Tec3r Manual Version 1.11
- Page 18 -
©2017 Electromotive, Inc.
A.4.e. Camshaft- & Distributor-Mounted Trigger Setups
While crankshaft mounted triggers are preferred, it is sometimes easier to install a camshaft- or
distributor-mounted trigger wheel. For these cases in which the trigger wheel is spinning at
half the engine
speed
, a 120(-4) tooth trigger wheel is necessary. This wheel has two sets of two missing teeth, spaced 180
degrees apart. As such, the input to the
Tec3-r
is identical to that of the crank-mounted 60(-2) tooth trigger
wheel. Electromotive offers 120 (-4) tooth wheels in 3.25” and 2.75” diameters.
It is often easy to use an old distributor rotor to serve as the mount for a 120(-4) tooth trigger wheel.
A simple nonferrous bracket would need to be fabricated to hold the sensor. The 3/8” chisel point sensor
(PN: 250-72212) must be used on 120(-4) trigger wheels. As such, the bracket for the sensor should use a
clamping arrangement rather than a setscrew to hold the magnetic sensor.
Just like the crank-mounted
trigger, the distributor/cam-mounted triggers require the sensor to be aligned with the trailing edge of
the 11
th
tooth after the two missing teeth when the engine is at TDC #1.
The same tolerances that apply
to the crankshaft-mounted trigger wheels (
Table A.4.1
) apply to the camshaft-mounted trigger wheels as
well.
A Note on Engines with High-Overlap Camshafts:
If your engine is equipped with a camshaft that has early intake valve openings or very long duration,
you may experience backfiring through the throttle during starting. This is caused by the intake valves
beginning to open on the exhaust stroke. Since the spark plugs fire on both the compression and the exhaust
strokes, the spark on the exhaust stroke may cause unburned fuel in the intake manifold to ignite, resulting in
a backfire.
To remedy this situation, advance the “mechanical” timing by manipulating the
DFU “A” Trigger
Wheel TDC
Parameter. If your crank sensor is aligned with the 11
th
tooth of the trigger wheel at TDC #1,
setting the Tooth Offset to a number LOWER than 11 will
add
mechanical advance. If the number “10” was
set for the Tooth Offset, the mechanical timing would be ADVANCED by 6 degrees (6 degrees per tooth).
This would require that you subtract 6 degrees from the values in your ignition advance table in Wintec to
obtain your desired advance value. That is, the timing table will have to read 30 degrees in order for the
engine to operate at 36 degrees advance. See
Section A.4.g.
for more details.
A.4.f. Full Sequential Applications – Cam Synchronization
When full sequential fuel operation is desired, a once-per-engine-cycle synchronization, or “sync,”
pulse must be received by the ECU. Typically, the sync pulse is generated by the installation of a 1-notch
(or 1-tooth) trigger wheel onto the camshaft. A standard Electromotive magnetic (inductive) sensor can then
be used to obtain the reading from this trigger wheel. A Hall effect sensor could also be used as a triggering
method instead of a magnetic sensor setup. With either method, the tooth must pass by the magnetic sensor
between 180
o
and 6
o
before TDC Compression (not exhaust) of the number one cylinder. See
Figure A.4.7
for installation details.
The Tec3-r will only trigger off a rising edge during the synchronization period (between 180
o
and 6
o
BTDC compression)
. A rising edge occurs when the metal on the cam trigger wheel becomes closer
to the sensor over a very short period of time. See
Figures A.4 6 and 7
for representative examples and
different cam trigger wheel designs, and their rising edge location.
