Sync MX

Overview

The Sync MX strategy is the most common synchronization strategy. It uses a missing tooth / teeth (or an extra tooth) on the crankshaft wheel to determine the engine cycle position.

Sync MX Options

The following options are used to detect the missing or extra tooth:

Option Description
option iconSync MX ON
option iconSync Cam Count OFF
option iconSync Crank S Count OFF
option iconSync Crank Divider OFF. This option has a major impact on timing interrupts and changing it requires an ECU reset.
option iconMissing Number of missing or extra teeth. Allowed values 0, 1, 2, -1. A value of -1 indicates the wheel uses an extra tooth (e.g. Honda 12+1).
option iconMX Sync Test Number of actual teeth before the missing tooth since the last missing section. For wheels with only 1 missing section or 1 extra tooth, set this to the physical number of teeth - 1. So for e.g. 36-2 this should be 34-1, which is 33. For more complex wheels with multiple missing sections (e.g. Rover K), set to the longest run of teeth without any missing teeth between them.
option iconMX Time Threshold for Missing Tooth detection. Percentage of prior tooth interval time to predict minimum interval to next tooth.
option iconStart MX Time Threshold for Missing Tooth detection (when cranking).
option iconSync Teeth Cam Synchronization, count of Cam sensor events that must occur to reset channel iconFuel Tooth No and channel iconIgn Tooth No.
option iconTest not Sync'd Set to ON so that while cranking, all opportunities are used for synchronization
option iconSync off Above Ignore the Cam sync above the specified channel iconEngine Speed, if non zero. This may be required at higher RPMs if cam and crank interrupts can interfere with each other, reducing timing precision.
option iconSync Err R/S Result in loss of synchronization (channel iconStat Sync'd => OFF) if this number of Sync errors are detected.
option iconSync Test A Tooth and option iconSync Test A enable move cam synchronisation decision at a specific channel iconA Tooth, rather than synchronisation test at last valid entry in Tooth control table. This is may be useful with variable cam control systems, where the cam signal used for synchronisation crosses the old fixed decision point. Only used with “Sync MX” Strategy.

Using a value for ‘Missing’ of 1 may be acceptable for wheels with 2 missing teeth in a row, depending upon the value of channel iconMX Time.

The value of option iconMX Time is a balance between the maximum tolerable deceleration of the engine and the ability to detect the missing tooth.

option iconMX Time or option iconStart MX Time is used to make channel icond Tooth Time that is compared with the new tooth time to detect the missing or extra tooth. If detected it is displayed in channel iconMiss Time.

This is a scaling factor for the tooth interval for giving a lower bound on when the next tooth should arrive.

If there are missing teeth then either 1 or 2 whole intervals will be added to this value, depending upon the value of option iconMissing. If there is an extra tooth then no extra intervals are added.

When the first tooth after the missing section on the wheel is detected then this deadline should be missed - and the ECU will consider this event as having just passed the missing tooth.

Missing Tooth Detection Missing Tooth Detection

For each time the table iconTooth Control table is successfully processed, the ECU will decrement the channel iconSync good count channel until it reaches 0.