The secrets of the new Harley-Davidson engine: Milwaukee Eight M8

As the moment is approaching every year (at the end of August) in which Harley-Davidson presents the new models next year. Although so far everything is rumors, it seems that the new Milwaukee Eight engine, currently installed in Touring models, will equip the entire Big Twin range of 2018.

We are going to review the technical details and characteristics of this new M8 engine that the Company engine launched 1 year ago and propelled the range of the 2017 Touring models and probably the rest of the brand's Big Twin models in the coming years.
Baptized as Milwaukee-Eight in honor of one of its main novelties, the use of 8 valves in the cylinder heads, offers more and power than its predecessors without losing the "heritage" of its iconic image, maintaining the angle to 45º between the cylinders .

The new M8 is the ninth engine of the Big Twin saga:
Atmospheric-Twin (1909)
F-Head (1911)
Flathead (1929)
Knucklehead (1936)
Panhead (1948)
SHOVELHEAD (1966)
Evolution (1984)
Twin-Cam (1999)
Milwaukee-Eight (2017)

Displacements and models
Milwaukee-Eight is presented in 2017 in 3 versions:
107CI (1745cc) with oil -refrigerated butts (Cooling Precision) for Street Glide Special, Road Glide Special, Road King/Road King Classic and Freewheeler models.
107CI (1745cc) with water-refrigerated butts (twin-cooled) for ultra limited/ultra limited Low models, road glide ultra and tri glide ultra.
114CI (1870cc) with water-refrigerated butts (Twin-Coold) for exclusive Custom Vehicle Operations CVO Limited and CVO Street glide models.

Twin-Cam with steroids?
Although at first glance the outer aspect is quite similar to its predecessor the Twin-Cam, the truth is that this new propeller has been completely designed from the beginning, improving the strengths of the previous models and correcting the deficiencies produced by the incessant cylindrated and power increases in recent times. Let's review the main changes:

• More power: The M8 has 11% more torque, than together with the largest displacement contribute a significantly high power and performance.
• More acceleration: the M8 weighs the same as its predecessor and when this adds to its power of power, an acceleration is obtained by 11% higher than that of the Twin-Cam 103CI.
• Reduced consumption: Thanks to the use of double spark plug by cylinder, optimized ignition and high flow butts with 4 valves per cylinder the engine efficiency is improved, lowering fuel consumption.
• Improved temperature management: with the new design it has been possible to keep heat inside the engine (which is where it must be) reducing the temperature absorption of the cylinders and butts, helped by cooling (by oil or water) in the hottest points of them.
• Greater comfort for the pilot: a new primary transmission lid, thinner, and the low air filter lid down the pilot's leg space around the engine, facilitating access to the ground for many pilots. All models with the Milwaukee-Eight engine have a hydraulic drive of the "Assist and Slip" clutch "improved, which reduces the stress in the handle by 7 %.
• Pleasant vibrations: for the first time of has mounted a balanced axis inside the engine attached to the chassis using silentblocks, which gives unprecedented softness without losing "character."
• Enriching exhaust sound: Many of the changes in the propeller have had the objective of minimizing the sounds of the engine in order to increase the sound of the exhaust at the same time that the regulations are met in terms of sound emissions. As it was said when the Evolution engine was presented "we reduced noise to increase music."
• Improved electric charge: modern motorcycles are increasing The Engine a idle, to be able to meet these and future demands at the electrical level.
• Renewed exterior design: engineers have wanted to respond to the aesthetic demands of the most faithful customers have given the M8 a "muscular" appearance, wrapping the mechanical parts in a more direct way, as if it were a mechanical skin, letting us intuit us The components that hide under the tapas. The surface of the cooling fins has also been increased, providing functionality and creating a more massive look.

Technology and tradition
The goal was not simple: replace an engine that works very well and meet the demands of modern customers of a globalized market, creating a refined product that meets expectations in terms of quality and brand inheritance, all at a competitive price inside of "premium" products. In order to achieve this and all the previous points at the same time that reliability is increased and the strictest regulations for the different markets, Harley-Davidson engineers have faced many mechanical design challenges that have been solved In various ways, taking advantage of the experience of a brand with more than 100 years and applying the latest manufacturing technologies.

Eight valves, four spark plugs ... and a camshaft
With the incorporation of four valves per cylinder, several objectives are achieved at the same time. This system allows to create a flatter combustion chamber (with less surface and therefore lower absorbed heat), increasing compression to 10.5: 1 and the air outlet and air inlet by 50%. The valves are hydraulic drive as in previous models and do not require any type of adjustment and allow the use of springs lighter than the preceding models.
Hydraulic pushers are moved by a single camshaft (as in Evolution and previous models) operated by chain from the crankshaft and adjusted by a hydraulic tensor. The choice of a single camshaft simplifies mechanics and reduces friction and unwanted sounds.
With double spark plug for each butt we have an improved and faster combustion, at the same time increasing efficiency and consumption. Two sensors have also been installed (one in each butt) that capture the vibrations of the engine for a better adjustment of the ignition, advancing as much as possible without reaching the "chopped" or detonation. This system replaces the previous "Ion Sense", and has a greater resolution, working together with the programming of the switchboard so that the combustion is as complete as possible.
The cooling systems of the inherited ass of the Rushmore project are reused, providing internal passages to the points where more heat accumulates, and making oil or water pass through them, depending on the model. Both the oil pump and the water pump have been redesigned to move a higher volume per minute, and now the revolutions to the idle have dropped from 1000 rpm to 850 rpm.
As we have previously commented on a way to prevent the engine from accumulating excessive temperature is to make combustion gases as quickly as possible to the outside. Next to the largest surface of the valves and the optimization of the ignition, the new exhaust design with the relocated catalyst facilitates this task in a more effective way, moving the radiated heat to the driver and passenger.

Reinforcing the foundations
Obviously the increases in displacement and torque have to be seen accompanied by a low reinforced motor. The crankshaft axis has been oversized and the bearings are capable of supporting more load. The new crankcase is 23% stronger than the previous one, and still weighs the same. This has been possible thanks to the fact that unnecessary material has been removed, making the appearance that now the tapas "embrace" the internal parts, following their form.
The new balanced contract consists of a mass that rotates in the opposite direction to the crankshaft managing to absorb much of the vibrations emitted by it.
Another challenge in a large displacement engine with dry crankcase is the evacuation of the pressure when the pistons fall, for this needy new motor vents have been created that more efficiently separate the air from the oil in suspension and connect with the crankcase of transmission, preventing it from being in the air filter, as often happened in previous engines.

Primary and transmission at engine height
With the increase in cubic, improvements in primary transmission are required. Converting the brutal torque generated by the pulses of 2 huge pistons up and down in a soft and dosing rotary movement is not an easy task, unless a huge crankshaft is used, subtracting efficiency. In this case, it has been chosen to redesign the primary transmission, improving the ramps and fastening of the compensator and adopting a clut clutch (with hydraulic brembo pump) by 7% without losing power. At the same time this device will avoid posterior wheel locks in abrupt decelerations (anti-blocker clutch).
The starter engine is now more powerful, it has gone from 1.2 kW to 1.6 kW and the solenoid has modernized. ECM helps during start by activating decompressors located in the ass and adjusting the ignition conveniently.
As for the transmission, one of the main novelties also refers to the elimination of internal noises, for which a "constant contact" system has been used in one of the gears to eliminate clearance between them and improve synchronization.

SDBV suspensions
One of the most demanded points for potential users of Touring Harley-Davidson models in the United States foreign markets is the improvement in suspensions, both in vehicle control and in march comfort. The design team has presented a totally new system that allows an adjustment in the preload of up to 30% higher than the previous ones in a quick and simple way.
The front suspension has a new suspension technology "Showa Dual Bending Valve" with the damping benefits of a competition cartridge fork, with a
more linear and less weight behavior. Basically this means that the fork adapts its hardness and real time functioning, "detecting" changes in the firm of the land or in the speed of march.

Screamin 'Eagle
As could not be otherwise, in the catalog of HD enhancement and high performance accessories (Eagle) already included a multitude of components and kits to turn M8 into an adrenaline generator. We can find from escapes and air filters of higher performance to “stages” of potentiation that will transform the Milwaukee Eight, reaching 117ci (1917cc).

Conclusions
When judging such a novelty we have to do so with a criterion based on current circumstances and the evolution of the needs of the global market. Harley-Davidson needed to update its product after 17 years, under a very restrictive regulation that makes the homologation of a large displacement motor with dry and air-cooled engine very difficult, all maintaining the traditional aesthetic of the brand. The new clients ask for modernity, power, softness and reliability, but with "retro" minimalism and tradition.
It seems that Harley-Davidson has returned to the height, surprising with a blunt engine, which meets such varied requirements with a devastating balance. For many more years.

Frank Burguera

#mecanicaharley