Harley-Davidson's new Milwaukee-Eight engines all set to replace the Twin Cams
Say hello to Harley-Davidson's future - the new Milwaukee-Eight engines. The latest engine from the American brand will power the new Touring line of motorcycles and could also soon power all the Big Twin motorcycles. Unlike the Rushmore engine that were reworked Twin Cams, the Milwaukee engines have been designed ground up and have been created to deliver more torque and power while remaining emissions compliant and more fuel-efficient.
There are three variants of this engine right now - the Milwaukee-Eight 107, the twin-cooled Milwaukee-Eight 107 and the twin-cooled Milwaukee-Eight 114. The 107 will power the Street Glides, Road Glides, Electra Glide Ultra Classic, Road King and the Freewheeler trike. The twin-cooled 107 will power the Ultra Limited/Ultra Limited Low, Road Glide Ultra and Tri Glide UItra. Finally, the twin-cooled 114 will power the CVO Limited and CVO Street Glide.
The primary difference among the three 45-degree V-twins is in displacement and cooling. The 107s are 1,750cc motors while the 114 displaces 1,870cc. The 107 is oil cooled, while the twin-cooled 107 and 114 are liquid cooled with radiators.
107 engine Milwaukee Eight
A big highlight of the new motor is better heat management. The engines are designed to transfer less combustion heat to moving parts and to keep it isolated in the combustion chamber. For this, the surface area that is in contact with the primary combustion process has been reduced by using a flatter piston and four-valve head instead of the hemispherical piston and head. The bridge between the two exhaust ports now gets additional cooling, thanks to oil or coolant (in case of the twin-cooled engines) passing around them. This also has the added benefit of reducing the chance of valve warp. Further, the speed of combustion has been increased by using twin spark plugs and more advanced ignition timing.
The better heat management makes the Milwaukee-Eight engines tolerant to higher operating temperatures which in turn lets them run a higher compression ratio (close to 10.5:1). This together with airflow capacity that has been enhanced by 50 per cent and a new 50mm throttle body has increased power and torque outputs. All three engines now deliver 10 per cent more torque than the engines they've replaced while weighing the same. H-D says that the added power and identical weight translate into the 107 being 11 per cent quicker to 100kmph with the 114 being 8 per cent quicker. The more efficiently running engine has also improved fuel efficiency to some extent.
Harley also claims that the Milwaukee-Eights are far more refined than the Twin Cams. The rubber-mounted engines use a new counter-balancer that reduces vibrations by 75 per cent. H-D did try a set-up with 100 per cent vibration reduction, but soon abandoned that design to keep the character of the Harley Big Twin Alive. There is also new ECU-linked knock sensor that is capable of cancelling out engine knocking by retarding the ignition timing within one to two detonations. The new single, four-lobe camshaft further enhances refinement since there are lesser moving parts.
The new motors also get exhaust components that have been rerouted to move heat away from the passengers, a mechanically quieter engine and a hydraulic clutch that is lighter to use. There is also a new alternator that delivers 50 per cent more power at highway revs to power additional accessories.
Expect the new engine to arrive in the Touring line in India by the end of this year when Harley usually announces its new model year plans.