New cars -- Porsche 968

4-cylinder Evolution

"Evolution not revolution" was the Porsche plan to progress from 944 to 968, but we are not sure that they begun with the right basis for progress versus an increasingly prestigious (Mazda winning Le Mans, Toyota the World Rally Championship) Japanese opposition. Their large (2990cc) 4-cylinder is not the smoothest of units and when asked to yield 80.26 bhp a litre, even the counterbalancer shafts of Lanchester/Mitsubishi ancestry have a job to tame all the resonances and vibrations that emanate.

Porsche feel they have wrapped up the right combination of low weight and emissions versus (considerable) performance, in either 6-speed manual or optional Tiptronic 4-speed form, convertible or coupé body. Our driving impressions, based upon four of the primary choices in the new range, left us wondering if this evolution had left too many loopholes for an increasingly sophisticated and cheaper, opposition to commercially exploit? In other words 240 bhp and 156 mph coupled to 19.1 (Urban) to 39.2 mpg (75 mph) are fine statistics for the cheapest model in a car range, especially when coupled to a 0-60 mph time of some 6.5 seconds. The big "but" is that this entry level model also has the UK statistic of a predicted £40,000 starter price when it arrives in the spring of 1992.

Porsche directors assure you that features such as standard ABS anti-lock braking, twin air bags (LHD only) and 150 mph abilities mean you are "getting one helluva a lot of car for the money." That assertion rings truer in its native Germany, where the initial cost is around £31,000, but with just the RHD steering wheel air bag installed and £9000 on the cost it could ring false. Especially when you can buy a twin turbo Nissan V6 for far less.

"More torque than any other 3-litre, normally aspirated, production car engine," trumpets the company press pack for the 968 successor to the 1981-90 Porsche 944. Such pulling power is owed partially to the VarioCam variable valve timing system to enhance torque between 1500 and 5600 rpm, which is lightweight and is able to use the existing cylinder head casting, albeit with modified water passages and cores. The 3-litre unit of fashionable 16-valve DOHC configuration has "only the oil pump and sump, plus the twin counterbalancer shafts" in common with its 211 bhp predecessors, stated engines engineering chief Paul Henzler.

Porsche VarioCam action comes via central camshaft chain drive, the chain tension modified on electronic instruction (from the omnipotent and reprogrammed Bosch Motronic) to delay drive relay to its slave-driven opposing intake camshaft up to 15 degrees. "Minor overlaps" enhance the torque curve between 1500 and 5600 rpm, when the tensioning saddles are extended. The basic valve timing commands are reinstated and the motor travels on to a bhp peak of 6200 rpm and 240 bhp, just 10 bhp down on the previous turbo model, but of more accessible power.

A peak of 305 N.m (413 lb ft) at 4100 rpm has benefited by up to 40 N.m (plus 13 per cent), but the reality is in having more than 83 per cent (260 N.m) of maximum torque available present between 2000 and 6600 rpm. Porsche say the unit is superior to most sixes and eights of similar capacity in torque delivery and that seemed true on the road.

Why does the engine claimed to have World-beating torque need a six-speed gearbox? Porsche executives will sensibly tell you that you only need a six-speed gearbox primarily for the sheer fun of driving. Porsche believe they have obtained this elusive quality with their weighty but creditably amiable sextet because the Porsche-designed and Getrag-manufactured unit groups five gears closely for maximum acceleration. It then deploys an overdriven top to realise a maximum speed of 156 mph at 6298 rpm, or 2822 rpm at the British 70 mph limit.

A second generation of the Porsche Tiptronic appears, their transformation of the ZF 4HP 18FL 4-speed automatic gearbox into a selection of apparently effortless shifts. The snag is a perceptible drop in acceleration that is reflected in Porsche performance claims. Overall, the company maintain that 80 per cent of the 968 is all new, or "much modified." Porsche senior engineering staff frankly told us that "chassis parts — especially the semi-trailing arm rear axle and MacPherson strut forward suspension — have most in common with the old 944 turbo." This means that the chassis is one of the very best. Porsche naturally put their best equipment on the press launch, installing the optional 17 inch diameter alloy wheels. This package comes complete with massive Michelin MXX3 covers — covering 7. 5J front and 9J rear alloy wheels — and enlarged ventilated disc brakes. That option replaces a production 16 inch diameter, and standard springs (torsion bar at the back, as before), front and rear anti-roll bars, plus the gas damping). An unusual showroom feature is that the sports option also allows adjustment of the ride height via the spring plates.

Harm Lagaay and the Porsche team of designers were told to preserve a family tie with that other front-engine rear-transaxle Porsche (the V8 928). This would be achieved by external cladding, rather than costly changes to the basic steel body in white.

The changes are efficiently wrought, but the rubber surrounds, rather than flush bonded glass, tell you how constrained body development was. A factor emphasised by the moderate aerodynamic drag factor of 0.34Cd. However, on the autobahn, speeds up to a constant 137 mph showed that Porsche had retained enviable stability in this body.

From the legible fascia that the 944 bequeathed, to the ever stiffer sports suspension, the 968 is recognizably a further step along the 944 path. Yet the sheer amount of road grip available would be unrecognisable from the first 160 bhp 944s.

The engine echoes the previous 211 bhp 3-litre that propelled the S2 variant of 944, but it has (unfortunately) become no smoother in such evolution. Engine-related resonances haunt both coupé and Cabriolet bodies, but in the coupé it is the 5000 rpm loudness over that is a strain. The largest four I have driven is best at 4000 rpm, installed in the convertible body and experienced whilst exercising six forward gears vigorously. Porsche expect to produce a minority of Cabriolets (split roughly 40-60%), which continue to have their reinforced bodies built via two time-consuming trips to the German offshoot of the American Sunroof Corporation (ASC). The 968 is a worthy successor to the 944 S2 in its later 211 bhp/3-litre trim, but in the comparison with the 250 bhp Porsche Turbo is not so flattering. I did not find it a driving improvement over the Turbo, and for those that like to work for their fun beyond 5000 rpm there are more rewarding motors. -- JW