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The next generation in big twin performance from Harley-Davidson

14th July 2006 Print
Harley-Davidson launch an all-new Big Twin powertrain for 2007, as the Twin Cam 96/96B engine, active intake and exhaust system (for European and select international models only) and 6-speed Cruise Drive transmission feature on all Touring, Softail and Dyna models.

The new engine, with standard Electronic Sequential Port Fuel Injection (ESPFI), offers a nine per cent increase in displacement and up to a 19 per cent increase in torque (varies by model) over the Twin Cam 88/88B engines it replaces. It also features a number of design changes intended to make it smoother, more reliable and convenient to operate.
“The Twin Cam 96 has been the biggest new-engine programme in the history of Harley-Davidson,” said Skip Metz, programme manager - Big Twin powertrain. “There are more than 700 new parts associated with Twin Cam 96/96B. The only areas that didn’t change are the cylinders, rocker arms, rocker boxes, and items in the top part of the engine. Crankshafts, connecting rods, crank cases, transmission cases, and all the transmission parts are new. We think this next-generation Twin Cam will set a new V-Twin standard for the industry.”

The Twin Cam 96 displaces 1584cc, compared to the 1450cc of the Twin Cam 88 engine it replaces. The added displacement was achieved by increasing stroke from 101.6mm to 111.1mm. The Twin Cam 96 cylinder bore is 95.3mm, the same as that of the Twin Cam 88. The Twin Cam 96B is designed to be rigid-mounted in Harley-Davidson Softail models, and is equipped with internal counterbalance shafts that quell 90 per cent of primary engine vibration.

The Twin Cam 96 produces up to 123 Nm of peak torque at 3400 rpm, compared to the Twin Cam 88 at up to 109 Nm at 3400 rpm. Performance improvements vary by model.

New Active Intake and Exhaust for European Market Big Twin Motorcycles

Another piece of headline-making news for all the new 2007 Harley-Davidson 1584cc, 6-speed Big Twin models is the arrival of a highly innovative and sophisticated active air intake and exhaust technology system developed by Harley-Davidson which significantly improves power, torque and sound quality whilst meeting strict European noise and emission regulations.

Valves in the exhaust and air intake open and close in response to Engine Control Module programming and a throttle position sensor. The valves close to reduce air intake and exhaust noise at certain rpm and throttle position settings. This minimises noise when riding at low speeds such as in an urban environment. Out on the open road the valves open to optimise performance and sound quality - exhaust gases flow freely through both mufflers and engine performance is further enhanced because of the improved gas flow and full utilisation of the revised airbox volume and geometry.

And the result? The 2007 Fat Boy for example, has 15 per cent more peak power and 19 per cent more peak torque and an even sweeter, more distinctive engine note when it’s time to ride. Power and torque increases vary by model but all models receive a healthy performance boost.

As you would expect from Harley-Davidson, the new technology is discreetly designed and integrated so that the classic looks of the motorcycle and profile of the V-Twin engine remains unspoiled.

New 6-Speed Cruise Drive Transmission

The new 6-speed Cruise Drive transmission has gear ratios optimised to match the torque curve of the new Twin Cam 96/96B engines. The addition of a lower-ratio sixth gear reduces top-gear rpm by 11 per cent, compared to the previous 5-speed Big Twin transmission. At 75 mph, engine speed is reduced by 368 rpm, from 3227 rpm to 2859 rpm, offering a more relaxed ride. Second through fourth gears have helical-cut teeth for quieter operation.

Twin Cam 96 Highlights

Traditional V-Twin Styling: The Twin Cam 96/96B powertrain remains the styling centrepiece of each Harley-Davidson Big Twin model, and it retains the look, sound and feel that has always been part of the Big Twin legend. The Twin Cam 96 preserves the styling characteristics of the Twin Cam 88 and the heritage of its predecessors.

New Crankcase Design: The starter is now bolted directly to the inner primary housing, eliminating the starter jackshaft for improved starter performance. An integral oil filter adapter eliminates gaskets and hardware. Internal oil passages between the engine and transmission on the Twin Cam 96 eliminate external oil lines and fittings on all Dyna and Touring models.

Reduced Reciprocating Mass: Lighter pistons and lighter, shorter connecting rods increase performance and reduce vibration. Despite an increase in displacement, the Twin Cam 96 and the counter-balanced 96B are noticeably smoother than the Twin Cam 88 at most engine speeds.

Improved Camshaft Design: The new cams are lighter and use improved materials for enhanced durability. New multi-piece assembled camshafts replace the previous forged, single-piece cams. New hydrostatic, plain cam bearings replace the previous roller bearings and offer increased durability, reduced complexity, and quieter operation. A new, more durable hydraulic automatic cam chain tensioner replace the previous spring-loaded mechanical tensioner.

Improved Oil Pump: A new oil pump assembly provides 10 per cent more flow and 23 per cent more scavenging capacity than the previous design. The Twin Cam 96 also has an integrated oil cooler adapter.

Improved ESPFI: New 25 degree fuel injector nozzles offer better fuel atomisation and spray targeting than the previous eight degree injectors, and help reduce exhaust emissions and improve driveability. A new O2 feedback sensor in the exhaust helps fine-tune EFI performance and reduce exhaust emissions.

New Primary Chain Tensioner: A new automatic primary chain tensioner eliminates the manual service adjustment of the primary chain. The inner and outer primary drive covers are redesigned to improve the appearance of the painted, polished or chromed surface.

Bolt-On 103 Big Bore Kit: An increase in displacement to 1688cc can be achieved easily by adding a bolt-on Big Bore Kit with 98mm bore cylinders and matching pistons from Harley-Davidson Genuine Motor Accessories. It is no longer necessary to add a stroker kit to get to 1688cc.

6-Speed Cruise Drive Transmission Highlights

New Transmission Case: Larger internal bearings, larger gears and a stiffer transmission housing all combine to improve overall durability, and torque-carrying capacity is increased by 28 per cent. The transmission for Dyna and Touring models has internal oil passages that eliminate external oil lines and fittings and the opportunity for leaks. The Softail transmission retains external oil lines.

New Gears: Helical-cut gear teeth, initially developed for the VRSC family, present a larger contact area than the previous straight-cut gears, so they are stronger and also quieter. A new cassette gear cluster is easy to remove for improved serviceability.

Smoother Shifting: Shift effort is significantly reduced because steel “dog rings” that slide to cause gear changes replace moving gears. Because the dog rings have less mass than gears, shifting is quicker and smoother, and the throw of the shift lever is reduced.

Reduced Clutch Lever Effort: Reduced clutch spring rates, a revised ball-and-ramp design, and a new, more efficient clutch cable combine to reduce clutch lever effort by up to seven per cent (varies by model).

New Gear Ratios: New gear ratios have been selected to match the torque curve characteristics of the Twin Cam 96 engine. Roll-on acceleration performance is improved in all gears. Top gear cruising ratios are reduced significantly with the addition of the sixth gear and passing capability is improved.

Service Intervals: The primary chaincase drain interval is doubled from 8,000km to 16,000km, while the transmission drain interval is also doubled from 16,000km to 32,000km.