Glossary & Abbreviations

Common abbreviations used throughout automotive service literature, grouped by subject.

Engine Position & Timing

AbbreviationMeaning
TDCTop Dead Center — piston at the top of its stroke
BDCBottom Dead Center — piston at the bottom of its stroke
BTDCBefore Top Dead Center (e.g. 8° BTDC initial timing)
ATDCAfter Top Dead Center

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