Guide: Porsche 911 3.3 Turbo (964)
Background
The 911 Turbo (930) was originally conceived as a limited production special to homologate a forced induction racing variant for the new Group 4 and Group 5 racing classes that would come into effect from 1976.
Porsche hoped there would be sufficient demand to sell the 400 road cars required by the FIA. However, customers flocked to buy the new model and it was soon decided to make it a permanent fixture in the firm's line up.
Thanks to a combination of supercar-rivalling performance, real world practicality and Porsche's renowned build quality, the 911 Turbo occupied a unique position in the market. In speed terms, it could match a Ferrari BB or Lamborghini Countach but, unlike its Italian rivals, the 930 was suitable for everyday use.
The arrival of the 930 also helped save the 911 from an early demise. Porsche had planned to discontinue the 911 in favour of the conventional front-engined 928.
Sales of the 928 were routinely lower than even the expensive 911 Turbo though and when Peter Schutz took over from Ernst Fuhrmann as Porsche Chairman in 1980, the decision was made to stick with their most iconic model.
By this time, the three-litre engine used in the original 930 had been enlarged to 3.3-litres. For the 1987 model year, the Turbo (which had so far only been available as a Coupe) was also offered as a Convertible and Targa.
A wickedly expensive 935-style Flachbau variant was officially introduced at the same time.
For the 1989 model year, Porsche launched arguably the most heavily re-engineered 911 yet seen. Dubbed the 964, this latest iteration of the normally aspirated 911 featured a host of cosmetic and mechanical modifications including four-wheel drive.
A rear-wheel drive iteration followed soon afterwards and Porsche revealed a turbocharged variant at the Geneva Motor Show in March 1990.
Production began in September 1990 for the 1991 model year. By this time, the original 911 Turbo had been out of production for just over twelve months.
Right-hand drive cars were produced from early 1991, but unlike the old 930, the 965 was only available as a Coupe.
The 964 Turbo provided Porsche with a useful boost in sales at a time when the firm were beginning to feel the effects of the early 1990s economic downturn.
Chassis
The new Turbo was based on the rear-wheel drive 964 Carrera 2 bodyshell.
Size-wise, the 964’s hot zinc-dipped steel bodyshell was almost identical to its predecessor. Changes included a new underbody complete with centre tunnel for the torque tube required on the four-wheel drive version.
To accommodate the front differential and driveshaft assemblies for the four-wheel drive system used by the Carrera 4, all 964s came with a re-shaped luggage compartment that was reduced in size compared to previous iterations of the 911.
The 964 also ushered in a new heating and ventilation system which was imported to the Turbo.
Among the most important new features ushered in on the 964 platform was an updated suspension arrangement.
The revised configuration did away with torsion bars in favour of coil sprung dampers. A MacPherson strut layout was retained at the front while the back end used the cast-aluminium semi-trailing arms from the 930. The 964 Turbo was further enhanced with thicker anti-roll bars.
Overall, the reworked suspension of the 964 improved handling and ride quality and lessened road noise.
The 964’s brake system was effectively imported from the 928 S4. Ventilated discs of 298mm were fitted at the front along with 299mm discs at the rear. Four-piston aluminium calipers were installed at either end. The 964 Turbo came with bigger 322mm cross-drilled and ventilated discs up front.
As per the 964, power steering and ABS were fitted to the Turbo. Neither had been used on the 911 prior to the arrival of these updated variants.
Wider wheels and tyres had long since been a trademark of the 911 Turbo. For this latest iteration, the 16-inch Club Sport rims used by the normally aspirated 964 were switched to 17-inch diameter Cup Design alloys. The front rims were widened from 6 to 7-inches while those at the back went from 8 to 9-inches.
Porsche offered a choice of Bridgestone, Pirelli or Yokohama tyres.
Underneath the front lid was the same 77-litre fuel tank used by the Carrera 2 and Carrera 4.
Engine & Gearbox
Whereas the 964 was equipped with a thoroughly reworked 3.6-litre engine, the Turbo adopted an improved version of the existing forced induction engine as used by the outgoing 930.
A turbocharged version of the 3.6-litre engine would eventually come on stream in October 1992 for the 1993 model year.
For now though, the 964 Turbo ran a 3.3-litre power unit derived from the Type 930/66 engine as used in the 930 since 1982.
A displacement of 3299cc was the same as every 930 produced since August 1977. It was achieved thanks to a 97mm bore and 74.4mm stroke.
Once again, an all-alloy construction was utilised along with single overhead camshafts, two valves per cylinder and dry-sump lubrication.
The Type M30/69 engine fitted to the 964 Turbo came with a series of updates over its predecessors.
There was a revised air intake system and a new exhaust which now featured a single pipe per side instead of twin pipes exiting from the left.
New Bosch Motronic engine management offered more power and torque, improved fuel consumption and reduced emissions.
A larger KKK turbocharger featured a new impeller for improved low-speed response and the intercooler offered 50% more air flow.
Porsche were able to reduce the turbo pressure from 0.8 bar to 0.7 bar and still see notable output gains.
Compact closed loop catalytic converters were fitted to all cars, regardless of destination.
To reduce vibration, the engine was mounted on hydro-bushings. Cockpit noise was supressed thanks to a new dual mass ZMS flywheel as used by the 964.
The compression ratio was kept at 7.0:1.
In this configuration, the Type M30/69 engine produced 320bhp at 5750rpm and 347lb-ft at 4500rpm. For comparison, the standard motor in the outgoing 930 developed 300bhp at 5500rpm and 303lb-ft at 4000rpm.
The 964 Turbo used a five-speed Getrag gearbox as per the 1989 model year 930 which had been the first iteration of the 911 Turbo not to run a four-speed ‘box.
The G50/52 unit found in the forced induction 964 differed from the old G50/50 gearbox on account of its revised ratios and more precise gear shift mechanism.
A limited-slip differential was standard.
Bodywork
Visually, the 911 Turbo had always differed from its narrow-bodied normally aspirated compatriots thanks to its more aggressive spoilers and flared wheelarches. This latest iteration was no different.
All four fenders were modified to accommodate the wider wheels and tyres.
At the back was a new Whale Tail spoiler. Unlike the 964, which came with an electronic rear wing, the one installed on the Turbo was fixed in position.
Earlier iterations of the 911 Turbo had needed an additional front chin spoiler to balance the aero profile, but this was now deemed unnecessary.
The 964 Turbo also ushered in a new type of aerodynamically formed exterior mirror that was later adopted on regular models.
Otherwise, this latest Turbo received all the cosmetic updates added to the 964.
This included one-piece bumpers fabricated from deformable thermoplastic and mounted on aluminium subframes (or telescopic dampers in the case of American-spec. examples). The 964 also adopted a new tail light arrangement plus extended fibreglass sill covers down each flank.
Like the regular 964, the Turbo used low profile rubber for the windscreen surround and smaller drip rails to improve aerodynamics. Similarly, the rear windscreen was more neatly integrated and the underbody had been made smoother.
Interior
While the exterior modifications made on the 964 range were among the most dramatic yet seen on the 911, interiors were little changed.
The new Turbo’s fixtures and fittings were imported directly from the 1991 model year 964 which included a new centre console and glove compartment.
The Turbo also came with an onboard computer similar to that used by Tiptronic 964s. The computer fitted to the Turbo had the added benefit of a digital boost indicator.
Otherwise, as per every 964, the seats, instrument binnacle, dash and door panels were all imported from the old 3.2 Carrera / 930.
The familiar five gauge instrument layout comprised a central tachometer with analogue boost gauge flanked to the right by a speedometer and clock. To the left were combined instruments for oil pressure / oil temperature and fuel / oil level.
Although the basic dash architecture was carried over from the previous model, there were some extra warning lights and subtle revisions to the instrumentation (which was now back lit).
As a result of the new heating and ventilation system, climate control switchgear from the 944 was imported and housed in the middle of the dash.
Air-conditioning, electric windows and electric mirrors were standard.
Options
Optional extras included full leather upholstery, a sunroof, airbags, sports seats, heated seats, twelve-way electric seats, body coloured wheel centres and a choice of audio equipment. There was also a Sport suspension upgrade with stiffer dampers and shorter springs that resulted in a 20mm lower ride height.
In addition, Porsche offered practically endless customisation through their Exclusive programme.
Weight / Performance
At 1470kg, this latest 911 Turbo was 135kg heavier than its predecessor.
Top speed was 169mph and 0-62mph took five seconds flat.
USA Version
The US version came with leather upholstery and airbags as standard. Rubber inserts were fitted between the front indicators and auxiliary lights.
1991 Model Year Production
During the 964 Turbo’s first year of production, 2962 examples were produced.
Of these, 674 were to USA specification and the remaining 2288 were dispatched to the rest of world.
1992 Model Year
There were no major changes for the 1992 model year although Porsche did launch a 381bhp Turbo S at the Geneva Motor Show in March 1992. Production examples were built during the 1993 model year.
These cars (covered separately) were effectively turbocharged widebody incarnations of the light weight 964 Carrera RS.
Optional 911 Turbo 3.3 Engine with Increased Output (X33)
Porsche also added a Type M30/69 S engine to the options list for the 1992 model year.
Available via the Exclusive department (Special Option number X33), the uprated engine came with enlarged inlet and exhaust ports, a new inlet manifold, modified camshafts and different valve timing.
The power rating went from 320bhp to 355bhp at an unchanged 5750rpm.
Peak torque was 347lb-ft at 5000rpm compared to 347lb-ft at 4500rpm for the standard engine.
These cars had a top speed of 174mph (up from 169mph) and 0-62mph time of 4.7 seconds (down from five seconds).
1992 Model Year Production
1145 cars were built during the 1992 model year. This figure comprised 309 US variants and 836 delivered to the rest of the world.
The 3.3-litre 964 Turbo was subsequently replaced by a more powerful 3.6-litre iteration for the 1993 model year.
Text copyright: Supercar Nostalgia
Photo copyright: Porsche - https://www.porsche.com
