_____________________________________________________
Tec3r Manual Version 1.11
- Page 50 -
©2017 Electromotive, Inc.
TDC events for the engine. Without concern for whether the TDC events are compression or exhaust, here is
the order of TDC events for the engine:
1 TDC
– 30
o
–
4 TDC
– 90
o
–
3 TDC
– 30
o
–
6 TDC
– 90
o
–
5 TDC
– 30
o
–
2 TDC
Where:
1 TDC to 3 TDC = 90
o
+ 30
o
= 120
o
3 TDC to 5 TDC = 90
o
+ 30
o
= 120
o
4 TDC to 6 TDC = 90
o
+ 30
o
= 120
o
6 TDC to 2 TDC = 90
o
+ 30
o
= 120
o
With the
Tec3-r
, this type of firing scheme is done quite easily. Coils A1, B1, and C1 fire 120
o
apart
from each other when a 6-cylinder Odd-Fire Engine is configured in the software. Similarly, coils A2, B2,
and C2 will fire 120
o
apart, but not at the same time as coils A1, B1, and C1. The
degree split
between
A1/B1/C1 and A2/B2/C2 is defined by the
TDC Tooth for DFU “2” Parameter
in the software.
Coil A2
must fire after A1 by the correct amount for the odd-firing sequence; in this case, since Cylinder 4 has
its TDC 30
o
after Cylinder 1, a 30
o
split is necessary.
The TDC Tooth Offset Parameter for the 2
nd
DFU
must therefore be set for 30
o
, or
5 teeth
of the trigger wheel (each tooth is 6 degrees). So, if the TDC Tooth
Setup Parameter for the 1
st
DFU is set at 11, set the TDC Tooth Offset Parameter for DFU “2” to
16
(from
the equation 11+5).
Coils A1, B1, and C1 will be wired to cylinders 1, 3, and 5, respectively. Coils A2, B2, and C2 will
be wired to cylinders 4, 6, and 2 respectively.
The most important step to setting up an odd-fire engine is to determine the TDC event order for the
engine, and to find the degree split between the first two TDC cylinders. Also, the concepts of TDC Order
and Firing Order must be separated in order to fully understand what is occurring on an odd-fire distributor
less ignition.
C.6.a. To find the TDC Event Order:
1.
Turn the engine to TDC #1.
2.
Rotate the engine in its normal direction of rotation.
3.
Record the order in which the cylinders have TDC’s. It does not matter that the TDC events are
mixed between compression and exhaust during this process.
C.6.b. TDC Tooth for DFU “2” needed for an Odd-Fire Engine:
1.
Turn the engine to TDC #1.
2.
Measure the crankshaft degrees between TDC #1 and the next TDC event for the engine.
3.
Take this Degree Number (
DN
) and divide it by 6. If the result has a decimal, round UP to the
nearest Whole Number (
WN
).
4.
Add WN to the number 11 to give you the necessary value for the
TDC Tooth for DFU
“2”
parameter.
5.
Perform the following subtraction: DN – WN =
X
.
6.
Enter
X
into the
Rotary Ignition Split
table for all RPM points.
C.6.c. Harley-Davidson Applications
The unique sound of the Harley-Davidson V-Twin is the result of an odd (uneven) firing pattern
between the two cylinders. To run this engine, select
2-cylinder Odd-Fire
for the engine setup. Since this
is a 45
o
V-Twin with one connecting rod lobe, the TDC events occur in the following fashion for one
complete engine cycle:
TDC A
– 45
o
–
TDC B
– 315
o
–
TDC A
– 45
o
–
TDC B