NG 900/9-3 Engines
Contents
Engines
The NG 900 was produced with a choice of four powerplants. Three of these were 4-cylinder units that were developed from the ones used in the 9000 and there was the introduction of a new V6 unit that was sourced from GM. They were as follows.
2.0i (B206i)
Swept Volume 1985cc Rating 133 hp Torque 180/4,300 Nm/rpm Top Speed 200 Km/h Engine Mangement System Bosch Motronic
2.3i (B234i)
Swept Volume 2,290cc Rating 150 hp Torque 210/4,300 Nm/rpm Top Speed 205 Km/h Engine Mangement System Bosch Motronic
2.0 Turbo (B204L)
Swept Volume 1985cc Rating 185 hp Torque 263/2,100 Nm/rpm Top Speed 240Km/h Engine Mangement System Saab Trionic with Saab Direct Ignition (DI) Turbo with intercooler
2.5i V6 (B258i)
Swept Volume 2,498cc Rating 170 hp Torque 227/4,200 Nm/rpm Top Speed 225Km/h Engine Mangement System Bosch Motronic
4-Cylinder Engines
Engine Block
All are water-cooled, four-cylinder, in-line engines with four valves per cylinder, twin overhead camshafts and two balance shafts incorporated in the sides of the block (the B206i engine has no balance shafts).
The engines have fuel injection and are of cross-flow type with the inlet valves on one side and the exhaust valves on the other.
The engine is transversely mounted and inclined forwards at an angle of 8°
The swept volume of 2.0 litres (B206i B204L) and 2.3 litres (B234i) helps to develop high torque even at low engine speeds, which is of particular benefit in normal driving conditions. The balance shafts are designed to overcome vibration and the forces generated by the moving parts of the engine and at the same time reduce the level of unwanted engine noise.
Cylinder block
Incorporated in the sides are the balance shafts (not fitted to the B206i or the B258i), the inner journals of which run in aluminium bearing shells press-fitted in the block. These can be replaced without the need for any subsequent machining.
Pistons
The pistons are made of light alloy and have grooves for two compression rings and one scraper ring.
The top compression ring is flat and coated with chromium or molybdenum. The second compression ring, which is slightly wider than the top one, also has an oil-scraper function. The scraper ring itself is in three parts.
Connecting rods
The connecting rods are forgings and incorporate bushes for the gudgeon-pins. The gudgeon-pin bushes and big-end bearing shells are replaceable.
The gudgeon pins are of the fully-floating type, being free to turn in both piston and connecting rod. Axial movement of the pin is limited by circlips inside the piston boss.
Crankshaft assembly
The crankshaft is a forging and has ground journals, which are surface-treated by induction hardening. This provides a hard surface finish which is highly resistant to wear. There are five main bearings, with the middle bearing also serving to locate the crankshaft axially. Lubrication is provided for through drilled oilways in the shaft. All main bearing shells are replaceable.
Cylinder head
The cylinder head, a light-alloy precision casting, is bolted onto the block. The combustion chambers are hemispherical with the spark plug in the centre, and there are four valves per cylinder. This design improves the flow of gases in the cylinders, ensuring effective combustion of the fuel-air mixture and so higher efficiency.
Timing cover and end plate
The timing cover and the end plate are both designed to match the shape of the cylinder block. The oil pump is mounted inside the timing cover. The timing cover and the end plate are both sealed against the block with flange sealant, part no. 93 21 795
V6 Engine
Engine Block
The engine is a water-cooled unit with six cylinders arranged in a 54-degree V configuration, two camshafts per cylinder head and four valves per cylinder. This results in an extremely compact power unit. Engine capacity (swept volume) is 2.5 litres.
The engines are fuel injected and equipped with the Motronic engine management system.
The camshafts are driven by an internally-cogged belt. The engine has automatic purging of the air in the oilways supplying the oil to the tappets, an integral heat exchanger for the engine oil and a torque member which stabilizes the block round the main bearings.
The heat exchanger has a dual function. It heats the oil when starting from cold and cools the oil when the engine has reached working temperature.
Cylinder block
The block is a special one-piece casting with the cylinder bored in the block. Special oilways for the lubricating system are also drilled in the block.
Pistons
The pistons are made of light alloy and have grooves for two compression rings and one oil scraper ring.
The top compression ring is flat and coated with molybdenum, the lower compression ring, which is slightly wider than the top one, also has an oil-scraper function. The oil-scraper ring itself is in three parts.
The gudgeon pins are shrunk into the connecting rods and are consequently not of fully-floating type.
Connecting rods
All connecting rods are one-piece forgings with a fractural impression or nick at the big end where the connecting rod is "snapped" into two parts, one of which forms the bearing cap. The bearing caps are bolted to the connecting rods. Connecting rod and bearing cap are both marked with a "protuberance" to prevent them being assembled the wrong way round. The connecting rods are not numbered.
Crankshaft assembly
The crankshaft has ground journals which are hardened by an induction hardening process. This provides a surface finish with hard-wearing properties.
There are four main bearings. Lubrication is provided through drilled oilways in the crankshaft. All main bearings are replaceable. The No.2 and No.3 main bearings have no grooves in the bearing caps.
The perforated disc, which is part of the engine management system, is bolted to the crankshaft.
Cylinder head
The engine has two cylinder heads, called the rear (cylinders 1,3,5) and the front (cylinders 2,4,6) cylinder heads. The cylinder heads are light alloy precision castings bolted to the cylinder block. The combustion chambers are hemispherical with four valves per cylinder and the spark plug in the centre. This design improves the flow of gases in the cylinders and also ensures effective combustion of the fuel-air mixture the engine runs at high efficiency.
