How can I install a tachometer in my late model ignition systems?

e are getting more and more requests for tach signal wires and connection points on all kinds of new vehicles, and virtually every new vehicle has at least a DIS (distributorless ignition systems, or coil pack as it is more commonly referred to). The days of the “old distributor and coil” are gone, friends. This is a whole new ball of wax. The automotive industry appears to be shifting toward an even newer ignition system – C.O.P. This stands for coil on plug ignition system, which consists of attaching a coil atop each cylinder’s spark plug, eliminating any coil pack, distributor, or plug wires. The computer for the vehicle controls the targeting for firing the plug when needed, supplies the voltage to the coil to discharge, and has a “monitor” to ensure that the coil did fire and at the appropriate time.

Ok, now you’re asking your self, “What does this mean to me?” The answer: if you have a late model vehicle (most ’99 and newer models) with C.O.P. ignition, it has everything to do with you.

We have had much success installing tachometers on c.o.p. ignition systems on late model vehicles where no available tachometer output is available. There are still some vehicles out there that have a useable tachometer signal, but for those that do not, all is not lost. We offer a tachometer adapter, model # 9117 which is universal to allow most vehicles without a tachometer signal to have a tachometer installed. For the installation of the tachometer adapter, it will require locating the power supply to the ignition coils and cutting the power supply prior to the power splitting between all of the coils. The tachometer adapter will have an in (red) and an out (red/green) wire. Wire the adapter between the two cut halves of the power supply. Ground the black wire and the last wire (gray) is your new tachometer output.

This is relatively easy on most vehicles, but depending on how the system is wired, you may be able to isolate the power to only half the coils. Chrysler V-6 and V-8 engines with individual coil on plug ignitions can be much more difficult, and you should contact our tech support department before installation on one of these vehicles.

This leads us to the next point and question, “Why can’t I just splice into the wire(s) that goes to the tach in the cluster?” This sounds like a viable option, but the signal to the cluster tach is not the same signal as what our tach needs to see (12v square wave). This is commonly referred to as Multiplexing, which is the process of communicating several messages over the same signal path or wiring. In most cases, the wire that has the tach signal also has the signal for any of the following:



LOW FUEL level indicator



The standard gauges; oil, water, fuel level and volts



Brake warning light


Seat belt


And so on…


As you can see, for this example ’99 Mustang there is a lot more than just the tach’s engine RPM signal going up to the cluster and our tach cannot derive the signal needed to operate, nor is it the correct signal. We have also found that the rate of refresh is very low, so it does not give as accurate readings as our tach needs to see.

Some vehicles, even to the day this article was written, had the new C.O.P. ignition system and also a devoted “tach signal” from which to work from. A few examples of such applications are:

  1. Ford Triton V-10
  2. GM LS1(used in the Camaro, Firebird, Corvette, Silverado)
  3. ’01 Honda Civics

As stated above, 1) the Ford Triton V-10 motor, which has what they refer to as a CTO (clean tach output) which our products, after some modification, are capable of working on. Also, 2) the new LS1 motors found in such vehicle platforms as the Pontiac Firebird, the Chevy Camaro, and the Chevy Corvette. And lastly, 3) ’01 Honda Civics, one of the latest additions to this listing, but they too have a tach wire to work off of. These vehicles have the C.O.P. ignition, yet the factory cluster tach has a wire that uses a signal our tachs can work off of from the computer that you can splice into to obtain the engine RPM signal from.

So with all this in mind, we are trying to do everything we can to stay compatible with the later model ignition systems, but don’t always have the answer. We STRONGLY urge you if you are looking to purchase one of our products that you check the ignition system first, to see what you have to work with, then step two should be to call us and inquire about the compatibility with your specific vehicle.