What is MPI engine through the eyes of an ordinary motorist
MPI is a fuel injection technology. It has two names: “Multi Point Injection”. – Multi Point Injection or “Distributed Injection” is a more accurate definition.
Today let’s look at this technology in simple language. At the end of the article you will see that it is the second definition that is more correct for MPI engines. I will tell their disadvantages and advantages.
History of appearance
We all remember carburetor engines. They were equipped with all domestic cars and foreign cars until the 80s. It was necessary to supply fuel in a certain proportion, so that it was mixed with air, forming a stoichiometric mixture.
This is a mixture in which certain proportions of oxidizer (air) and fuel are selected for complete and efficient combustion. Any breach in the ratio of the two components of the mixture led to improper combustion of gasoline, uneven engine performance, and increased emissions of harmful substances into the atmosphere.
Remember how hard it was to achieve an accurate ratio of the fuel-air mixture in the carburetor? Especially in old, worn out cars. Motorists had to adjust the carburetor by ear with “quantity” and “quality” screws for proper engine performance.
With the tightening of environmental regulations, the carburetor was replaced by the “mono-injector.” It was essentially the predecessor to MPI, distributed injection. Instead of the carburetor, a single nozzle was installed, which was responsible for injecting gasoline into the intake manifold. The computer was responsible for the quality of the mixture, the owner of the car did not need to adjust it himself, it was done by the engine ECU.
With the introduction of mono-injection technology, the engineers have achieved:
- Improved quality of combustion;
- Compliance of engines with modern ecological standards;
- Increased accuracy of gasoline dosage and reduced consumption;
- The technology spared the owners of cars with mono-injection to adjust the fuel-air mixture on their own, made people’s lives easier.
A new round of environmental hysteria is taking place. The emission requirements for engines are increasing. Mono-injection was no longer able to meet them. Now it is replaced by MPI – distributed fuel injection.
Highlights of the technology
In order to achieve a more accurate fuel dosage and stoichiometric mixture, the engineers decided to install several injectors instead of one. Their location was shifted to the intake manifold. If an engine has four cylinders, that means four injectors, each for its own cylinder.
Unlike the carburetor and mono-injection, where the fuel-air mixture was formed before the intake manifold, in distributed injection, the mixture is formed just before the engine intake valves. That’s where the MPI injectors of the engine are cut in.
What did it do?
- The fuel metering accuracy has improved. The powertrain computer was able to inject the necessary amount of gasoline for each cylinder more accurately.
- Combustion quality has been improved and, consequently, the emission of harmful substances into the atmosphere has been reduced.
- The fuel appetite of the vehicle is also reduced.
How it Works
- Outside air flows through the air filter into the intake manifold.
- Passes the mass air flow sensor DMRV.
- Meets the throttle valve. Unlike carburetor engines, in MPI engines the choke does not dispense the amount of fuel-air mixture, but the volume of air necessary to operate the engine. Remember, in a carburetor, opening the choke of the first or second chamber, a ready mixture would go into the intake manifold, but here only air.
- The air goes into the intake manifold, where the fuel injectors are installed.
- Depending on the engine modes, the ECU injects the necessary portion of fuel into each cylinder.
Advantages and disadvantages of MPI technology for the car owner
- Saving fuel;
- Exact dosage of gasoline for each engine cylinder;
- Complete combustion of fuel and reduction of atmospheric emissions;
- Dynamic control of the fuel-air mixture fed into the combustion chambers of the internal combustion engine. Information is gathered from several sensors, the computer can react instantly to changes in engine operation. The driver is spared this burden.
With the improvement of injection technology, the number of elements involved in it has increased. There appeared additional sensors, extra nozzles, additional electronics.
All this led to an increase in the cost of MPI engines and the complexity of maintenance and repair. Now not every garage can properly repair or service this injection system. The cost of repairs has gone up. Instead of one injector, for example, there are four, and that’s extra money to buy them when replacing them.
A more correct name for this technology is distributed injection . Because the fuel is distributed between each engine cylinder. Multi-point injection is injection into many points of the same volume, and this is not quite the same.
MPI technology is well proven. No matter how many motorists protested after replacing the carburetor and monopump with it, it brought relief to car owners.
What is and how does an MPI engine work? Pros and cons of the motor
The end of the last century and the beginning of the new century was a period of heightened interest in gasoline engines brand MPI. Deciphering this abbreviation sounds like Multi Point Injection. An unusual fuel injection scheme has served a good demand for cars with such engines. This scheme was created by the multipoint principle.
Due to the individual injectors in each cylinder, the most possible uniform fuel distribution in the cylinders takes place. With this design development, namely the release of engines with multipoint injection was taken over by Volkswagen. Due to which MPI engines subsequently appeared.
The emergence of such power plants have formed an alternative to carburetor engines. To more accurately understand the MPI engine it is necessary to thoroughly dismantle its competitive features.
Modernity of Multi Point Injection Engines
There is no future for MPI engines as it looked a few years ago, many even believed that the production of this type of motor had been suspended. The radical development of automobile developments and technologies is very quickly forcing not to remember yesterday’s quality benchmarks.
In fact, this is what is happening with MPI engines, many specialists in the industry claim that the economy and environmental safety are outdated.
But these conclusions are mostly true only for the European markets, and as for the Russian markets, it all seems to be partial here. Because the real potential of these units has not yet been fully revealed by domestic motorists.
Manufacturers betting on far-sightedness do not let this technology die and constantly implement it in cars designed for Russian roads. For example, on Skoda Yeti or Volkswagen Polo. The most memorable were the representatives of the MPI system with engines with the volume of 1.4 or 1.6 liters.
Design features of the MPI engine
The absolute absence of a turbocharger is another significant distinguishing feature of this system along with the multipoint injection system. The design of these engines includes a conventional gasoline pump, which at a pressure of 3 atmospheres supplies fuel to the intake manifold for subsequent mixing and feeding through the intake valve already prepared composition.
This scheme of operation is very similar to that of carburetor engines. With one difference that there is a separate injector on each cylinder.
Another unusual feature of the Multi Point Injection engine system is the presence of a water cooling circuit for the fuel mixture. This is due to the fact that the temperature in the cylinder head is very high, and the pressure of the incoming fuel is very low, so there is a high probability of gas-air congestion and consequently boiling.
Characteristic advantages of the MPI
Before switching to a car with MPI many motorists, who are more or less familiar with this system, will think long and hard about the set of advantages, due to which the units with multidirectional injection have earned a reputation in the world.
Simplicity of the unit
That’s not to say that these systems are simpler compared to carbureted models. If you compare the TSI model, which has an HPF and turbochargers in its design, then naturally the superiority is in your face. And the cost of the car will be lower and reduced operating costs and the possibility of self-repair.
Undemanding requests for fuel quality
Guarantee the proper quality of fuel and oils everywhere and always not possible, which is very typical for Russia. Using low-octane gasoline below 92 does not affect the performance of MPI engines, as they are very unpretentious. The minimum mileage of cars without failures, according to the developers, is 300,000 km, subject to timely replacement of oil and filter elements.
Minimum probability of overheating
The ignition advance angle is adjustable. The presence of a system of engine supports, which is designed for the use of rubber supports. Of course, it is not directly connected with the engine, but it is still important for the efficiency of the engine and the comfort of the driver.
Because at the expense of the support dampens the vibrations and various noises that occur while driving. An interesting feature is that the supports have automatic adjustment for different modes of the engine.
Characteristic disadvantages of the MPI
All the disadvantages of this engine are expressed precisely by its design features. The connection of fuel with air occurs in channels, rather than directly in the cylinders. Accordingly, there is a limitation of the intake system capabilities. This is expressed in lack of power and rather weak torque.
Proceeding from this it is not possible to get decent dynamics, sport injectivity, hot drive. In modern cars the presence of eight valves, as a rule, is not enough, so all these characteristics are increased. If to characterize this car with such system, it is quite suitable for family and quiet transport.
That’s why such cars are no longer in demand and are receding into the background into the past. Why does this happen, i.e. the world has made an assessment of the qualities of this system and decided that it is not enough and the designers have started to design more modern engines in terms of power. But no, there are unexpected surprises in automobile production.
The developers of Skoda have developed Russian version of Yeti SUV for family use and in 2014 they intentionally refused from turbocharged 1.2 engine in favor of 1.6 MPI engine with 110 hp capacity.
As the developers of the famous global concern said, this engine has almost nothing in common with the old 105 hp model. It most closely resembles the TSI models, but it lacks direct injection and turbocharging.
The departure of MPI engines from the world market is significantly affected by all of the above. These days, many car enthusiasts prefer more powerful modern cars, the pace of which is steadily increasing.
The need to equip cars with more powerful units significantly lowers the coefficient of demand for Multi Point Injection engines. In comparison with them, this motor is weak. But it is too early to write off the MPI engine, as developers Skoda Yeti trying to use it in full on Russian roads.