True, on the "old woman" to do this is somewhat more difficult than on a car with an injection engine: after all, there is no ECM unit - where to get route indicators? But if you follow the simple rules, you can still put a trip computer.
To do this, you need to buy a MK that has a block on the back, shown in photo 1. These are factory MKs for VAZ 2110-2112, Gamma, STAT and others. The purpose of the terminal blocks for everyone is the same (see Fig. 1), although the numbering may not coincide. For example, the conclusion “ignition”, no matter what number is indicated, remains in place. In other words, any computer listed above that is connected to the car’s shoe will work correctly. But there are exceptions: for example, the Navigator computer - in order for it to work, the company offers to rearrange the contacts in the standard block of the car. Well, who would come to mind! You should not get a computer from the Multitronics series - you are unlikely to want to make adapters for it.
In the diagram in fig. 1 one terminal (left, below the K-line terminal) is free. The K-line itself is designed to read errors in injection systems - we do not need it. If the purchased MK has this function, then when the ignition is turned on, the message “no connection” appears on the display, but after two seconds it goes off and the MK switches to reading route parameters: instant, average (in l / 100 km) or the total consumption for the trip fuel, vehicle mileage, average speed, maximum speed on the trip, etc. All indicators related to fuel consumption are displayed on the screen.
The two conclusions below in the diagram (see Fig. 1) are usually not involved. Some MKs do not have them at all. Sometimes firms use them to evaluate other parameters - for example, temperature overboard, etc.
So, we have a suitable computer. But for him to calculate what we expect from him, he needs information. First of all, from the DSA - vehicle speed sensor (item 1 in photo 2). Which one to buy?
Remember two important details. First: you need a DSA that matches the make of the car. How many revolutions, for example, should the speedometer shaft make for one kilometer? For passenger cars, VAZ is 1000 revolutions, and GAZ, AZLK, etc. - 760 revolutions. On the reverse side of the DSA, this is indicated. There are no other standards in Russia. But this is only a formal, mechanical calculation. The real speed is set not only by the wheel rpm, but also by the size of the tire, moreover, every tire wears out as it travels. And the readings of the speedometer (especially the usual mechanical one) to one degree or another “lie” depending on the calibration of its spring. We are interested in whether the purchased DSA matches the speedometer. If this is not certain (for example, for an unfamiliar foreign car), it is better to check the correctness of the choice directly: turn the speedometer manually. It will take several minutes, but the result is most reliable. The second requirement is the most elementary: the speed sensor (photo 3) must be securely attached to the gearbox and have an exit under the speedometer drive cable.
Another important informant for MK is the fuel consumption sensor (item 2 in photo 2). This sensitive device must be cut into the fuel line between the gasoline pump and the carburetor (photo 4). If the carburetor has a nozzle for draining excess fuel into the tank ("return"), such as Solex, plug it and provide a drain, as shown in Fig. 2. The design of the DRT provides for this. For cars without a "return" we use a scheme with a tee. (A fragment of such a scheme for the VAZ “classic” is shown at the bottom of Fig. 2.)
Of course, you need to refine the electrical circuit, having bought connecting blocks and wires, being guided by the scheme in fig. 2. The whole set of units and parts will cost 1600–1800 rubles.
Fuel consumption is controlled with very high accuracy, to fractions of a milliliter - the MK “rounds it up” and displays it with an accuracy of 0.1 l, which is quite enough for most motorists (photo 5). Indications do not depend on the level of fuel or its fluctuations in the gas tank.