# Knock Detection Delay **URL:** \ **Category:** EMU BLACK / CLASSIC\ **Created:** [November 12, 2024, 6:55pm UTC](https://community.ecumaster.com/t/knock-detection-delay/2751 "2024-11-12T18:55:14Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![xsd](https://avatars.discourse-cdn.com/v4/letter/x/b5e925/32.png) [@xsd](https://community.ecumaster.com/u/xsd)\ **Post date:** [November 12, 2024, 6:55pm UTC](https://community.ecumaster.com/t/knock-detection-delay/2751/1 "2024-11-12T18:55:14Z")
Hello, When I look at my log, there is a difference between the log in the graph and the value that is shown under “Knock Sensing”. ![KNOCKE](https://europe1.discourse-cdn.com/flex013/uploads/ecumaster/original/2X/9/979684d209c55fee05fb63397fb8174303787fc5.png) You can see that there is EVNT2 knock, but the sensor value in the log is only 2.73 volts, which is lower than the engine noise there with 2.98 volts. Can anyone tell me why there is a difference? ---
**Author:** ![Napkin](https://dub1.discourse-cdn.com/flex013/user_avatar/community.ecumaster.com/napkin/32/375_2.png) [@Napkin](https://community.ecumaster.com/u/Napkin)\ **Post date:** [November 13, 2024, 5:45pm UTC](https://community.ecumaster.com/t/knock-detection-delay/2751/2 "2024-11-13T17:45:55Z")
yep same here. never checked on an old version. but its not the first time this is reported ---
**Author:** ![xsd](https://avatars.discourse-cdn.com/v4/letter/x/b5e925/32.png) [@xsd](https://community.ecumaster.com/u/xsd)\ **Post date:** [November 14, 2024, 5:37am UTC](https://community.ecumaster.com/t/knock-detection-delay/2751/3 "2024-11-14T05:37:36Z")
@Jadzwin_ECUMASTER can you please explain? ---
**Author:** ![derUltraTT](https://avatars.discourse-cdn.com/v4/letter/d/ba8739/32.png) [@derUltraTT](https://community.ecumaster.com/u/derUltraTT)\ **Post date:** [November 14, 2024, 5:54am UTC](https://community.ecumaster.com/t/knock-detection-delay/2751/4 "2024-11-14T05:54:16Z")
I think this could be related to the measurement sampling rate of the client respectively the frequency the data transmitted to the PC. At 6000rpm u need 36kHz to have a resolution per 1 crankshaftdegrees, which is a lot and defenitly more than used in a decent channel logging. So i think the point is u just don’t see all knock sensor values with the needed sampling rate to see everything what is happening. But the ECU sees it and just reports the knock event. ---
**Author:** ![Jadzwin\_ECUMASTER](https://dub1.discourse-cdn.com/flex013/user_avatar/community.ecumaster.com/jadzwin_ecumaster/32/28_2.png) [@Jadzwin\_ECUMASTER](https://community.ecumaster.com/u/Jadzwin_ECUMASTER)\ **Post date:** [November 14, 2024, 11:14am UTC](https://community.ecumaster.com/t/knock-detection-delay/2751/5 "2024-11-14T11:14:54Z")
Change log draw style to dots. You will see the exact logging points. Now you look at the interpolation. Event 2 was registered later, not in the point you marked (one sample before). All channels for knock represents the maximum voltage value for knock from the last log sample ---
**Author:** ![xsd](https://avatars.discourse-cdn.com/v4/letter/x/b5e925/32.png) [@xsd](https://community.ecumaster.com/u/xsd)\ **Post date:** [November 14, 2024, 5:42pm UTC](https://community.ecumaster.com/t/knock-detection-delay/2751/6 "2024-11-14T17:42:58Z")
Where I find this ? Under Tools - Configurations I do not see it ---
**Author:** ![derUltraTT](https://avatars.discourse-cdn.com/v4/letter/d/ba8739/32.png) [@derUltraTT](https://community.ecumaster.com/u/derUltraTT)\ **Post date:** [November 14, 2024, 6:59pm UTC](https://community.ecumaster.com/t/knock-detection-delay/2751/7 "2024-11-14T18:59:16Z")
Rightclick on the graphlog and then set “change line style”. With every click u swap to the next style. There u can see that EMU has a samplingrate of 25Hz for the knock sensor values. To see only every max value from knock sensor of every ignition event at 6000rpm u need 200Hz. ---
**Author:** ![Jadzwin\_ECUMASTER](https://dub1.discourse-cdn.com/flex013/user_avatar/community.ecumaster.com/jadzwin_ecumaster/32/28_2.png) [@Jadzwin\_ECUMASTER](https://community.ecumaster.com/u/Jadzwin_ECUMASTER)\ **Post date:** [November 14, 2024, 9:33pm UTC](https://community.ecumaster.com/t/knock-detection-delay/2751/8 "2024-11-14T21:33:39Z")
There is a shortcut for that (I use it a lot) SHIFT + S It is important for knock channels, there is always the peak value logged between two logging points. That is important because you do not miss any knock situation, just the time will be quantized to 40ms (25Hz). ---
**Author:** ![ngt](https://dub1.discourse-cdn.com/flex013/user_avatar/community.ecumaster.com/ngt/32/1162_2.png) [@ngt](https://community.ecumaster.com/u/ngt)\ **Post date:** [November 18, 2024, 4:46pm UTC](https://community.ecumaster.com/t/knock-detection-delay/2751/9 "2024-11-18T16:46:42Z")
because voltage logging is not as fast as the detection happening so you have knock but you cant see the voltage spike in the log graph. You can also enable Check engine light if you dont have knock corrections so you know there was a voltage spike aka knock. I usually verify knock threshold with headphones on engine block