Cayenne Turbo (9PA) V8-4.8L Turbo (2008)
Compression Check: Testing and Inspection
Performing compression pressure check on DFI engines
Preliminary work
1. Open the hood.
2. Open lid of central electrics box. To do this, loosen the four fastening screws. -arrows-
Central electrics box
Warning
Risk of electric shocks from high-voltage ignition system and danger of damage to ignition rod modules!
Connected ignition rod modules can be damaged.
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Always remove the ignition rod module fuse.
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Always disconnect ignition rod module electrical connections.
Caution
Risk of damage to components that affect the exhaust system!
Unburned injected fuel enters the exhaust system.
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Prevent the fuel from injecting by removing the fuse.
3. Pull out the fuses for the ignition rod modules and the injection system. For latest assignment, see wiring diagram.
4. Remove spark plugs.
Tools and materials
Tools
Information
A commercially available compression tester with a maximum pressure of at least 25 bar is required for the compression test on V8 DFI engines.
The compression of V8 DFI engines is much higher than that of 4.5-liter intake manifold injection engines. The old compression tester
Moto-Meter Compression Recorder 1065 is not able to display the measuring ranges and will be irreparably damaged.
The compression tester used should be equipped with a removable adapter for the thread matching the spark plug recess (M14 x 1.25). A rubber
cone that is pushed in is not permitted as the cone will be lifted by the high compression and this will falsify the measurement result.
On compression testers with an analogue pointer, the measured value of the corresponding cylinder must be written down after each measurement.
Always follow the operating instructions provided by the equipment manufacturer.
Information
Test evaluation and test prerequisites
Information
The 4.8-liter V8 naturally aspirated engine has a compression of 12.1 : 1. The 4.8-liter V8 turbo engine has a compression of 10.1 : 1.
The 4.8-liter V8 naturally aspirated engine has higher compression values than the 4.8-liter V8 turbo engine. They are not comparable.
The measurement of two comparable V8 naturally aspirated engines can produce different pressure ranges. This is not a sign of wear or a defect.