Top Dead Centre (TDC)
Top dead centre is the position of the piston at the very top of its stroke.
What is Top Dead Centre (TDC)?
Ignition timing is given in degrees before TDC. Timing belt work starts by setting cylinder 1 to TDC. Bottom dead centre (BDC) is the lowest position. TDC on the compression stroke and TDC on the exhaust stroke look the same at the crank; the cam position shows which one it is. Timing marks on the crank pulley and covers help find it.
How it works
The crankshaft sensor and reference marks tell the engine where TDC is.
Why it matters for your car
Setting TDC wrongly during belt work can damage valves. Use the specified locking tools.
Other terms
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- Alternator Diode (Rectifier)
- Anti-roll Bar
- Differential
- Drive Cycle (OBD Drive Cycle)
- EGR Valve
- Fuel Rail
- Maximum Roof Load
- Network Sleep Mode
- NOx Sensor
- Number Plate Light (Licence Plate Lamp)
- Permanent Code
- Piston Ring
- Power Tailgate (Electric Boot Lid)
- Range Estimate (Guess-o-Meter)
- Refrigerant (A/C Gas)
- Roadster
- Rotary Engine (Wankel Engine)
- Transmission Adaptation (Relearn)
- Tyre Repair Kit (Sealant Kit)