The MoviChip Knock Sensor Controller is an external ECU to control an engine knock sensor. When the user programmed knock conditions are met it will output a 0-12 volt switched signal and also a 0-5 volt switched signal.
These outputs can be used to interface with the engine ECU and/or give the user an audible or visual indication that the knock threshold has been met.
The Knock Sensor Controller (KSC2) is designed to be mounted in the engine bay and is programmed via Bluetooth using the KSC2 Android app.
Knock Sensor Controller – Features
Adjustable knock frequency according to your engine, knock sensor location and engine characteristics
Adjustable tolerance for the knock frequency plus or minus Hz in hundred Hz steps
Adjustable volume monitoring
Adjustable knock volume threshold
Adjustable count threshold ie how many events will count as knock
When the volume threshold and count threshold are met or exceeded the unit will output a 12 volt signal (max 3 amps) and a 4.5 volt signal (max 2 mA). These can be used to integrate the knock signal with a device of your choice.
RPM dependent monitoring.
The MoviChip KSC2 uses a 0-5 volt rpm signal input. We use this signal so we can listen to knock, only when it is likely to occur, specifically within 60 degrees of crankshaft rotation relative to the spark event.
Base noise and count levels.
To get you started we have incorporated a logging feature into the accompanying Android app. When the engine has a tune that is known not to knock, by switching on the logging function we can see the maximum volume seen by the knock sensor and also the maximum number of events above this volume. We can then use these readings to give us a starting point for setting the knock threshold.
Audible Knock Monitoring
Using an audible knock sensor system can help you narrow in on the best settings to use with a specific engine. There are many audible knock monitoring solutions, both professional and DIY, which allow you to monitor engine knock. In our experience the best audible solution (which could also be the cheapest solution) was simply to use some free windows software and connect the knock sensor output to the mic input on the laptop.
You read more details of how you can make your own audible knock sensor monitor here.
Because this solution for audible monitoring is so cheap and effective we have not burdened the KSC with audible monitoring. If you only need audible knock monitoring then we highly recommend this free option.
Knock Sensor Controller – Benefits
Accuracy
We monitor RPM so we are only listening to the knock sensor input when knock is likely to occur.
Knock sensor solutions which do not know the RPM of the engine are listening to engine noise for the entire engine revolution, even when engine knock could not occur.
Visual & Audio
The 5 volt output allows you to connect the knock sensor to an ECU to gives an extra layer of safety and helps get the maximum power from the engine.
The 12 volt output allows you to have an audible (eg buzzer) warning when the KSC thinks it detects knock that exceeds the programmed thresholds and/or a visual indication (eg light) when the KSC thinks it detects knock that exceeds the programmed thresholds
Installation
The unit is designed to be mounted permanently on the vehicle, in the engine bay. This is typical of most MoviChip products and we do this to simplify installation. You do not need to find space to mount an ECU box in the cabin of the car and you do not need to runs wires from the engine bay into the cabin or splice into the wires inside the cabin. The KSC is designed to be a largely fit and forget item.
Adjustment
We like big screens and we dislike having to scroll through menus using arrows and buttons. This is why we harness the power of modern Android smartphones. Big screen means you do not have to dig through menus to get to what you need
Unobtrusive
You only need to use the app if you want to adjust settings or to check data coming from the unit. 99% of the time a control unit is simply not needed, why have a control box taking up space in the dash when you hardly ever need to use it?
Knock Sensor Controller – Specs
Connections
Ignition Power (12v)
Power Ground
Signal Ground
Knock Sensor +
Knock Sensor Ground
RPM Signal (0-5v)
ECU Knock Output+ (0-5v)
LED Power+ (0-12v, For visual indication)
LED Power –
Settings
Knock Signal Gain
Knock Frequency
Knock Frequency Tolerance
Knock Signal Count Threshold
Knock Signal Volume Threshold
Knock Sensor Controller – What Is Included
Knock Sensor Controller 2.0 Unit
Connector with crimps for products supplied without wiring loom
or
Connector with 1 meter wiring loom for product supplied with wiring loom
Android App – Downloaded from the MoviChip website
User Manual – Download from the MoviChip website
What else is required
Android device with Bluetooth.
Knock sensor – We recommend Bosch or Bosch-type knock sensors part number 0261231173 or equivalent.
Genuine Bosch sensor and connectors can be bought here.
Bosch-type knock sensors and connectors can be bought at online auction sites
Knock Sensor Controller – Quick Start Guide
Knock Frequency
We need to define what will count as a knock frequency, our knock frequency calculator will get you started. You may need to adjust the frequency and the tolerance according to the sensor your are using, the location of the sensor and general operating conditions. A starting point for tolerance could be 400Hz.
Using the App
Baseline
Use the vehicle as you would normally and in extreme conditions (you must be sure that the current map is creating zero knock) and monitor the volume of the knock sensor signal in the DIAG menu.
When you get a feel for where the volume is in normal use, go to the SET menu and enter the Sensitivity as this volume number or 1 or two points lower.
Now use the Baseline Calibration logging feature built into the app.
Turn it on, ensure all numbers go to zero, use the vehicle as you would normally and in extreme conditions (you must be sure that the current map is creating zero knock) and then return to the pits and before turning off the engine “Stop” the log and look at the peak numbers for volume.
This will tell you the normal engine volume in the frequency range you programmed in the previous step.
REMEMBER: You need to be sure that knock is not occurring at any time during this process.
Set your “Volume Threshold” to this peak number and repeat the last process but this time we will be finding the Count Threshold.
This time, when you return to the pits, look at the “Count” number. This is the number of times the volume from the sensor matched that peak volume level you entered earlier.
Enter this “Count” number as the “Count Threshold”.
You should now have a ballpark figures for the Sensitivity, Count and Volume for your engine in normal conditions. Whenever the Volume Threshold is exceeded and then the Count Threshold, the 5 volt and 12 volt output will a signal.
Adjust the threshold figures if you need to as the engine is tuned/used.
IMPORTANT
The Knock Sensor Controller should never be used as the exclusive device to monitor engine knock and for safe engine operation in general.
Engine safety and knock should be monitored by numerous sensors to ensure there is some redundancy if any sensor or device experiences a problem.
Notes & Possible Improvements
Engine Volume and RPM
During our research and development of this product we found conflicting information regarding the importance of taking RPM into consideration when monitoring engine knock volume.
Some studies make no mention of RPM playing an effect in engine knock volume while some knock sensing products say RPM plays a part.
Our Testing
For sure when listening to an engine with your naked ear the noise gets louder as RPM increases.
However in our research, when you narrow in on a specific frequency band coming from the knock sensor signal, the sound of ignition and detonation remains largely constant regardless of RPM.
What does change as engine RPM increases is the number of these sounds ie the number of ignition events per minute increase with RPM, as you would expect.
The Main Contribution to Knock Volume
What actually changes the volume of the ignition events and detonation events, is the amount of load on the engine. Less load equals a quieter detonation event, bigger loads cause higher volume detonation. This would make sense as there is a greater volume of air and fuel detonating/knocking as engine load increases.
Limitations & Future Development
The KSC2 is our entry into the knock sensor monitoring market, we believe as it is, without engine load sensing and for the price point, it is a good product and will serve many users.
If the KSC proves to be a popular product and/or enough customers ask for it, we will release a more advanced version of the KSC which will monitor knock relative to engine load.
Terminology
Knock Sensor Gain
The volume we will monitor, as outputted from the knock sensor during normal engine activity
Frequency
The frequency window we listen to for knock. We set the target knock frequency and also the threshold frequency.
Example. If knock frequency is 7000Hz and the threshold is 400Hz, our monitoring window for engine knock will be from 6600Hz to 7400Hz.
Knock Volume Threshold
What volume if exceeded will count as a knock event.
Our count threshold
How many of these volume events we will classify as knock
