Magnet Position Setting
In the last couple months we've had a few people call, being unsure of the procedure on setting the magnet offset values for the crank sensor which we call Magnet Position. This applies to CPI, CPI-2 and EM-5.
The most important aspect, which is often not remembered, is that you must know what timing mark you'll use on the flywheel to verify timing and set the Magnet Position value. Most Lycoming flywheels are marked on the back side with 0, 10 and 25 degree BTDC scribes.
If you choose to check timing at 10 BTDC for example, be sure to set 500, 750, 1000 and 1100 rpm timing at 10 BTDC and idle the engine at 750-1000 rpm. If these are set to anything else, it's easy to get confused.
On systems using the dual Hall sensor pickup, we find the settings should be 88 for primary and 97 for backup. Note that starting in late Spring of 2019, all dual Hall sensor cables are marked green for Primary and red for Backup so these can't be easily mixed up. CPI-2s have green and red paint dots on the ECU connector faces denoting Primary and Backup.
Once Magnet Position is verified, you can set RPM ignition timing to whatever values you wish. This is a one-time calibration.
On dual pickup systems (twin cables), you should not have to check timing with a timing light when using the values above, as long as you get the correct cables plugged into the correct ECU. If you mix these up, both ECUs will deliver the wrong timing for the engine.
On single sensor systems (one cable), the Magnet Position value should be around 92.
We recommend on all these systems that you keep the 500 RPM timing value at no more than 10 degrees as this value is used during cranking. The ECUs bring in 15 degrees of retard below 300 rpm so this should result in true cranking timing at about 5 degrees ATDC to avoid kickbacks.