Despite modest reduction in top end power, larger engine develops considerably more torque at lower speeds and shows a spectacular improvement in fuel economy. Use of collapsible spare tyre has allowed a substantial increase in tank capacity, thus further improving the range. Other detail changes render car even more practical and comfortable, but heating system still leaves room for improvement.
By comparison with most manufacturers. Porsche are-not at all influenced by fashion. The appearance of the 911 series has changed very little since the introduction of the 901 prototype (later to become the production 911) some 11 years ago. Most of the visible alterations such as they are, have been dictated by practical engineering considerations. Not that Porsche cars are any the less attractive as a result of this; with their classically elegant lines and superlative finish, they are amongst the most desirable cars on the road today.
Beneath the skin, a great deal has happened. The summer of 1966 saw the introduction of the higher-performance 911S version, with its distinctive light-alloy wheels. Internally-vented discs were adopted in May 1967 (1970 in the case of the 911T). Flared wheel housings accompanied a change to wider rims and fatter tyres a little more than a year later. At the same time (September 1968), the 911S acquired Bosch petrol-injection equipment instead of its former triple-choke carburettors. Also, an intermediate model (the 911E, with injection equipment) was added to the range.
For 1970, an increase in bore diameter upped the displacement from 2.0 to 2.2 litres. A year later, the engines were enlarged yet again – this time to 2.4 litres. This second stretch was achieved by lengthening the stroke, and . was accompanied by changes which allowed the units to operate on low-lead fuel. On the transmission side, there was a new strengthened gearbox derived from that of the racing 915.
The foregoing provides only the barest outline of 911-series history up to the autumn of 1973. At this time came the most significant development to date – the introduction of the current 2.7-litre models. Engines of this size (basically larger-bore versions of the 2.4-litre units) already were being built for the limited-production 911 Carrera RS series. However, the new 911 and 911S power plants (the 911E version now having been dropped) have been developed more for flexibility and economy than for all-out performance. Unlike Carrera engines, whose radical valve timings dictate the continued use of timed mechanical injection, both the newcomers feature Bosch K-Jetronic continuous-flow equipment.
In the case of the 911S, peak power is down in comparison with that of its 2.4-litre counterpart (now 175 bhp DIN at 5,800 rpm, compared with the former model’s 190 bhp DIN at 6,500 rpm). This was very much a deliberate move, being an inevitable side-effect of the measures taken to improve economy and mid-range performance. From the latter viewpoint, an indication of the effectiveness of the changes is provided by the substantial increase in maximum torque (now 174 lb. ft. at 4,000 rpm, whereas the smaller unit developed a peak of 159 lb. ft. at 5,200 rpm). Even more revealing is the current unit’s ability to develop more torque throughout the 3,250-5,500 rev- band than did its predecessor at the very peak of its curve.
Of equal importance to long-distance drivers is the model’s substantially increased fuel capacity (now 17.6 gal, instead of 13.6 gal). This has been achieved without sacrifice of luggage space, simply by adopting a special B. F. Goodrich SpaceSaver collapsible tyre for the spare wheel (a move which provides room for the bigger tank).
In view of the fact that the spare wheel is carried in the fully deflated condition, Porsche supply an electrically driven compressor for inflation purposes. Of Canadian manufacture (Webster), this is rated at 108 watts and is plugged into the car’s cigarette lighter socket.
Although the SpaceSaver tyre is safe for continuous speeds of up to 100 mph, it is not intended for regular use. For this reason, the rim itself is of the pressed-steel variety. When restowing is necessary, simply deflating the tyre causes it to revert to its original, compact form.
Also larger is the oil tank. Still to the right of the engine, concealed within the side of the body, this now holds 19.4 pints (formerly 17.6 pints). The extra volume, together with associated changes to the vessel’s shape, provide greater protection against oil-surge problems. To put this into perspective, it must be added that earlier models ran into trouble only if the oil level was allowed to become exceptionally low.
Porsche are famed for their attention to detail. Typical of this is the change which has been made to the screen-washing system. The excellent four-jet arrangement is the same as before, but the reservoir’s capacity has been quadrupled to almost two gallons. This has more than compensated for the availability of headlamp wash/wipe equipment as an extra cost option, and for the model’s greatly improved cruising range.
Inside, there are new front seats with integral head restraints. Also new arc factory-fitted seat belts, with neatly concealed inertia reels. Sensibly, belts are no longer regarded as an extra.
Whilst retaining the stalk switching, system for the three- speed wipers, 2.7-litre cars have the benefit of a variable pause facility. This is controlled by a separate, facia-mounted switch. Also new arc side-window demisting vents at the facia’s extremities.
From the back, the badges and the massive “5 mph” bumper indicate the current 2.7-litre Porsche 911S. Note the simple, single exhaust pipe used in preference to some more decorative arrangement.
Performance and economy
Checked in an 8 mph cross- wind on a level stretch of autobahn, the Porsche reached a speed of 142 mph in both directions. Although this possibly is down on what might have been achieved by the 911S 2.4 (not tested by Auto-car), it is commensurate with the model’s 10 bhp advantage over the 139 mph 911E 2.4 tested some two and a half years ago (Autocar, 25 November 1971).
|True a speed MPH||Time in sec||Car Speedo MPH|
|Standing 1/4-mile||15.0 sec 93mph|
|Standing kilometre||27.4 sec 117mph|
|Mileage recorder:||0.7 per cent over-reading|
Again typifying the care Porsche take over their cars, the gearing on the upper two ratios has been changed in accordance with the engine’s lower peak revs (5,800 rpm, with the tachometer red-lined at 6,300 rpm). Even so. the test model reached a little over 6,200 rpm when flat-out in fifth. Under these conditions, the large tachometer indicated 6.300 rpm – a pleasing standard of accuracy for an instrument of this kind. The speedometer, too is acceptably true; it over- reads by just 2 mph over most of the speed, but exaggerates to the tune of 4 mph at the very top end.
More important than a car’s maximum is its ability to cruise at high speeds. In the Porsche’s case, the rate of progress is largely what the driver cares to make it; at no time is there any feeling of stress. In Germany, indicated speeds of around 120 mph were held for long periods without the oil temperature ever exceeding 200 deg. F. At the conclusion of the run, oil pressure still was a healthy 60 psi at 4,000 rpm.
The 911S is equally at home on give-and-take roads. Few cars can match the electrifying step-off which enables it return a 0-30 mph time of only 2.2 sec. Several factors are involved here. First, there is the model’s excellent power – to – weight ratio. A further contribution is made by the relatively low gearing in first; last, but by no means least, there is the excellent traction which results from having nearly 60 per cent of the total weight over the rear wheels. The latter meant that we were quite unable to provoke wheel-spin when conducting acceleration checks on MIRA’s high-mu surfaces. Any attempts to do so resulted in appreciable clutch fade. This is in no way a reflection on the clutch itself – a view confirmed by the consummate ease with which restarts could be executed on the 1-in-3 test hill.
Despite the need for two gearchanges (into second at 33 mph and third at 57 mph), 60 mph comes up in an astonishingly short 6.1 sec. Changing again at 83 mph, the quarter-mile is reached in 15.0 sec. at which point the speed is 93 mph. The “ton” comes up just 2.5 sec later, with 0-120 mph occupying a total of just over half a minute (30.4 sec).
|MAXIMUM SPEEDS AT TEST|
This far, we have considered only flat-out performance. Of more practical value is the model’s behaviour when driven relatively gently. This, in fact, is where the latest changes show up to best advantage. It is entirely feasible to allow the engine to pull at speeds as low as 1,500 rpm, even in the higher gears. There never is any display of temperament under these conditions, but one can detect a greater sense of eagerness as the tachometer climbs towards the 3,000 rpm mark. At 3,500 rpm, things are happening in earnest; around this speed, the engine’s note hardens appreciably and the car begins really to fly. Interestingly enough, this seems to coincide with a noticeable kink in Porsche’s published torque curve for this model.
The bumper, rubber-faced, again tends to dominate the front view. It is attached to the chassis by tubular members which deform progressively in a collision. The beard-type spoiler beneath it has been added to improve high-speed stability, but also reduces drag and so increases the maximum speed
Driving impressions are all very well, but what of the actual acceleration times? The 911S has nothing to fear on this score. Even in fifth gear, only above 90 mph do those for each 20 mph speed increment exceed 10 sec. By way of contrast, the lower-geared 911E 2.4 exceeded this value both at the lower end of the speed range (up to 50 mph) and above the 70 mph mark. In third gear (identical ratios on both models), the improvement is even more marked, 10-30 mph times being 4.4 and 7.3 sec for 911S 2.7 and the 911E 2.4 models respectively. This is especially significant when it is remembered that the “S” version of the 2.4-litre range would have been even less flexible than the “E”.
From an economy viewpoint, the car’s achievements arc little short of miraculous. In our report on the 911E 2.4, we were mildly critical of the overall economy figure of 15.6 mpg. This was tempered by an observation that 20 mpg might just be possible if the model were driven with considerable restraint. In sharp contrast, this considerably more potent descendant returned an overall of 23.2 mpg when being driven with great verve almost the whole of the time. Particularly revealing is the fact that 24.8 mpg was achieved over a 236-mile continental journey during the course of which a deliberate effort was made to maintain a true 100 mph.
Adding to the model’s appeal is the fact that it calls for only regular-grade (91 RM) fuel. Looked at from a cost-per-mile angle, this makes its 23.2 mpg overall figure equivalent to 24.5 mpg from a car which requires top-grade fuel.
Thanks to improved economy and a larger tank, the range now is well in excess of 350 miles. Those who wish to take advantage of this need have no fears concerning the lubrication side, for the engine’s consumption of Shell Rotella 30 is a modest pint per 500 miles. Reassurance is provided by facia-mounted gauges which monitor the oil’s temperature, pressure and level. Interpretation of level indications calls for a modicum of intelligence, for the instrument is designed to read correctly only when the oil is hot (140-175 deg. F.) and the engine is idling (900-1,000 rpm). Full-scale deflection is equivalent to a level difference of around three pints – an arrangement which provides for considerable peace of mind.
As is customary Porsche practice, the oil level gauge issupplemented by a dip-stick which lives within the tank’s filler neck. Again, this is meant to be used only when the oil is warm and the engine is idling. Here, however, the 3-in. span between the upper and lower marks is equivalent to 2.5 litres (a little under 4.5 pints).
The petrol filler cap lives beneath a hinged flap on the left-hand front wing. Alongside it is the filler for the screen-wash reservoir. Topping up with petrol is both quick and easy; a nice touch is the provision of a small plastic “apron” to safeguard against damage to paint.
Topping up with oil is a trifle more difficult, for the angled filler neck (located on the right-hand side of the engine bay) is not altogether compatible with the larger sizes of tear-top can (quart size). The external fuel cap arrangement used on 2.4-litre models may have had an edge on this score.
Before leaving the subject of performance, it is as well to look at how the 911S compares with equivalent models of rival makes. Looking at the comparison table (see data pages), it will be noted that its maximum speed of 142 mph is bettered only by the Jaguar E-Type – a car having a V12-cylinder engine of almost twice the displacement. Even then, the difference amounts to only 1 mph.
Through-the-gears acceleration times reveal much the same situation. The 911S and the E-Type are pretty evenly matched, the German car having the edge up to 60 mph, but the Jaguar being the faster over the standing quarter-mile and up to 100 mph. Next in line comes the BMW, followed by the Montreal and (some way behind) the 350SL R107.
Despite this latest model’s much improved flexibility its high gearing in top results in acceleration times which exceed those of its rivals. Indeed, the Jaguar’s times in top are better than those of the Porsche in fourth.
Offsetting any possible in-convenience occasioned by the need to change gear more frequently, the Porsche’s fuel economy is almost in a class of its own. Its nearest rival is the BMW 3.0 CSi E9, whose 20-7 mpg is 2.2 mpg down. At considerably more of a disadvantage are the Alfa Romeo, the Mercedes and the Jaguar, all three of which returned between 14 and 15 mpg.
Engine and transmission
The foregoing already will have provided a fair indication of the car’s character, but certain aspects call for further comment. Starting, for example, is quick and certain; however, the British concessionaires recommend that a set drill be followed at all times. All it involves is the use of the hand throttle, irrespective of whether the engine is hot or cold. The aim is to eliminate risk of backfire through the intake tracts – an occurrence which can dislodge the rubber hose which connects the injection system’s throttle-valve body with the sensor-plate housing. Should this happen, the engine may well refuse to start. In any event, it will run very badly.
The Bosch K-Jetronic injection system incorporates an electromagnetic enrichment valve to aid cold starting. This is arranged to feed additional fuel at a point just downstream of the throttle plate, and is controlled by the hand throttle. Supplementing it is a warm-up regulation system which monitors the temperature of number-two intake tract and regulates the mixture strength accordingly. Despite this apparent complication, the equipment works well enough in practice. The engine pulls strongly from cold, even with the hand throttle closed. Initially, however, there are signs of over-richness. Moreover, the engine needs to be thoroughly warm before it will idle reliably with the throttle closed.
Clutch pedal effort (40lb) is quite acceptable; so is the pedal’s total travel of 6.0in. Moreover, the release mechanism has a pleasantly light feel, and the clutch itself takes up the drive smoothly. On the debit side, it is necessary to fully depress the pedal in order to avoid a trace of drag.
The gearchange is light and quick, although the mechanism lacks the absolute precision of some of the better direct- control ones. As on the 2-4-litrc models (but not earlier cars), the lower four ratios are arranged in conventional H-pattern, with fifth and reverse in a slot to the right. Oddly, the lever moves freely across the left-hand half of the gate, but is spring-loaded away from fifth and reverse.
From the outside, a briskly driven 911S sounds pretty noisy. Whether the noise itself is objectionable or not is a matter for conjecture; some regard it as hard and raucous, whereas others revel in the sense of crisp efficiency which it conveys.
Inside, the car is very much quieter – this despite the growl from the engine and the considerable (but not excessive) amount of wind noise at three- figure speeds. In fact, one is more aware of extraneous noises when the car is being driven comparatively gently. Below 50 mph in top, there is noticeable transmission whine; this possibly emanates from the spiral-bevel (as distinct from hypoid) final-reduction gears.
As always, Porsche instruments are large and clear with the rev counter treated as most important of all. Red lure at 6000 rpm is backed up by ignition cut-out at 6,400.
Much worse is the pronounced heterodyne boom I which occurs around 3,000 rpm in fourth; this peaks at a road speed of 55 mph. Yet another grouse concerns the mild gear rattle (clutch thrash) which results from making the engine pull at very low speeds. By-and-large, however, these situations are untypical of Porsche motoring, and sympathetic drivers are unlikely to think that there is much amiss.
Ride, handling and brakes
Although firm at speeds below around 30 mph, the Porsche’s ride compares very favourably with that of rival GT cars – even those which weigh 50 per cent more when unladen. Adding to the feeling of well-being is a good standard of road noise insulation. There is some bump-thumping, of course, but this is confined largely to the lower end of the speed range. There is also a trace of the front-end bounce which afflicts some of the rear-engine designs, but this is scarcely enough to be noticeable.
The redesigned front scats make a useful contribution to passenger comfort. Soft and accommodating, they are shaped to hold one in place without causing obstruction when getting in and out. Some inconvenience results from the integral head restraints but, in the main, they are an improvement over the previous pattern.
No changes have been made to the individual scats at the rear, which retain the same vestigial cushions and back-rests. The latter can be lowered individually to serve as load-carrying platforms. In this position they provide an incidental bonus in the form of concealed stowage for odds and ends in the cushion wells.
The new, built-in spoiler at the front appears to do a pretty good job. There still is some sensitivity to gusty cross-winds, but the car’s behaviour at maximum speed inspires absolute confidence.
So well balanced is the feel of the car that there is little indication that the engine is at the rear. When cornering under power on dry roads one can feel a modicum of understeer at normal speeds. If the car is really pushed, this understeer assumes considerable proportions; however, lifting-off results in a fairly abrupt (but by no means vicious) change to a more nose-in attitude.
Despite the model’s excellent traction, there is sufficient power to spin the wheels quite furiously on wet surfaces. The car is unusually controllable in such circumstances – chiefly because of its superb steering. Geared to give quick response without any hint of hyper-sensitivity, the mechanism conveys an impression of being extraordinarily efficient mechanically. This results in the driver’s being able to sense precisely what is happening at the road surface. Inevitably, this leads to some degree of kickback on rough surfaces, but this is not in any way objectionable.
The one aspect of the model’s handling which causes concern is its behaviour on water-logged roads. In torrential rain on Belgian motor-ways it surprised us a number of times by aquaplaning its front end at comparatively low speeds.
Because of the absence of a servo, brake pedal efforts are comparatively high. Even so, the system inspired every confidence, being well able to cope with the high speed of the car.
Living with the Porsche
As a long-distance car for two people it is an excellent proposition. With the rear scats folded there is ample luggage carrying space for most people’s needs.
Wet-road handling is generally well-balanced, but the test car suffered from front-end aquaplaning when there was standing water on the surf /toll angle is large enough to be noticeable
Engine accessibility is never a strong point with rear-engined designs. In the Porsche, it is made more difficult by the cooling fan and the massive induction system. Oil filler is awkwardly placed at top right.
New front seats are very comfortable and afford excellent sideways support General standard of interior finish is very high: there are lidded pockets In the doors, and pop-up locks are easily reached
Goodrich SpaceSaver spare tyre permits larger fuel tank without encroaching on limited luggage space. Electrically-driven inflator serves to blow it up if needed: excellent tool kit is provided.
When additional passengers have to be carried the situation is a little less rosy. Often the driver will have to settle for a compromise seating position in order to make room for legs and feet behind him. Equally inconvenient is the fact that the crew will be totally dependent on the front-mounted boot for carrying luggage. In fairness, the latter is more spacious than its shallow appearance suggests. Nevertheless, it would be wrong to regard the Porsche as anything but a 2+2.
The car’s only real fault is the erratic behaviour of its heating system. This stems from the fact that the engine’s own fan is employed to feed heated air into the passenger compartment. This means that the flow-rate fluctuates markedly with changes of engine speed. In contrast, the flow of ambient air into the car is boosted by means of a commendably quiet electric fan (with three speed settings) – an arrangement which makes for substantially constant flow. The net result is that the temperature of the blended air within the car is inordinately dependent on traffic conditions. If Porsche were to rectify this shortcoming, possibly by using an Electric fan for the heated air, we would then be hard put to criticize the model in any significant way.
Conclusions it is true the 911S does not necessarily set the standard under any particular heading. Nevertheless, it is so good in so many ways that many well-informed people regard it as the most thoroughly engineered car available today. Viewed in this light, its considerable price of almost £7,000 must be regarded as totally realistic
|Car||1974 Porsche 911 2.7|
|Car type||Rear engine, rear-wheel drive|
|Cylinders||6 horizontally opposed|
|Main bearings||7, plus 1 outrigger|
|Cooling system||Ducted air, with 11-bladed fan|
|Bore / Stroke||90.00mm (3.54in.) 70.40mm (2.77in.)|
|Displacement||2.687 c.c. (163.97 cu. in.)|
|Valve gear||Single overhead camshaft per bank, finger tappets, chain-driven|
|Compression ratio||8.5-to-1. Min. octane raring: 91RM|
|Induction||Bosch K-Jetronic continuous flow Injection|
|Fuel pump||Bosch electric. roller type|
|Oil filter||Full-flow. disposable canister|
|Max. power||175 bhp (DIN) at 5.600 rpm|
|Max. torque||174 lb. ft (DIN) at 4.000 rpm|
|Clutch||Single dry plate. 8.9in. dia|
|Gearbox||5-speed, all-indirect, all-synchromesh|
|Geer ratios||Top 0.724|
|Final drive||Spiral bevel. 4.429-to-1|
|Mph at 1,000 rpm in top gear||22.9|
|CHASSIS AND BODY|
|Construction||Integral, with steel body|
|Cd drag coefficient||0.39|
|Front||Independent; MacPherson struts (Koni), Longitudinal torsion bars, anti-roll bar|
|Rear||Independent: splayed trailing arms, transverse torsion bars, anti-roll bar, telescopic dampers (Koni)|
|Make and type||ATE/Dunlop ventilated discs front and rear. Dual hydraulic systems. Mechanical, drum-typo parking brakes in naves of rear discs|
|Dimensions||F, 11.1 in. dia|
|R. 11.4in. dia|
|Swept area||F. 235 sq. in.. R. 208 sq. in. Total 443 sq. in. (350 sq. In./ton Laden)|
|Type||Porsche forged light alloy, 5-stud fixing. 6in. wide rim|
|Tyres make||Dunlop SP Sport Super (German-made)|
|type||Radial ply tubed|
|Battery||12 volt 66 Ah.|
|Headlamps||Bosch halogen. 120/110 watt (total)|
|Screen wipers||3 speed, plus variable pause|
|Screen washer||Standard, electric|
|Heated backlight||Standard, dual-stage|
|Safety belts||Standard. Repa inertia reel|
|Interior trim||Cloth scats, pvc headlining|
|Floor covering||Cut-pile nylon carpet|
|Jack||Geared screw pillar|
|Jacking points||1 each side under sills|
|Underbody protection||Underbody galvanized and pvc coated|
|Fuel tank||17.6 Imp, gallons (80 litres)|
|Oil tank||19.2 pints (11 litres) SAE 30 Change oil every 12.000 miles Change filter every 12.000 miles|
|Gearbox and final drive||5.25 pints. SAE 90EP. Change every 12.000 miles|
|Valve clearance||Inlet 0.004in. (cold) Exhaust 0.004in. (cold)|
|Contact breaker||0.014in. gap; 35.41 deg. dwell|
|Ignition timing||5 deg. ATDC (stroboscopic at 900 rpm)|
|Spark plug||Type: Bosch W225T30. Gap 0.028in.|
|Compression pressure||130-160 psi|
|Tyro pressures||F. 29; R, 34 psi (all conditions)|
|Max. payload||716lb (325kg)|