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Knock - how much is too much?

Practical Reflash Tuning

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How much knock is considered acceptable? With the factory tune on my Honda J35Z2, the ECU is reading about one knock per minute on average. Assuming these are legitimate, should I be concerned?

Is it in the same locations every time you do a pull? Have you hooked up a knock monitor and listened for knock with headphones?

How much is too much?

This depends on the amount of specific power you're making.

I was once at a track day, and a 4AGE naturally aspirated corolla was there doing laps, pinging to loudly you could hear it from the pits. It ran all day and drove home no problems.

A 1000hp per litre drag engine running at 10,000 rpm would only last a few seconds at best under the same level of knock intensity.

Your factory stock car will keep running forever and meet its expected design life still.

A lot of factory calibrations tend to be over advanced and rely on the knock control strategy to fix this. Personally this isn't an approach I like to take as it can be damaging over the long term but just as importantly it also results in an erratic power delivery as the timing is constantly being pulled when knock occurs. You can often gain power by retarding the timing and avoiding knock.

My guide is that if you're seeing consistent knock at the same combination of load and rpm, retard the timing. It's not unusual however to get an occasional knock event that isn't repeatable.

As Andre says, a lot of factory tunes ride the knock sensor so its potentially nothing to be concerned about.

You may find if you run premium fuel the ecu completes its max advance strategy and the knocking ceases.

I've no direct Honda O.E knowledge to be honest but Certainly Ford and Mazda are running a strategy that uses knock feedback to determine fuel octane and they literally dont operate to their optimum limit without knocking occasionally.

They use this feedback to choose timing tables and load limiting tables to run from and blend between them based on knock intensity which is transposed back as octane ratio. I have written a few blogs on such O.E strategies if your interested to learn more.

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