Detonation is a characteristic metallic sound that occurs when a car engine is running. Inexperienced auto mechanics often confuse knocking sounds with the clatter of valves with an unsettled clearance or with the ringing of piston fingers. To distinguish a detonation sound from others like it, you should pay attention to some points.
Instructions
Step 1
First of all, pay attention to the moment the detonation occurs. If there was no such effect before, it can occur after refueling with low-quality gasoline, in case of a violation of the ignition regulation or after prolonged operation of the engine at low powers.
Step 2
Secondly, check how the engine reacts to load changes. Most often, knocking occurs at low speeds at maximum load in engines with a low compression ratio, and at maximum power with the corresponding speed for this load in engines with a high compression ratio. In the first case, detonation should sharply increase with increasing load at low speeds. In the second case, the detonation should sharply increase when driving at a submaximal speed.
Step 3
Distinguish short-term detonation from long-term detonation. If you only hear 3-4 knock knocks, ignore this phenomenon. In this case, the knock effect has more positive effects on the engine than negative ones.
Step 4
Pay attention to the color of the exhaust gases. The presence of a black or greenish haze indicates a recent detonation, even if you have not heard the characteristic knocks. Such smoke arises from the collapsing aluminum piston and indicates a critical level of detonation and the need to replace pistons and piston rings.
Step 5
If detonation is found after the next refueling with gasoline of the corresponding brand, do not rush to adjust the ignition. Detonation can be caused by carbon deposits on the combustion chamber parts. Ride for 20-30 minutes. If the knock does not disappear, start gradually decreasing the ignition timing. After a while, if necessary, continue to decrease the angle value until the detonation stops completely. If you cannot cope with the detonation effect, look for the cause of the extraneous sounds in the malfunction of the components and mechanisms of the motor.
Step 6
A knock-like effect can occur when the ignition is turned off. In this case, the engine, despite the absence of a spark from the candles, continues to twitch for some time. In fact, this effect has nothing to do with detonation and is called diesel. The reasons for this effect are associated with the use of low-octane fuel and are more typical for new engines, the real compression ratio of which is higher than that recorded in the passport.
