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EZ116K Distributor Ignition

EZK Quick Facts

  • Maximum knock controlled retardation 14 deg BTDC
  • Knock retardation step 2.6 deg if RPM < 4895
  • Knock retardation step 2.3 deg if RPM > 4895
  • Re-advance step 0.375 deg
  • Re-advance interval: Specified number of engine revolutions, depending on speed
  • When the car is being started ignition timing is only dependent on engine speed (RPM) and engine coolant temperature (ECT).
  • When the engine is idling ignition timing is only dependent on engine speed (RPM).
  • At temperatures below 55°C ignition is retarded according to temperature.
  • Below 60°C no regard is given to knock sensor (KS) signals.
  • If the engine is over-revving the control module uses the power stage to provide a spark only to every other spark plug so that engine power is reduced.

Dwell control

The control module controls the ignition voltage so that it is independent of battery voltage and engine speed (RPM). At low battery voltage the control module sends a signal to the ignition discharge module (IDM) to start charging earlier thereby extending charging time.

If there is no signal from the knock sensor (KS) the ignition is retarded 10°. If there is no load signal from LH 2.4 ignition timing is calculated for full load except when the throttle position switch (TP switch) indicates that the engine is idling. If there is no engine temperature signal ignition timing is based on the engine being warm. If there is no throttle position (TP) signal the control module takes account of load even when the engine is idling.

The EZ 116 K system receives information about load from the LH 2.4 control module. At high loads, large amounts of fuel/air, ignition is retarded. If engine load changes rapidly the ignition is retarded significantly on all cylinders to revent knocking.

If one of the cylinders begins to knock the ignition is retarded for that cylinder until the knock ceases. When the knocking stops the ignition is advanced by degrees. The rate of advance is dependent on engine speed (RPM). This rate is faster at low engine speeds (RPM) and slower at high speeds.

If the engine is heavily loaded for a long period the ignition will often be retarded by the knock control. To prevent knocking this will cause the control module to retard the ignition by 1° on all cylinders for as long as the engine is unusually loaded

Knock-controlled fuel enrichment

Knock-controlled fuel enrichment means that the injector opening period is extended to enrich the fuel/air mixture, reducing the combustion temperature and brin ging the uncontrolled combustion under control. The function is activated if the ignit ion system control unit detects that knock is occurring in all cylinders above a certain threshold value. On receiving a signal from the knock sensor (2) and having established that knock is present in all cylinders, the control unit (1) connects a terminal on the fuel injection system control unit (3) to ground, causing the latter to transmit a signal to the injectors (4) to extend the opening period.

EZ-116K on B234 F: Retardation of at least 3-4 deg in all cylinders in response to knock detector signals at engine speeds above 3800 r/min and above a certain minimum load.

Theory of temperature-compensated timing advance

Advancing the ignition timing increases the cylinder temperature while reducing the exhaust gas temperature. Under certain conditions, this also yields a reduction in coolant temperature. The higher cylinder temperature is due to the higher pressure of the fuel/air mixture as it is ignited, while the lower exhaust gas temperature is due to the relatively late scavenging of the gases at the end of the combustion process. The lower coolant temperature achieved by advancing the timing when idling is partly due to the fact that the setting is already well retarded and that a relatively high proportion of the fuel does not. as a result. produce mechanical work, the energy being dissipated in the form of heat losses. Advancing the timing under these conditions greatly improves the efficiency of combustion, increasing the amount of energy converted into mechanical work and reducing the amount of heat discharged to the coolant.

Theory of temperature-compensated timing retardation

Although it reduces the cylinder temperature, retarding the ignition increases the exhaust gas and coolant temperatures. The lower cylinder temperature is due to the reduced pressure of the mixture when it is ignited, while the rise in exhaust gas temperature is due to scavenging of the gases closer to the exhaust valve opening point. The higher coolant temperature is attributable to the fact that less of the energy content of the fuel is converted into mechanical work, a higher proportion being dissipated in t he form of thermal losses. As a result, a higher quantity of heat is transferred more quickly to the cyl inder wall, exhaust gas port, intake manifold and coolant passages.

Timing compensation on cold engine

Temperature compensation of the timing on a cold engine usually involves advancing the timing to shorten the warm-up period. However, temperature-controlled functions which retard the timing in a cold engine are also used. One of the effects of this is to bring the catalytic converter up to working temperature more quickly, while another is to increase the coolant temperature, accelerat ing the defrosting action of the climate cont rol system. The temperature sensor signals may also be used by the control unit to determine when the knock sensor signal should be switched in. Blocking this signal when the engine is cold ensures that the control unit is unaffected by spurious signals caused by the mechanical noise typically emilled by the engine as it warms up.

Timing compensation on hot engine

Temperature compensation of the timing on a hot engine means advancing the timing to reduce the coolant temperature. This prevents the engine from boiling (although the cooling water will not begin to boil while the temperature is below approx. 120-125°C, due to the fact that the system is pressurized). The timing advance is normally applied only when idling, since t he setting is normally fairly retarded under these conditions.

The timing will be altered by approx. 3° if the CPS pick-up leads are reversed. Although the magnitude of the induced voltage wilt increase with flywheel speed, the voltage regulator in the control unit ensures that the voltage supplied to the circuits remains constant

Ignition systems supplied by Bosch for Volvo 4-cylinder engines feature a type 60-1 toothed profile. This means that the profile is provided with 60 drilled holes and with one 'long' tooth of twice the length of a 'short' tooth. In other words, the profile is provided with 58 (60-1x2) short teeth and one long tooth which represents the crankshaft position reference point. The angular pitch between two adjacent short teeths is 6.0" (360 deg/60).

The control unit identifies TDC as the point 90 deg after the passage of the long tooth. The type 60-1 toothed profile is used on the EZ-116K system. This means that the control unit applies a factor of 16 to improve the resolution of the pick-up signal. In effect, the control unit can adjust the timing in steps of 0.375 deg.

Knock control

The knock sensor monitors the combustion process continuously. If knock occurs, the device delivers a special signal to the control unit, which takes corrective action by retarding the ignition in the cylinder affected.

Knock control characteristic

The principle of knock control is more or less the same in the case of all systems equipped with knock sensors. The vertical coordinate shows the ignition setting in degrees in relation to the basic timing (indicated here by the angle ALPHA, while the horizontal coordinate is the time scale (which normally varies with engine speed).

Stepped control

The control unit continuously computes the optimum timing on the basis of the running conditions. On detecting knock, the unit retards the ignition by a step of a few degrees (2-3° depending on the system) in the cylinder affected. If the phenomenon persists, the setting is retarded by a further step, and so on until the condition has been corrected. The maximum retardation in relation to the basic timing is approx. 10-16° in the case of EZ-K systems.

Re-advance following correction of knock

After knock has been eliminated, the control unit maintains the retarded setting for a specified number of engine revolutions, depending on the speed (applies to EZ-K systems) before re-advancing the ignition in small steps (0.1-1°), either until the original characteristic has been restored or until the engine again starts to knock. The maximum retardation must not deviate excessively from the basic setting if an excessive rise in exhaust gas temperature is to be avoided. Information on engine speed and/or load is also essential to enable the control unit to impose the maximum retardation, if necessary.

knock retard per cylinder -- 4 elements map? coding plug for different octane rating - pins 18-19? gearbox - auto/manual ? knock counter

max ignition retard map If the engine has detonation (“pinking” or “pinging”) while under test the ignition will be retarded in steps of 3 degrees up to a maximum of 9 degrees. See the “max ignition retard map” description on Page 57. If the knock does not continue, the ignition is automatically advanced in much smaller steps until the mapped value is attained. Note that it can take up to 15 seconds for the timing to be advanced back to the correct value.

This retard is only carried out on the cylinder(s) that have detonation. The EZK can differentiate which cylinder is knocking, as long as the knock and Hall sensor signals are present.


knock retard step in degree (3) recovery time in sec (10-15)

Transient conditions Retard when throttle opened at idle 5.6 deg Retard when throttle opened after deceleration 11.6 deg Retard when sudden increase of load 5.6 deg Max. advance increase rate (deg. per spark event) 1.1 deg

steps 0.375

Cruise warmup map Idle map Idle warmup map WOT map WOT warmup map

Max ignition knock retard map RPM based 1x16 [0]3, [15]9

Connector pinout

Advance/Retard control via selector pins

here are 5 unused pins on the EZK connector. Four of these (pins 18, 19, 21, 25) are so called "selector pins". The EZK software uses only 2 of these pins - 18 and 19. Below you can see how the selector pins are interfaced to the CPU:

EZK selector pins to CPU interface

Table below shows the mapping of the pins with the CPU port bits:

Connector pin CPU port bit
Pin 18 P4.4
Pin 19 P4.5
Pin 21 P4.6
Pin 25 P4.7

Normally when all pins are unconnected (floating) the CPU sees zero on the port P4. By grounding all or none, or some combinations we can get 16 possible combinations:

binary hexadecimal decimal
0000 0x00 0
0001 0x01 1
0010 0x02 2
0011 0x03 3
0100 0x04 4
0101 0x05 5
0110 0x06 6
0111 0x07 7
1000 0x08 8
1001 0x09 9
1010 0x0A 10
1011 0x0B 11
1100 0x0C 12
1101 0x0D 13
1110 0x0E 14
1111 0x0F 15

The selector pins occupy the high nibble of the P4. Only the first two bits of the high nibble are used by the software to form an index and use it for map lookup like shown in the code fragment below:

MOV DPTR, #L1E80             ;137C 90 1E 80
ACALL L1510_2D_MAP_ACCESS    ;137F B1 10      main advance table lookup
MOV R0, A                    ;1381 F8         result from lookup stored to R0

MOV A, P4                    ;1382 E5 E8      read port P4 
NOP                          ;1384 00         sync
SWAP A                       ;1385 C4         swap byte nibbles
ANL A, #0x03                 ;1386 54 03      leave only first 2 bits

MOV DPTR, #L1FF8             ;1388 90 1F F8   selector pin table
MOVC A,@A+DPTR               ;138B 93         lookup from the table using selector pin combination as index

ADD A, R0                    ;138C 28         add to the result from main advance lookup
MOV R0, #0x84                ;138D 78 84      
MOV @R0, A                   ;138F F6         store to RAM result for later use

EZK dwell maps

stock 0 227 400 208 dwell table
6500 5600 5100 4650 4250 3850 3500 3000 2650 2250 1900 1500 1200 900 750 500
low 255 255 255 255 255 255 255 255 255 255 225 174 135 106 83 62
norm 255 255 239 215 194 176 159 138 119 100 83 65 50 38 29 20
high 165 151 140 125 113 102 92 80 68 56 48 36 26 19 14 9
modified dwell table for VAG coils
6500 5600 5100 4650 4250 3850 3500 3000 2650 2250 1900 1500 1200 900 750 500
low 190 175 160 150 140 125 110 100 85 70 55 40 25 20 15 7
norm 135 125 100 95 85 75 65 55 45 35 30 25 19 15 13 9
high 120 110 95 85 75 70 60 50 40 30 25 20 12 10 8 4
stock dwell constants
hex dec
140F 4 4
1414 78 120
1405 87 135
13FF FB 251
VAG modified dwell constants
hex dec
140F 1C 28
1414 AC 172
1405 53 83
13FF E3 227

related addresses 09B1 AC