Setting the Ignition Synchronisation strategy.

Questions relalting to all engine GEMS ECUs

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Setting the Ignition Synchronisation strategy.

Post by RickS » Thu Dec 12, 2019 2:41 pm

Ignition timing
The ECU recognises the engine position by a missing / extra tooth on a pattern of evenly spaced teeth or by a pattern of cam teeth. Different manufacturers have this reference in a different place on the trigger wheel so the ECU needs to have adjustment for this.

The numbers are known for some manufacturers and can be set in the start-up map but if they are unknown or if you are using a GEMS external 36-1 wheel, you will need to find this value yourself. To find this value you will need a strobe light and an accurate TDC mark on the engine.

The process will be:-

• Press the start button
• Attempt to start the engine. The ignition timing may be wrong by a large amount so it may not start. If the engine will not start you will need to alter the option Spark Sync until it does. As this value is specified in an internally calculated number by the ECU (internal teeth) a change of 1 in Spark Sync would adjust the timing by 30° for 12 internal teeth (18° for 20 internal teeth or 36° for 10 internal teeth).
• Once started, hold the engine at 2000-3000 rpm, somewhere out of the idle condition to where the ignition timing is stable.
• Check the engine speed shown on the strobe light. Some strobe lights will see the wasted spark on DIS systems and so will show double engine speed so doubling the ignition events. If this is the case, halve all ignition timing figures shown on the strobe.
• Check the ignition timing with a strobe light and compare this number to the number in the parameter Spark Total.
• If the strobe light shows an ignition timing number lower than the ECU, then decrease the value of option Spark Sync. If the strobe light shows a number higher than the ECU, then increase the value of the same option. The Timing Alignment/Spark Sync parameter is measured in "internally calculated teeth" from the [Tooth Control] table, so if Spark Teeth is set to 12, a change of '1', is a change of 30 crank degrees, so changes to Spark Sync should be very small. (Spark Sync has 4 decimal places)
• If you reach a tooth value of 0.0000 for Spark Sync and want to continue to a lower value, then you can move the ignition further by starting at the value of Spark Teeth and continuing to count backwards. So if the value of option Spark Teeth is 12, then set Spark Sync to 11.999, 11.990, 11.985 etc. to continue. This allows you to loop the synchronisation value through the complete 360°/720° cycle, to find the correct synchronisation point.
• The value for Spark Total in the calibration software will not change, but the timing mark on the engine will move, so each adjustment will require that the strobe light be reset.
• Repeat these changes until the strobe light timing figure agrees with the timing figure shown by parameter Spark Total.