| 00:00 |
- Given the damage that knock can cause, manufacturers have been including knock detection and control systems on their ECUs for many years.
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| 00:09 |
This includes both factory-fitted ECUs and those in the after-market.
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| 00:14 |
The idea behind these systems is to include a sensor fitted to the block that can pick up the vibrations associated with knock occurring.
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| 00:23 |
From here the ECU can process this data and if it decides that knock is occurring it can retard the ignition timing to help safe guard the engine.
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| 00:33 |
These systems can be very powerful and particularly with the newest generation of ECUs, knock detection and control can be surprisingly accurate and effective.
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| 00:44 |
When we start to modify the engine though, this can change the noise profile that the engine produces which is essentially what the knock sensor is listening to.
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| 00:55 |
This means that on a heavily modified engine the knock control system may struggle to accurately detect knock.
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| 01:02 |
This is potentially a big problem if you're relying on the knock control system to keep your engine in one piece.
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| 01:09 |
I've also struck some engines that were completely stock yet for some reason the knock control system was falsely indicating that the engine was suffering from knock.
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| 01:19 |
This sort of situation is safe enough as it's unlikely to result in engine damage.
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| 01:25 |
However, the ECU will be retarding ignition timing in response to what it thinks is knock occurring and hence, you're probably going to be leaving some power on the table as a result.
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| 01:37 |
More dangerous however, is the situation where the engine actually is suffering from knock and the ECU isn't able to pick this up.
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| 01:45 |
I've seen this situation numerous times.
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| 01:48 |
So, blindly assuming that the ECU is able to do its job as intended can sometimes be a dangerous assumption to make.
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| 01:57 |
For those reasons I always like to use audio knock detection equipment when tuning any engine.
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| 02:03 |
And we'll discuss what this is and how it works shortly.
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| 02:07 |
It's important to understand that a knock control system isn't there as a substitute for correctly tuning the engine.
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| 02:16 |
Instead it's there as a safety backstop in case you end up with a bad batch of fuel with a low octane rating or perhaps the engines operating conditions end up vastly outside those that were experienced when the engine was tuned.
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| 02:31 |
In particular, the knock control system is reactive not proactive.
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| 02:36 |
This means it can't do anything until knock actually occurs.
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| 02:41 |
While minor levels of intermittent knock are unlikely to cause damage immediately in a low or moderately powered engine, in highly tuned engines, knock can be very damaging very quickly.
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| 02:53 |
This is where it's so important to ensure that the engine isn't suffering from knock when it's being tuned.
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