Knock Listen Device
Contents
1. This guide will explain how to build a low cost knock sensor listening device that can be used to detect engine knock well before it will be audible on the interior of the vehicle by utilizing the factory knock sensor This setup 1s intended to be easily installed and transferred from one vehicle to another All of the components can be purchased from Radio Shack except for the headphone amplifier which can be found on Amazon com for 20 Operation is very straight forward The knock sensor is a simple piezoelectric microphone The only thing that needs to be done to listen to the signal is amplify it The 01 micro farad capacitors need to be in place to isolate the amplifier from the ECU so that the amplifier does not interfere with the ECU s monitoring of the sensor Any OluF capacitors will do as long as they are not polarized For easy install and removal of the system solder in a couple of jumper wires with female spade connectors to the knock signal wire s and the signal ground usually attached to the shield around the knock signal wire at the back of the ECU connector These jumpers will stay permanently installed on the vehicle The pins for these signals vary from vehicle to vehicle so please refer to the service manual for the vehicle that you are doing the installation on In the version that I use my OluF isolation capacitors are connected to a 1 8 stereo mini jack that can be disconnected from the 1 8 mini extension cable Th2. is is optional you can solder the spade connectors and OluF caps directly to the 1 8 mini extension cable without the jack I find the jack convenient 1f I want to use different length cables in different vehicles for instance Titan ECUS are all the way in the engine bay where Z G ECUS are in the cabin In my system I use two isolation capacitors so that I can hook up to both sensors on vehicles that use two such as Nissan V8 engines so that I will hear one bank in one ear and the other bank in the other ear When I m using the system on a vehicle with a single knock sensor I simply jump the two together so that I will hear the signal in both ears I have used many different amplifiers to amplify the signal from home brew amplifiers to PC audio cards to off the shelf headphone amps and I ve found the FiiO E5 headphone amplifier to suite my needs quite well It is VERY small has good volume control great response and an internal Lilon battery that charges conveniently off of any USB port Audible knock will sound like clicking or crackling If you would like to view knock visually you can also download a FREE program called Spectrogram 5 0 which is a dual channel visual spectrogram program Pings and knock events will show up on the spectrogram chart as bright white lines in the 10 12K Hz range To use spectrogram you do not need the amplifier Simply run the 1 8 mini jack extension cable with 1solation capacitors in place into
3. the mic input on your computer The computer s audio card will handle amplification You will be able to listen to the signal from your computer s speakers while recording as well as record and save files for later review This setup will run any set of headphones but I would recommend using noise canceling headphones which will help block out any background noise which there will be a LOT of when running at WOT Below is a schematic and a picture of the system I use Please contact me if you have any questions Jared UpRev com Sparc CONNECTORS For Quick INSTAGL Ye STERIO ANN DACK Lefr Bank NPUT e e la x nd JumPER Fer UN SINGLE Knock RIGANT Olm F SENSOR SYSTEM BANK NPLT ENGINE DLO Out PUT To Notse CANCELING Heap Prov ES Fi O ES HEADPHONE mpPuiFIER Em
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