Precision Turbo and Engine BigStuff3 GEN3 Powertrain Controller Ignition Setup Tutorial User Manual
Page 16
15
Find GM Cam Sync Falling Edge
To find the Cam Falling Edge a voltmeter and a jumper wire are required.. A crankshaft degree wheel
is also recommended.
The following outlines the process.
• Roll the crankshaft back 30
o
Before Top Dead Center (BTDC). A crankshaft degree wheel or
balancer timing tape will help expedite the process. If neither is available, the following
formula can be used to measure the distance, on the surface of the balancer that equals 30
o
.
Multiply the diameter of the balancer by 3.14. Divide the result by 360, and then
multiply by 30 (representing the 30
o
).
Example based on a 7” balancer: 7 x 3.14= 21.98. 21.98/360= .06105” (per
degree). .06105” x 30
o
=1.8316”. From the TDC mark on the balancer, measure
forward (clockwise) about 1-13/16” and make a mark, which will represent 30
o
BTDC.
• Make sure the main wire harness camshaft connector is attached to the stock LS1 camshaft
sensor and the main wire harness Switched 12-Volt wire is connected and “live”. The main
harness battery connections also must be in place.
• Attach the Voltmeter’s red lead to the main wire harness terminal E3 (Signal) and the
Voltmeter’s black lead to the main wire harness terminal J2 (Gnd). These terminals are
attached to wires routed back to the camshaft sensor. The easiest way to accomplish this is to
insert sewing needles between the Voltmeter’s positive and negative alligator clamps, and then
push them into the aforementioned header connector terminals. Also, a jumper wire must
also be connected from pin J2 to the negative side of the battery. This test procedure will
not work without this ground strap.
Note:
Make sure the probes (sewing needles) inserted into the E3 and J2 terminals do not
touch each other. Doing so will damage the main wire harness!
Note: It is important to use probes with tapered tips (like sewing needles) rather than blunt tipped
probes (like paper clips) to avoid damaging the main harness header connector terminals
• Rotate the crankshaft back to 30
o
BTDC position and the voltmeter attached to the E3 and J2
terminals, the voltmeter should read 12 Volts (the Switched 12-Volt wire on the main harness
must be is connected and “live”).
• Very slowly, rotate the crankshaft clockwise towards TDC. As soon as the voltmeter reading
drops to zero Volts (or very close to zero Volts) stop rotating the crankshaft. Make note (write
it down) of the reading from the crankshaft degree wheel. Use this value in calculations shown
in bullet 7, on page 12
.