Porsche 924 Turbo

Cigar lighter

Rear window defogger

Rear window defogger

Headlights

Cars for USA and Canada have halogen sealed beam headlights as standard equipment.

Porsche 924 Turbo Oil Catch Can

Instruments

Oil pressure gauge with symbol (dripping oil can). Voltmeter with symbol (battery).

Oil Pressure Gauge Porsche 924Parking Brake Symbols Manual

The parking brake indicator light in instrument cluster has a symbol (P).

Steering Column Switch

All cars are fitted with a new steering column switch (modified operating lever and housing).

The word f=cjf=isc:he is inscribed in the door trim panel of all cars.

The word f=cjf=isc:he is inscribed in the door trim panel of all cars.

Two-tone Horn

The cars have two two-tone horns (as Turbo 924).

From model year 1981 all cars fitted with a radio as optional equipment will have a speaker balance control mounted on the center console.

Porsche 924 Center Console

The following modifications have been made on the Porsche 924 Turbo for the new model year.

— Increase in engine power output by 5 kW (6 HP)

— New fully electronic ignition — digital ignition timing

— Modifications to turbocnarger

— New steering column switch (as 924)

— New symbols for controls (as 924)

— Brake fluid level indicator light, instead of brake circuit failure indicator light (as 924)

— Instruments with white letters/numbers (formerly green) These modifications are described in detail on the following pages.

The major modifications on the 924 Turbo concern the engine and ignition system. A new ignition system and changes to the fuel system and an increased compression ratio have increased engine power.

In the model year 1981 the 924 Turbo will be built with the following engine version.

USA, Canada

M 31/04

Photos Block Engine Porsche 924 Turbo

Engine type Power output formerly

The crankshaft drive {except the pistons), engine block and cylinder head have not been changed. Modifications:

Pistons

The pistons — nominal diameter 86.5 mm — have a centric, somewhat flatter combustion chamber recess than before.

Compression ratio: USA, Canada = 8.0:1 (formerly 7.5 : 1)

The installed position is indicated by an arrow stamped in the piston crown (faces forward to pulley).

The piston pin bore is offcenter by 1.5 mm.

Porsche 924 Flywheel Timing Marks

Flywheel, Clutch Plate

The flywheel is new. It has milled teeth the digital electronic ignition system.

The TDC mark (Z 1) and 9° before TDC ignition timing mark (dot) are on the flywheel.

Flywheels with 9° before TDC ignition timing marks are identified with "USA".

Important!

The flywheel is a press-fit on the crankshaft.

The flywheel must be heated to install.

Flywheel mounting bolts are 2 mm shorter than before.

For identification the bolts have a 4 mm dia. hole 2 mm deep in their heads.

Crankcase Vent (USA, Canada)

Ist Der Geber Beim Porsche 924

a — Oil trap b — Return line to oil pan c — Oil feed to turbocharger d — Oil return from turbocharger e — Air trap f — Vent lines

Crankcase Vent

The blowby gas travels from the crankcase via a hose into the air-cleaner. The vent line has an oil trap (a) with a return line (b) to the oil pan.

Trap Gas Defrost Oil Return

Return line from oil trap to oil pan a — Oil trap b — Return line

Turbocharge Oil Return

There is a vent line with an air trap (e) in the oil return from the turbocharger to the oil pan. The vent line connects to the crankcase vent ahead of the oit trap.

Perfect oil return flow is guaranteed even with unfavorable conditions (pressure in crankcase).

Turbocharger

The turbocharger is a new refined version of the previous turbocharger. The vanes on the compressor have been changed and provide a better degree of efficiency. A smaller turbine housing has been selected to improve engine pickup when accelerating in the low speed range.

Collar bolts (external teeth) and dowel sleeves are used to boll the turbocharger on the exhaust manifold.

A sealing ring is installed between the exhaust manifold wastegate pipe and turbocharger front pipe to improve sealing.

This modification required the following new parts:

Exhaust manifold, turbocharger (these parts have a groove for the sealing ring and a wastegate pipe from the exhaust manifold to the wastegate.

New Wastegate

The wastegate is new for 1981, however the boost pressure remaining the same as previously. Boost pressure 0.43 to 0.47 bar

1981 Porsche 924 Distributor Pictures

Throttle Housing

It now houses only one throttle plate (formerly two).

An 0 ring is used for the pressure lube seal (arrow).

The pressure tube and intake air distributor have been changed due to the new throttle housing adapters.

Fuel Injector Installation

The injector holder has a metal insert for better sealing and holding. A seal is installed between the fuel injector and holder (previously the holder was only made of plastic without a metal insert).

The new fuel injector holder can aiso be installed in cars before the 1981 models.

A digital ignition liming control (DITC) has been developed for the Porsche 924 Turbo. Unlike previous mechanical ignition systems, control of the ignition timing is fully electronic with the DITC. With this system, it is possible to have optimum ignition timing for the special requirements of the engine in regards to power output, emission control and fuel consumption under all operating conditions.

Engine speed and intake vacuum still serve as input factors.

However, intake air temperature and throttle position (coasting or idling) also influence timing with this system.

The chief components of the digital ignition timing control are the timing control unit (1), the pressure sensor (3) installed in the control unit, the temperature sensor (4), the throttle switch (5) and the flywheel sensor (6).

1981 Porsche 924 Turbo Diagram

1 — Timing control unit

3 — Pressure sensor

4 — Temperature sensor

5 — Throttle switch

6 — Flywheel sensor

7 — Flywheel teeth

8 — Reference mark

9 — Ignition control unit

10 — Ignition coil

11 — High voltage distributor

The timing control unit (1 ) is located underneath the center console. It has a multiple-pin plug and hose connection (2) for the pressure sensor.

Intake vacuum is taken via a threaded connection on the intake air distributor.

Vacuum Connection 924 TurboPorsche 924s Flywheel SensorsPorsche 924s Flywheel Sensors

Throttle switch (5) and temperature sensor (4) are shown in the picture to the side.

The flywheel has an additional ring of teeth (7), and a reference mark (8).

The flywheel sensor (6) is located on the bell housing above the flywheel teeth.

Bellhousing Porsche

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Operation

A flywheel sensor (6) is mounted on the clutch bell housing to determine engine speed and flywheel (crankshaft) position The flywheel has a extra ring of 100 teeth (7)

Because the flywheei sensor '6» receives two voltage pu'ses for each of the additional flywheel teeth, it can sense every 360'/200= 1.8° of crankshaft rotation.

One of the flywheel teeth called the "reference mark tooth" (8) has a special soft iron insert. When lho "reference mark tooth" passes the flywheel sensor, it creates two voltage pulses which are stronger than those producted by the other teeth.

By counting the flywheel teeth which pass the flywheel sensor after the "reference mark tooth", the timing control urn: can instantaniously calculate the crankshaft position n relation to F.D.C.

The timing control unit aiso calculates engine speed by counting the number of teeth wheh pass the flywheel sensor per time unit.

Information about engine speed, throltle position, intake vacuum, and intake air temperature is processed by the immg control unit and the correct ignition timing for these conditions is selected from the control unit's memory. When the crankshaft is at the correct position, 'he timing control unit sends a signal to the ign non contr I unit '9 which's turn switches )ff 'he pr mary voltage to the ignition coil (10) causing the coil to "fire".

The distributor (11) distributes the high voltage from thie ignition coil to the correct spark plug.

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