DMRV: measuring the air

I'm sure many motorists still remember such a thing necessary for the machine, as the carburetor. Indeed, the solution for the preparation of the working mixture is very witty. Gas flows from the nozzles himself under the influence of low pressure in the diffuser, all systems are somehow enrich the fuel-air mixture, with one exception - the main metering. The producers of carbs was time to think about design, carry out the necessary calculations and experiments. The design of this device was improved, became more complicated, improved power characteristics, reduces fuel consumption. In general, the work was done in the right direction. With the advent of the automobile market by Japanese manufacturers work went even faster. Appeared solenoid valves, carburetor itself under the hood, entangled in many rubber tubes and spiked with incomprehensible solenoids and sensors of unknown purpose, strikes fear into the auto-service employees. At the last carbureted cars from the Land of the Rising Sun has already stood, and the engine control unit, and oxygen sensors. This complex design was no one in the teeth, and the owner of this car, when faced with failures of fuel system, often reluctantly bought a new piece for an incredible amount. But technological progress does not stand still, and has been honored old carburetor thrown from the vehicle, replacing the aforesaid nozzle. Can be one - monovprysk, we can injectors per cylinder - distributed injection. First, the needle injector to adjust the pressure - K-Jetronic, and then began to open electricity - L-Jetronic, the last stage of the distributed injection was the unification of the ignition system and power supply in one unit. The management of this whole was entrusted to the engine control unit, a signal with multiple sensors - Motronic. Now came the most advanced injection system to date: GDI - direct injection of fuel into the combustion chamber. How now to determine how much fuel is injected into the cylinder or intake manifold? If this happened in the carburetor itself, but now the number of sucks in air to somehow calculate that the fuel / air mixture has turned such a need for each mode of the engine: to disperse - output-enriched (up to a reasonable extent), with a measured movement - a stoichiometric or close to it on multiple injection and depleted - by GDI (again, to a reasonable extent). Such a purpose is one of the most complex sensor injection system - DMRV sensor, mass airflow. Some way to measure the mass of the engine air, and quite accurately. Need to consider everything - temperature, vacuum (in the mountains, for example). Accordingly, DMRV changes over time and improved. Different companies offer different solutions, therefore, this product is different in terms of accuracy, performance, price and performance (!). The latter, incidentally, is well taken into account beginners tuning. "Burn" DMRV on some cars - a piece of cake, so before you put a turbine with high performance boost controller, tuned to the supraliminal pressure would be nice to ask, and whether such on this particular machine. The very first DMRV worked on the principle of deflection damper connected to a rheostat, whose signal and was used to calculate the mass of air. To avoid inaccuracies in the sensor has been created the next generation - the wire. Air flow was measured in the following way: thermistor, a thread of platinum-iridium alloy, heat to about 140-170 oC. Thread cleaned the air flow going into the engine, respectively, is trying to cool down, but in so doing, it prevents the flow of additional stress. Current required to maintain the temperature of the wire filament runs through the calibration resistor, it appears the voltage by which the electronic control unit, and calculates the amount of injected fuel. When operating a platinum thread is polluted, so after ignition is turned off it for one second heated to 1000 oC, and all adhere to it dirt burns. Have DMRV another sensor that adjusts the testimony of the ground, measuring the ambient temperature. Next Generation DMRV uses not thread, ceramic base, with tape stuck in it mounted measuring and compensating resistors. Heating temperature of film sensors is much smaller - about 100 degrees. This design makes it more reliable and cheaper, but less accurate. Accuracy strand probe of the order of 1%, the same film - 4%. Unfortunately, the film speed sensor wire is somewhat lower. But low cost and manufacturability - the value for the automaker is now a priority. In addition, the introduction of an additional lambda probe can adjust quickly enough to the extent necessary amount of fuel injected. Time does not stand still, accuracy and speed of recent developments DMRV increase due to application of new materials, flash microcontroller, in general, are working on filling. I mentioned not all the varieties of sensors, there are others. Many complain about the unreliability of modern and reliable sensors of earlier editions - to choke. When tuning in general uses a different scheme with pressure sensors, some experts point to a serious advantage when using the analog sensor membrane. In general, many people, so many opinions. In recent years cars have become more sophisticated, and their service all the easier. The paradox, right? Now no one at random or deep thinking will not look for the fault diagnostic tester is connected to the bus - and forward. And if the tester did not show fear in this life you will not help anybody, except maybe a repair of the old school. Only where they now find another like him?