General Motors Europe’s new one-litre, 12 valve, three cylinder petrol engine will make its debut in the Adam city car at next month’s Geneva show.
The new Opel/Vauxhall I3 is all aluminium and will come with two power outputs, 90PS and 115PS, both with 166Nm of torque from 1,800 rpm.
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With start/stop standard, the 90PS version gives the Adam combined cycle fuel consumption as low as 62mpg, with CO2 emissions of 99g/km. Efficiency enablers include direct fuel injection, variable valve timing, the all-alloy construction and a switchable water pump.
This is the first of a new family of small displacement petrol engines and follows the 2013 introduction of new 1.6-litre petrol and diesel engine lines.
For the I3, engineers focused on eliminating ‘off-beat’ running characteristics which traditionally detract from the economical driving appeal of three-cylinder engines.
“We not only set out to minimise fuel consumption and CO2 emissions, we also wanted to demonstrate that three cylinders can be just as refined as four or more,” said Matthias Alt, chief engineer, small gasoline engines.
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By GlobalData“We tackled at source the balance, noise and vibration issues typical of conventional three cylinder engines and we’re confident customers will be enthusiastic about the results.”
The cylinder block, in high pressure die-cast aluminium, is designed to reduce radiated and structure-borne engine noise as well as reduce weight. The high-pressure fuel rail and injectors are also structurally isolated from the cylinder head to minimise the transmission of pulsing while both the fuel pump and fuel line are acoustically treated.
A further contributor to running refinement is the installation of a balance shaft in the oil sump. Driven by a chain with inverted teeth for quiet running, it counter-rotates at crankshaft speed and is mass-optimised to offset the inherent vibrations of a three cylinder operation.
Other noise attenuation measures include: acoustically-optimised covers for the top and front of the engine, the intake manifold and camshaft housings; crankshaft isolation with iron main bearing inserts; inverted teeth for camshaft drive chains; a low-hiss turbo charger, and a lower oil pan in steel.
GME claims th new I3 is not only more refined than other three-cylinder engines but also quieter than many I4s. In bench testing at full throttle, it emits lower noise levels across all engine speeds than similarly powerful petrol naturally-aspirated engines of 1.6-litre displacement.
Small engine with big appeal
The exhaust manifold is housed in the aluminium cylinder head, to which the tiny, low-inertia, water-cooled turbocharger is directly bolted. This compact installation contributes to the delivery of a fast boost charge which gives strong, low-end power.
The six-vent fuel injectors in the direct injection system are centrally located above each piston to provide efficient combustion, and dual cam-phasing enables variable valve timing for optimum engine breathing. A twin displacement oil pump and a switchable water pump, which is disengaged when the engine coolant is cold in order to accelerate warm-up, also contribute to low fuel consumption.
The I3 is mated to a new generation six-speed manual transmission with a compact design and a dry weight of only 37kg, about 30% lighter than units it replaces.
Featuring superior shift quality and excellent precision, with a short lever travel and low effort, the new transmission incorporates many of the smooth gear change refinements recently introduced by GME such as the use of gears with wide, asymmetrically-cut dog teeth and triple-cone synchronisers for first/second gear, with double cones for third/fourth. Reverse gear is also synchronised. The ‘box is also destined for other Opel/Vauxhall models.
