21083-1107010	95	97,5
21073-1107010	107,5	117,5
21051-1107010	105	110
21083-1107010-31	95	100
21083-1107010-35	95	100
21083-1107010-62	80	100
21412	95	95

Table of sizes and applicability of GDS air jets for Solex carburetors

Carburetor models	1st camera	2nd camera
2108-1107010	165	125
21081-1107010	165	135
21083-1107010	155	125
21073-1107010	150	135
21051-1107010	150	135
21083-1107010-31	155	125
21083-1107010-35	150	125
21083-1107010-62	165	125
21412	160	100

air jets, fuel jets, emulsion tubes and Solex carburetor wells

- Modify existing jets

Thin drills of 1 mm, 1.5 mm, 1.75 mm, 2 mm, etc. are available for sale. They can be used to drill nominal nozzles to the required size by increasing their throughput. In some cases it is possible to solder the orifice hole with tin and re-drill it.

Jets selection technology

We start the selection from the GDS fuel or air jets of the first carburetor chamber. We install a jet of a reduced or increased cross-section (as a rule, only one hundred square meters) instead of the standard one and check the dynamic characteristics of the car or its fuel efficiency. If necessary, adjust the idle speed with the screws "quality" and "quantity".

We install an even larger jet, check the dynamics or efficiency. And so several times, until there are obvious failures in the operation of the engine in different modes. The work is painstaking, requiring time and nerves. Then we take a step back, setting the jet of the pre-existing dimension. We carry out a similar setting for the second carburetor chamber (in most cases, they are limited to the first).

This process (in combination with other modifications of the carburetor) is described in detail in the articles on the website,.

Checking the throughput of the nozzles to control the conformity of their marking can be checked by making a homemade device (See).

Notes and additions

- The selection of jets described above is a minimal intervention in the operation of the carburetor with minimal consequences (an increase in power by 5-10 percent or economy within a liter per hundred). You can tune your carburetor more strongly and effectively if you add to the selection of jets, both small and large, pick up emulsion tubes, modify the mixing chambers of the carburetor, the accelerator pump and change the sequence of opening the throttle valves. A set of measures will allow to fully reveal the hidden reserves of the engine, which will ultimately change and improve the necessary characteristics of the car for the requirements of each particular car owner.