Lotus Turbo Esprit
enthusiast driver's dream car
Road & Track, January 1981
by Doug Nye, pictures by Geoffrey Goodard
In times of recession, a visit to a specialist car company is not recommended to the faint-hearted. After the first 'great oil crisis' there was the grisly sight of the Lotus Group lightening ship at its Hethel Factory near Norwich. What had been a packed, open office complex became virtually a huge, empty gymnasium of a place, with scattered desks here and there manned by a few hardy survivors. Out in the factory, production had sunk so low there was hardly any activity to be seen. That time Colin Chapman, Fred Bushell and the rest of the board made the right decisions and kept the ship afloat; the new car ranges developed and grew and the marque matured.
Recently when I received a phone call from Don McLauchlan of Lotus saying, 'Come on up and try the Turbo Esprit,' I braced myself for another eyewitness experience of Lotus fighting for survival. But after a day spent behind the wheel of the turbocharged mid-engine 2-seat coupe and a good look around the Hethel works and research and development shops, I drove home happy and relaxed, content that this historic marque is vigorously alive despite the trade depression. Diversification has insulated Lotus from its worst effects, allowing some truly startling new developments spearheaded by the most impressive Turbo Esprit.
Don't think of the turbocharged Esprit as just another ordinary production Lotus Esprit will all its good and bad points and hopped-up with a bolt-on turbocharger. In face, the Turbo represents an almost total redesign and detail restyle, the well-known slant-4 doch 16-valve Lotus engine is forced-induction from sharing relatively few parts with its atmospheric-induction brethern. The chassis and running gear that carry it have been highly developed to handle the quite remarkable power and torque it delivers with impressive fuel efficiency.
The story began in 1978 with an engineering team at Hethel in Lotus' think tank at nearby Ketteringham Hall tackling the engine, chassis and running gear package. Simultaneously, Giorgetto Giugiaro's Ital Design studio in Turin was commissioned to rework his original Esprit styling exercise to a more aggressive, yet aerodynamically sound, form. The original Esprit had some problems with engine cooling when idling which would obviously be exacerbated by the extra thermal load of turbocharging. Also, the early model's stressed engine mounting was blamed for a notoriously insufferable booming period that jangled the nerves of road testers and enthusiasts alike. What Lotus and Giugiaro have done breaks down as follows.
Chassis & Body
It's still a T-shape fabricated sheet steel backbone with the independent coil-and-wishbone front suspension hung on the arms of the T, but the chassis design is entirely new and will be adopted throughout the Esprit range. The crosspiece is wider, with wider-spaced wishbone pickups. The basic design is the same as before upper wishbones, and a transverse link and the anti-roll bar forming lower wishbones but steering geometry changes were made to improve low-speed feel, and indirectly produce a tighter turning circle.
The tail of the T no longer ends in a stressed engine mounting, instead using a multi-tube cradle providing 4-point engine mounts plus separate suspension pickups, relieving the crankcase of suspension loads. Earlier Esprits used the halfshafts for lateral wheel location whereas the Turbo chassis employs unequal-length nonparallel links with the usual Lotus fabricated radius arm rigidly attached to the hub carrier locating the wheel fore-and-aft. All suspension loads are fed directly into the chassis structure, which is galvanized for rust protection.
It comes as something of a surprise to find solid front brake discs instead of the ventilated type which currently have such cachet in the high-performance exotic market. Don't think this is cheapskate cost cutting. The design and development team, under Mike Kimberely and Tony Rudd, tested vented front discs out discarded them when the severe use induced distortion and pad kick-back which gave some queasy pedal effects. The Turbo's solid front discs are larger than those of the normal Esprit S2, the inboard rears being identical. A larger brake master cylinder and vacuum booster are used.
The 15-inch diameter, 3-piece alloy wheels are 7 inch wide up front and 9 inch at the back. Standard are Goodyear eliptical-sidewall, low-profile NCTs, 195/60VR15 front and 235/60VR15 rear.
Giugiaro has adopted wraparound bumpers and the Turbo Esprit also carries nose and tail air dams and deep aerodynamic sills along either side between the front and rear wheels. The Lotus team fine-tuned the Turinese styling house's aerodynamics, and in final form the under-nose air dam is claimed to reduce front-end lift from 64lb at 100mph to 50lb, while tail lift as on the standard model is claimed to be 71lb at that speed. Fore/aft aerodynamic balance is controlled by a lip moulded into the leading edge of the tailgate. There's an enclosing undertray beneath the car's nose and also under the engine bay. The bay is cooled by a NACA duct sunk into the rocker panel/sill area on either side, the undertray being shaped to deflect cool air upward around the power unit. The bay is covered at the top by a Dzus-fastened fibreglass panel with an air exit matching the tailgate. Hot air is vented from the engine bay though the horizontal tailgate slats which in the Turbo replace the standard Esprit's glass rear window. Wide-spaced, near-vertical double-glass panels behind the cockpit provide noise, wind and weather insulation, while the slats in the tailgate barely obstruct rear vision.
While the rounded underbelly of the standard Esprit gives that model a very lightweight and slender appearance, the air dam and suspended sill flanks of the Turbo give an effect of much greater presence and muscle. It's a deep-chested and handsome design, one which immediately calls BMW's M1 to mind; I haven't driven the German car but from what I read of it, the Lotus in essence is as similar in deeds as in appearance.
The all aluminium slat-4 Lotus engine has been criticised as being not exactly the most silky-smooth power unit ever built. But it is irrefutably one of the most efficient. In European form it delivers 155bhp at 6500rpm and 140lb ft of torque at 5000rpm from just 2 litres, and that's very respectable by production car standards. Not so long ago 100bhp/litre was a magic standard for any self-respecting racing engine, and now in the Turbo Esprit we find 210bhp at 6000-6500rpm and 200lb ft torque at 4000-4500rpm from 2174cc. The Turbo's long-throw crank 2.2 litre engine has a bore and stroke of 95.3 x 76.2mm for increased low-speed torque. Throttle lag is the classic bugbear of turbocharged engines and the more off-boost torque available, the less noticeable any throttle lag becomes. But there are more special features than just a long-throw crank.
The Turbo uses dry-sump lubrication, and instead of a conventional turbo layout in which the compressor sucks mixture from the carburettors, here it blows through them. Dry-sumping was considered expedient because of the extremely high cornering, braking and acceleration loads the turbo can generate conditions which would send uncontrolled wet-sump oil charging around like swirling dregs in a coffee cup, flooding one end of the engine while starving the other. The dry sump also improves temperature control over the oil, and the use of a neat sump casting incorporating the main bearing cap frame considerably stiffens the engine's bottom end.
Mounting the carburettors downstream from the Garret AiResearch T03 turbocharger compressor was adopted when the Lotus R&D crew decided it would offer improved throttle response, plus better fuel distribution even though such a design increases complexity because of the need for sealing the carburettors. It is also suspected that a turbocharger downstream of the carburettors tends to separate out by centrifugal action the atomised fuel droplets, disturbing proper mixing. The carburettors are twin-choke Dell'Orto 40 DHLAs which have proved a great success for performance plus fuel economy/low emissions. Fuel metering headaches were expected with a mounting downstream from the compressor. With the carburettors set up for the right mixture on peak boost, one would expect wild over-richness on light throttle or low load with near-zero boost. In fact, Lotus found an easy answer to mixture control and isn't talking about it. A regulating spring and diaphragm system maintain fuel pressure to the float chambers at a constant level above boost pressure.
With good inherent low-range torque from the normally aspirated 2.2-litre engine, the design team further reduced throttle lag problems by using the shortest possible inlet tracts with the carburettor butterflies as close to the inlet valves as physically possible: another good reason for the about-face turbo/carburettor arrangement. To enhance off-boost mid-range torque still further, a sophisticated exhaust manifold was developed to sustain pulse separation to the turbocharger's impeller inlet. A study of airflow from the compressor resulted in the development of a diffuser duct feeding the carburettor plenum chamber. Revised-lift camshaft designs were also adopted.
Adjusted on the wastegate bypass, the turbocharger provides 6.3psi boost at 2500rpm. 7.0 at 3500 and a peak of 8.0 at 4500. The Turbo packs more torque at 2000rpm than the normally aspirated engine's peak at 5000rpm. If the wastegate sticks shut, a blowoff valve bleeds excess pressurised air to the air cleaner.
To avoid detonation, less squish is used in the Turbo engine's head and piston design than on the standard unit. Pistons with shallower bowls and thicker crowns speed heat transfer. To assist head dissipation still further, a high-capacity water pump and increased water-flow around the now sodium-filled exhaust valves have been adopted. Harder-material valve seats are fitted. The standard Esprit's 8.5 inch clutch has been replaced by a 9.5 inch type in a necessarily enlarged bell-housing, while the Citroen-Maserati 5-speed transaxle remains unchanged, with a BMW-type Getrag being introduced elsewhere in the model line-up.
The first 100 production Esprit Turbos are finished in the metallic rich blue with red and chrome-film livery of David Thieme's Essex Oils concern, major sponsor of the 1980 Lotus Formula 1 team. The cars are offered individually numbered as the Essex Commemorative Esprit Turbo with quarter panels carrying badges numbered individually from 001. Other colour choices will be offered after the commemorative 100 the normal Esprit S2 continuing unchanged in any case. Pity the Formula 1 team has achieved so little worth commemorating in Essex colours, but the road car puts that right.
It's very much a car whose seats you sit in rather than on. The car I drove is trimmed in opulent red leather, beautifully formed and stitched, wonderful to look at, to fondle and to smell. But bad news on a hot day beneath that greenhouse windshield, despite the quite impressive Lotus-made air conditioning system. That's fine for cooling your legs and chest and face; but my back and shoulders, pressed into that leather with a high centre chassis tunnel under my left elbow and a leather-clad door under my right, got hot and stayed hot. I'm big; the place where the driver goes is small and we didn't click. Click. Cloth-insert seats would be vastly more practical and that virtually completes my criticisms.
After a lengthy churn on the starter, the Turbo engine grumbled into life with a muted snarl behind my left shoulder. The noise level at rest is low enough to allow normal conversation and high enough to tell driver, passenger and bystanders there's 210bhp in this little wedge of a car.
The stubby-lever gearbox is direct and pleasant to use, much improved from the original Esprit cable change. Now it's very much flick and have confidence, and the change is slick and crisp though not quite up to Ferrari's exceptional standard. Grumbling gently around the factory grounds remember if the 'Old Man'' runs into you here it'll be your fault the Turbo immediately impresses one with its tractability. Under 30mph in 4th is no problem; try 5th, the system complains but still pulls.
Once warmed-up and out onto the winding lanes around Hethel, the Turbo Esprit shrinks around its driver and makes him feel at home. I had arrived expecting to find an explosive stop-go projectile, a racer, and what I found instead came as a delightful surprise; a mild-mannered thoroughbred with immense but smooth performance, a superbly controlled ride quality and exquisite steering, light yet full of feel at anything above parking speed, despite those fat tires.
Steady 70-80mph cruising along winding, undulating country roads was simply a question of cock the wrists, occasionally brush the brakes and generally recline there and enjoy it I even forgot my hot, sticky back. There's little sense of body roll in corners and I found myself driving faster and faster, the Norfolk countryside reeling under that flat dipping nose like a roller map while the pursuing camera car, a normally aspirated Esprit, had long since disappeared from my rearview mirror . . . and that's a quick car; this is a fast one.
The Turbo proved itself incredibly surefooted for comfortable high-speed touring with just the vaguest suggestion of a booming resonance on the over-run but nothing like the problematic level of earlier Esprits.
The brakes are impressive, hauling in this quite light car foursquare without a hint of lock or fade, despite harder than normal use. On the road I was never conscious of throttle lag except in the extreme case of flooring the throttle from around 60mph in 5th. Then there was a little bit of hesitation from the engine room before it sorted itself out and whistled-up power. And then it doesn't come in with a thump, just that steady irresistible pressure against one's shoulders that's typical of a turbo and the mildest tail-down squat as the Esprit launches itself in a civilised manner toward its believable claimed peak of 152mph.
The boost gauge needle flicks a rather irritatingly indecisive path around its dial from 2000rpm on up, peaking at around 3000 and quivering there all the way up to 7000rpm on the tachometer. There's a considerable but not unpleasant rasp from the engine under flat-out acceleration this is not a silent car but generally its smoothness and willingness to rev are outstanding.
On Hethel's test track I achieved 7000rpm in 4th, much to my astonishment for 120-plus mph shouldn't come up so fast nor with so little drama, and then I was jumping onto those powerful brakes and looking over that surgically effective steering for the track's diabolic rough-surface hairpin. Taking off at 5000rpm by popping the clutch should delight any traffic-light exhibitionist with snick-snick gear changes and that terrific smooth endless thrust from only 2.2 litres to send you on your fuel-efficient way.
Ant it is incredibly fast . . . smoothly, deceptively fast. Factory figures quote 0-30mph in 2.1 seconds, 0-60mph in 5.6, 0-80 in 9.3 and 0-100 in 14.7 sec. It covers the standing-start quarter mile in 14.4 seconds, with a terminal speed across the line of 98mph, and the standing-start kilometre takes 26.1 secs for 124mph. I hand timed 0-60mph in around 6.2 seconds with a lot of wheelspin and 0-100mph in 15.8 seconds or thereabouts, which included negotiating a curve in mid-flight. The opportunity for more accurate timings did not present itself. It doesn't matter because the Turbo's civilised manner makes performance deceptive. But if you pay attention, it feels very fast, which is what the customer will want.
In sheer driving satisfaction, the Turbo Esprit aims high and decisively hits its target, but as always there's the question: Can Lotus produce a quality car that provides consistently trouble-free driving enjoyment? That perhaps is the highest mountain the Lotus engineering team has to climb, but as a flagship model the Turbo Esprit impressed me. There's a lingering prejudice in some circles that a plastic-body exotic can never be a supercar. I guess for those people the Turbo Esprit would have to have a metal shell to match the likes of Porsche, Ferrari and Lamborghini. Perhaps it's a commentary on past Lotus quality that it seems to be BMW's M1 which has brought respectability to the plastic shell. But remember that the Lotus Group has developed plastic bodyshell technology to a highly sophisticated degree, and it has been the bolt-on mechanicals which have in the past let Lotus down. The latest Lotus could be utterly outstanding if its manufactures and the weakness of the US dollar give it the chance. Look for it in the US sometime in 1982.