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IGNITION TRIMS Tab

[-] IGNITION

IGNITION TRIMS Tables

IAT IGNITION TRIM

ECT IGNITION TRIM

ECT IDLE IGNITION TRIM


ADVANCED Parameters

Advanced Ignition Parameters
These parameters are used to set the minimum and maximum timing deltas and absolute limits.
(TPSITA is "TPS Ignition Timing Adjustment", or ignition trim due to throttle movement.
See
ACCEL IGNITION TRIM Parameters below for TPSITA details.)


[-] COIL DWELL

DWELL PARAMS

DWELL BATTERY VOLTAGE FACTOR Table

DWELL @12V Table


[-] KNOCK

Knock System Description
The knock system has 2 parts: Knock Detection and Knock Analysis

Knock Detection:
Knock detection is performed during the power stroke for each cylinder. The ECU maintains a weighted average knock voltage for each cylinder. These cylinder voltages are initialized to 2.56V and the weighted average knock voltage for each cylinder is controlled by VOLTAGE SENSITIVITY.

If the current knock voltage is greater than the average knock voltage for the current cylinder plus the CYLINDER KNOCK VOLTAGE LIMIT for that cylinder at the curent RPM, the Knock Count is incremented, otherwise the weighted average knock voltage for that cylinder is updated.

Basically the ECU maintains a weighted average noise level (average knock voltage) for each cylinder, and when the noise from a cylinder goes above this level plus the "knock noise limit", knock is detected and the Knock Count is incremented.

Knock Analysis:
If Enable Knock Analysis is set, knock analysis is performed every 10msec. While the engine is operating within the knock analysis zone specified by knock_zone_min_load and knock_zone_max_rpm, and the throttle is open, the ECU maintains a knock_adjustment value.
The knock_adjustment is increased (advance) or decreased (retard) based on the following:
Every 100 msecs, knock_adjust_advance is added to knock_adjustment
If Knock Count is greater than 0, knock_adjust_retard is subtracted from knock_adjustment

If knock_adjustment indicates retarded timing, Knock Trim is then set based on knock_adjustment. If engine operation takes it outside the knock analysis zone, and the throttle is still open, Knock Trim is set to the average knock_adjustment while operating in the knock analysis zone.

Finally Knock Trim is checked against the previous adjustment to keep the maximum delta below MAX RETARD DELTA. It is then compared and limited to the knock retard limit from the KNOCK RETARD LIMIT table.

Note that Knock Trim is applied AFTER the IGN RETARD MAX limit is checked!

KNOCK PARAMS

KNOCK Parameters

ANALYSIS ZONE PARAMETERS
These parameters specify the limits of the lower right (high load, low RPM) quadrant of the timing map, or knock analysis zone, where knock analysis is performed.

ADJUSTMENT FACTORS


CYL VOLT LIMITS

CYLINDER KNOCK VOLTAGE LIMIT Tables
These table contain the stock knock voltage limits for each cylinder, based on RPM. Looking at the values in these tables, the levels for cylinder 3 are higher than those for cylinder 2, which are higher than those for cylinders 4 and 1. This is due to the physical location of the knock sensor on the block and the acoustic signature of each cylinder relative to the knock sensor location. Where the table values are 5.10V, knock detection is effectively disabled because the knock voltage can never be above 5.0V.


RETARD LIMITS

KNOCK RETARD LIMIT Table


[-] ACCEL IGNITION TRIM

ACCEL TRIM

Description
Accel Ignition Trim, also called "TPS Ignition Timing Adjustment" (TPSITA), provides initial throttle opening, or "tip-in" retard, which in the old carburetor days, was called "vacuum advance".

TPSITA occurs in 2 phases. The first phase is called "Tip-In Retard" and is based on TPS opening rate of change (dTPS). This reduces spark knock at throttle tip-in. The second phase is called "Tip-In dRPM Ignition Trim" and is based on RPM rate of change (dRPM). This helps maitain engine power while the RPM is fluctuating as the clutch is engaged.

There are a number of criteria that must be met to activate the "Tip-In Retard" phase. If ECT is at least MIN ECT, and vehicle speed is below MAX SPEED, and engine load is below either MAX MAF LOAD or MAX MAP LOAD (depending on the current load source), and the change in TPS percent is at least dTPS DEADBAND, and rpm is above MIN RPM, and no more than MAX RPM, and gear is below or equal MAX GEAR, the "Tip-In Retard" phase is initiated. This initializes the tpsita_decay_factor to its maximum value and starts the tpsita_timer. If the transmission is shifted above MAX GEAR, TPSITA is canceled.

TPSITA Criteria

Tip-In Retard Phase
During this phase, TPS Trim = tpsita_retard x tpsita_decay_factor. (tpsita_retard is set from the TPSITA dTPS Retard Table) If at any point, the newly calculated tpsita_retard value is greater than the previous value, it is used, thereby maximizing the amount of retard based on rate of throttle opening. Every 10msec, DECAY DECREMENT is subtracted from the tpsita_decay_factor which decays the value of TPS Trim. When tpsita_timer = dTPS Time, the "Tip-In dRPM Ignition Trim" phase begins.

TPSITA dTPS Retard Table
Sets the initial value of tpsita_retard based on the rate of throttle opening, or dTPS.

Tip-In dRPM Ignition Trim Phase
During this phase, the change in rpm per engine cycle (180) is evaluated every 10msec. As long as the RPM is increasing or steady, TPS Trim continues to decay to 0. If at any point the RPM drops, from that point on, TPS Trim is set based on the rpm difference and wheather it is falling, rising, or steady:

RPM Falling:
TPS Trim = RPM FALLING ADVANCE * dRPM/50
RPM Falling and tpsita_decay_factor = 0:
TPS Trim = RPM FALLING DECAY * dRPM/50
RPM Steady:
No changes.
RPM Rising:
TPS Trim = RPM RISING RETARD * dRPM/50

This phase continues until tpsita_timer = DURATION TIMER, at which point TPS Trim is reset to 0.

TPSITA Limits
The calculated value of TPS Trim is kept between MAX ADVANCE and MAX RETARD.


[-] CYLINDER TRIMS

CYLINDER TRIMING

CYLINDER IGNITION TRIM Tables
These tables provide individual cylinder ignition timing trim capability.


[-] CRANKING

CRANKING IGN

CRANKING IGNITION Table
This table contains ignition timing values used while in cranking mode. (See also
Cranking Mode Definition.)

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