Trigger pattern advisory note

[pat]

In recent weeks an odd behaviour in the G10 synchronisation pattern has been observed. Only a small number of cars were affected and all were with built engines. The symptom is that the engine will just cease responding to the throttle, sometimes with some pops out the exhaust. Allowing the engine to stall and re-fire would cure the fault. No synchronisation faults would be detected or logged, there would be no sync error log to show the cause.

The cause of this condition has been identified and a fix is given below. The actual cause of the loss of synchronisation is a phantom tooth on the crank input which was not being detected as being incorrect due to two reasons : a) the tooth gaps on the G10 pattern are very large, so the minimum gap verification must allow large changes to be valid to achieve syncronisation during cranking where angular speed changes can be very significant in the space of a tooth gap and b) the "cam is critical" flag in the timing processor was not being set correctly. Either of these two features should detect a phantom tooth but both were ineffective.

The setting of the "cam is critical" flag is deferred until the engine has completed a few revolutions and it is done whilst still in 360 sync. The vehicles exhibiting the symptoms were all configured to enter 720 sync as soon as possible (2 turns after 360 sync), which was bypassing the setting of the "cam is critical" flag; it was therefore possible to lose the cam signal altogether and not generate a critical cam error. Since an early crank tooth would be accepted, and cam checking was not occurring, it could cause the syncronisation to jump one tooth and not be detected as a fault. Configuring the minimum number of revs for 720 sync to 4 or more will ensure that the "cam is critical" flag is set in the timing processor and a phantom crank tooth will be detected (as a critical cam error, and logged in the sync error log).

Unless there is a very good reason not to do so, it is advised that the minimum number of revolutions for 720 sync be set to 4 or more regardless of which sync pattern is in use. The parameter can be found under Starting -> Valid Cam Signal Revs for 720 Sync. In the event of a CDI ignition system being fitted which is incapable of running as wasted spark (both MSD DIS-4 and M&W PRO-14 exhibit this fault) the "Starting Waits for 720 Sync" should be set and the Valid Cam Signal Revs for 720 Sync should be reduced one step at a time and cam sensor unplugged with the engine running; the engine SHOULD stall as a result, if it does not, the Valid Cam Signal Revs for 720 Sync must be increased until the engine does stall as a result of cam signal loss.

[pat]

A new version of S6 firmware which addresses this synchonisation glitch can be found here. Please note that this new firmware ensures that the Cam Is Critical flag is set when then ECU enters 720 sync, regardless of the minimum number of revolutions for 720 sync setting, thereby obviating the need to check that parameter and ensuring that it is set adequately high. There are also some useful additional features in the new firmware so even if the calibration has been adjusted as per the above advisory, it is probably worth upgrading anyway.