Definition of top dead centre in English:

top dead centre


  • The furthest point of a piston's travel, at which it changes from an upward to a downward stroke.

    ‘the figure shows the piston at top dead centre’
    • ‘The reciprocating piston 15 of the second combustion chamber 12 has a top dead center position and a bottom dead center position.’
    • ‘The Ikona tooth form is a patented non-involute profile consisting of a specifically matched external and internal tooth pair that provide maximum performance in the smallest size possible with no contact at top dead center.’
    • ‘It calls for the top dead centre of the piston motion to be kept fixed, while the bottom dead centre is varied.’
    • ‘This causes the piston to shift in the opposite cylinder wall just before top dead center greatly reducing piston slap (aka: noise).’
    • ‘In a typical spark-ignition gas engine, the inlet valve might open 20 degrees before top dead center to start the induction stroke, and close 20 degrees after bottom dead center.’
    • ‘By that time, the piston has moved so far from top dead center, no work of any value was being performed.’
    • ‘After the competition at Ford's proving grounds, we were checking the engine's timing - looking for top dead center - with the valve covers off when the fuel mist ignited.’
    • ‘As the engine load increases, the head tilts by up to four degrees in order to lower the effective compression ratio by altering the volume of the combustion chamber with the piston at top dead center.’
    • ‘The internal cylinder pressure reaches a peak directly in proportion to the fuel-per-air ratio, and in Braly's test stand, those pressures are measured from the piston position of top dead center.’
    • ‘Use a timing light that is known to be accurate, and ensure that when the number-one piston is on top dead center, the harmonic balancer on the front end of the crankshaft is in alignment with the zero marker.’
    • ‘According to the present mode of operation, the stroke length, i.e. the distance the piston travels between the top dead centre and its bottom dead centre is dependent on the flow rate which a user has selected at the user interface 42.’
    • ‘Mixing prior to auto-ignition can also be achieved by direct injection well before top dead center.’
    • ‘Starting involved manipulating an ignition advance-retard lever and choke, easing the kickstart to get the piston a bit before top dead centre and then giving an almighty heave.’
    • ‘Bring the piston to 10 degrees before or after top dead center (BTDC or ATDC).’