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The 2.0 Liter SOHC Engine (1995 - 2005) and “the first Neon”

neon 2.0 liter engineThis engine was developed for the Neon and was also used in the export PT Cruiser, Plymouth Breeze, and Dodge Stratus. It was similar to the DOHC engine used in the Neon, Avenger/Sebring, Mitsubishi Eclipse, and Eagle Talon small cars; and it was seriously considered by BMW for the 3-series before American BMW owners objected. It was the basis for the 1.8, the minivan-PT 2.4, and the 1.4/1.6 used in the first-generation BMW Mini. The final use of the engine family was/will be in 2010 when the final PT Cruisers are made.

For development and design notes, see our Neon powertrain development page

Designed and built by Chrysler, the 2.0 liter engine originally produced 132 horsepower, with 129 lb-ft of torque - at a time when most of its rivals failed to beat 100 horsepower. Even the Civic EX, with 125 horsepower, couldn't come close to the Neon engine’s torque, despite variable valve timing. Gas mileage is good given the power and weight of the vehicles it is used in. (The exception, the 2000-2003 Neon, had an unfavorable gear ratio).

See the Neon repairs for repair tips, and the Neon performance section for performance tips.

prototype Neon engine bay

Dan Minick, a columnist for Automotive Rebuilder, pointed out:

The Mopar 2.0 blocks [SOHC and DOHC] have the same casting number. There may be machining differences for mounting.

The SOHC cylinder head is only used on the 2.0 SOHC. The DOHC Neon shares a cylinder head with the 2.4. The Avenger/Sebring/Eclipse 2.0 DOHC head is unique and has reversed flow.

The 2.0/2.4 uses the same bore and bore centers as the old 2.2/2.5. There are quite a few similarities with the lower end of the block of the 'new' 2.0/2.4 and the 2.2/2.5. However the cylinder head of the 2.0/2.4 DOHC is an outright copy of the Mitsu 2.0 G63 DOHC, while the SOHC version of the Chrysler 2.0 borrows heavily from Mitsu's early 90s G15 1.5 colt motor.

2 liter engine trenton engine workers

A factory worker wrote:

The 1.8 liter export engine was based on the 2.0; it was a smaller bore, with the same rods and crank as the 2.0, but different pistons. The block line would change over the tooling for the smaller bore and run a few thousand per month, but you had to make sure there were no 1.8 blocks in the system afterwards — if you tried to bore out a 1.8 liter, rough-bored block to the 2.0 liter bore size, the tooling wouldn’t take it. It happened a few times.

The Neon had the same 96 mm cylinder centers and the same bore as the 2.2 engine, with a shorter stroke to give it 2.0 liters of displacement; this saved on tooling. The engine was designed with a shallow skirt to save weight; a cast iron bedplate replaced the separate bearing caps used on other engines, to add stiffness. The combustion chamber had a pentroof setup.

Common repairs: head gaskets, coils, and engine mounts

2.0 liter dodge engineFor the 1995-97 models, the Neon head gasket typically lasted about 60,000 miles. Most buyers who called Chrysler got a new head gasket for $100 at most. The new three-layer head gasket design was far superior, and one engineer said it was close to the originally specified design which did not make it into production. Symptoms of a bad head gasket are oil in the antifreeze, oil on the engine, or antifreeze in the oil. (A leaking valve cover gasket can also spill oil onto the engine, though this is much less common). The revised (MLS) head gasket was reportedly put into late 1997 and all newer models, eliminating the problem.

The front and rear engine mounts tend to wear out on manual-transmission Neons, with a lifespan of around 100,000 miles on average, much less when racing. These are easy to replace or repair. Some suggest adding window urethane to stiffen up the front mount, which is more appropriate for racing than daily drivers but may be handy for enthusiasts (the stiffer the mount, the smoother the shifts but the more engine vibration is transmitted into the cabin). Most people recommend the Mopar Performance replacement mounts.

Early coils tended to fail early, resulting in a loping idle and misfiring. The problem is barely noticeable but can hurt gas mileage and power. Replacing the coil is a ten minute job.

Finally, the timing belt can skip a tooth, leading to poor performance and gas mileage, as well as gurgling noises when driving uphill with the air conditioning on.

welders

SOHC Engine Specs (1994-99)

132 bhp (98 kW) @ 6000; 129 lb-ft (174 N-m) @ 5000.

Gas mileage in the 1995-99 Neon: 29 city/38 highway (with five-speed). Mileage in the Breeze and Eclipse was lower due to added weight. Mileage varied in the 2000-2004 Neons due to different gearing. The 1995-99 DOHC produced 150 horsepower in the Neon and 140 horsepower in the Eclipse (due to packaging issues).

Bore x stroke: 3.44 (87.5) x 3.27 (83) (Bore-to-stroke ratio -- 1.05:1)
Block height: 8.35 (212.0)
Rod length: 5.47 (139.0)
Connecting rod L/R: 3.35:1
Compression ratio: 9.8:1
Displacement: 121.8 cubic inches (1996 cc)

prototype - the original Neon

Most of the following information is from Chrysler press releases.

Chrysler - Dodge - Plymouth 2.0 liter engine details from Chrysler

The cross-flow cylinder head was made of cast aluminum, with pent-roof combustion chambers and four valves per cylinder. The camshaft was installed axially, from the front of the head. Spark plug tubes were pressed into the head and held with anaerobic sealer, sealing against the underside of the cylinder-head cover.

Connecting rods and rod caps were forged from powder metal and machined in one piece, allowing weight reduction through greater dimensional control and eliminating the small-end balance pad.

% stronger than
traditional drop forging
HS150HS160HS170
Ultimate tensile strength 1.0%6.6%11.6%
Yield strength18.3%19.9%24.7%
Compressive yield strength12.2%13.5%21.3%
Shear strength3.7%9.7%16.6%

After machining, a parting line between cap and rod was scribed on both sides of the rod by a laser beam, a patented process used for the first time in the industry. Pressure on the inside diameter of the rod end then fractured the rod along the scribe marks. The uneven mating surfaces provided perfect alignment during engine assembly. The cap bolts were threaded directly into the shank of the rod, easing assembly.

Mike Volkmann, who provided the chart above-right, wrote:

All powder-forged rods are made from one three types of mix composition designed for high strength: 3Cu5C, 3Cu6C, 3Cu7C, all containing 3% copper, and 0.50%, 0.57%, or 0.64% carbon, respectively. (The corresponding Metaldyne trade names are HS150ª, HS160ª, and HS170ª.) For the 2.0 and 2.4 engines:

  • All 1995-1997 connecting rods are made from HS150.
  • All 1997-2005 DOHC (except SRT) and standard SOHC rods are made from HS160.
  • All 2001-05 Magnum SOHC and SRT are made from HS170. (The 6.1 and 6.4 SRT Hemi also have HS170 rods)
  • The 01-05 Magnums have the strongest available rods available for a 2.0 engine.

A source from Metaldyne wrote that the 6.1 and 6.4 Hemi have HS150 rods, and that there are five mixes for powder forged rods. He said that there were five types of mix: 2Cu5C, 2Cu6C, 3Cu5C, 3Cu6C, 325Cu7C. The first two are 2% copper, the third and fourth are 3% copper, and the last is 3.25% copper. The carbon level is 0.50% for 5C, 0.57% for 6C, or 0.64% for 7C. The corresponding Metaldyne trade names are LS120™, MS130™, HS150™, HS160™, and HS170M™.) For the 2.0 and 2.4 engines, all 1995-2010 connecting rods are made from LS120; the SRT V8s are made from HS150. The 2.4 Turbo (SRT) had Mahle forged steel connecting rods made with C70 material.

installing the 2.0 engine into a dodge neon

Chrysler minimized weight by using cast aluminum pistons with a shallow crown; pins were held in place by a press fit in the rods.

The cast iron block was 8.35 inches (212 mm) high, and ended at the centerline of the crank shaft; the top deck was open to cut weight. The crank was supported by a bedplate under the block, made up of a perimeter wall and transverse webs, which also added structural rigidity to the engine for durability and quiet operation. The bedplate, which also provided a flat sealing surface for the oil pan, attaches to the base of the block.

Coolant flowed around all cylinders, and the water pump housing was cast into the front of the clock.

Manifolds

The intake manifold was injection molded of 30 percent glass-filled nylon, which provided a far smoother air path compared with metal manifolds, while slashing weight from around 9 lb to 4.1 lb (1.8 kg). It had 16.5 inch (420 mm) primary runners to optimize low-speed torque; they were curved to increase their length. One runner feeds both valves of each cylinder. A tapered plenum and elbow section deliver air to the runners.

Neon 2.0 liter engine

Manifold attachment points at the head included compression limiters that assure proper sealing without damaging the plastic material. The exhaust manifold was a compact, lightweight nodular iron casting that allows exhaust gas to quickly heat the catalytic converter to operating temperature for low emissions.

Valve Train

Powdered-metal valve seat inserts and valve guides were pressed into the head. The intake ports developed turbulence in the cylinders to speed combustion.

chysler neon 2.0 liter engineA single, centrally-mounted camshaft set four valves per cylinder in motion (DOHC versions used separate cams). Intake valves were 1.3 inches (33 mm) in diameter, exhaust valves 1.1 inches (28 mm). Valves had a 42° included angle, exhaust valves rearward, intake valves forward; intake valves were splayed 3.6° for clearance to the spark plug tubes.

The valve train could control valve actuaction to 7200 rpm. The camshaft was post-hardened nodular iron with three lobes per cylinder (two for intake valves and one for exhaust). The camshaft operated aluminum center-pivot rocker arms with roller bearing cam followers and miniature hydraulic lash adjusters above the valve tips. Exhaust rockers were forked so they could operate two valves. The rocker arms pivoted on shafts clamped to the head. The lightweight valves needed only single valve springs.

The camshaft was driven by a cog belt, with extra strength to handle the load of operating 16 valves. A spring-loaded automatic tensioner with hydraulic damping pushed an idler pulley against the back of the belt (it should generally be replaced with the belt). Low-inertia sprockets of powdered metal were spaced away from the clock to reduce the belt operating temperature. The belt is completely enclosed by a two piece close- fitting molded plastic cover to keep dirt and moisture out.

Crankshaft and bearings

The modular iron crankshaft had counterweights on both sides of each crank pin to balance the bearing rods for smooth, quiet operation, and weighed 33 pounds (15 kg). Counterweights straddling each crank pin allow smaller bearing diameters, cutting friction. Diameters of the main bearings were 20% smaller than past practice and diameters of the rod bearings were 8% smaller.

A conventional inertia-ring vibration damper is mounted on the nose of the crankshaft. The inertia-ring has machined-in pulley grooves to drive the alternator and accessory belts. The damper minimizes engine noise and vibration.

The camshaft operates directly in the cylinder head without bearing inserts. The main and rod bearings have high-load bi-metal inserts.

Neon engine lubrication and cooling

The powdered metal gerotor oil pump mounted in the front of the block and is driven by the crankshaft; the lubrication system was designed to prevent aeration.

The block was inclined to the right (rearward in the car) to allow the oil to drain from the head at the right face of the block. The crankcase was ventilated through openings on the left side of the head; oil capacity was four quarts, plus filter. SAE 5W-30 oil, grade SG/SH, was recommended [we found most dealers wanted to use 10W30]. A half quart oil filter mounted vertically to an extension of the bedplate, providing easy access for service.

The water pump housing was built into the block; the water pump was driven by the timing belt. A single molded plastic unit acted as thermostat housing, filler neck, radiator hose nipple, and overflow nipple. The cooling system filler neck was attached to the engine, and was the highest point in the cooling system.

The thermostat had an air vent and a check ball that allowed air in the coolant to escape when the system was cool, but seated with a tight fit to assure rapid engine warm up. Allowing air to escape the vent help prevent swings in coolant temperature during warm up, and made refilling the system easier because it prevented air entrapment.

Sealing

Neon and other 2.0 engines tended to be far more tightly sealed than the 2.2 that preceded them.

  • The crankshaft rear main seal (which used a Teflon lip for longer life) was pressed into the black-and-bedplate assembly, instead of into a bolt-on housing, to eliminate a potential leakage path.
  • The oil pump cover also houses the crankshaft front main seal.
  • The oil pan and cylinder head cover gaskets were state-of-the-art in design and material — molded silicone with a steel backbone and compression limiters.
  • The block bedplate design creates a secure oil pan seal, with its flat, continuous, machine sealing surface.
  • The top surface of the cylinder head was machined flat for easy, precise sealing.
  • The spark plug tubes were sealed to the cylinder head covers with individual molded seals.
  • A silicone-rubber gasket, molded onto the thermostat, created a high- integrity seal between the thermostat housing and the cylinder head.
  • A molded seal on the oil pan drain plug prevented leakage.

Chrysler electronic fuel injection and ignition systems

The sequential multi-port injection system used four cone-spray injectors; a slot in the top of each intake port allows proper location of the injector spray so fuel was directed into the intake valves.

The throttle body had a 2.05 inch (52 mm) bore on automatic-equipped cars; manuals had a slightly smaller throttle body. The throttle body had a contoured bore in the off-idle area that limits the amount of air flow to the engine at low throttle; the two throttle bodies were contoured differently so tip-in was greater with the automatic, providing greater responsiveness, and lighter with the manual, providing smoother shifts and better control.

Fuel-flow control software in the PCM (powertrain control module) cuts driveline shock and oscillation from rapid changes in throttle opening. The fuel injection control software in the PCM adjusts the injection pulse duration for the varying pressure differences between the fuel supply system and the intake manifold.

The 2.0-liter engine had a direct ignition system (DIS) with crankshaft and camshaft sensors. The crankshaft sensor sensed two patterns of four slots, each 180° apart, in the counterweight. The slots feed data for engine speed, while the positions on the crankshaft establish engine timing. Spark advance and injection timing were computed from slots that were 20° apart; the “signature” slot was 60 degrees wide while the others were around 5° wide. The sensor output from the "signature" slot combined with the signal from the camshaft sensor to determine the cylinder ready for fuel and ignition.

The camshaft sensor is on the rear of the cylinder head, triggered by a ring magnet in the end of the camshaft. The magnet's four poles are arranged at 150° and 210° intervals; their relationship to the signature slot is established in less than one turn of the crankshaft, allowing injection to begin and bringing fast starts.

The four-lead direct-ignition coil pack was mounted above the cylinder head cover, so only short secondary-wire leads were required, reducing cost and maintenance.

2.0 Engine Comments

Wheatking wrote:

My father has the same engine in his Avenger and it's about 200,000 miles now, on the original head gasket. We found out it's not so much a problem with the gasket; the head bolt on the back outside of cylinder #4 can bottom out on some blocks, so it doesn't exert enough pressure on the headgasket to make a good seal.. grinding a few threads off the bolt does the trick if it’s leaking a little. The new MLS gasket is thicker than the old gaskets, one reason why it works better.

This engine is one of the first produced in America to be used in a Japanese vehicle [Mitsubishi Eclipse, in DOHC form; and BMW/Rover Mini, in smaller-displacement form].

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