Engineers and accountants — the two professions are at opposite ends of the spectrum; the ultimate goal may be the same, but the targets are vastly different. On the one hand you have a group of men determined to do everything to a predetermined price, while the other group have problems of a practical nature, but whose ultimate raison d’être is to extend the frontiers of technology. As tooling up costs in the motor industry now reach billions of pounds, the influence of the money men is far greater today than that of the engineers. Every so often, though, the management do let them have one last fling.
It is to General Motors’ great credit then that they have gone ahead with the Lotus Carlton. Who would have thought that the mighty General, once so opposed to cars of this nature, would authorise such a vehicle? The work may have been carried out by one of its smaller specialist satellites, Lotus in this case, but you can rest assured that the decision could only have come from the very top in Detroit.
Some have made the cruel jibe that having acquired Lotus Cars, what on earth were GM going to do with it and that the answer was to keep them quiet developing and producing a four-seater executive rocket. It would have been much easier, less expensive and quicker to have badge-engineered the top of the range Cavalier into a Lotus Cavalier. Again, much to GM’s credit, they did not do so.
So what is the Lotus Carlton? Is it a badge-engineered job, albeit of a more exclusive nature, and does it justify the criticism it has received from some quarters of the population?
It must have been a dream come true for the Lotus engineers when they were told to develop the 3-litre Vauxhall Carlton, which was already a good car, into a class leading performance car which had to reach 0-60 mph in under six seconds, have outstanding handling and braking, have efficient aerodynamics and yet still be a comfortable four-seater. You could almost see them rubbing their hands with glee at the mouth-watering prospect.
Naturally development fell into different areas. The engine, where 100 bhp per litre was the target, came in for a lot of attention. To begin with it was enlarged, stroked out to 3615cc (95mm bore x 85mm stroke) and turbocharged, which naturally necessitated a wholesale change internally and externally. The forged aluminium pistons, for example, have been supplied by Mahle and have a specially treated graphite-impregnated surface while the crankshaft has been uprated to complement it.
Externally the cylinder block has been reinforced, there is a new induction system including manifold and throttle bodies, and an increased coolant flow to cope with the increased heat from the two relatively small Garrett T25 turbochargers. Unusually for a production car they are water, not air, cooled with its own plumbing arrangement which is not linked to the main water system, this over-design enabling the engine to be run flat out at maximum torque while at the same time eliminating turbo lag.
To meet the tough US 83 and Swiss emission regulations, the car has two closed-loop ceramic catalytic convertors and therefore has a cleaner exhaust than that required in the rest of Europe. It will run on 92, 95 or 98 RON lead-free petrol, but runs best on the highest octane, losing, for example, 30-35 bhp on 95 RON.
The spark timing and boost are controlled by a new Delco system which, unlike the Bosch equivalent, measures the speed density air flow for a more efficient operation. Each pair of spark plugs has its own coil, a distributorless ignition system which ensures optimum efficiency at high rpm.
To accommodate the 377 bhp achieved, beating the 100 bhp per litre target, and the 419 lb ft of torque, there is a new 9½ inch Fichtel & Sachs pull-type clutch. The gearbox itself is the six-speed ZF gearbox, the central part of which has been virtually carried over complete from GM’s Chevrolet Corvette. Overall transmission refinement and the reduction of gear rattle has been achieved by using a dual-mass flywheel which is interconnected by springs and hydraulic damping.
The rear axle, with a ratio of 3.45:1, is a development of the Holden unit, built in Australia and unique to the Lotus Carlton. The limited slip differential has a very low setting.
The suspension has been substantially modified with alterations to the MacPherson strut at the front and redesigned geometry at the rear. It is still semi-trailing, but there is now an extra link between the hub and the new rear axle while the whole system has been lowered by 15mm; both changes are designed to reduce the disadvantages associated with this type of suspension set-up. All the bushes have also been changed so that the springs on the Lotus Carlton are in fact softer than the base Vauxhall which means that the dampers are more in control of the ride motions. The toe-in, which is negligible when stationary, become slight toe-out when the car is on the move, a design made to reduce the chances of sudden snap oversteer.
330mm ventilated front and 300rnm ventilated rear discs are fitted to the car which comply with the basic guidelines evolved over the years at Hethel about the size of brakes required. The one-piece discs have been selected for durability and economy. The four pot calipers on the front and the twin pots on the rear have been supplied from AP and are the result of that company’s Group C programme, but modified for Lotus’ needs on the Carlton. Road-type asbestos-free pads are fitted as standard but are of a good enough quality to live with circuit use if necessary.
The four-channel electronic anti-lock braking system has been recalibrated for the Lotus Carlton as Vauxhall were not convinced that the standard system was up to par, although in Lotus’ opinion it gave the best overall performance.
Engine torque, more than anything else, dictated that a 265 section tyre was the smallest tyre possible on the rear. At the same time, the size of the brake disc dictated that a 17″ wheel on the front be used and that a 235 section was the most sensible choice. The result is specially made Goodyear Eagle 235/45 ZR17s on the front and 265/40 ZR17s on the rear fitted on one-piece wheels designed and produced by Ronal in Switzerland.The aerodynamic additions to the car are the result of wind tunnel tests in Stuttgart. The impressive Cd figure of .307 has been achieved despite increased frontal area with the wide tyres and the addition of two very large oil coolers which have been integrated into the front of the car. At the rear is a wing which ensures zero lift and yaw and helps stability. There have also been modifications to the wheel arches — those at the rear, for example, have been cut away which transforms the look of the car — and there have been GRP additions to the lower half of the doors, rear bumpers and side mouldings.
Much work has been done on NVH (noise, vibration, harshness) to reduce interior noise, the main source of which is the tyres. Much to the engineers’ astonishment, one of the main gains in this area was by carpeting the boot.
The seat frames are a carry-over from the original car, but have been retrimmed in Connolly leather at Lotus. Each car is identified by its own limited edition number on the glovebox and you can choose any colour as long as it is GM’s Empire Green pearlescent paint — a shade of black by any other name.
Altogether there have been 1000 new components which have gone into the car and the engine is totally built from parts. There are a total of five engine builders at Lotus and each one is responsible for an engine from start to finish.
A morning’s run in the car was enough to appreciate that here was a car that was special. We were allowed to take it to the Proving Ground at Millbrook where we could run it round the two-mile High Speed Bowl. The automatic levelling suspension — which maintains the camber at all times for stability and tyre durability — worked here against us as it would have been fooled by the Bowl’s banking and would continually try and adjust itself. We were thus restricted to a mere(!) indicated 140 mph.
I have been on this banking before at speeds lower than this and have found even some performance cars have been a handful, but the Lotus Carlton reached this speed with such finesse and lack of fireworks that one felt “so what”, it was that impressive.
Around the tight and twisty, slightly damp handling course, the car was surefooted, although on the exits the tail could be made to go out of line by stomping down on the throttle. That the car was remarkably stable, though, was proved by the fact that when braking or lifting off while cornering, the car did not twitch.
Apart from the sheer speed of the machine, the most remarkable aspect was the tractability. Although the maximum 419 lbs ft is available at 4200 rpm, some 2000 rpm before the red line, 300 lbs ft of it is developed at just 2000 rpm. 30-50 mph takes just 3.3 secs, 40-60 mph 2.9 secs, 50-70 mph in 2.8 secs and 70-90 mph in 3.1 secs, all in third gear are the mid-range acceleration figures. Fourth gear almost becomes redundant and such is the tall gearing in sixth — over 40 mph per 1000 rpm — that it is utterly pointless. In fact it would have been better if sixth gear had been blanked off for it really serves no useful purpose, other than perhaps in Germany.
On the car we drove, number 004, the build quality was a little suspect. There was a rattling gear lever knob for example and the gear change was very notchy. It was so solid that one could well have been driving a Scammell truck.
With those great wide wheels there was a suspicion that the car might tramline, but in the test route we were given, this phenomenon was barely experienced.
Altogether it was a mean machine. Following another one, it was the wide rear wing above the fat, chunky tyres which was the most impressive sight. Should you be overtaken by one of those cars you know the driver means business.
There is no obvious rival to this car. The BMW M5 leaps to mind as does the Alpina BiTurbo, but the former is not so powerful and the other is £12,000 more expensive at £60,000 and only available in left-hand drive.
Altogether only 1100 are going to be made, at the rate of one a day, over a 36 month period, 440 of which will be staying in Britain in right-hand drive form. They are sure to be snapped up.
As a model it joins the Calibra in stretching the boundary of where Vauxhall is. GM cannot hope to amortise the cost of the operation over just 1100 cars, but that is not the intention. It is primarily an image builder, one that Vauxhall needs, for it is not the products of that company but the name which puts many people off, especially in the upmarket executive car bracket. If the everyday Vauxhall Carlton can be perceived as a junior Vauxhall Lotus Carlton, then the whole exercise, bad publicity and all, will have been worthwhile. It also kept the lads at Lotus busy as well. WPK
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