Knock Correction

Engine knock, if severe enough, can cause engine damage. Combustion chamber design, gasoline octane, air/fuel ratio, and ignition timing all affect when knock will occur. Under most engine conditions, ignition timing needs to be near the point when knock occurs to achieve the best fuel economy, engine power output, and lowest exhaust emissions. However, the point when knock occurs will vary from a variety of factors. For example, if the gasoline octane is too low, and ignition takes place at the optimum point, knock will occur. To prevent this, a knock correction function is used.

Correctional Control SystemsE27 Lampdolder Wiring

T852f150

Knock Contrrol Signal Toyota Agya

When engine knocking occurs, the knock sensor converts the vibration from the knocking into a voltage signal that is detected by the ECM. According to its programming, the ECM retards the timing in fixed steps until the knock disappears. When the knocking stops, the ECM stops retarding the ignition timing and begins to advance the timing in fixed steps. If the ignition timing continues to advance and knocking occurs, ignition timing is again retarded.

Knock Contrrol Signal Toyota Agya

The ECM is able to determine which cylinder is knocking by when the knock signal is received. The ECM knows the cylinder that is in the power stroke mode based on the NE and G signals. This allows the ECM to filter any false signals.

Some mechanical problems can duplicate engine knocking. An excessively worn connecting rod bearing or a large cylinder ridge will produce a vibration at the same frequency as engine knocking. The ECM in turn will retard the timing.

Was this article helpful?

0 0
Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

Don't pay hundreds of dollars to find out what is wrong with your car. This book is dedicated to helping the do it yourself home and independent technician understand and use OBD-II technology to diagnose and repair their own vehicles.

Get My Free Ebook


Post a comment