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 versions are 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 our EX versions to advance ignition timing up to 4 degrees beyond the original equipment module. Thus the maximum advance curve in the EX versions 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 versions are 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 ignitions have sufficient advance adjustment range for most applications using the advance slope switch settings. When used with our PC Link Evo 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® and Sportster® 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® models?

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 engines.

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 Cam 88® 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® security system?

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 sensor.

Not all vendors support the optional H-D® security 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 www.digikey.com. 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 black connector.

The tach signal is at pin 12 on the black connector. The tach signal should drive most aftermarket tachs intended for H-D® applications.

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.

We supply Twin Cam wire harnesses suitable for custom applications. 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.