Note: Refer HERE for a general overview of Knock Control.
Knock Setup:
Selects the operating mode of the Knock Control function. The following modes are available:
·OFF - Knock Control is disabled.
·Ignition Trims - Knock Control will retard the ignition angle to reduce or prevent further knock.
·Fuel Trims - Knock Control will richen the air fuel mixture to reduce or prevent further knock
·Ignition and Fuel Trims - Knock Control will retard the ignition angle and richen the air fuel mixture to reduce or prevent further knock.
·Normalised Ign - Knock control will use a normalised noise level and will retard the ignition angle to reduce or prevent further knock.
·Normalised Fuel - Knock control will use a normalised noise level and will richen the air fuel mixture to reduce or prevent further knock.
·Normalised Ign & Fuel - Knock control will use a normalised noise level and will retard the ignition angle and richen the air fuel mixture to reduce or prevent further knock.
Both knock modes determine knock to be when the Knock Level of a cylinder is larger than the value in the Knock Threshold Table.
The regular knock modes uses the filtered noise value whereas the normalised modes take that current knock level and normalise it to the value of 1. This means that if the level of noise is constant the knock level will be a value of 1 in the normalised modes regardless of the actual noise level, if however one sample is significantly larger than the other recent values this will make calculated knock level higher than 1. This means that the knock control setup constantly corrects for any ongoing background noise and only shows up short lived sudden noise making it more useful over a range of engine conditions and less engine specific.
Note: When the knock level goes above the threshold in a normalised knock mode it changes the normalising filter calculation. This can result in a small reading just above the threshold causing knock level runaway on that cylinder which looks likes a gentle slope up rather than a sudden spike. Setting the RPM Delta Level value lower or having a slightly higher threshold value can prevent this false knock from occuring.
This setting enables the user to select an input which when active will temporarily turn off knock detection (for the duration of the input being active). This can be used to prevent false knock readings during gearshift or other situations.
This setting sets the sensitivity of the ECU to a particular knock signal frequency range. The correct frequency range can be identified by using a Knock Amplifier (such as the Link Knockblock) or by consulting the suggested frequency settings list in this help manual. PCLink contains a feature, Knock Audio, that can be helpful in determining the correct frequency filter to select for your engine.
The following options are available:
·Filter = OFF - No filtering at all, only use this setting for testing.
·4-10 kHz - Wide Band - Knock input is sensitive to frequencies between 4 and 10 kHz.
·10-16 kHz - Wide Band - Knock input is sensitive to frequencies between 10 and 16 kHz.
·X kHz Narrow Band - Knock input is most sensitive to frequencies around X kHz. X can be 3.5kHz, 4kHz, 5kHz, 6kHz, 7kHz, 8kHz, 9kHz, 10kHz, 11kHz, 12kHz, 13kHz, 14kHz, 15kHz, 16kHz.
A good rule of thumb is Knock frequency (kHz) = 1800 / (3.14 x Piston Dia (mm)).
Sometimes the second harmonic frequency can give a better SNR (Signal to Noise Ratio), this frequency is 2x the base knock frequency.
Note: This setting is only available when using the Ignition Trims, Fuel Trims or Ignition and Fuel Trims modes (not the Normalised modes).
This setting adjusts the overall gain of the knock circuitry amplifier, a higher gain number will result in larger Knock Level numbers for a particular signal input. Use this adjustment to get a better range of Knock Level numbers, if Knock Level numbers are reaching full scale then reducing Gain Channel will bring them back into range. A gain number of zero will disable the knock signal.
This settings allows the user to set the Knock Trim Tables to be cleared at key on. When this setting is OFF the trim tables will retain the values they contained last time a STORE was performed. This setting can be used to permanently store retard values in the Knock Ign and Fuel Trim Tables, if this is done the ECU will power up and the engine will run retarded until the Knock Control system tries to put timing back into the engine. I.e. the engine will start in a safe state and the ECU will advance timing until knock is detected or the entire trim is removed.
Warning: If this setting is set to OFF it is essential that the retard tables have the correct values in them when a store is performed!
When this setting is set to ECU Power-On, all Knock Ignition and Fuel Trim Tables will be set to zero at key on. This setting will cause the engine to be run initially in its most advanced state and timing will be removed after detonation is detected, this is the most commonly used setting.
The engine position in degrees after the ignition event at which the knock window signal will start. e.g. If the current ignition timing is 15 degrees BTDC and the start point is set to 10 degrees, the window will become active at 15 - 10 = 5 degrees BTDC. See the Window Length section below for calculating the maximum value.
The duration in crankshaft degrees of the knock window. eg a value of 40 degrees makes the window finish 40 degrees after it starts.
The Window Length plus the Ignition Retard Limit must be less than the number of degrees between the shortest two ignition events.
Knock Control will not operate below this engine speed (RPM).
Knock Control will not operate above this engine speed (RPM).
Knock Control will not operate below this throttle position (TPS(Main)).
Knock Control will not operate if the rate of change of throttle position (TPS Delta) is greater than this value.
A value of 0 will stop TPS delta lockout from being checked.
Fuel/Ignition Trim Settings:
This setting is used to select whether the Ignition Advance Delay, Ignition Advance Rate, Fuel Decay Delay and Fuel Decay Rate use seconds or Engine cycles as their time unit.
Note: This setting is only available when using an ignition retard knock mode.
Controls the rate at which ignition is retarded, the amount of ignition timing removed (retard) is dependent upon the amount by which the Knock Level exceeds the Knock Threshold.
For 'Ignition Trims' and 'Ignition and Fuel Trims' Modes the number entered in the Ignition Retard Gain setting is the amount of retard that will occur per percent that the Knock Level is above the Knock Threshold.
This means:
·If the Knock Level is 1% above the Knock Threshold and the Retard Gain is 1.0 then 1 degree of timing will be removed per knock event.
·If the Knock Level is 20% above the Knock Threshold and the Retard Gain is 0.5 then 10 degrees of timing will be removed per knock event.
For 'Normalised Ign' and 'Normalised Ign & Fuel' Modes the number entered in the Ignition Retard Gain is multiplied by the detected knock value (when it is above 0) to get the amount of retard to be applied.
This means:
·If the Detected Knock Level is 1 and the Retard Gain is 1.0 then 1 degree of timing will be removed per knock event.
·If the Detected Knock Level is 15 and the Retard Gain is 0.5 then 7.5 degrees of timing will be removed per knock event.
Basically, a higher number in this setting will result in more retard per knock event, a typical value for Retard Gain is 0.5.
Note: This setting is only available when using an ignition retard knock mode.
Sets the maximum amount of ignition timing in degrees that can be removed (or maximum amount of ignition retard), this limit avoids the ECU removing too much timing if the value in the Knock Threshold Table is set too low.
Note: This setting is only available when using an ignition retard knock mode.
The ECU will eventually attempt to reintroduce the more advanced ignition timing after it has been removed by the Knock Control system. Ignition Advance Delay sets the time that must pass with no knock events before the ECU will attempt to reintroduce the removed ignition timing.
Note: This setting is only available when using an ignition retard knock mode.
After the Ignition Advance Delay time has elapsed, the ECU will start to reintroduce the removed ignition timing that has been removed by the Knock Control system. Ignition Advance Rate sets how fast the ignition timing will be reintroduced in degrees per second.
Note: This setting is only available when using a fuel enrich knock mode.
Controls the rate at which the fuel trim is increased, the amount of fuel added is dependent upon the amount by which the Knock Level exceeds the Knock Threshold.
For 'Fuel Trims' and 'Ignition and Fuel Trims' Modes the number entered in the Fuel Enrichment Gain setting is the amount of fuel added that will occur per percent that the Knock Level is above the Knock Threshold.
This means:
·If the Knock Level is 1% above the Knock Threshold and the Enrichment Gain is 1.0 then 1% fuel trim will be added per knock event.
·If the Knock Level is 20% above the Knock Threshold and the Enrichment Gain is 0.5 then 10% fuel trim will be added per per knock event.
For 'Normalised Fuel' and 'Normalised Ign & Fuel' Modes the number entered in the Fuel Enrichment Gain is multiplied by the detected knock value (when it is above 0) to get the amount of enrichment to be added.
This means:
·If the Detected Knock Level is 1 and the Enrichment Gain is 1.0 then 1% fuel trim will be added per knock event.
·If the Detected Knock Level is 15 and the Enrichment Gain is 0.5 then 7.5% fuel trim will be added per knock event.
Basically, a higher number in this setting will result in more fuel added per knock event, a typical value for the Fuel Enrichment Gain is 0.5.
Note: This setting is only available when using a fuel enrich knock mode.
Sets the maximum amount of fuel trim in % that can be added, this limit avoids the ECU adding too much fuel if the value in the Knock Threshold Table is set too low.
Note: This setting is only available when using a fuel enrich knock mode.
The ECU will eventually attempt to reintroduce the leaner air fuel mixture after it has been richened by the Knock Control system. Fuel Decay Delay sets the time that must pass with no knock events before the ECU will attempt to remove the added fuel trim.
Note: This setting is only available when using a fuel enrich knock mode.
After theFuel Decay Delay time has elapsed, the ECU will start to reintroduce the leaner air fuel mixture that was richened by the Knock Control system. Fuel Decay Rate sets how fast the fuel trim will be removed in % per second.
Normalise Delta Settings:
Note: These settings are only available when using one of the Normalised knock modes (Normalised Ign, Normalised Fuel or Normalised Ign & Fuel).
RPM Delta Learning Rate & Load Delta Learning Rate
These settings are used to alter the rate at which the normalising filter operates during transient conditions.
When Knock Engine Speed ROC is greater than the RPM Delta Level the RPM Delta Learning Rate is applied.
When Knock TPS Delta is greater than the TPS Delta Level OR Knock MAP Delta is greater than the MAP Delta Level the Load Delta Learning Rate is applied
When Knock Engine Speed ROC is greater than the RPM Delta Level AND (Knock TPS Delta is greater than the TPS Delta Level OR Knock MAP Delta is greater than the MAP Delta Level) the faster of the two learning rates is applied.
·Normal - The learning rate during transient conditions is the same as during stable conditions.
·Medium - The learning rate during transient conditions is faster than during stable conditions.
·Fast - The learning rate during transient condition is significantly faster than during stable conditions.
Knock Engine Speed ROC Filter Level, Knock TPS Delta Filter Level & Knock MAP Delta Filter Level
Knock control sometimes needs a more filtered version of the Engine Speed ROC, TPS Delta & MAP Delta values and so these settings are used to add filtering of various levels. The filtered values which are used to determine when to apply Delta Threshold Gains and Delta Learning Rates are called Knock Engine Speed ROC, Knock TPS Delta & Knock MAP Delta respectively.
This setting controls how long the Delta Threshold is applied after the transient condition has stopped occuring, units are number of Engine Cycles.
When the Knock TPS Delta is greater than this value it is considered to be a transient engine condition and so the normalising filter rate is changed to the Load Delta Learning Rate value and the Knock Threshold value is set to the Knock Threshold Table value multiplied by the Load Delta Threshold Gain.
Note: A value of 0 means that this delta level isn't checked.
When the Knock MAP Delta is greater than this value it is considered to be a transient engine condition and so the normalising filter rate is changed to the Load Delta Learning Rate value and the Knock Threshold value is set to the Knock Threshold Table value multiplied by the Load Delta Threshold Gain.
Note: A value of 0 means that this delta level isn't checked.
When the Knock Engine Speed ROC is greater than this value it is considered to be a transient engine condition and so the normalising filter rate is changed to the RPM Delta Learning Rate value and the Knock Threshold value is set to the Knock Threshold Table value multiplied by the RPM Delta Threshold Gain.
Note: A value of 0 means that this delta level isn't checked.
Load Delta Threshold Gain & RPM Delta Threshold Gain
The knock threshold often needs to be temporarily increased during transient conditions, the value in these settings are used as a multiplier of the knock threshold table value which is applied during transient conditions. For example a Load Delta Threshold Gain value of 2 and a Knock Threshold Table value of 3 will result in a knock threshold value of 6 when TPS Delta is greater than the TPS Delta Level OR MAP Delta is greater than the MAP Delta Level.
When Knock Engine Speed ROC is greater than the RPM Delta Level the RPM Delta Threshold Gain is applied.
When Knock TPS Delta is greater than the TPS Delta Level OR Knock MAP Delta is greater than the MAP Delta Level the Load Delta Threshold Gain is applied
When Knock Engine Speed ROC is greater than the RPM Delta Level AND (Knock TPS Delta is greater than the TPS Delta Level OR Knock MAP Delta is greater than the MAP Delta Level) the larger of the two Threshold Gains is applied.
This table allows different levels of gain to be applied to the ignition retard and or fuel enrich depending on how much larger the current knock level is than the threshold.
Cylinder Setup:
Each cylinder can have a table assigned to it that will be used to display the amount of ignition retard due to the Knock Control system. The Cyl X Allocation setting determines which table is allocated to a particular cylinder. The way in which cylinders are allocated depends on user preference.
When using a group fuel mode (not Sequential or Sequential Staged) the ECU has no way to know which injectors are feeding which cylinders and so the ECU treats all cylinders the same with the greatest value from that cell in all of the fuel trim tables being added to every injector. The Ignition Mode doesn't matter as Link G4X ECUs can provide individual spark timing to each cylinder in any ignition mode (requires full trigger sync).
Ignition Trims or Ignition and Fuel Trims mode
The ECU has the ability to detect knock on each individual cylinder.
If using a group fuel mode the greatest value from all of the fuel trim tables will be applied to all of the injectors.
Assume 6 cylinder with firing order: 1-5-3-6-2-4.
Cylinder 1 = Cylinder 1 Allocation
Cylinder 2 = Cylinder 2 Allocation
Cylinder 3 = Cylinder 3 Allocation
Cylinder 4 = Cylinder 4 Allocation
Cylinder 5 = Cylinder 5 Allocation
Cylinder 6 = Cylinder 6 Allocation
Fuel Trims mode and a group fuel mode
The ECU has the ability to detect knock on individual cylinders but doesn't know which injectors control which cylinders.
Assume 6 cylinder with firing order: 1-5-3-6-2-4.
Cylinder 1 = Cylinder 1 Allocation
Cylinder 2 = Cylinder 1 Allocation
Cylinder 3 = Cylinder 1 Allocation
Cylinder 4 = Cylinder 1 Allocation
Cylinder 5 = Cylinder 1 Allocation
Cylinder 6 = Cylinder 1 Allocation
These examples illustrate the highest level of individual cylinder/rotor detection (i.e. as many tables used as possible).
It is possible to reduce the number of tables used by further pairing of cylinders. This allows the following combinations to be achieved:
·An individual knock ignition trim and knock fuel Trim table for each cylinder.
·One knock ignition trim and one knock fuel trim table used for all cylinders.
·Separate knock ignition trim and knock fuel trim tables for groups of cylinders. e.g. one table for left bank, one table for right bank or One table for front three cylinders and another table for the rear three cylinders.
These settings can cause confusion so are best illustrated with examples.
Individual table for each cylinder (4 cyl engine):
·Cyl 1 Allocation = Cyl 1 ITrim Table
·Cyl 2 Allocation = Cyl 2 ITrim Table
·Cyl 3 Allocation = Cyl 3 ITrim Table
·Cyl 4 Allocation = Cyl 4 ITrim Table
One table for all cylinders (4 cyl engine):
·Cyl 1 Allocation = Cyl 1 ITrim Table
·Cyl 2 Allocation = Cyl 1 ITrim Table
·Cyl 3 Allocation = Cyl 1 ITrim Table
·Cyl 4 Allocation = Cyl 1 ITrim Table
One table for each bank (V8 engine odds on left bank, evens on right bank):
·Cyl 1 Allocation = Cyl 1 ITrim Table
·Cyl 2 Allocation = Cyl 2 ITrim Table
·Cyl 3 Allocation = Cyl 1 ITrim Table
·Cyl 4 Allocation = Cyl 2 ITrim Table
·Cyl 5 Allocation = Cyl 1 ITrim Table
·Cyl 6 Allocation = Cyl 2 ITrim Table
·Cyl 7 Allocation = Cyl 1 ITrim Table
·Cyl 8 Allocation = Cyl 2 ITrim Table
One table for front cylinders, one table for rear cylinders (inline 6 cyl engine):
·Cyl 1 Allocation = Cyl 1 ITrim Table
·Cyl 2 Allocation = Cyl 1 ITrim Table
·Cyl 3 Allocation = Cyl 1 ITrim Table
·Cyl 4 Allocation = Cyl 2 ITrim Table
·Cyl 5 Allocation = Cyl 2 ITrim Table
·Cyl 6 Allocation = Cyl 2 ITrim Table
Note: This setting is only available when using the Ignition Trims, Fuel Trims or Ignition and Fuel Trims modes (not the Normalised modes).
The Knock Level Gain X setting can be used to apply a multiplier to the knock level on individual cylinders. This settings is useful for amplifying cylinders located at varying distances from the knock sensor. (e.g., Cyl1 and Cyl4 will require more gain than Cyl2 and Cyl3 on a four cylinder engine with a central knock sensor).
Gains are relative to the Cylinder Allocation, and not the actual cylinder. Gains relating to allocations not defined have no effect.
·A Gain of 1.00 represents no change to the level.
·A Gain of 0.50 represents the level being reduced to half of the original level.
·A Gain of 2.00 represents the level being doubled.
Adjust the individual knock level gains so that all cylinders are reading an equal value when free reving the engine without it knocking.
Knock Control:
The Knock Threshold Table will become visible when Knock Mode is set to something other than OFF. This table sets the allowable engine noise for a given engine speed/Load, each engine will have different noise characteristics. Engine noise is generated by mechanical clearances, valve train noise and even valves closing against the seat! Knock Control will reduce ignition advance and/or increase the fuel trim when the actual measured level of engine noise is above the value in the Knock Threshold Table. This table must be manually filled out for each particular engine. Knock Threshold values can range from 0 (minimum noise) to 1000 (maximum noise).
Use the Table Axis Setup menu to adjust the Knock Threshold Table axis parameters and change rows/columns.
The Knock Ignition Trim X table shows the amount of ignition retard being applied by the Knock Control system to a particular cylinder or group of cylinders. Each time the magnitude of the knock signal exceeds the Knock Threshold value for that particular engine speed/Load ignition timing will be decremented from a cell in this table. The Knock Ignition Trim X Table can be used to determine where knock has been detected as each cell that has its retard value changed will turn blue (this only occurs while the ECU is connected to PCLink).
See Cylinder X Allocation for information on setting up which table relates to a particular cylinder.
The Knock Ignition Trim X tables are cleared when the ECU is turned off if the changes haven't been stored. Ignition changes made by the Knock Control function are NOT stored permanently and require the user to connect with PCLink and store the tune.
The Knock Fuel Trim X table shows the amount of fuel enrichment being applied by the Knock Control system to a particular cylinder or group of cylinders. Each time the magnitude of the knock signal exceeds the Knock Threshold value for that particular engine speed/Load the fuel trim will be incremented in a cell in this table. The Knock Fuel Trim X table can be used to determine where knock has been detected as each cell that has its fuel value changed will turn blue (this only occurs while the ECU is connected to PCLink).
See Cylinder X Allocation for information on setting up which table relates to a particular cylinder.