Engine General

GENERAL 100-1

Full-power curves 100-2

Acceleration curve 100-3

Engine case (crankcase) 100-4

Crankshaft 100-5

Pistons 100-5

Connecting rods 100-5

Cylinders 100-6

Cylinder head and valvetrain 100-6

Lubrication system 100-7

Engine cooling 100-8

MECHANICAL TROUBLESHOOTING . . .100-9

TABLES

a. Engine Specifications 100-1

b. Engine Mechanical Troubleshooting 100-9

Opposed Porsche Crankshaft

GENERAL

^ The 1984-1989 Porsche Carrera models are fitted with a 3.2 liter, air cooled, horizontally-opposed engine. General engine specifications are shown in Table a. Note that there were slight variations in the engine used in 1987 and later cars.

The 3.2 liter Carrera engine uses an advanced engine management system called Digital Motor Electronics (DME), sometimes referred to as the Motronic system. In the DME system, fuel injection, ignition, and other functions, are combined under the control of the engine control module (ECM). See 200 Engine Management-General for more detailed information on system operation.

Table a. Engine Specifications

Model

Engine code

No. of cylinders

Displacement liters (cu. in.)

Compression ratio

Horsepower SAE net @ rpm

Torque Ib-ft SAE net @ rpm

Carrera

1984-1986

930/21

6

3164(193.1)

9.5:1

200 @ 5,900

185 @ 4,800

1987-1989

930/25

6

3164(193.1)

9.5:1

217 @ 5,900

195 @ 4,800

Full-power curves

Main Vent Vacuum Valve

0019408

Acceleration curve

Porsche 911 Carrera Idle Control Valve
Crankcase and oil tank venting system
Porsche 911 Carrera Idle Control Valve

B Main vent

C Vacuum control for auxiliary vent D Temperature switch E Vacuum switching valve F Idle air control valve G Crankcase vent

B Main vent

C Vacuum control for auxiliary vent D Temperature switch E Vacuum switching valve F Idle air control valve G Crankcase vent

Engine case (crankcase)

The two-piece engine case is cast aluminum and is bolted together along the centerline of the engine around the crankshaft. The crankcase does not use an oil sump. Instead a dry-sump lubrication system is employed. The oil drain plug for the crankcase is located on the left (driver's) side of the case.

^ To prevent throttle body icing in the cold weather, an auxiliary crankcase venting system is used. The auxiliary vent is connected from the oil tank (A) to the intake system via a vacuum controlled switching valve (E). The switching valve is operated using engine vacuum when the temperature switch (D) is open. The temperature switch opens at temperatures below 10°C (50°F). At temperatures above 10°C (50°F), crankcase gasses are vented into the engine via the main vent.

Crankshaft Dowel Pin 4mm

Crankshaft

^ The crankshaft rotates in replaceable split-shell main bearings. Oilways drilled into the crankshaft provide bearing lubrication. Flexible lip seals are installed at both ends of the crankshaft. The crankshaft has a stroke of 74.4 mm (2.93 in.).

The fully counterweighted crankshaft is the same crankshaft as used in the Turbo model, except that a different flywheel mounting arrangement is used owing to the DME engine management system. A threaded pin (A) for the TDC/refer-ence signal, a toothed wheel (B) for the crankshaft speed /rpm signal, and a locating dowel pin (C) for timing the flywheel to the crankshaft are the main differences.

Engine Dowel Pin 4mm

Pistons

The forged pistons are of the three-ring type with two upper compression rings and a lower one-piece oil scraper ring. The pistons have a nominal diameter of 95 mm (3.74 in.). Full-floating piston pins are retained with circlips.

Full Floating Piston Pins System

Connecting rods

The connecting rods use replaceable split-shell bearings at the crankshaft end and solid bushings at the piston pin end. The bolts are stretch type bolts and should always be replaced during engine assembly. The bolts are tightened using the torque angle tightening method for a more accurate torque.

Cylinders

Individual aluminum cylinders are Alusil® or Nikasil® coated for long life. The cylinder sealing surfaces are machined with a small amount of runout towards the outer edge. The runout is approximately 0.04-0.08 mm (0.0016 - 0.0032 in.).

Cylinder head and valvetrain

^ The aluminum cylinder heads use chain-driven overhead camshafts and two valves per cylinder. The cylinder heads employ a crossflow design for greater power and efficiency. Intake air enters each combustion chamber from one side while exhaust gasses exit from the other. Oilways in the camshaft housings provide lubrication for the camshaft(s) and valvetrain. Oil is returned to the crankcase via six oil return tubes. The valve heads have a diameter of 49 mm (1.929 in.) on the intake side and 41.5 mm (1.634 in.) on the exhaust side.

1984 Porsche Exhaust

0019525

Porsche 911 Oil Cooler Air Dam

0019410

Camshaft chain tensioner

Camshaft chain tensioner

1984 Porsche Oil Tank

^ The camshaft chains are tensioned via hydraulic tensioners. Oil feed lines at the front timing chain covers supply oil pressure directly to the tensioners.

Lubrication system

The unique 10.5-liter (11 quart) lubrication system is a dry sump design. A tandem oil pump (return/delivery) supplies pressurized oil to engine and also pumps the oil back to the oil tank. The pump is gear driven directly off the intermediate shaft.

1. Oil tank

2. Oilfiller

3. Engine oil cooler

4. Auxiliary oil cooler relief valve

5. Finned auxiliary oil cooler, fan and thermoswitch (late production)

Engine Thermoswitch Regulator

0018407

Engine lubrication system components

1. Oil tank

2. Oilfiller

3. Engine oil cooler

4. Auxiliary oil cooler relief valve

5. Finned auxiliary oil cooler, fan and thermoswitch (late production)

The engine oil is cooled via two oil coolers. The primary oil cooler is mounted to the side of the crankcase. Flow through it is controlled via a thermostat that prevents oil from circulating until the oil has reached a specified temperature.

An auxiliary oil cooler is mounted ahead of the right front tire. An auxiliary oil cooler thermostat/pressure relief valve also controls flow into this cooler. On later models, a thermostatically-controlled fan is used with the auxiliary oil cooler. See 170 Lubrication System for additional information.

Porsche 911 Oil Cooler

Engine cooling

^ Engine cooling is provided by the alternator driven fan V-belt. Ducting provides control of the air over the engine. The fan aids in cooling the alternator via the slots in the fan hub (arrow). A 92 amp alternator is used.

Fan Hub Releif Switch

The electric heater blower motor (arrow) also assists in engine cooling under the following conditions:

• Vehicle stationary

• Ignition switch on

• Engine compartment temperature of at least 128° C (260° F)

The heater blower fan will come on to cool the engine compartment. A temperature switch in the crankcase vent cover at the rear of the engine controls the heater blower motor operation.

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