Tech Notes
Aviation Resources' Magneto Timing Process Optimized for Cirrus SR22 Aircraft
1. Insure magneto switch is off. Remove key.
2. Remove top cowl.
3. Remove battery ground strap.
4. Remove all top spark plugs, keeping track of copper gaskets.
5. Find TDC of #1 cylinder. Identify prop blade face convenient for viewing digital protractor.
6. Install protract with double black tape and retention tape at end of prop blade selected in step 5. (Double-back tape helps to remove any associated jiggle when 'bumping' the prop while checking the timing unit point 'open' lights).
7. Back-up prop and install TDC finder plug.
8. Using digital protractor, locate 'normal' rotation stop point, noting location angle #1. Reverse prop direction and locate stop point, noting location angle #2. Remove stop pin. Do not move prop. Perform math (#1 angle - #2 angle)/2 = TDC angle. 'Back' prop by rotation to the TDC angle and continue to 'back' prop to the mag-to-engine timing degree setting (22 degrees). Insure protractor reading is "normalized" and note this angle number. This angle number is the BTDC angle of mag-to-engine timing. Further check that impulse couplings have released and install the timing indicator light tool to both mag "P" leads. DO NOT REMOVE THE "P" leads from mags. Install key in mag switch and turn to "BOTH" position. Install and 'activate' timing indicator unit and check the "point open" lights as prop is rotated. Note starting indications on digital protractor, i.e. 22.5 degrees left mag and 21.2 degree right mag. (Log these numbers by mag to evaluate future mag-to-engine timing drift.) Adjust one mag to proper timing of 22 degrees by using digital protractor indication. Time second mag to first mag and check with digital protractor.
Note: Common digital protractors have a .1 degree resolution. Timing to .1 degree or less is possible in 'mag-to-mag' as well as 'mag-to-engine' timing. Most digital protractors have 'auto shutdown' after a period of inactivity. Reactivate (turn 'on') to view without worry of losing the 'angle.'
9. When timing is set to your satisfaction, remove protractor, remove timing indicator tool, ensure mag switch is 'off' and remove key. Check and service spark plugs for proper gap, lubricate threads, replace copper gaskets, install and torque to proper specs, clean lead ends with isopropyl alcohol, ensure springs and contact buttons in spark plugs are clean of any corrosion, debris, etc., and install. Install ground strap to primary battery, install top cow with all hardware (screws in front!). Perform ground run and test function of mag switch, engine operation, and mag drop/split. Perform required documentation for approval for return to service.
Note: The BTC timing may vary by engine model. Check latest information for correct timing settings!
1. Insure magneto switch is off. Remove key.
2. Remove top cowl.
3. Remove battery ground strap.
4. Remove all top spark plugs, keeping track of copper gaskets.
5. Find TDC of #1 cylinder. Identify prop blade face convenient for viewing digital protractor.
6. Install protract with double black tape and retention tape at end of prop blade selected in step 5. (Double-back tape helps to remove any associated jiggle when 'bumping' the prop while checking the timing unit point 'open' lights).
7. Back-up prop and install TDC finder plug.
8. Using digital protractor, locate 'normal' rotation stop point, noting location angle #1. Reverse prop direction and locate stop point, noting location angle #2. Remove stop pin. Do not move prop. Perform math (#1 angle - #2 angle)/2 = TDC angle. 'Back' prop by rotation to the TDC angle and continue to 'back' prop to the mag-to-engine timing degree setting (22 degrees). Insure protractor reading is "normalized" and note this angle number. This angle number is the BTDC angle of mag-to-engine timing. Further check that impulse couplings have released and install the timing indicator light tool to both mag "P" leads. DO NOT REMOVE THE "P" leads from mags. Install key in mag switch and turn to "BOTH" position. Install and 'activate' timing indicator unit and check the "point open" lights as prop is rotated. Note starting indications on digital protractor, i.e. 22.5 degrees left mag and 21.2 degree right mag. (Log these numbers by mag to evaluate future mag-to-engine timing drift.) Adjust one mag to proper timing of 22 degrees by using digital protractor indication. Time second mag to first mag and check with digital protractor.
Note: Common digital protractors have a .1 degree resolution. Timing to .1 degree or less is possible in 'mag-to-mag' as well as 'mag-to-engine' timing. Most digital protractors have 'auto shutdown' after a period of inactivity. Reactivate (turn 'on') to view without worry of losing the 'angle.'
9. When timing is set to your satisfaction, remove protractor, remove timing indicator tool, ensure mag switch is 'off' and remove key. Check and service spark plugs for proper gap, lubricate threads, replace copper gaskets, install and torque to proper specs, clean lead ends with isopropyl alcohol, ensure springs and contact buttons in spark plugs are clean of any corrosion, debris, etc., and install. Install ground strap to primary battery, install top cow with all hardware (screws in front!). Perform ground run and test function of mag switch, engine operation, and mag drop/split. Perform required documentation for approval for return to service.
Note: The BTC timing may vary by engine model. Check latest information for correct timing settings!
