The secrets of the new Harley-Davidson Revolution Max engine

If you are fond of the world of motorcycles, you have surely heard about the launch of the first Harley-Davidson model of the "Adventure" segment, disseminated in streaming as world scoop: 1750 pan America.

This model marks a very important milestone in the story of the brand, as it incorporates the driving plant that most new models of the next few years will use: the Motor Revolution Max.

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

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

We are going to review the most differentiated characteristics of this engine, both with respect to the rest of Harley-Davidson models and similar options of the competition.

Liquid refrigeration

In order to comply with the emission regulations, it is necessary to have the temperature under control. The high temperatures require a greater amount of 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 the temperature thereof. The water subsequently passes through a radiator with forced ventilation, which manages to transmit part of this heat abroad, cooling the liquid again. Water shirts isolate the sound of the engine, so the manufacturer can devote more decibels to the escape, within the legality.

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

Double overhead camshaft

The DOHC system is used in automotive since 1910. Dual Over Head Camshaft means that the valves are driven directly by the camshafts, which are located above these, with a tree for admission and another for escape. They are eliminated, therefore, pusher rods and rockers (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 imprecision (by torque), which implies that the engine can be revolutionized faster and to the highest number of RPM without harming it. The DOHC engines have an expensive and complex maintenance of the valve clearance (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 it must be different, so hydraulic tachies are used, which eliminate the valve setting.

Variable distribution

Perhaps the most important novelty of this engine, which differentiates it also from many of the competition, lies in the VVT ​​system (Variable Valve Timing) 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 capable of Change the camshaft by another different, in real time.

To understand the advantage that this supposes, it is necessary to understand the operation of the camshaft. It is not an element that contributes more or less power, it is simply going to mark where the maximum torque is delivered, defining the "character" of that engine. To the same engine we can install a "Touring" cam tree, which offers us a lot of low and a couple that does not end, so we will have a quiet motorcycle, very easy to drive and very hard. On the other hand, if we installed a "Sport" camhead, we will obtain a more fun and aggressive engine, and we will have to change running at high rpm to avoid pushing.

Well, the VVT ​​offers us the best of these 2 worlds, or 3, 4, or infinite, since it is capable of modifying the angle of attack on the opening and closing of valves so that at all moment we obtain the ideal behavior in Any regime, improvement of boot, emission control, traction control, etc. As in the technologies mentioned above, this adds greater complexity, both in maintenance and in programming, since the camshaft should be "mapped" depending on the rest of the engine management maps.

Other technical characteristics

• The motor Revolution Max. From Harley-Davidson is a bichilíndrico at 60 degrees that cubes 1250cc and delivery 150cv at 9000 rpm.
• This engine is a component that supports External stress, that is, it collaborates as part of the chassis by providing rigidity, allowing this smaller and smaller chassis mode. The center of gravity has remained as low as possible, to provide stability underway and stopped.

• The engine tapas (Clutch, alternator and camshafts) are magnesium, a high-tech detail, since weigh only two thirds of its aluminum equivalents.
• We have 5. Different driving modes and cruise control.
• Exhaust valves stuffed with sodium That the refrigerated in a process similar to human sweat: it evaporates by eliminating heat and becomes drops that slide below the valve to begin the cycle again.
• Balanced of the crankshaft. As a curious data, we will discuss that the crankshaft and counterbalance axes allow perfect balance, reducing virtually any vibration, but have been "incorrectly" by the purpose, so that the user (especially those from the traditional sector of the brand) do not lose That power sensation.
• Motor block design. In this type of motors, the cylinders are usually part of the engine block. In the purest tradition Harley-Davidson these cylinders are removable, allowing the installation of Big Bore kits and, probably, smaller cylinders if models of medium displacement are developed in the future. The cylinder heads have a double spark plug to improve the efficiency of combustion.
• 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 came by doing with the Big Twin engines) and driven by 3 Independent oil pumps (central, right side and left side). This is possible to reduce the inner pressure of the crankcase and the efficiency of the pistons is improved, as in the competition engines (again, another inherited technique of Big Twin engines with dry crankcase).

Apart from the engine

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

• Adaptive system of variable height, the first of these characteristics of any motorcycle (in production) on the market. When the bike detects that we are going to stop, it lowers its height so that the rider can rest comfortably, bringing it back up depending on the speed.
• Semi-active suspension. True to the Showa brand for many years, Motor Company engineers have created control software for both suspensions, which varies suspension behavior depending on the use of the bike through the ECM control unit (the main computer of the bike, which also controls engine management). The rear shock incorporates the BFRT (Balance Free Rear Cushion) control system from racing bikes.

• Slope start control. 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 get off on a slope.
• Improved curve control. With the help of an IMU (Inertial Measurement Unit) device, the bike's computer will help us maintain the trace while lying on corners, acting on torque, braking and suspension. As if 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 bastion of internal combustion engines of the brand, before the electric models monopolize the market.

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

Frank Burguera

#mecanicaharley