SAE J1667 is a recommended practice published by SAE International (a professional engineering organization, not a government body). It describes a stationary snap-acceleration smoke test for heavy-duty diesels using light-extinction smokemeters, including equipment requirements, how the test is performed, the quantification algorithm and factors that can affect the result. Ontario's DriveON program applies this procedure, referenced under O.Reg. 169/22, for heavy-duty diesel opacity testing.
J1667 is designed as a stationary test: the vehicle is secured, the transmission is in a position appropriate to the procedure, and the snap-acceleration event is performed without a road load cycle. That allows repeatable exhaust-opacity measurements at a yard or fixed VIC when site conditions are suitable.
Under DriveON, a heavy-duty diesel emissions inspection includes a pre-test check before opacity readings. The technician may not continue if vehicle condition, safety risk, or equipment/property damage concerns block a valid procedure. Eligible vehicles may also receive an OBD system test according to model year and GVWR.
The engine must be at the normal operating temperature required by the procedure before snap-acceleration readings are taken. A short idle alone does not automatically mean the engine is ready.
With the engine at normal operating temperature and idling, the throttle is opened from idle for the snap-acceleration event while the smokemeter records the required exhaust-opacity measurements. The sequence follows the standardized DriveON / SAE J1667 procedure rather than an informal single pull of the throttle.
Approved light-extinction (opacity) meters measure how much light is obscured by the exhaust plume. That optical measurement is the basis for the smoke-density values used in the calculation — not a visual guess by the technician.
During the standardized snap-acceleration sequence, approved light-extinction equipment records the required exhaust-opacity measurements. The equipment then calculates the overall opacity result according to the applicable DriveON and SAE J1667 procedure. That overall result is compared with Ontario's model-year limit.
An opacity pass or fail is a compliance measurement at the time of the test. It is not a full diagnostic of DPF, SCR, injectors or long-term aftertreatment health, and it is not a warranty of future performance.
Related guides: Ontario DriveON opacity standards and common causes of high opacity. Mobile testing through Piotr Service.
