Guide: the Land Shark Gets More Bite - a Historical & Technical Appraisal of the Porsche 928 S

Mar 18

Mar 18 Guide: the Land Shark Gets More Bite - a Historical & Technical Appraisal of the Porsche 928 S

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BACKGROUND

With the rear-engined 911 not anticipated to survive for more than another decade, 1971 saw Porsche begin work on an upmarket front-engined Grand Tourer that could better adopt to ever-changing safety and emissions legislation.

As a consequence of its more conventional layout, the resultant 928 was also expected to have broader market appeal than the somewhat quirky and occasionally difficult to handle 911.

Following its introduction at the Frankfurt Motor Show in September 1977, the 928 went on to be voted 1978 European Car of the Year – the first time this prestigious accolade had been bestowed upon a sports-type machine.

During its first year of production, Porsche managed to shift a little under 4000 examples of the 928 (3830 to be precise). However, despite having been a superior proposition to its ageing rivals from Ferrari, Mercedes-Benz, BMW, Jaguar, Aston Martin and Maserati, there was a feeling that, with its conservatively tuned low compression engine, the 928 was yet to reach its true potential.

Accordingly, just two years after the 928 broke cover, a further enhanced variant was added to the range for the 1980 model year: the 928 S.

Unveiled at the Frankfurt Motor Show in September 1979, the 928 S was priced at around 15% more than a regular 928 (but still 10% less than a 911 Turbo). For that not inconsiderable premium, customers received a car most notably equipped with an enlarged and 25% more powerful engine plus new forged alloy wheels and a downforce-inducing spoiler pack.

Unfortunately though, as a consequence of its more polluting engine, the 928 S was not initially offered for sale in North America. Instead, customers from this region had to make do with a regular 928 dressed up to resemble an S model.

ENGINE / TRANSMISSION

The Type M28 engine fitted to the 928 was Porsche’s first production V8 and, in its original 4.5-litre state with low 8.5:1 compression ratio, offered great potential for future displacement and horsepower gains.

An all-alloy water-cooled motor with single overhead camshafts, two valves per cylinder, wet-sump lubrication and Bosch K-Jetronic fuel-injection, the original M28 engine displaced 4474cc thanks to a bore and stroke of 95mm and 78.9mm respectively.

For the 1980 model year, compression was increased from 8.5:1 to 10.0:1 which, although did not affect the horsepower rating of 240bhp at 5500rpm, did lead to a substantial torque gain: 279lb-ft on tap as opposed to 257lb-ft at an unchanged 3600rpm.

For the 928 S, Porsche enlarged the M28’s cylinder bores by 2mm (from 95mm to 97mm) while stroke remained unchanged (at 78.9mm). This resulted in a gain of 190cc taking overall displacement from 4474cc to 4664cc.

Arguably even smoother than the original on account of its revised camshaft profiles, the S engine had to run on four-star fuel whereas the original 4.5 could tolerate inferior two-star petrol.

Type numbers were M28/11 for manual transmission examples and M28/12 for automatics.

Power output of the 928 S leapt from 240bhp at 5500rpm to 300bhp at 5900rpm.

There was also a moderate torque gain, albeit higher up the rev range than before, with 283lb-ft now on tap at 4500rpm compared to 279lb-ft at 3600rpm for the standard 1980 model year 928.

Examples of the 928 S destined for the Japanese market developed 270bhp at 5750rpm with an identical torque rating to Rest of World iterations.

The standard gearbox offering on the 928 S was a five-speed manual, but more popular with customers was an optional three-speed automatic.

For optimised weight distribution, Porsche had designed the 928 with a transaxle arrangement that combined the gearbox, axle and differential as part of an integrated unit.

CHASSIS

Like every 928, the S was built on a hot-dip galvanised steel bodyshell with a 2500mm wheelbase. An 86-litre fuel tank was fitted under the trunk floor.

Front suspension was via a multi-link MacPherson strut arrangement while at the back Porsche fitted their famed Weissach multi-link set up. An evolution of the semi-trailing arm configuration, the Weissach axle replaced the front pivot bushing of a trailing arm layout with a short link that allowed the suspension to adjust itself during cornering. The result was a dramatic reduction in lift-off oversteer and much improved stability.

Coil sprung shock absorbers were fitted at each corner along with an anti-roll bar at either end.

Ventilated brake discs had a diameter of 282mm at the front and 289mm at the rear. Like other Euro market 928s for the 1980 model year, stopping capacity was improved thanks to thicker discs with redesigned calipers and larger pads.

Unique to the 928 S were new forged alloy disc wheels instead of the cast alloy Teledial rims found on the regular variant. They measured 16 x 7-inches all round and were originally shod with Pirelli P7 225/50 VR 16 tyres.

Power steering was again fitted as standard.

BODYWORK

Externally, in addition to that handsome new set of forged alloy wheels, the 928 S most obviously differed from its less powerful sibling by way of an aero kit designed to increase high speed stability.

At the front, the nosecone was modified to incorporate a pair of brake cooling ducts and a satin black plastic chin spoiler that wrapped around to the leading edge of the front wheelarch.

Down each flank, the body coloured rubbing strips that were optional on the entry level 928 were fitted as standard. Like the regular 1980 model year 928, side-mounted indicators were added to the front fenders.

Located to the rear of the 928 S was a distinctive new polyurethane lip spoiler. A 928 S script was also added under the Porsche text embossed into the tail fascia.

As a consequence of these aerodynamic improvements, the 928’s crag coefficient dropped from 0.41 to 0.38.

As normal, the 928 S featured a hood, doors and front fenders fashioned from aluminium in the interests of optimal weight distribution. The bumpers were made from deformable body coloured polyurethane elastic while pretty much everything else was steel.

INTERIOR

Inside, Porsche also added some additional equipment to their new front-engined flagship that was not found on the 4.5-litre version.

Most noticeably, the 928 S was the first model to come with the Stuttgart company’s four horizontally spoked steering wheel which replaced the three-spoke item used previously. Uniquely, this was embossed with a 928 S script on the horizontal horn pad.

There was also a thermostatically controlled heating and air-conditioning system with the latter now fitted as standard. Three-way electric seats were also installed as standard along with a cassette holder under the centre armrest and (in most markets) heated and electric exterior mirrors.

The rest of the switchgear (ventilation controls, radio etc.) were located on the central console that adjoined the slim forward section of the transmission tunnel. This widened dramatically towards the back of the car and meant the rear seats were no more spacious than those in the 911.

OPTIONS

In addition to Porsche’s cast alloy Teledial wheels, 928 customers could enhance their car with the aforementioned automatic transmission, a 40% locking limited-slip differential, sports seats, leather upholstery, two-tone leather upholstery, contrast seat piping, fabric seat and door inserts, Bilstein dampers, an electric sunroof and tinted glass.

WEIGHT / PERFORMANCE

Porsche quoted the 928 S at an unchanged 1450kg regardless of which transmission was selected.

Top speed went from 143mph to 155mph in the case of the manual version and from 140mph to 152mph in the case of the automatic.

0-62mph times dropped from 6.8 to 6.4 seconds and from 8 seconds to 7.1 seconds respectively.

1980 MODEL YEAR

During the course of the 1980 model year, the gearbox fitted to all manual 928s was modified with a shorter torque tube and different rear subframe.

Porsche constructed 1456 examples of the 928 S in its first twelve months of production (all to Rest of World specification).

1981 MODEL YEAR

No major changes were made to the 928 S for the 1981 model year. Production dipped from 1456 units to 1409 (1408 Rest of World and 1 Japan).

1982 MODEL YEAR

For the 1982 model year, Porsche added a vibration damper to the torque tube bearing between second and third gears on manual transmission cars and behind second gear on automatic variants. The manual version also now came with a reverse gear lock out.

928 S production figures rose slightly on the previous year with 1452 examples built (all of which were to Rest of World trim).

928 S JUBILEE SPECIAL EDITION

To mark Porsche’s 50th anniversary as a company, Jubilee special editions of the 928 S, 911 SC and 924 were offered in Rest of World markets in late 1981 (during the 1982 model year).

Each Jubilee 928 S came with Meteor Metallic paint, full Burgundy (Weinrot) leather, Burgundy velour seat and door inserts with Silver pinstripes, Burgundy carpet, front headrests emblazoned with Ferry Porsche’s signature and Green tinted windows. Automatic transmission was offered as a no-cost option.

140 Jubilee edition cars were built.

1983 MODEL YEAR

For the 1983 model year, new hydraulic motor mounts replaced the original engine shocks.

Additionally, production of the original 4.5-litre 928 was discontinued as the S was finally made available in the US market.

In order to comply with local emissions legislation, 928 S engines fitted to cars bound for the United States came with additional smog equipment, Bosch LH-Jetronic fuel-injection (instead of K-Jetronic), a lower compression ratio (9.3:1 instead of 10.0:1), softer camshaft profiles, smaller valves and smaller diameter intake manifolds.

As a consequence of these changes, the horsepower rating dropped from 300bhp at 5900rpm to 243bhp at 5500rpm.

The torque rating was 263lb-ft at 4000rpm as opposed to 283lb-ft at 4500rpm for the Rest of World derivative.

Uniquely, the US 928 S was available with a four instead of three-speed automatic transmission which required some modification to the bodyshell and torque tube in order to accommodate the slightly longer gearbox.

These US spec. engines were given new type numbers: M28/19 for the five-speed manual and M28/20 for the four-speed auto.

Compared to the 1450kg Rest of World derivative, the weight of US spec. derivatives rose to 1520kg (manual) and 1535kg (auto).

With the 928 S now offered in the USA, production figures jumped from 1452 during the 1982 model year to 5296 for the 1983 model year. This figure comprised 1912 Rest of World examples, 2086 for the US and 2 for Japan.

1984 MODEL YEAR

A significant change for the 1984 model year concerned Rest of World derivatives which now got the same four-speed automatic gearbox introduced a year earlier on US variants to replace the old three-speed unit.

In addition, the Rest of World 928 S got the latest Bosch LH Jetronic fuel-injection and digital Bosch EZF ignition with twin distributors that enabled the compression ratio to be increased from 10.0:1 to 10.4:1.

These changes led to a modest horsepower gain (from 300bhp to 310bhp at an unchanged 5900rpm), but more significant was the additional torque on offer: 295lb-ft at 4100rpm as opposed to 283lb-ft at 4500rpm. Fuel consumption was also significantly improved.

Engine type numbers were switched to M28/21 (manual) and M28/22 (auto).

Both versions tipped the scales at 1500kg which represented a 50kg gain.

Top speeds were unchanged (155mph and 152mph respectively), but the 0-62mph times dropped from 6.4 to 6.2 seconds (manual) and from 7.1 to 6.7 seconds (auto).

Across-the-board changes to the 928 S for the 1984 model year included revised front suspension lower ball joints, heated windscreen washer nozzles, a central locking override button on the centre console and an electric tailgate with driver and passenger-side release buttons.

There were also a couple of new optional extras: a Bosch Anti-lock Brake System (ABS) and low compression engines (9.3:1) for certain markets such as Switzerland, Sweden and Australia.

In markets like the UK and Australia, the 1984 model year 928 S was dubbed the 928 S2.

Production dipped slightly from the previous year’s high of 5296 units to 5095. Of these, 2028 were Rest of World variants, 2219 were US spec. and 100 headed to Japan.

1985 MODEL YEAR

Undoubtedly the most significant change for the 1985 model year was the arrival of a five-litre dual overhead cam 32 valve engine for the US market.

Replacing the 4.7-litre single overhead cam 16 valve engine of old, these Type M28/43 (manual) and M28/44 (automatic) motors were enlarged to 4957cc which represented a gain of 293cc. This was achieved by enlarging the cylinder bores from 97mm to 100mm. Stroke remained unchanged at 78.9mm.

In addition to twin cam heads with four valves per cylinder, the enlarged engine featured spark plugs located above new pent-roof combustion chambers, uprated manifolds, modified valve timing and a 10.0:1 compression ratio.

The horsepower rating went from 243bhp at 5500rpm to 288bhp at 5750rpm.

There was also substantially more torque on offer much lower down the rev range: 302lb-ft at 2700rpm compared to 263lb-ft at 4000rpm for the old 4.7 motor.

Both manual and automatic versions were officially quoted at 1520kg.

As a consequence of its substantially modified engine, these US spec. iterations were unofficially dubbed the 928 S3.

Universal changes to the 928 S for the 1985 model year included a radio antenna integrated within the windshield (as opposed the mounted on the back of the eleft-hand rear fender) and new high-backed four-way electric seats of a similar design to those introduced on the 911 Carrera and 930.

Rest of World derivatives now came with ABS as standard.

Production figures were down again on the previous year with 4487 cars built. This figured comprised 2168 in Rest of World spec., 2219 in US spec. and 100 for Japan.

1986 MODEL YEAR

For the 1986 model year, a lower 9.3:1 compression version of the 32-valve DOHC engine complete with a modified exhaust system and catalytic converter became an option in some Rest of World markets.

Mid-way through production, US-spec. examples of the 928 S were further enhanced with the suspension and four-piston brake calipers that would be added to the 1987 model year 928 S4. Such examples are sometimes referred to as 1986.5 variants.

4881 examples of the 928 S were built during its final year in production.

Of these, 1911 were to Rest of World specification, 83 went to Japan and 2887 were to US trim (an initial batch of 877 cars followed by an additional 2010 that were 1986.5 variants).