Vehicle Type:
911 GT3 (991)

Concerns:
Evaluating overspeed events using the Vehicle Analysis Log (referred to below as “VAL”).

Situation:
Damaged unit parts due to high engine speed.
The information below is intended to help you to evaluate engine damage, which may occur as a result of one or more overspeed events. Using the values entered in the VAL, you can also evaluate the assignment of “Porsche Approved Warranties” better and check entitlement for processing repairs under warranty and goodwill, for example.
Engines are designed to operate at a maximum permitted speed. This engine speed is not exceeded when the vehicle is driven normally. However, driving and operating problems (e.g. “changing to the wrong gear” on vehicles with manual transmission) or manipulation (e.g. tuning) can cause the maximum permitted engine speed to be exceeded when the vehicle is driven.
Overspeed events are stored in the DME control unit. The following values are also recorded:
- Number of ignition attempts in each overspeed range 1), and,
- Status of the hourmeter during the last overspeed event 2).
1) Overspeed range = Defined rev ranges with classification of expected engine damage, e.g. engine damage possible, ... probable, ... very probable, engine damage has generally occurred; see section ⇒ 'Rev ranges'.
2) For technical reasons, overspeed events are entered in a preset time interval. As a result, there may be entries in a higher rev range (e.g. range 2), while no entries are stored in the lower range.
Typical faults and symptoms as a result of overspeed events may include the following:
• Damaged valves and/or pistons (impact marks on the valve, valve impressions on the piston, valve bent).
• Cylinder liner damage (even “piston seizure”).
• Damaged or displaced connecting rod bearings.
• Loosened or loose fastening screw(s) on the crankshaft pulley.
• Loosened or loose fastening screw(s) on the camshaft gear.
• Loosened or loose connecting rod bolts.
• Cracked timing chain(s).
• Changed timing.
• Irreparably damaged clutch elements (pressure plate and/or drive plate).
• Vibrations and/or engine imbalance due to irreparably damaged clutch elements.
• Vibrations around the transmission.
• Defective synchronisation.
Information
If such faults or symptoms are present together with engine damage, the VAL that was created must be checked for overspeed entries.
If overspeed entries are found and if the difference between the current hourmeter and the status when the last overspeed event was recorded is less than 200 operating hours, there is a high probability that the damage was caused by overspeed event(s).
The value “200 operating hours” should be seen as a guide. The possibility of engine damage occurring much later due to previous overspeed event(s) cannot be ruled out.



Rev ranges - 911 GT3 (991):
Create the VAL before deleting the fault memory. Overspeed events are documented as follows in the VAL:


Rev range 1: 9,000 -1 ... to 9,200 -1
⇒ Maximum permitted engine speed exceeded; engine damage possible.

Rev range 2: 9,200 -1 ... to 9,500 -1
⇒ Maximum permitted engine speed clearly exceeded; engine damage probable.

Rev range 3: over 9,500 -1
⇒ Engine damage has generally occurred.



Information
• In the event of damage:
Before repairing the engine or carrying out any other work, it is important to check whether there is a potential link between damage and overspeed events.
⇒ If this is the case, the work cannot be carried out under warranty or goodwill and neither can it be settled as a warranty or goodwill case.
• Before assigning a “Porsche Approved Warranty”, existing overspeed events must also be evaluated:
⇒ For a technical evaluation, please contact the Technical Hotline.
⇒ Further information and details about evaluating overspeed events can be found in the guideline:
“Dealing with overspeed events in the VAL when assigning a Porsche Approved Warranty” (see PPN - Porsche Warranty & Goodwill Guidelines).