Precision Turbo and Engine BigStuff3 GEN3 Powertrain Controller Ignition Setup Tutorial - Manual (Page 25)

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For example, with the Crank Reference set to 50
o
BTDC, the rotor needs to be retarded by 30
o
(crankshaft degrees) to achieve good rotor phase for a desired advance of 20
o
. The table below
outlines how this number was derived.
Reluctor Repositioning Calculations
Normally Aspirated Engine
BTDC
Maximum Timing Advance Engine will See (high speed
light load)
45 o
Plus 5
o
timing advance (buffer for ECU) 5
o
Equals Crank Reference (angle) Value Inputted Into
BigComm Software
50 o
Cam Sync - Degrees Need Before Crank Reference +15 o
Cam Sync and Crank Angle
position cannot be the same
or the engine will not run.
Equals Cam Sync signal Position 65 o
Less Total Timing Advance Engine Will Operate under at
Peak Power
-38
o
Want best rotor phase here!
Equals Total Degrees (Crankshaft) 27 o
Total Degrees (Camshaft) the reluctor needs to be
advanced on the distributor shaft for rotor and cap
terminal to be “in-phase” at peak power.
14 o
Convert Crank Degrees to
Cam by dividing by 2
Boosted Engine
Maximum Timing Advance Engine will See 40
o
Plus 5 o timing advance (buffer for ECU) 5 o
Equals Crank Reference (angle) Value Inputted Into
BigComm Software
45 o
Cam Sync - Degrees Needed Before Crank Reference +15
o
Cam Sync and Crank Angle
position cannot be the same
or the engine will not run.
Cam Sync signal Position 60
o
Less Total Timing Advance Engine Operate at -20 o Want best rotor phase here!
Total Degrees (Crankshaft) 40
o
Total Degrees (Camshaft) the reluctor needs to be
advanced on the distributor shaft for rotor and cap
terminal to be “in-phase” at peak power
**20 o
Convert Crank Degrees to
Cam by dividing by 2
**If the number of degrees that the reluctor needs to be repositioned on the distributor shaft is more
than 10
o
, an adjustable rotor may need to be used in conjunction with repositioning the reluctor. Hand
modifications like adding a pin slot at 20
o
, may also need to be made to the reluctor. If hand
modifications are required, the new pin slot needs to be the same width and depth as the original slot so
that the reluctor does not move!
The following paragraphs explain how to reposition the reluctor on the distributor shaft of a MSD Pro-
Billet distributor so that cap and rotor are in-phase at peak power.