Opel’s First „Inline Triple“ Engine Debuted 25 Years Ago in MAXX

• Future urban vehicle: MAXX convertible, pick-up, off-roader et al all on same platform
• European first: Opel developed MAXX’s three-cylinder engine to production readiness
• Semi-exposed cage: MAXX featured aluminium sections instead of steel panels
• State-of-the-art sequel: new inline triple turbo powers today’s bestselling Opel Astra

Rising consumer demand for low fuel consumption and increasingly strict regulations for CO₂ emissions have made high-efficiency three-cylinder engines a popular choice. Opel offers such power units throughout its passenger car range, with petrol or diesel fuel. The new Astra with its state-of-the-art inline triple turbos is even CO₂ champion in its class.

“The new Astra is the most efficient ever, with up to 21 per cent lower CO₂ emissions”, said Opel CEO, Michael Lohscheller. “Five of its seven powertrains are under the magic 100g-mark for CO₂ per kilometre in the NEDC cycle. With its new-generation engines and transmissions, the Opel Astra sets standards when it comes to low emissions.” Opel looks back on 25 years of three-cylinder engine development. The premiere was in 1995 at the Geneva Motor Show, in the Opel MAXX.

Twenty-five years ago, three-cylinder power units – even naturally aspirated ones – were still quite rare, despite their inherent advantages over four-cylinder engines, such as higher efficiency, lower weight and lower frictional losses. The status quo began to change dramatically at the Geneva show, when Opel unveiled the MAXX, an innovative concept for a future urban vehicle powered by a state-of-the-art, three-cylinder, petrol engine.

The MAXX and its “high tech” power unit astonished the Geneva show visitors. Less than 12 months later, Opel surprised the world again by announcing its intention to put the “in-line triple” into series production. The decision made Opel the first European automotive manufacturer to develop a modern three-cylinder engine to production readiness.

The MAXX was a concept for a future urban vehicle. Instead of pressed steel panels, the body was made of extruded aluminium, so that the factory could easily produce sections of various sizes and shapes.

The sections were welded together to form a cage, partly exposed and included in the exterior and interior designs.

Key to MAXX concept: extruded aluminium cage formed basis for modular design

The cage provided not only optimum safety, but also the basis for the modular construction, which was the key to the MAXX concept and a forerunner of modern flexible vehicle platforms. A convertible, a pick-up, an off-roader, a van or a kind of taxi were possible on the same platform – the customer decided when they ordered the vehicle.

Although customers could not alter dimensions, they could change the exterior appearance and the interior equipment, even after taking delivery of the vehicle.

With a length of 2,975mm and a width and height of 1,575mm, the short two-door MAXX already offered plenty of space.

If the customer wanted to carry lots of luggage, they could opt for two seats plus a cargo area about the same size as that of an Astra estate. A rear bench seat installed in the aluminium structure provided accommodation for four.

Safety was just as important as versatility. In addition to the stable aluminium structure, the MAXX featured a driver airbag and anti-lock braking (ABS). In a technology transfer from the midsize and upper-midsize market segments, the MAXX had McPherson strut front suspension based on the Dynamic SAfety principle (DSA) from the Opel Vectra and the Omega. The engineers placed the fuel tank between the rear wheels for optimum safety, while the extruded aluminium structure enclosed the rear end and provided a deformable structure at the front.

“High-tech”: inline triple with twin overhead camshafts, four valves per cylinder

Another important objective was environmental compatibility. Aluminium is not only easy to recycle; it is also light in weight. The MAXX weighed only around 650kg and that permitted additional energy savings.

The MAXX’s three-cylinder engine provided additional energy efficiency. Compact, light and economical, refined and powerful too, the new gasoline power unit was the first developed to production readiness by a European automobile manufacturer. Featuring a displacement of 973cc, twin overhead camshafts and four valves per cylinder, the “high tech” engine completed its first kilometres in two prototypes of the MAXX concept car.

With about 330cc displacement per cylinder, the new member of the ECOTEC engine family had an optimum bore-stroke ratio, the advantages of which were reflected in impressive maximum torque of 90Nm at just 2,500rpm, and peak power of 37kW (50hp) at 5,000rpm.

Thanks to such figures, the 1.0-litre engine surpassed its four-cylinder contemporaries and gave the MAXX a lively performance: zero to 100km/h acceleration in 12.1 seconds and a top speed of 151 km/h. Most impressive was the economical use of energy – with its 10.1:1 compression ratio, the MAXX’s three-cylinder engine consumed only 3.9 l/100km at a constant 90km/h, according to the contemporary “Euromix” test cycle.

More than 25 years after the MAXX’s debut, the characteristic high efficiency of three-cylinder engines remains a prominent feature of the Opel powertrain portfolio – especially in the Corsa, the model that gave Opel’s innovative 1.0-litre inline triple its debut in 1997 and continues to feature ultra-modern, three-cylinder engines today.