Test procedure

A "sooted" engine will have greater valve overlap combined with problems with residual gases, and as a result it will run more roughly than a "clean" engine. This can be measured using rough running values that indicate combustion consistency within the engine.

Switch off all electrical equipment and always connect a battery charger in order to minimize the load on the engine.

• Engine temperature should be below 45 °C, as the effects of carbon deposits are more difficult to detect when the engine is warm. Steps should also be taken to prevent the electric fan from starting during the test
• The timing of the exhaust valve is locked in, while the intake valve's timing is continuously adjusted from advanced to retarded in order to cover a range extending from maximum to minimum valve overlap.
• The rough running values indicating combustion consistency are simultaneously recorded for subsequent evaluation.
• The result that is then issued indicates whether it will be necessary to clean the intake ports.