2018 Honda GoldWing Engine
- Extensively revised flat six-cylinder engine 6.2kg lighter, with 4 valves per cylinder
- Throttle By Wire (TBW) adds 4 rider modes to tailor power output
- The rider modes also manage HSTC, suspension damping and brake force
- Idling Stop and Integrated Starter Generator (ISG) on DCT version
- Hill Start Assist (HSA)
- 6-speed manual gearbox with assist/slipper clutch
Core to the previous Gold Wing’s appeal was its turbine-smooth flat six-cylinder engine, which produced torque from low rpm with a distinctive power delivery and feel that quickly became addictive.
To realise the handling ambitions of the new chassis the 1,833cc engine too has been redrawn. Still as a horizontally-opposed flat six, but now with four valves per cylinder rather than two, much more compact in size and 6.2kg lighter.
Peak power of 93kW arrives @ 5,500rpm, with peak torque of 170Nm delivered @ 4,500rpm. The bore size of 73mm (from 74mm) has been optimised to stroke of 73mm and bore pitch shortened 9mm; the left and right cylinders are offset 4mm and the cylinder sleeves are now aluminium. Compression ratio is set at 10.5:1.
The Unicam cylinder heads – the inlet valves are operated by finger-follower rocker arm, the exhaust valves by roller rocker arms – also employ a co-axial rocker-arm shaft for both inlet and exhaust, doing away with the old model’s valve lifter structure.
The combustion chambers are now a 4-valve ‘pentroof’ design (rather than a 2-valve ‘bathtub’) with the inlet ports designed to promote ‘tumble’ flows inside the cylinders thus improving efficiency. The piston skirts wear a molybdenum coating to reduce friction.
A stiffer crankshaft, constructed from SCM440H steel, allows a pin offset of -4mm and compared to the previous design the new engine is 33.5mm shorter in length. The crank sensor (which detects engine speed and piston position for EFI and ignition) has been moved from the front of the engine to the rear, reducing the distance between the front cover and crankshaft by 7mm.
The addition of Throttle By Wire (TBW) has brought with it 4 rider modes to alter the engine’s character and power delivery, linked to Honda Selectable Torque Control (HSTC), suspension damping and the Dual Combined Brake System (D-CBS).
TOUR mode is the base setting for comfort and power. It gives a direct 100% opening ratio between throttle grip and throttle body butterfly, with ‘default’ damping and front/rear brake force distribution.
SPORT serves up the highest throttle to butterfly ratio and delivers strong acceleration, with firmer damping and rear brake lever pressure.
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ECON mode offers maximum fuel economy and easy cruising, with lower throttle to butterfly ratio and default damping and brake force.
RAIN turns the dial down to suit wet and slippery conditions, with lowest throttle to butterfly ratio, default braking force distribution and soft suspension damping.
In all 4 riding modes HSTC constantly allows controllable acceleration in slippery conditions.
A single throttle body has replaced the dual throttle bodies of the previous design, with revisions to the diameter and thickness of the intake manifold to save weight. Intake manifold volume, from the throttle valve to intake valve has been reduced by approximately 10%, speeding up airflow and improving response.
There are two air intake ducts sited front left and right rear. This structure generates swirling as the air is drawn in – the result is more effective use of the air filter’s entire surface area and reduction in resistance. The internal shaping of both ducts has been optimised to align with the intake pulses of the engine’s low-rpm range, improving response and torque from smaller throttle openings.
The sound and feel of the Gold Wing’s engine has always been its calling card. While the new dual exhausts maintain the internal structure of the old model – 2 internal chambers plus a resonance chamber – the glass wool has been removed to save weight.
To complement the engine’s deep bass signature the exhausts now emit a powerful throb, without excessive noise. The cross-sectional areas of the exhaust pipes have been reduced 20% for two out of the six cylinders, bringing about the change in sound volume and depth.
The ISG (Integrated Starter Generator) combines the generator and starter motor into one component, with the generator effectively becoming the starter motor when supplied with reverse power.
The damper used for the coupling joint that transmits the driving force from both the ISG side and the crankshaft side has been changed from the viscous type used for the generator of the previous model to the mechanical, using an arc spring and rubber; weight is reduced by approximately 2.4 kg for the system as a whole. Helical gears are employed for the ISG driving gears, reducing the mechanical noise of the engine.
Key characteristics of the Idling Stop system are the ultra-quiet start-up of the engine thanks to the use of ISG, and the smooth starting feeling achieved through a combination of DCT and TBW control. When stopping at a traffic light with the Idling Stop system on, the engine automatically stops after 3 seconds and, when restarting, the rider only needs to turn the throttle, which immediately starts the engine.
The system is controlled so that hydraulic oil pressure is applied in advance to the DCT line that activates the clutch when the engine starts, so the time lag from when the rider opens the throttle to movement is reduced. To curb any abruptness the TBW makes the throttle butterfly open gradually following the throttle opening – thus the smooth acceleration befitting of a Gold Wing. Idling Stop can be turned ON or OFF from the right handlebar switch.
Hill starts on a conventional motorcycle often involve simultaneously releasing the brakes, opening the throttle and engaging the clutch according to the grade of the slope. To ease this effort, the new manual transmission Gold Wing has adopted Hill Start Assist (HSA).
After stopping on a slope, further squeezing the brake lever quickly results in the ABS modulator generating hydraulic pressure for the rear brake caliper. When setting off – even when the brake lever is released – the hydraulic pressure temporarily retains braking force (for about 3 seconds) so starting on the uphill slope with the throttle is possible. When in operation, the HSA indicator is switched on to inform the rider.
The new 6-speed manual gearbox lowers the engine speed when cruising at 100km/h, compared to the previous 5-speed design. It’s also fitted with a ‘cam damper’ between the clutch and transmission, separating each inertial mass, reducing noise and improving shift quality/durability.
A cam assist and slipper clutch (with fewer discs and reduced hydraulic friction in the release mechanism) has replaced the hydraulic assist clutch. This has reduced clutch load at the lever by 20% and also smoothed downshifts; the slipper mechanism also contributes to the high-quality downshift feel. The reverse mechanism is exactly as it was on the previous Gold Wing.
