TC88 Ignition for Twin Cam 88®
What is the difference between
EX and race versions?
The new EX version of our
TC88 has been given Air Resources Board Executive Order (ARB E.O.)
D-641-1. This makes the TC88 EX exempt from the prohibitions of the
California Vehicle Code and 50 states street legal. The maximum spark
advance curve in the EX version is more conservative in the lower RPM range.
The figure below compares the maximum advance curves (advance slope set to
9) at wide open throttle for the two versions.
The EX version is suitable
for all street driven applications, including large displacement and high
compression engines where spark timing must be retarded from stock settings
to avoid destructive engine detonation. As a compliance criteria, the Air
Resources Board allows products such as the TC88 EX to advance ignition
timing up to 4 degrees beyond the original equipment module. Thus the
maximum advance curve in the TC88 EX is still very aggressive and allows a
performance improvement when using 92-93 octane gasoline with stock engines.
The maximum advance curve for the
race version is only suitable for true race engines where a long
duration/high overlap camshaft reduces cylinder pressure in the lower RPM
range and high octane race gasoline is used.
Both the EX and race versions
of our TC88 have sufficient advance adjustment range for most applications
using the advance switch settings. When used with our PC Link TC88 software,
both the EX and race versions allow creating a custom advance curve and no
limitation exists on retarding the spark timing to solve a detonation
problem which is the most common reason for creating a custom curve.
What is the difference between
TC88 and TC88A ignitions?
The TC88 is for 1998-2003
carbureted Twin Cam 88®
models that have an ignition module with two 12 pin connectors. The TC88A is
for 2003-2004 carbureted Twin Cam 88®
models that have an ignition module with a single 12 pin connector. Sportster®
models changed from an internal ignition to the new TC88A style ignition in
2003. All 2004 carbureted Twin Cam 88®
models use the new TC88A style ignition. However, H-D®
appears to have also shipped a limited number of 2003 carbureted Twin Cam 88®
models with the new style ignition. If you have a 2003 Twin Cam 88®,
you need to check the ignition module.
The TC88A supports the J1850
data bus used on the new 2003-2004 models for communications between the
ignition module, turn signal/security module (TSM/TSSM), instrument cluster,
and scan tools.
What is the difference between
1998-2000 and 2001-2003 Twin Cam 88®
With the exception of few
motorcycles manufactured in late 2003 (as explained above), the carbureted
versions of all these models use an ignition module with two 12 pin
connectors. H-D® did
away with the camshaft position (CMP) sensor on 2001 and later models. There
were reports of problems with these sensors. They may also have deleted the
CMP sensor as a cost cutting measure made possible by the more sophisticated
Delphi® electronics on the newer models.
Without the CMP sensor, there
is no direct means of identifying which cylinder is on the compression stroke.
The ignition system must use an algorithm that detects the slight reduction of
crankshaft angular velocity on the compression stroke during cranking. This is
not a trivial problem and not all the companies selling aftermarket ignitions
have solved it.
If the ignition can't identify
the compression stroke, the system must operate in wasted spark mode. In this
case, each spark plug is fired twice - once on the compression stroke and
again on the exhaust stroke. This is not as bad as the old dual fire, but it's
certainly not what the designers of the Twin Cam 88®
engine had in mind.
The TC88 is compatible with all
1998-2003 carbureted Twin Cam 88®
models using an ignition module with two 12 pin connectors. The TC88 does not
require a camshaft position sensor (CMP) and this sensor may be unplugged or
removed on 1998-2000 models. If the CMP sensor fails, it may cause a short
circuit that will prevent the TC88 from operating. Since the CMP sensors have
a questionable history, we suggest unplugging the sensor.
Will the Twin Tec TC88 solve my
hot starting problems?
Some Twin Cam 88®
engines are prone to hot starting problems. When cranked after a short hot
soak, the engine may “kick back.” Over
time, this will cause damage to the ring gear and starter pinion.
The TC88 module uses an
improved starting algorithm that includes a programmable cranking delay. The
TC88 module is shipped with a zero cranking delay: it fires on the first
recognized compression stroke. This works best on stock and mildly modified
High compression engines may
exhibit a “dieseling” phenomena after a hot soak. This can be verified
by temporarily disconnecting the 3 terminal coil primary connector to
disable the ignition. If the engine still kicks back or runs for several
revolutions after cranking, the problem is dieseling. The only solution is
to install compression releases. When compression releases are installed,
best starting results will be obtained by programming the TC88 module for a
1-2 revolution cranking delay. This can be done by means of the PC Link TC88
software and optional interface cable.
What coil is recommended for use
with the Twin Tec TC88 ignition?
The Twin Tec TC88 is for Twin
engines that use an original equipment coil
with .5 ohm primary resistance. You cannot use any coils with higher
resistance. All available aftermarket coils for Twin Cam 88® applications,
including our P/N 2008, have the same
electrical characteristics as the original equipment version. Unless
your original coil fails or you suspect that it has become degraded, there is no valid reason to replace it.
Does the Twin Tec TC88 support
all the stock sensors on Twin Cam 88®
models including the optional H-D®
Yes, with the exception of the
camshaft position (CMP) sensor
that H-D® deleted on 2001 and
later models. As explained above, we don't require the CMP
Not all vendors support the
system (TSSM). The customer may be left with a false sense of security.
If the motorcycle is left unlocked and the ignition system does not support
the TSSM interface, the motorcycle is easily "hot-wired."
How do I wire up a custom bike
with a Twin Cam 88 Engine®?
You can easily do this with our
TC88 ignition. Wire harnesses are readily available from your local H-D®
dealer or Wire Plus (read further on for more details) and you can use the wiring diagram in the H-D®
manual. At a minimum, you must hookup the crankshaft position (CKP) sensor,
manifold pressure (MAP) sensor, ignition coil, power, and ground. If you have
an early Twin Cam 88®
engine with the camshaft position (CMP) sensor, you can
leave this sensor disconnected.
We highly recommend that you
leave the H-D®
data link plug intact or buy a harness that has provision for the data link, as it is required for
PC link programming. If you are not using
the stock (or a Twin Cam 88®
compatible) instrument cluster, leave the TC88 check engine LED output (on pin
4 of the black connector) unconnected. This signal cannot drive a lamp bulb.
However, you can connect a 12 volt LED (these have an internal current
limiting resistor). Suggested LED part numbers include L50151, L50261, and
L50311 available from Digi-Key at
These LEDs have red and white wires. Connect the red wire to switched +12 volt
power and the white wire to the TC88 check engine LED output on pin 4 of the
signal is at pin 12 on the black connector. The tach signal should drive most
aftermarket tachs intended for H-D®
If you are not using a bank sensor or TSM/TSSM module, you must
ground the wire going to pin 10 on the black connector.
Wire Plus (www.wire-plus.com)
supplies Twin Cam wire harnesses suitable for custom applications. Contact
them for details. Note that you must ground pin 10 on the black connector (required when not using a
bank sensor or TSM/TSSM module.
If you are making your own wire
harness, please be advised that all the H-D®
manuals and wiring diagrams show an incorrect view of the MAP sensor and
mating connector. The wire colors shown for terminals A, B and C are correct
but the view is reversed. If you don't pay attention to the terminal letters
engraved on the connector, your wiring harness will be incorrect and the
ignition will not run. The correct view is shown below.