Total timing rate is obtained at what engine condition?

• A. Idle rpm
• B. Accelerated rpm rate
• C. Redline rpm
• D. Normal operating rpm

Answer: (B)

Total timing is the spark timing value when all advancing mechanisms have contributed, which happens when the engine is under load and accelerating. At accelerated rpm, the centrifugal (mechanical) advance has come in, and vacuum advance is typically reduced or cut off, giving the maximum practical timing used for performance. Idle rpm doesn’t reach the full mechanical advance, and redline or normal cruise conditions aren’t the conditions where this full, combined advance is defined. So the condition where total timing is obtained is during accelerated rpm.