GM and Opel SIDI Engine Family Explained

Opel Astra 1.6 SIDI Turbo engine 1 photo
Photo: Opel
Opel is the name of GM's European crisis. While US safe risen hugely in the past few years, and Chinese market sales are bolstering their numbers, the slump in Europe is hurting them to the point where investors want Opel to be cut loose.
Fixing Opel will take a long time, but it really would be a shame to kill a brand so many people hold dear. From the Kadett and Calibra to the Astra and Insignia, iconic cars made by this German company are not easily forgotten by fans.

The company's problems cut deep. In Europe, GM hasn't recorded a single annual profit for well over a decade. While GM is somewhat restricting the development of brand new Opel models, they have allowed them to come up with a whole new engine family. About 80% of Opel engines will reportedly be all-new within the next three years.

With this, the Russelsheim company is joining the trend for engine downsizing – reducing displacement, increasing specific output and reducing polluting engine emissions. While Volkswagen, Ford, Renault or even Fiat have all long finished their first small turbo engines, Opel is only now announcing a 1-liter SIDI engine that's will enter production with the Adam city car in 2014.

However, the Szentgotthard factory in Hungary already makes a new 1.6-liter SIDI engine for the company's compact cars and a new turbo diesel.

The 1.6 SIDI Turbo engine could easily be confused with the one it replaces, the so called "Turbo" fitted to the Astra. Heck, it even makes 10 less hp than the old engine. With Opel taking its first steps in downsizing, we wanted to take a look at this growing family of L3 and L4 engines.

1.0 SIDI Turbo / GM Small Gasoline Engine (SGE)

The 1.0-liter SIDI Turbo engine announced for the Opel Adam is only the first unit of a family of small 3-cylinder and 4-cylinder gasoline engines with displacements between 1L and 1.5L. The family is being developed together with Shanghai GM, Chinese carmaker SAIC and Pan-Asia Technical Automotive Center, which made the Sail and an MPV for China called the GL8.

This modular system will combine direct injection, turbocharging and the capacity for alternative fuels like ethanol. Rumor has it the GM Small Gasoline Engine will soon also be used by the Chevrolet Aveo/Sonic in 2014, the new Chevrolet Cruze sedan in 2015 and the the MG3 supermini the same year.

For its maiden application, Opel has given their 1.0-liter turbo benchmark engine an output of 85 kW/115 hp and 166 Nm from 1,800 to 4,700 rpm. This output is lower than Ford's 1.0 EcoBoost, but the figures come in lower in the rev range. Engineers say that together with a start/stop system CO2 emissions will drop below 100 k/km.

“We tackled at source the various 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 on driving fun. Put simply, it’s big on refinement and performance but small on fuel consumption,” said Dr. Matthias Alt, Opel’s Chief Engineer, Small Gasoline Engines.

SIDI stands for Spark Ignition Direct Injection, however, that's not the full extent of this engine's technology package. Engineers developing this unit worked hard to contradict conceptions of harshness regarding three-cylinder engines. So it uses high-pressure direct fuel injection for power, aluminum construction for lightness and a cylinder head-integrated exhaust manifold for efficiency.

To specifically offset typical vibration of straight-3 engines, they installed a small balance-shaft mounted longitudinally low down in the oil sump. This is driven by a chain with inverted teeth and spins in the opposite direction to the crankshaft.

The drive chain assembly has also been optimized for efficiency and reduced noise, using an inverted tooth belt and specially designed tensioning, wrap and guides.

Just for the sake NVH levels, they also used an acoustically-developed cylinder block, a sump-mounted balancer shaft, structural isolation of the fuel injection system and crankshaft, drive chains with inverted teeth and engine covers designed for acoustic attenuation.

The 3-cylinder engine features dual overhead camshafts, operating four valves per cylinder with low-friction, hydraulic roller finger followers, are hollow in section.

Perhaps the most important part of the 1.0 SIDI Turbo packaging is of course the turbo, a small system that there to generate the necessary grunt lower down. The turbo fan is just 35mm in diameter, which is very small, yet its low-inertia setup generates 1.5 bar of pressure using only one scroll to spool up. Using engine exhaust gasses, the 40 mm compressor spins the shaft up to 250,000 rpm and generates up to six times normal pressure in 1.5 seconds from as low as 1,500rpm.

1.6 SIDI Turbo / GM Medium Gasoline Engine (MGE)

The first SIDI engine announced by Opel is a 1.6-liter turbo featuring an grey cast-iron block with aluminum bedplate. It belongs to General Motors' new Medium Gasoline Engine (MGE) medium-displacement 4-cylinder family. It was designed to replace the 1.6 L Family 1 Ecotec engine, followed by the 1.8-liter Chevrolet engines. The block is all new and has a 1598 displacement: 79.0 mm bore and 81.5 mm stroke.

Two versions have already been developed for Opel applications. The first is the Eco model fitted to the whole Astra J family as well as the Zafira Tourer and Meriva. It makes 170 PS / 125 kW at 4,250rpm and 260 Nm (192 lb-ft) of torque, or 280 Nm (207 lb-ft) with overboost.

The more muscular one made its debut in the Cascada convertible and offers 200 PS at 4,700 rpm and a peak torque of 300 Nm (221 lb-ft), which will arrive starting with 1,700 rpm.

Through 2016 Opel will also introduce three completely new engine families and 13 new powertrains. We'll have more details for you are they become available.
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About the author: Mihnea Radu
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Mihnea's favorite cars have already been built, the so-called modern classics from the '80s and '90s. He also loves local car culture from all over the world, so don't be surprised to see him getting excited about weird Japanese imports, low-rider VWs out of Germany, replicas from Russia or LS swaps down in Florida.
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