Originally Posted by scooterbum46

Uhh - no.... Current knock sensing is done using ion-sensing (as described if you read this thread from the beginning). There is no microphone/transducer that would "hear" an exhaust pipe hitting the frame..

Originally Posted by Joe_G

My response was in the previous posters referral to the knock sensors in cars.

Originally Posted by scooterbum46

Oops - somehow I lost track of the thread ......

Originally Posted by CVORoadKing2013

On the 2014 and Newer bikes ( at least the touring models) Harley changed the strategy for the ion sense or knock sense. They are actually trying to prevent any knocks. They will actually start to pull timing before a knock occurs. As they sense an increase in resistance they will actual pull timing to stop a knock. Then that value is stored and used every time you hit that area ( map pressure, RPM , throttle positions)

Think of it as a dynamic timing table. The timing will continue being pulled for x time if it doesn't sense a resistance change again.

My bike has never pinged but you can see it pulling timing and increasing the knock count. I turned off my knock sense and could see the knock counts increasing with no ping heard at all. ( using PV to see the data)

This is a very basic explanation and I may not be describing it 100% correct but this is my understanding from FM

Originally Posted by CVORoadKing2013

On my 2103 CVO you would hear a sound ( pre knock ) then a second ping and you would see the knock count increment and the timing being pulled. But it would not pull timing again until the next event.

On my 2015 going down the highway at 65 MPH 25-2700 RPM it can pull from .25 degrees up to 6-7 Degrees. after the first time it does it it will continue to do it even though you do not see the knock count increment. Then after a period of time it will just stop.

I have shut off the knock control on a day when I was seeing timing pulled like that got back on the highway and and road the same way and never heard a single ping or knock.

I do not like this new way of handling spark knocks but there is nothing I can do other than turn of the knock control until I start actually hearing a knock

Originally Posted by 98hotrodfatboy

I remember back in the eighties when Oldsmobile first started using knock sensors. It really didn't work all that well and any abnormal engine noise would knock the **** out of the timing and those 231 v6 motors didn't have any power to begin with. I can remember just tapping on the motor would be enough to activate it. That's when the EPA standards had all motors running wicked lean. So what we would do to compensate was to drill out the carbs and increase the jet size on the 02 solenoid. I'm sure they work a little better today. You gotta remember they didn't have ecm's then...

Originally Posted by JustDave13

I remember having to monkey around with electronic controlled feedback carburetors... Glad it's over.

Originally Posted by HDF Tech

First ION knock detection is the direction most applications are going to use. The old PEZIO sensor relied on a vibration ( caused by some level of knock ) to register at the sensor, It is very hard to detect low levels of knock and seperate the singal ( knock from detonation ) from normal engine vibrations, such as valve closings on a Harley engine. On most vehicle applications the knock sensor can sense true knock from noise, but may not READ every cylinder in a multi-cylinder engine at every cylinder at every RPM, But most system use a GLOBAL retard scheme where any knock will retard spark to all cylinders at the same amount. New systems are going to indidvidaul cylinder knock detection where only the cylinder producing knock is retarded and only until knock ( detonation stops) so in a V8 or V6 you might only have one or two cylinders with any amount of retard.

The advantage of the ION system is it is not dependent on a sensor location and it can be calibrated to detect each cyclinder at all engine speeds and loads.


ION sensing knock detection does not use a Sensor that is externally mounted on the engine. The name ION sensing is derived from the fact that as detonation happens IONIZATION at the plug tip changes the resistence to fire the plug. The actual detection to this change in resistance is internal to the coil and the signal is sent back to the ECM. Software tables are then calibrated using model based software. The way it is calibrated is important to understand WHY some folks are having TROUBLE. A very sophisticated Combustion measurement system is placed on a development engine and actual cylinder pressures are recorded vs. crank angle degrees and coil operating ranges, as the engine is running at set speed and loads. By reading "NORMAL" outputs from the ignition module electronics to the ECM input and noting the change when detonation casues Peak cylinder pressures to rise, a model can be developed that as long as the signal from the ignition module is outputing the "expected NORMAL" signal back to the ECM no retard will occur. A change in resistence value and amount can be correlated to a given rise in pressure in the chamber during combustion.Detonation causes very large spikes in pressure even at very low levels of detonation, so the model can and does detect even before "audilble detonation ( that that can be heard ) happens. It is a very good system and very reliable with one HUGE exception. Detection is dependant on the values calibrated in the software that represent knock, and are based on a stock engine ( or a known modified engine such as the STAGE I,II etc.) with a GIVEN set of Production intent parts.ie , Spark plugs, wires, and even compression ratio can and does change the resistance at the coil. So once folks start changing wires, Plugs ( to non-factory specs) and modifing the engine cams, compression ratio etc,( and even expected A/F ratios, and therefore combustion temperature) the values derived form a production engine are no longer valid and may cause the software to "determine" that knock is present when it's not or fail to dectect knock when it is.

Just as production vehicles such as cars and trucks use similar schemes for many functions but most folks don't change parts or "hop-up" current cars with fuel injection systems... As an aside most people really don't know that if you change the aircleaner system or duct work ,even with a MASS AIRFLOW sensor you change the output of the mass airflow sensor. Those sensors are calibrated to read correctly only with a known set of induction parts. There is some amount of adaptablity in the fuel system but it is possible to get even a closed-loop system, to where the softeware cannot adapt enough for some changes that one might make. EXHAUST, intake etc.


So Harley knock detection is really not that different than other vehicle manufactures, it's US the users that may not understand the impact on a calibrated system

Originally Posted by abhibary

Could anyone tell me which model of HD (model name and number) uses Ion sense for knock detection ? Thanks in advance.