What is the BAR allowed timing variance for ignition timing tests?

The timing variance allowed for ignition timing tests as specified by the Bureau of Automotive Repair (BAR) is +/- 3 degrees and +/- 100 RPM. This tolerance is crucial for ensuring that vehicles are operating within acceptable limits for emissions, as ignition timing can significantly affect engine performance and emissions output.

Maintaining the ignition timing within this variance helps ensure that the engine ignites the air-fuel mixture at the optimal moment, which can lead to better fuel efficiency and reduced emissions. By allowing both a degree of variance in timing and in engine RPM, technicians can be more flexible in their assessments during testing, accommodating slight variations that might occur due to engine wear or calibration.

The other options provide narrower ranges, which would not align with the BAR's specifications for a practical and effective testing approach.