Saab's 16-valve Turbo: It's all torque!

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At the Frankfurt Show last September a number of manufacturers indicated that they had come to the same conclusions about existing and impending emission controls, by introducing multi-valve cylinder head layouts. Saab was one of them, the Swedish company going a stage further than most in combining a new four-valve head with turbocharging, and including an intercooler and the APC system which controls the boost pressure taking a number of variables into account.

The Turbo 16 is now in production, and will reach Britain late in May priced at £13,490 for the four-door saloon and at £14,490 for the 16S three-door hatchback which also has sideskirts, special alloy wheels and anti-roll bars front and rear. Although BMW and Porsche had led the way with turbocharging as means of extracting more power from a comparatively small power unit, Saab applied some new thinking back in 1978 to use the turbocharger as a means of giving the 99 and 900 models more sparkle in the States, and particularly in California, where emission regulations had starved the 2-litre power units of power. The performance additive was particularly beneficial to the torque curve, and it is interesting to see that the new 16-valve head not only gives the engine another 30 bhp and lifts the turbo version into a high-performance class, but results in a torque curve that, compared with other European cars of comparable performance, is inferior only to the Audi Quattro and the Jaguar XJ6 — but at lower engine speeds.

What Saab now calls its first generation turbo back in 1978 boosted the power output to 145 bhp in European form, with a compression ratio of 7.2:1 and a maximum boost pressure of 0.7 bar. The introduction of the APC system in 1980 allowed Saab to raise the compression ratio to 8.5:1 at the same boost pressure, and though the power and torque figures remained the same the engine became more economical and could run on poorer grades of fuel. An intercooler, which reduces the temperature of the charged air from 120 degrees Centigrade to 60 degrees, in itself tends to increase the power output, and better breathing from the four-valve heads makes its own contribution. The biggest factor, though, is the raising of the compression ratio to 9:1 and the boost pressure to 0.85 bar (ca. 12 pounds), the combination of factors in the third generation engine raising the power by 20 per cent to 175 bhp at 5,300 rpm, and the torque by nearly 16 per cent to 27.8 kgm (201 lb.ft) at a mere 3,000 rpm. The latest power unit can run on lead-free fuel if necessary, but the consumption figures are better than hitherto even though an urban cycle figure of 22.34 mpg is not particularly impressive.

The new cylinder head is cast in one piece rather than the more usual two-piece casting, with chains driving the camshafts. Hydraulic camshaft followers are used, and Saab claim that the previously inherent problems normally associated with multi-valve heads have been eliminated in the 16 model. In order to run on lead-free fuel the valve seats are made of an alloy with a high chromium content which increases the hardness of the material and does away with the need for a lubricating lead additive. A new type of fuel injection system from Bosch, the microprocessor based type LH electronic design which is lighter than the K and L Jetronic systems, and runs at a lower fuel pressure (3 bar rather than 5.2 bar) than the former CI system. Another interesting feature of the Saab 16 power unit is that the Garrett turbocharger has a special by-pass valve designed to route the intake air past the intercooler at low temperatures.

Put to the test

When Eric Carlsson tells you to leave a Saab in high gear and let the torque curve do the work, you tend to obey! The Swedish rally legend had devised a demanding 370 mile route for the rest run, starting at the Dutch importer’s new premises in mid-Holland and running on autoweg and autobahn to Frankfurt, taking in a leisurely lunch near Aachen and some nice, fast German roads in the Eifel region around the Nurburgring. A running average of over 70 mph was required, and any stops to admire the scenery had to be taken out of the lunch stop or the tea break! It is not very surprising that we spent most of our time in Germany flat-out in fifth keeping up with this interesting schedule, or that our overall fuel consumption was 19.5 mpg, though a figure nearer 23 mpg was recorded by journalists who preferred a more relaxed speed. We were able to check the speedometer at maximum speed, 130 mph, finding that it was less than 1 mph fast, and even saw speeds approaching 140 mph on downhill gradients, though we wouldn’t care to pass other traffic at such a velocity.

Even at 90 mph and upwards, the Saab 16 has a slightly higher level of noise than we would have expected; the 16-valve four cylinder engine is sweet enough, but the degree of mechanical noise, combining with wind and road sounds, and noticeable lurching from the engine due to turbocharger lag, made us think that the car is not perfectly refined. Maybe we are being hypercritical, since the Saab is smooth and quiet up to 90 mph, but the route gave priority to very high speed impressions, and would give Saab’s engineers some ideas on how to improve the saloon when a new body shape becomes due.

The 16S version which we drove, having anti-roll bars on the front and rear suspensions, cornered very flatly and with minimal understeer, handling generally being exemplary. The gearchange was not as slick as we’d have liked and the all-wheel ventilated disc brakes felt rough, which may not have been surprising after a three-week exercise, but they weren’t lacking in efficiency.

In the £13,500 to £15,000 saloon car bracket the Saab 16 and 16S are in for some tough competition. So far as sheer performance is concerned, and ease of driving with the high-torque characteristics, the Saab is in a class of its own, as a German Porsche 924 owner would confirm. The level of equipment is good, the quality of build is excellent, and Saab UK’s target of 480 sales in the remainder of this year should be easy enough to achieve. M.L.C.

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