Vauxhall has unveiled a new high-tech 1-litre three–cylinder gasoline engine in time for next month’s Frankfurt International Motor Show, ahead of its debut in the ADAM city car next year.
The 1-litre turbo petrol, known as SGE (small gasoline engine), represents a new benchmark for refinement in three-cylinder engines, according to Vauxhall, with noise, vibration and harshness (NVH) characteristics superior to many four cylinder units.
Developing 115PS, the new engine delivers a low-end torque of 166Nm from 1,800 to 4,700rev/min, belying its small size.
The 1-litre spark ignition direct injection (SIDI) turbocharged unit generates more torque throughout its operating range than equally powerful, higher displacement engines, while fuel efficiency is improved by 20 per cent compared with the current 1.6-litre naturally aspirated unit that powers the Astra.
Set to appear first in the ADAM next year with an all-new six-speed gearbox, the 12-valve, 1-litre turbo is the first in a new, modular family of three and four-cylinder Vauxhall petrol engines up to 1.6-litres.
Technologies include direct injection, continuously variable valve timing, and a lightweight aluminium cylinder-block, are key to the engine’s efficiency. Vauxhall expects the new engine family to deliver impressive fuel economy and CO2 emissions significantly lower than 100g/km.
“In developing this small engine, we not only set out minimise fuel consumption and CO2 emissions. We also wanted to demonstrate that three cylinders can be just as refined as four or more,” said Dr. Matthias Alt, chief engineer, small gasoline engines. “We tackled at source the balance, noise and vibration issues typical of conventional three-cylinder engines, and we’re confident customers will be pleasantly surprised by the results. This is a very lively and refined three-cylinder engine which doesn’t compromise driving fun.”
Vauxhall engineers started with a clean sheet of paper, which enabled a series of measures to eliminate the typical, ‘off-beat’ running characteristics which have traditionally accompanied three-cylinder engines.
The die-cast aluminium cylinder block is designed to reduce radiated and structure-borne engine noise, as well as reduce weight. The high-pressure fuel rail and injectors are isolated from the cylinder head to minimise transmission of pulsing, while the fuel pump and fuel line are acoustically treated.
Another factor aiding refinement is the requirement of a balancer shaft in the oil sump. Driven by a chain with inverted teeth for quiet running, the counter-rotating shaft runs at crankshaft speed and is mass-optimized to offset the inherent vibrations from a three cylinder operation.
Other noise attenuation measures include: acoustically-optimized 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 compressor; and a lower oil pan in steel.
As a result of these features, Vauxhall claims the 1.0 SIDI Turbo is not only more refined than other three cylinder engines, but also is quieter than many four-cylinder units. For example, in bench testing at full throttle, the engine emits lower noise levels across all engine speeds than similarly powerful gasoline turbos up to 1.6-litres displacement.
Its inherent refinement is so good, according to Vauxhall, that the need for additional in-car sound insulation, or complex engine mountings and sub-frames, is significantly reduced, thus reducing costs elsewhere in the vehicle.
Power and torque
The 1.0 SIDI Turbo generates more torque than Vauxhall’s current 1.6-litre, naturally-aspirated engine, as well as the same 115PS maximum power output.
The exhaust manifold is integrated within the aluminium cylinder head, which is bolted directly to the low-inertia, water-cooled turbocharger. This compact installation contributes to the delivery of a fast boost charge for strong, low-end power. Maximum torque of 166Nm from just 1,800 rpm is almost 30 per cent higher than the 1.6-litre engine generates at the same rpm.
The six-hole fuel injectors 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 1.0 SIDI Turbo is mated to an all-new, six-speed manual gearbox specially designed for medium torque applications. With a dry weight of only 37kg, it is about 30 per cent lighter than its current counterpart. It is also extremely compact, measuring just 375mm along its axis. ∎
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