Saturn I4 engine

Infobox Automobile engine


name =Saturn engine
aka ="Single Cam" or
"Twin Cam"
manufacturer =General Motors
type =Straight-4
bore =82.0 mm (3.23")
stroke =90.0 mm (3.54")
displacement =1.9 L (116 in³)
weight =SOHC: convert|196.74|lb|abbr=on
DOHC: convert|220.22|lb|abbr=on
block =Aluminum
head =Aluminum
valvetrain =SOHC 8V (LK0/L24)
DOHC 16V (LL0)
fuelsystem =LK0: TBI
L24/LL0: MPFI
fueltype =Unleaded fuel, 87 octane
oilsystem =Pressure feed
coolingsystem =Watercooled
power =LK0: 85 hp (63 kW)
L24: 100 hp (75 kW)
LL0: 124 hp (92 kW)
torque =LK0: 110 ft·lbf (149 N·m)
L24: 114 ft·lbf (155 N·m)
LL0: 122 ft·lbf (165 N·m)
compression =LK0/L24: 9.3:1
LL0: 9.5:1
specpower =LK0: 44.73 hp/L
L24: 52.63 hp/L
LL0: 65.26 hp/L

The powerplant used in Saturn S-series automobiles was a straight-4 aluminum piston engine produced by General Motors. The engine was only used in the Saturn S-series line of vehicles (SL, SC, SW) from 1991 through 2002. It was available in chain-driven SOHC or DOHC variants.

This was an innovative engine for the time using the lost foam casting process for the engine block and cylinder head. Saturn was one of the first to use this casting process in a full-scale high-production environment. Both engine types used the same engine block.

Engine block

The engine utilized a water-cooled aluminum block. The main bearing caps were made of cast iron and held in place with two bolts each. The cylinder block bores had interference fit cast iron liners for the piston rings to sit against. The engine block was made from 319.1 aluminum alloy and the liners were made from D5506 ductile iron.

Crankshaft

The crankshaft was supported by five main bearings with thrust taken at the middle bearing. 1991 and 1992 engines had a different crankshaft than 1993 and later engines. 1993 and later crankshafts had ten degrees advanced reluctor ring slots to aid in startability. 1991 to 1998 crankshafts incorporated 4 counterweights. 1999 to 2002 crankshafts incorporated 8 counterweights.

Connecting rods and pistons

The connecting rods were forged steel with standard type crank pin bearings. The piston pins floated in the connecting rod bushings. The pistons were cast aluminum alloy with the piston pins being retained with snap rings.

Timing chain

The timing chain was hydraulic tensioned and had a ratchet mechanism to keep the chain tight. The timing chain rode on one pivoting chain guide resting on the ratchet tensioner and one fixed guide attached to the engine block and cylinder head. The 1991 to 1998 DOHC engine had an upper timing chain guide in between the camshaft sprockets. The timing chain was lubricated via cast-off from the top of the cylinder head and one 'squirter' on the oil pump housing. The SOHC and DOHC engines used different timing chain sets.

OHC LK0/L24

The SOHC (LK0/L24) cylinder head had 8 valves and was made of lost foam cast aluminum. The camshaft was located in the center of the cylinder head and driven by a chain off the front crankshaft sprocket. Motion from the camshaft was transmitted to the eight valves by the hydraulic lifters and rocker arms.

The LK0 engine first used TBI (Throttle Body Injection) for fuel delivery and was rated at 85 hp (63 kW) and 110 ft·lbf (149 N·m) of torque from 1991 to 1994.

The L24 engine received MPFI (Multi-Port Fuel Injection) in 1995 which increased power output to 100 hp (75 kW) and 114 ft·lbf (155 N·m). This engine was used from 1995 to 2002.

The SOHC engine was available on the base model S-series vehicles (SC1, SL, SL1, SW, SW1)

DOHC LL0

The DOHC cylinder head had 16 valves and was made of lost foam cast aluminum. The camshafts were held in the cylinder head with bearing caps and driven by a chain off the front crankshaft sprocket. Motion from the camshafts was transmitted to the 16 valves by direct-acting hydraulic lifters.

All LLO engines used MPFI and were rated at 124 hp (92 kW) and 122 ft·lbf (165 N·m). The DOHC engine was available on the upper-level model S-series vehicles (SC, SC2, SL2, SW2). A revision of the LL0 appeared in 1999 and used a roller camshaft with hydraulic lifters and rocker arms

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