Porsche 928 S4/GT/GTS (1987-1995)

BOTTOM LINE: Porsche's renewed commitment to its boxer engine models and abandonment of the 928 left one of its best models in limbo. A late model 928 providing it comes with the right history and a swag of service receipts can deliver a genuine supercar experience for the price of a Falcon XR6.

HISTORY
There were good reasons for Porsche to start developing the 928 in the 1970s when coming safety, emissions and noise regulations threatened the 911's flat-six with its extra noise and variable air-cooling. Replacing the Porsche 911 was never going to be easy and in the end, Porsche had to abandon the idea but that makes the 928 no less worthy.

Spreading the mechanical components throughout the 928 meant there was no single noise source to blast a test microphone in one hit and a water-cooled front engine made it easier to pass crash and emissions tests. A rear-mounted transaxle left the 928 with perfect weight distribution and looked set to give Porsche a break from having to rework the flawed rear-engined 911 platform each time power was increased. The revolutionary Weissach rear axle with its toe control generated unbelievable roadholding limits with benign handling. The 928 seemed the way of the future and in so many ways this proved to be the case. What changed?

The simple answer is that the 928 was too good and not involving enough compared to the 911. There is some merit in this when a 911 feels alive the minute you engage first gear while the 928 can feel quite soulless by comparison until it is working really hard. For Australians, there is more to it than that.

The 928 especially the later S4 and GT/GTS models have capabilities so far beyond the speed limit that few drivers ever get to experience their awesome depth of ability. The 928 in Europe and UK was a serious alternative to a light plane, able to post similar speeds while delivering its pilot door to door. Owners who used a 928 for this purpose were rewarded by their choice as they rolled up huge distances with reasonable reliability, outstanding long distance comfort and all weather capabilities.

In Australia, the 928's price generated huge expectations in a car that didn't look as exotic as its price tag and it was illegal to drive at speeds where it could deliver its best. Later 928 models cost well into the quarter million dollar range, an elite positioning that most Australians still don't recognize.

Even if they were styled by different Porsche designers, the 928's family resemblance to the 924 was a huge drawback especially after much cheaper Japanese models picked up the same design cues. Most of these had a bigger impact in Australia than Europe. The 924 probably did more harm than good to the Porsche name and 928 in Australia. The two are too often dismissed together as non-Porsche models when they couldn't be more different.

The 924 was built to a price, a factor that became painfully obvious as paint and trim deteriorated with indecent rapidity in Australia. It was a parts bin special originally intended for Volkswagen, based on a light truck engine and VW transaxle upgraded with Audi bits before it evolved into the 944.

The Porsche 928 was every millimeter a Porsche and the very best at that. Its integrated urethane bumper fascias and cockpit-style dash and instrument panel layout led the way for virtually every production car today. Lights similar to the Lamborghini Miura gave it an exotic touch as did its perfect, rounded proportions. Yet it still resembled the 924.

Unlike the 924, everything including the 928's all alloy engine was purpose-designed and built by Porsche. Its transmission internals were inside the wheelbase, not behind as in the 924 with its VW-Audi transaxle. Even the transmissions, while drawing on other manufacturers, were specific to the 928. The auto was based on a Mercedes-Benz transmission but few parts are interchangeable. Likewise, the manual first came with Porsche synchros, later models had Borg Warner. The clutch was mounted at the engine end while a torque-tube took care of power delivery to the rear-mounted transmission. The auto was a four speed from 1984.

Australia's switch to low octane unleaded dictated major changes for the 1986 928S which provided the foundation for the S4 and the other models that followed. The single biggest change was a new four valve per cylinder engine which had a 3mm bore increase for a 4957cc capacity, a useful boost over previous 4.5 and 4.7 models. It lost power (down to 212 kW) but the torque peak arrived earlier which made it better to drive locally.

These earlier power figures were well inside HSV's best figures for Holden's pushrod V8 which is why some earlier 928 models have been re-powered with a variety of simpler V8 engines, sacrilege for Porsche purists but understandable.

The exhaust cams of this later 32 valve engine stayed in the same position as the single cam engine with belt drive but the separate inlet cams were moved inboard and driven by an auxiliary centre chain with its own damper and tensioner. Hydraulic lash adjusters were also specified avoiding the manual adjustment of 32 valves but dictating high quality, clean oil. The new engine featured a different unequal length inlet manifold but little else changed when it was a short-lived interim model. Brakes were upgraded with four piston calipers.

From 1986, the 928 went from strength to strength as it gained a second but ultimately terminal lease of life as the S4 with its GT/GTS derivatives. The 928 is known in some quarters as the "land shark" and gatherings are suitably described as "frenzies" but should not be confused with that other more prosaic creature with a similar name, the Austin 1800 "landcrab".

KEY 928 S4 CHANGES

Each MY released at close of previous year depending on stock levels.

MY87: New S4 launched with revised rounded styling at both ends. Power boosted to 221kW. Look for separate rear spoiler which hinged, flush aero panels underneath, radiator cooling flaps, single plate clutch in manual, larger front brake calipers.

MY88: Rear spoiler fixed to body.

MY89: Roof mounted antenna, electric central locking, tyre pressure monitoring, S4 power boosted to 235kW. New GT announced with 242kW with Club Sport wheels, rear wheel spacers standard, limited slip diff, twin exhaust outlets.

MY90: Electrically adjustable headlights, trip meter and dash lighting rheostat moved, standard PSD (Porsche Slip Diff), engine oil cooler mounted under radiator with transmission cooler moved to top. GT gains Design 90 cast rims.

MY91: Leather covered handbrake, rear wheel arch covers, lighter steering from high output power steering pump. S4 withdrawn in August.

MY92: GTS launched with 257kW. Wider rear wheel arches and rear wheel spacers, 7.5 and 9 X 17 inch alloys, full width tail light panel, uprated transmission, larger front brakes.

MY93: Driver airbag and non-CFC R134a air-con.

MY94: Revised auto kickdown, sound system changed from Blaupunkt Symphony to London, particle filter in heating-ventilation system. Model was withdrawn in August 1995.

SPECIFIC 928 S4 CHECKPOINTS

General Warning: All 928 models pack an unbelievable amount of exotic high technology hardware and electronics within a relatively small car and the youngest example is now 10 years old. This can dictate patient and time-consuming dismantling to access even minor problems. To avoid major failure, there are key items that must be monitored and addressed by specialists. It is not uncommon for most Porsche models to be purchased by a second or third owner who does not have the maintenance budget to match today's replacement price then sells it before the repercussions show up. When $10,000 won't look at the catch-up maintenance required on some examples, the final price is more contingent on outstanding maintenance than market forces.

Thus paying over the odds for the right car with the right history may prove far cheaper than bringing a lower priced car up to scratch. Porsche sold less than 300 of the 32 valve S4 models locally and few GT and GTS models sold more than 10 per year with manual versions virtually one-off deliveries. It is conceivable that rarity and the last of series styling of post-1987 examples could generate future interest.

Body
All locally delivered Porsche models are recorded in fine detail right down to trim colour and type. If something doesn't add up, it is worth a call to Porsche Australia. Private imports are not uncommon and can be hiding extra problems.

Check the paint finish and gaps on all panels for consistency. Painted urethane bumper fascias require special paint finish so look for cheap or bodged repairs with crazing or cracks. Make sure that spoiler type and finish is correct for that year. Check for damaged lights especially those mounted in the bumper and gouged alloys.

There are several crash crumple zones that must be replaced if damaged, not pulled back into shape. Check all structural members for clamping and evidence of repair.

All late model Porsches have ID tags and self-adhesive paper bar code stickers spread strategically throughout the body. Get to know what each should look like and if one is missing or changed or tampered with, find out why. Make sure that all specs and numbers match up with year of registration, compliance plate and ID tags. If books are missing, leave no stone unturned in establishing past history.

Check that all instrument panel display functions including clock are operational and all warning lights operate as they should. Check for smooth and speedy operation of power windows and sunroof as these can be problem areas in earlier cars. Airbag sensors can also malfunction. Check that sound system is correct and working and all speakers work. Electric mirrors and switches can fail.

Climate control system depends on complex array of vacuum pods behind dash which can leak with age. Check operation of all controls carefully especially recirculation mode as accessing these can be expensive. Fan switch may not work for every speed so check it.

Central locking including hatch release and courtesy lights can play up. Check that remote locking and interior lights do what they should.

The contoured sides of all Porsche sports seats are vulnerable to being spread by owners who sit across them to enter and exit which will cause a mismatch between the trim and seat contours. The 928 was available with several exotic cloth trim choices, some of which are no longer available as they become very brittle with age. To replace these trim panels may require a complete retrim in leather which will cost thousands. Check that electric seat adjustment works.

Check all leather for sun damage and scratching. Any leather is now old enough to warrant regular applications of conditioner. German plastics are prone to UV damage but most can be reskinned. The labour costs for removing these parts ready for repair are the main concern.

Mongrel owners will sometimes remove air-compressor for special spare wheel so make sure it's there or subtract hefty penalty at which point it might suddenly appear.

Consider a pre-purchase inspection by a Porsche specialist who is familiar with how the car should drive and how it left the factory and can then provide a realistic assessment of what needs spending.

Drivetrain
All alloy engine relied on Nikasil bores which can now be rebored if required but at a cost. Generally the 928 engine is as tough as nails and long-lived providing all its componentry is kept fresh and in new condition. Far better to maintain fresh high quality oil to avoid wear in the first place.

Radiators can leak at the seal between header tank and aluminium core and will only take so many repairs before the aluminium tabs weaken at which point it has to be replaced. Cross-mixing of engine oil, transmission fluid and coolant at various points will generate disasters that can take out several mechanical systems and must be avoided. Make sure all hoses and belts are fresh and supple.

Throttle linkages and cables can bind with wear and age. Make sure that acceleration is smooth and progressive throughout the rev range. Cold start sensors and other electronic glitches can create problems so be suspicious of cars warmed-up ready to drive.

Make sure that maintenance records have covered time requirements as well as distance as overdue coolant and hydraulic fluid changes in the various power steering and brake systems can wreak havoc in the aluminium componentry. Caliper rebuilds with multiple pistons are expensive.

Cam belt changes are required more frequently than most at which point a selection of support components should be addressed including tensioner wheels, oil seals, cam seals. Camshafts can snap at pulley end if lash is not kept in check. Water pump should also be replaced as matter of course at same time.

Engine is now old enough for heat hardened oil seals and gaskets to spring leaks. Check cam covers, sump and other components with seals.

The auto transmission can also vary according to how it has been looked after. Check for jerky shifting or delayed selection from drive to reverse while stationary. Some cars have more driveline vibration than is desirable which can be torque-tube bearings.

Battery needs to be high quality and correct specification to push through the wiring and deliver healthy zap for accessories and engine electronics and fuel system.

Major worry is incorrect tension at the engine driveplate following transmission repair which can destroy engine's main bearings for huge expense.

Suspension and Brakes
Disc rotors are routine replacement items so check for excessive lip and shudder through pedal.

Sophisticated front and rear suspension depends on many bushes and joints that last well but combination of huge tyres and constant low speed steering will take its toll on front ball joints and various steering joints and bushes. Complex rear axle wears well but doesn't like to be hit by kerbs or disturbed in a crash so check rear tyre wear carefully. Be suspicious if tyres are brand new and make sure all tyres meet specified V or Z rating otherwise they may need to be replaced.

Standard dampers are a compromise for ride and handling and can become too soft with age. Many owners prefer an upgrade to Koni or Bilstein.

Check that ABS is working.

Check for underbody damage as chassis competence encourages push-on driving.

Thanks to Porsche specialists Auto Coupe (03) 9431 1663