The secrets of the new Harley-Davidson Revolution Max engine

If you are fond of the world of motorcycles, you have surely heard the launch of the first Harley-Davidson model of the "Adventure" segment, spread in streaming as worldwide first: bread America 1250.

This model marks a very important milestone in the history of the brand, as it incorporates the motor plant that will use most new models of the coming years: the Revolution Max engine.

The design of this engine has been carried out starting from scratch, without being conditioned to having to fit within any particular chassis or model, which has allowed engineers to have freedom to innovate in their characteristics. This freedom, of course, is limited to:

• Comply with emission regulations in the different markets.
• Create a competitive product in price and benefits.
• Stay within a budget determined by the competition.
• Get an attractive product to the current and new customers of the brand.

We will review the most differentiating characteristics of this engine, both with respect to the other Harley-Davidson models and the similar competition options.

Liquid cooling

In order to comply with the emission regulations, it is necessary to have the temperature under control. High temperatures require more fuel to cool the walls of the cylinders and at the same time, generate polluting gases and toxic particles. The liquid cooling engines make this fluid pass through the hottest areas, stealing heat to the surfaces and lowering their temperature. The water subsequently passes through a radiator with forced ventilation, which manages to transmit part of this heat to the outside, re -cooled the liquid. Water shirts isolate the sound of the engine, so the manufacturer can dedicate more decibels to the exhaust, within the legality.

Apart from issues related to emissions, having temperature control in an engine implies that the components dilate less, tolerances are more precise and greater power and longevity are obtained. All this in exchange for an increase in the complexity of engine design and maintenance.

Double head camshaft

The DOHC system has been used in automotive since 1910. Dual Over Head Camshaft means that the valves are directly operated by camshafts, which are located on top of them, with a tree for admission and another for escape. Therefore, pushing rods and rockers are eliminated (they are reduced to the minimum expression).

The main advantage is that we are eliminating components that generate a lot of inertia (for their weight) and inaccuracy (for torsion), which implies that the engine can be revolutionized faster and the greater the number of RPM without harming it. Dohc engines have a expensive and complex maintenance of valve slack (if you have ever tried to do it in a V-ROD you know what I am talking about). But this engine is Harley and has to be different, so hydraulic tachies are used, which eliminate valve adjustment.

Variable distribution

Perhaps the most important novelty of this engine, which also differentiates it from many from the competition, lies in the VVT ​​system (Valve Timing variable) of variable distribution.

In a very simplified way, we can say that this system is based on an electric motor that is capable of varying the position of each camshaft at all times, so it is as if instead of a fixed camshaft we were able to Change the camshaft for a different one, in real time.

To understand the advantage that this means, it is necessary to understand the functioning of the camshaft. It is not an element that contributes more or less power, it will simply mark us where the maximum motor torque is delivered, defining the "character" of that engine. To the same engine we can install a “Touring” camshaft, which offers us a lot of low and a pair that does not end, so we will have a quiet motorcycle, very easy to drive and with great force. On the other hand, if we install a “Sport” camshaft, we will obtain a more fun and aggressive engine, and we will have to change the rpm of high rpm so as not to lose thrust.

Well, the VVT ​​offers us the best of these 2 worlds, or 3, 4, or infinity, since it is able to modify the angle of attack of the opening and closing of valves so that at all times we obtain the ideal behavior in Any regime, boot improvement, emission control, traction control, etc. As in the technologies mentioned above, this adds greater complexity, both in maintenance and programming, as the camshaft must be "map" depending on the other motor management maps.

Other technical characteristics

• The engine Revolution Max from Harley-Davidson is a 60-degree bicylinder that Cubica 1250cc and delivers 150cv to 9000 rpm.
• This engine is a component that supports external stress, that is, it collaborates as part of the chassis providing stiffness, thus allowing smaller and light chassis. The center of gravity has remained as low as possible, to provide stability in motion and standing.

• Motor covers (clutch, alternator and camshaft) are magnesium, a high-tech detail, since only two thirds of their aluminum equivalents weigh.
• We have 5 different driving modes and cruise control.
• Sodium stuffed exhaust valves that refrigerates them in a process similar to human sweat: it evaporates eliminating heat and becomes drops that slide under the valve to start the cycle again.
• Balanced crankshaft. As a curious fact, we will comment that the crankshaft and the counter -chered axes allow a perfect balance, reducing virtually any vibration, but “incorrectly” has been configured on purpose, so that the user (especially those from the traditional sector of the brand) does not lose That powerful engine feeling.
• Motor block design. In this type of engines, the cylinders are usually part of the motor block. In the purest Harley-Davidson tradition, these cylinders are removable, which allows the installation of Big Bore kits and, probably, smaller cylinders if models of half-displacement are developed in the future. Cunes have double spark plug to improve combustion efficiency.
• Lubrication system. In this case, Harley-Davidson applies techniques from the competition to obtain a high performance lubrication system, consisting of injecting oil from the end of the crankshaft axis (as it had been doing with the Big Twin engines) and driven by 3 Independent oil pumps (central, right side and left side). With this, it is possible to reduce the interior pressure of the crankcase and the efficiency of the pistons is improved, as in the competition engines (again, another technique inherited from the Big Twin engines with dry crankcase).

Apart from the engine

The electronic management system of an engine as advanced as this allows, in turn, to take advantage of the resources (centralitas, sensors and actuators) to offer advanced functionalities, already available in the PAN America 1250 model:

• Variable height adaptive system, the first of these characteristics of any motorcycle (in production) of the market. When the motorcycle detects that we are going to stop, it lowers its height so that the pilot can support comfortably, again raising it based on the speed.
• Semi-active suspension. Faithful to the Showa brand for many years, engine engineers have created control software for both suspensions, which varies the behavior of the suspension based on the use of the motorcycle through the ECM switchboard (the computer main motorcycle, which also controls motor management). The rear shock absorber incorporates the BFRT control system (Balance Free Rear Cushion) from racing motorcycles.

• Starting control in earrings. Indeed, it is a Hill Holder system that, with the help of ABS brakes and the traction control system, will make it easier for us to leave unemployed in a slope.
• Improved curves control. With the help of an IMU device (inertial measurement unit), the motorcycle computer will help us keep the draw while we lay in the curves, acting on the motor torque, braking and suspension. As by magic, it will seem that our driving skills have increased.

Conclusion

We have before us the engine that will probably equip the new generation of Sportster models and that could be the last internal combustion engines of the brand, before electric models monopolize the market.

It is a powerful and modern engine, which will have to win with its reliability the loyalty of the current owners of Harley-Davidson motorcycles and also be able to attract customers of other brands, a challenge.

Frank Burguera

#mecanicaharley