Lotus Carlton

Lotus Carlton
Overview
Manufacturer	Lotus (General Motors)
Also called	Opel Lotus Omega Vauxhall Lotus Carlton
Production	1990–1992
Assembly	United Kingdom: Hethel, Norfolk
Body and chassis
Class	Sports saloon
Body style	4-door saloon
Layout	FR layout
Platform	V-body
Related	Opel Omega A Holden Commodore VN Holden Commodore VP
Powertrain
Engine	3.6 L C36GET I6 TT
Transmission	6-speed ZF S6-40 manual
Chronology
Predecessor	Lotus Cortina

The Lotus Carlton (other names include Vauxhall Lotus Carlton, Lotus Omega and Opel Lotus Omega) is a Vauxhall Carlton/Opel Omega A saloon upgraded by Lotus to be a 177 mph (285 km/h) sports saloon with acceleration to equal contemporary supercars. Like all Lotus vehicles, it was given a type designation—Type 104 in this case. The external differences were minimal with the addition of a rear spoiler, vents on the bonnet, Lotus badges on the front wings and bootlid, a bodykit and considerably wider wheel arches distinguishing it from a standard Carlton/Omega.^[1] The car was only sold in one colour, a shade called Imperial Green, a very dark green that in anything but direct light appears black.

Engine and drivetrain

Carlton engine bay

Lotus Omega

Performance modifications started with an upgraded engine, which was enhanced by Lotus from the standard Opel 2969 cc 24v straight six unit (used in the GSi). The engine was enlarged to a capacity of 3615 cc.^[2] Lotus then added twin Garrett T25 turbochargers, which provide up to 0.7 bar of boost from about 1500 rpm. The original distributor ignition system of the engine was replaced with a three-coil wasted spark system. The distributor drive was re-purposed as a water pump drive for the water-air intercooler circuit. The intercooler itself is manufactured by Behr and is capable of reducing the temperature of the compressed charge from 120 °C to 60 °C.^[3][4]

In addition to fitting two turbochargers and an intercooler system, Lotus directed a number of engineering changes to the engine so that it would perform reliably with the higher power output. To cope with the higher cylinder pressures (about 95 bar), the external webbing on the engine block was reinforced. The crankshaft was replaced as well; early development crankshafts were machined from billet steel in Italy, but the production units were forged by Opel and sent to Maschinenfabrik Alfing Kessler for machining. The cylinder head was left mostly the same as the 24-valve head from the Opel Omega, although the combustion chamber was milled to reduce the static compression ratio to 8.2:1 (from 10.0:1). The engine is fitted with forged slipper pistons produced by Mahle. Piston connecting rods were replaced with new units made to an original Lotus design.^[3]

The same six-speed manual ZF transmission as fitted to a contemporary Chevrolet Corvette ZR-1 was used to transfer this power to the rear wheels via a rear limited-slip differential from the V8 Holden Commodore.

Chassis, brakes, and steering

The multi-link suspension of the Omega, already praised by the automotive press, was modified by Lotus for better high-speed stability and improved handling dynamics. To combat the problem of significant camber change (seen with the car at high speed and when fully laden), the self-leveling suspension from the Opel Senator was fitted. Also borrowed from the Senator was the Servotronic power steering system, which provides full power assist at parking speeds, and reduces the power assist as the road speed increases. The Lotus engineers would have preferred using a rack and pinion steering arrangement, but cost and space constraints limited them to the worm-and-roller arrangement.^[3]

Initial sketches for the wheels showed a split-rim composite design, but this was ultimately abandoned in favor of a monoblock wheel design, with cited concerns over the durability of the wheels in poor road conditions. The final design for the 17" wheels was manufactured by Ronal, along with wider tyres than those used on the Opel Omega.^[2] The Omega is fitted with Goodyear Eagle tyres. The tyre compound used is the same as that on the Lotus Esprit Turbo SE, with a combination of oils and low hysteresis. This allows for improved high-speed stability and better performance in wet conditions.^[3]

The car is fitted with 12.9 in (328 mm) brake discs with four-piston AP calipers at the front and 11.8 in (300 mm) discs with two-piston calipers at the rear.^[3]

Performance

The Lotus Carlton produced 377 bhp (281 kW; 382 PS) and 419 lb·ft (568 N·m) (of which 350 lb·ft (470 N·m) was available from 2000 rpm.)^[5] The car is capable of 0–60 mph in 5.2 seconds and achieve 0–100-0 mph in less than 17 seconds. Tall gearing allows it to achieve approximately 55 mph (89 km/h) in first gear. The Lotus Carlton/Omega held the title of the fastest four-door saloon car for some years.

In the United Kingdom, the Carltons/Omegas were a favorite target of joy-riders and other thieves. This posed a problem for the police, who had nothing quicker than the 24V Senator Bs. A gang of robbers used one in a string of ram-raids of off-licence liquor stores and newsagents, stealing tens of thousands of pounds worth of cigarettes and alcohol. The small 'panda cars' used in urban policing were limited to just 90 miles per hour (140 km/h), leaving police unable to give chase.^[6]

Because the Carlton/Omega could equal or exceed the performance of many contemporary sports cars while also carrying four passengers, it generated some controversy among the automotive and general press. Bob Murray, then editor of Autocar magazine, wrote: "Nobody buying this car could possibly argue he either needs or will be able to use a top whack which is claimed to be around 180 mph." Murray went on to suggest that Vauxhall should follow the example set by German automakers (who had begun electronically limiting the top speed of their high-performance cars to 155 mph.) This sentiment was picked up by newspapers and talk radio stations, who would interview people calling for the car's ban. Ultimately, the Opel executives associated with the project voted unanimously to not restrict the car's top speed, and it was released to acclaim from the motoring press.^[3]

Production

Production of the Lotus Carlton/Omega began in 1990, four years after the original Omega went on sale. Opel had hoped to build 1,100 cars in total, but owing to the recession of the early 1990s, the £48,000 cars were not selling as well as anticipated and production at Lotus was halted in December 1992. Only 950 cars were completed: 320 Carltons and 630 Omegas, 150 short of the original target. The cars are now starting to become modern classics as low-mileage, well-looked-after examples become rare. As of 2007, UK values ranged between approximately £12,000 and £20,000.^[7]

In 1991, the design house Pininfarina produced a styling concept named the "Chronos" that was designed to accept the drivetrain from the Lotus Omega. The single example of the Chronos (sans engine) was displayed at the 1991 Detroit Auto Show.^[3]

Other markets

While the base Omega A and the Lotus Omega were never federalised for sale in the USA, the Lotus Omega is now allowed to be imported into the USA under the DOT's "Show or Display" exemption.^[8]

Specifications

• Top speed - +176 mph (283 km/h)
• Peak power - 377 bhp (281 kW; 382 PS) @ 5200 rpm
• Acceleration - 0-60 mph (97 km/h) : 5.1 sec., 0-100 mph (160 km/h) : 11.1 sec.^[9]
• Peak torque - 419 lb·ft (568 N·m) @ 4200 rpm
• Engine displacement - 3615 cc
• Engine type - Twin turbocharged straight six-cylinder
• Configuration - Front-engined, rear-wheel drive
• Transmission - Six-speed ZF S6-40 manual
• Weight - 3,666 lb (1,663 kg)
• Production - 950 units
• Price - £48,000

References

External links

Wikimedia Commons has media related to Opel Omega Lotus.

• Photo
• Audi RS6 v Jaguar S-Type R v BMW M5 (v Carlton) - evo magazine