‘Milwaukee-Eight’ – tourers only?
At last – is this the Harley engine that won’t burn your legs, shake your teeth out and leave you last at the lights.
Well, not quite, especially where power comparisons with competitive offerings (Indian Motorcycle aside) are concerned. But that hasn’t stopped Harley from boasting (with justification) that the all-new ‘Milwaukee-Eight’ (M-8) engine delivers more power and an improved motorcycling experience for riders and passengers while retaining the iconic look, sound and feel of its predecessors.”
True, it is a mostly all-new design, certainly as far as the heads are concerned, and the look is okay, even if the sound is more race-bike than “potato, potato” now. The M-8 is said to offer “quicker throttle response, more passing power, purer sound, a smoother ride and more of the feeling riders want from a Harley-Davidson Touring motorcycle engine.”
In other words, is Harley accepting that the Twin Cam offered relatively poor throttle response, poor power in real-world traffic conditions, and ran too hot with way too much noise and way too much in the way of vibrations?
It kind of sounds like that to go by the wording of their press release, and note the possible implications buried in the detail of their remarks here – “more of the feeling riders want from a Harley-Davidson Touring motorcycle engine.”
One line of speculation suggests that in a parallel to what happened with the two-stage introduction of the Twin Cam in 1999/2000, there is likely to be a ‘B’ version of the ‘Eight’ next year for the cruisers – or in a new mid-cycle cruiser-esque launch or launches.
Alternately, are Harley quite clearly signalling here that, in fact, the ‘Milwaukee-Eight’ is destined to be a tourer engine “only”?
In which case, will the cruisers be allowed to trade on the Rushmore hype of the Twin-Cooled motor for some years to come, or (could we be this lucky?) is there in fact another big step in refreshment and refinement of the offer still to come with, whisper it softly, another engine platform also about to emerge at some stage in the next six to 24 months?
Either way, the new ‘Milwaukee-Eight’ engines will power every 2017 Harley-Davidson Touring and Trike motorcycle model. They will be offered in two displacements and three variations.
The 107-inch version (1750cc) features precision oil-cooled cylinder heads for the Street Glide/Street Glide Special, Road Glide/Road Glide Special, Electra Glide Ultra Classic, Road King, the Freewheeler trikes and two of the CVOs.
Based on the existing cooling technology first seen on the Rushmore tourers, a Twin-Cooled 107 incher (107 CID, 1750cc) features liquid-cooled cylinder heads for the Ultra Limited/Ultra Limited Low, Road Glide Ultra and Tri Glide Ultra models.
Then a Twin-Cooled ‘Milwaukee-Eight’ 114-incher(1870cc) featuring liquid-cooled cylinder heads will power the CVO Limited and CVO Street Glide models.
The “strategic cooling” of the “Twin-Cooled” concept (namely liquid and air) allowed the classic finned look to remain functional rather than just being visual and brand value. However, the concept is destined to struggle to keep up with the increased heat generated by the increased power. That is why Harley has embraced the reduction in combustion chamber surface area geometry that the eight-valve chamber redesign requires.
The new engine is said to produce 10 percent more torque than the engine it replaces in Touring models. In addition to increased displacement, it features a higher compression ratio and 50 percent more intake and exhaust flow capacity. The valve train is said to require no adjustment as the design of the rocker arms enables valve lash to be set at the factory for life; dual spark plugs for each cylinder (and advanced ignition timing) contribute to more efficient combustion. A single chain-driven camshaft is lighter and mechanically less complex, creating less friction and noise.
Weighing the same as the lower-powered engine it replaces, the power-to-weight ratio of the ‘Eight’ is another of the significant factors in delivering increased power - there can be no doubt that even as you read this, the aftermarket will be busy working on lighter weight, higher strength components to push that ratio way further.
The 107-inch version of the ‘Eight’ is said to accelerate 11 percent quicker 0-60 mph (equal to a two to three bike length improvement), and 11 percent quicker from 60-80 mph in top gear (equal to a one to two bike length improvement), compared to the Twin Cam High Output 103.
The 114-inch version is said to accelerate 8 percent quicker 0-60mph, and 12 percent quicker 60-80mph than the Twin Cam 110.
Heat has always been the big issue for the Twin Cam. Harley describe the ‘Eight’ as offering “improved rider and passenger thermal comfort due to reduced heat absorption, increased heat rejection and a redesigned exhaust system. With a precision cooling strategy [developed for the Rushmores] based on the specific demands of the motorcycle model, using a targeted flow of either oil or liquid coolant around the hottest areas of the cylinder heads.
“A new knock sensor for each cylinder enables more precise timing control. The rear exhaust pipe is repositioned and the exhaust catalyst is relocated to move heat away from the passenger. Idle speed is lowered from 1,000 rpm to 850 rpm.” The new sensor is based on reading acceleration to enable the ECM to manage ignition timing rather than the ion-sending knock detection of the Twin Cam.
The mapped (command) based system of the Twin Cam ECM has been replaced with a torque-cased system – the rider throttle position triggers a torque rather than throttle command.
By doing so Harley may have presented the manufacturers of existing aftermarket engine management devices with a challenge; the business opportunity Harley may think they can expect to see as a result may go some way to explaining the timing of their settlement of the EPA action they’ve been facing.
Rider comfort is also enhanced by the new, slimmer primary drive cover, and the low-profile shape of the (less than aesthetically nourishing) air cleaner cover, providing improved rider legroom around the engine and an easier reach to the ground for many riders. All Milwaukee-Eight powered models are fitted with an Assist and Slip Clutch with improved hydraulic actuation that reduces clutch lever effort by 7 percent.
The rubber-mounted engine features a single internal counter balancer that is said to cancel 75 percent of primary vibration at idle (rather than 100 percent), “for a more refined feel and comfortable experience for rider and passenger while retaining the classic character of Harley V-twin engines.”
Lighter valves, a single camshaft, optimized cover designs and improved driveline components are said to eliminate mechanical powertrain noise. The engine intake and air cleaner are designed to reduce intake sound while ensuring maximum air flow. As a result, the new engine is mechanically quieter, “enabling a richer exhaust tone, meeting all global noise and emissions standards, while allowing the unmistakable rumble of its exhaust note to resonate.”
The charging system delivers 50 percent more output to the battery at idle to “better support the power demands of Touring riders, including accessory lighting, performance audio, and heated gear and other accessories.”
Brad Richards, Harley-Davidson’s Director of Styling, is quoted as saying: “The ‘Milwaukee-Eight’ engine is styled to project power. I compare it to the back of a swimmer, lean in the waist but broad and muscular in the shoulders.
“The rocker covers look like skin stretched taut over muscle, like the rocker arms are about to burst out of the engine. For the first time since the Knucklehead, the rocker covers reflect the action going on below. And they are massive. When you sit on the bike you can look down and see more of this engine.”
The all-new front and rear suspension components “enhance the comfort, control and performance of all 2017 Harley-Davidson Touring model motorcycles. New emulsion-technology rear shock absorbers offer 15 to 30 percent more pre-load adjustment than previous standard Touring shocks, with a single knob to hydraulically adjust pre-load.
“Pre-load can now be adjusted to match the load of rider, passenger and gear without tools or an air pump,” said Paul James, Harley-Davidson Director of Motorcycle Product Planning. “Once set, the pre-load will not leak down or require further adjustment.”
The front suspension features new Showa SDBV suspension technology that is said to deliver the damping performance of a racing-style cartridge fork with linear damping characteristics and reduced weight.