Structure & Refinement

To ensure that Opirus is exceptionally roomy inside, with more leg, head and shoulder room than most of its competitors, a generously proportioned bodyshell was required. The internal space - front legroom is 1,110 mm and rear is 945 mm, while headroom is 1,015 mm and 975 mm and shoulder room is 1,475 mm and 1,460 mm across the rear - does ensure that passengers travel in complete comfort. Those internal dimensions inevitably demanded that Opirus would also have substantial external dimensions. Making a large bodyshell stiff and impact resistant presents engineers with some tough and very specific design challenges.

The Opirus´ monocoque bodyshell is computer designed to minimise deformation of the passenger compartment in the event of a collision. Crumple zones at front and rear absorb and disperse collision forces from both head-on and offset collisions while side-impact bars and reinforced A and B pillars enhance passenger safety in the event of a side collision. High-tensile steel bumpers covered with an energy-absorbing composite at front and rear deflect minor collisions up to 8 kph.

Kia engineers worked hard to ensure that the Opirus bodyshell had high torsional stiffness - for good handling and refinement - as well as progressive resistance to impacts. Numerous computer simulations of both driving and crash scenarios, led to the adoption of five key developments during the creation of the bodyshell design. The changes included the use of tailor-welded blanks in the front chassis members, a reinforced joint between the front wing tops and the base of the A-pillars, the use of one-piece inner and outer side panel pressings, more robust cross-members under the front seats and between the B-pillars and strengthened rear fascia inboard of the rear lamp clusters.

Despite the adoption of shallower side sills - to ease occupant entry & exit from the cabin, in production form, Opirus boats a torsional rigidity figure of 24.3 x 104kg f mm2/ rad.

To enhance resistance to side impacts, the A-pillar was strengthened and the joint between the roof and B-pillar was given increased rigidity. To resist intrusion, the overlap between the side impact beams in the rear doors and the bodyshell wheel arches was increased and the deformation characteristics of the B-pillar were modified so that it follows an S shape after impact, intruding less into the passenger area at shoulder height.

The overall strength of the Opirus bodyshell design and its controlled deformation characteristics, lead Kia to anticipate at least a 4 Star rating in the Euro NCAP crash safety tests.

Refinement

The Opirus is an exceptionally quiet vehicle, employing a number of different structural and technological refinements to reduce noise, vibration and harshness.

At the front of the car, a wave-type blade on the radiator fan improves airflow and reduces noise from this source by around 2dB. At the rear of the car, a variable valve inside the exhaust muffler reduces exhaust noise by closing at low speeds. At higher speeds the valve opens to reduce exhaust back pressure and improve engine performance.

The Opirus structure contains a wide range of sound-deadening materials, including foam padding within the wheel arches and urethane insulation pads in the primary pillar sections. The floor pan, roof and dashboard contain sound deadening pads that minimise interior noise and vibration when the car is moving. The rigidity of the doorframe around each window is also enhanced to minimise distortion and wind noise.

The result is an interior noise level of 39 dB with the engine idling, and 74 dB while driving at speed with the air-conditioning switched on. Road noise and driving interior noise are kept down to 64 dB at 60 kph on rough roads and 62 dB at 100 kph on smooth asphalt roads, respectively. This combines to provide a superbly quiet ride.