Water injection, to fund: all the secrets about the water injection BMW M4 GTS

This year, we have been talking long and hard about the water injection, since BMW raised this alternative mode of prototype, until his official confirmation as one of the technologies that makes the BMW M4 GTS the M most radical to date. It is not a technology that is unprecedented, the injection of water in competition has its years. Its application in cars on the street, in which the BMW M4 GTS yes that would be a pioneer, is not without significant challenges and many doubts (until Mercedes-Benz looks askance, and with a certain disdain, the decision of BMW). And that is why with the presentation of the new BMW M4 GTS, we went straight to getting to know all the technical details you have provided us with the German mark. how it Was possible to achieve these objectives without water injection? What BMW is selling water, or smoke? Why they took this decision? this is what you’ll see below. Of time stay with a piece of data, the BMW M4 GTS has increased its power at 16%, up to 500 HP, and consumes 8.3 litres/100 kilometres (according to approval). Is it all a matter of consumption?

Think that your goal is to to increase the power of a sports since the 431 HP BMW M4, up to the 500 HP of the BMW M4 GTS. To deal with this company, you can resort to different solutions. You can use a motor of greater displacement, or you can take to limit your boost, look for a increased pressure from the turbo or use turbochargers more forceful.

it Is possible that the inline six from BMW is already close to those limits, or that they at least would have come to a barrier that BMW did not want to pass on. Hence, as I told my partner David Clavero, tirasen file, opened the drawer of sastre, and put on the table a solution that was there from a long time ago, but no one had seen fit to apply in a street sports car, the injection of water.

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BMW could have resorted to other solutions, since the hybridization or the improvement of the systems of supercharging, and the use of a new engine. But they chose to improve the combustion and to do so with a technology unheard of in passenger cars away from the tracks.

The most obvious solution, which used virtually all of the manufacturers when it comes to improve performance, and not to sacrifice the consumption happens by working with the turbo. That has been the key to the downsizing of modern engines. But there is still a solution that is more exciting, full of technical challenges, improving the combustion. The thermal conditions of the engine dictate the limits which are very difficult to overcome. Even small improvements require technical solutions very complex, and sometimes a process of research and development really tedious.

BMW decided to improve the combustion, and to approach those limits the thermal performance of your inline six supercharged. Increase the load of a turbocharged engine with a double, with two turbo Mono-Scroll; with a high compression ratio (to 10.2:1); and capable of operating with fuels of low octane (from 95 octane); it means to approach the barrier of the autodetonación (or self-ignition), combustion uncontrolled that can undermine your performance or, in the worst cases, destroy the engine of your car. The electronics allows a precise control of this autodetonación, but to achieve the benefits they were looking for the team of BMW M GmbH, it was necessary an extra that will guarantee that this engine can run with a performance so high, and loads are very high, in any circumstance.

And the solution found in the injection of water, that step was a great technology to reproduce the technology transfer that occurs between the competition and sports and cars street. After premiere in the BMW M4 used as safety-car in MotoGP, the injection of water, will be premiered in the BMW M4 GTS.

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The main function of air is to cool the air that sucks the engine. With your system of water injection BMW manages to lower its temperature approximately 25°.

why water? Remember that we are talking about the thermal performance of a motor and the water has a very interesting property, that of extracting energy from the environment that surrounds each drop, and dissipate it through evaporation. Do not think in a stream of liquid, or in a jet is constant, the water comes into the manifold of the module of aspiration as a fine mist that makes the air sucked in to cool. This is really interesting in a engine with turbo as the inline six of the BMW M4. Think that the intake air becomes heated to temperatures up to 160 degrees, although playing with a good cooling system, an intercooler, the temperature may be lowered to 70 degrees.

The fine mist in the manifold causes the temperature of the intake air to descend at approximately 25º. Thanks to this solution we have achieved that the engine reaches a degree of efficiency really high, increasing the advance of the spark, decreasing the maximum temperature – which in turn allows you to squeeze out even more the limits of the block – and avoiding the risk of auto-ignition.

is Not the only beneficial effect of this technique. The greater density of the air ensures a higher content of oxygen in the combustion chambers, and a medium pressure greater, which also results in a better utilization of power and torque throughout the rev range. By reducing the average temperature of service, the engine also is subject to less thermal stress, which should ultimately extend the life of engine components.

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The BMW M4 GTS has increased its power by 69 HP (+16%) with respect to the M4, but its consumption and emissions officers are exactly the same.

The figures of the BMW M4 GTS are really important. Let’s look at the 500 HP that develops BMW with this engine six-cylinder in-line, at 6.250 rpm, compared to 431 HP, which develops a BMW M4 between 5,500 and 7.300 rpm. The maximum torque also increases to 600 Nm between 4,000 and 5,000 rpm, compared to the 550 Nm between of 1,850 and 5,500 rpm, the M4. In the graphic above you can see the power and torque curve of the BMW M4 (left) and of the BMW M4 GTS with water injection (right).

In terms of fuel consumption, the BMW M4 GTS – which will employ an automatic change of double clutch – approvals exactly the same numbers that the BMW M4 with automatic change, despite having increased its power in nearly 69 CV. We speak of 8.3 litres/100 kilometres in the combined cycle of 6.7 litres/100 kilometers in the cycle to the suburban and 11.1 liters/100 km in urban cycle. This engine also complies with Euro VI, of course, and their emissions are also kept at 194 g/km of CO2.

How does the water injection? BMW M GmbH has used three injection valves in the air manifold, each of which is responsible for two cylinders of the engine. So that the distribution occurs in a homogeneous way and respecting the geometry of the system.

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The water tank of 5 litres, is under the boot and has to be filled in by your driver at least once every five fill-ups. Driving is very demanding circuit, we have to fill it every time repostemos gasoline.

But then come the challenges faced by a system of injection of water.

The device requires a deposit of water of five litres, as well as a pump, sensors, and valves, which have been installed under the trunk. The water reaches the nozzles with a pressure of approximately 10 bars, and the distribution depends on the engine load, revolutions and temperature. That is to say, there is a policy of consumption of water so that it does not exceed what is necessary. Although in the last few months, BMW had dropped that water could be obtained from the condensation of the compressors and heat exchangers of the air-conditioning equipment, will eventually be the user who has the responsibility of filling the water tank in function of the needs of the system.

BMW has planned that, in circumstances of normal operation, fill in 5 litres of water once every five fill-ups. By the account of the old, we estimate that there will be to fill the tank every 3,500 miles. But this metric is actually very variable, the water consumption can vary a lot depending on the use that we make. It will not be the same to drive on the motorway at legal speeds, that do it in town, or even in circuit.

In fact, BMW says that they plan on a very intense, in the toughest conditions that you can afford a BMW M4 GTS, that would be the pilot it in-circuit, the water tank should be filled every time that repostemos (and no more). That is to say, if you are going to be driving in circuit or refer to our M4 GTS driving is very extreme, we should remember to fill the gas tank and do the same with the water tank.

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If the M4 GTS depletes the water of your tank, it will begin to work in a security mode in which you will lose power (we understand that their benefits will be limited to that of an M4 normal, or a bit less), but will continue to be functional.

And what happens if the system of water injection runs out of fluid?

Although a priori the system of injection water does not require any maintenance, we have to be aware of the machine that we have between our hands and the special requirements that you have, as you fill your tank. If we don’t, the water reservoir is depleted and, to protect the motor, the diagnostic system of the BMW M4 GTS us know of the event and will activate certain functions to avoid serious damage.

In a situation like this, the pressure of the turbo would be reduced, the time of ignition retard and the car would still function perfectly, though with power slightly reduced. Even with a normal operation, the system of water injection with a protocol of action to protect themselves, such as making sure that the water content in the pipes returns to the tank, to avoid problems of freezing if outside temperatures are very low. The water tank, on the other hand, is protected suitably to avoid the risk of freezing.

As you can see, the system of injection of water is incredible, but also very complex.

All the inconveniences that you have had to solve BMW are probably the reason why other manufacturers have had, and continue to have, a reluctance to bet on this technology in sports of the street, as we saw with Mercedes-Benz. On the other hand, the peculiarity of its functioning

Source: BMW