spark plug poll
- Thread starter 00BUCKSHOT
- Start date
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Jack Klarich1
Guest
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
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
"Detection is dependant on the values calibrated in the software that represent knock, and are based on a stock
On an engine that is already lean from factory almost anything you change will make it run leaner. The only tuner from Harley that will let you tune past that limit is the SEPST Pro tuner.
But that tuner isn't compatible with your warranty.
The knock sensor system is a good thing to not mess with. If the spark settings & fuel settings are set correctly there won't be any knock with the standard knock sensor settings.
One other thing to check is the plug wires to see that they are the correct resistance. Many aren't correct new.
If your plug is white white you most likely need more fuel in those knock areas. Not much of a change can be enough to take care of it. Sometimes it does take a large adjustment in both spark & fuel .
The late Evo thru TC engines do not like changes, The M8 can and does tolerate along with ALL can bus systems, your ride you decide
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
"Detection is dependant on the values calibrated in the software that represent knock, and are based on a stock
On an engine that is already lean from factory almost anything you change will make it run leaner. The only tuner from Harley that will let you tune past that limit is the SEPST Pro tuner.
But that tuner isn't compatible with your warranty.
The knock sensor system is a good thing to not mess with. If the spark settings & fuel settings are set correctly there won't be any knock with the standard knock sensor settings.
One other thing to check is the plug wires to see that they are the correct resistance. Many aren't correct new.
If your plug is white white you most likely need more fuel in those knock areas. Not much of a change can be enough to take care of it. Sometimes it does take a large adjustment in both spark & fuel .
The late Evo thru TC engines do not like changes, The M8 can and does tolerate along with ALL can bus systems, your ride you decide
Blue Wide Glide
Junior Member
I use HD plugs. HD trusts them, and without them nothing else matters!