0 items: $0.00

Call Us:336.644.8668

Want to Run COIL ON PLUG Ignition?

TFI Distributor Shutter Wheel

Availability: In stock

$49.99

Quick Overview

The Truth About TFI Ignition, And Aftermarket TFI Distributors


The Ford TFI ignition system may best be known for the troublesome TFI module that would fail when it got hot. The engine would run for about half an hour, the TFI module would fail, and you’d be stuck on the side of the road. After some time to cool off, the engine would start back up, and you’d be on your way, but once it warmed back up again, you were again stuck on the side of the road.


It’s truly a shame that this is how TFI will be remembered. The truth is that the TFI ignition system was actually pretty ingenious. Yes, there were issues, but Ford did address them, and today a TFI system built with genuine Ford parts is actually a very good and very reliable ignition system.


The ingenious part of the Ford TFI system was that it allowed you to use the distributor as a camshaft and crankshaft position sensor, which allowed the ECU to fire the fuel injectors sequentially. Today, we actually use this same principal to fire multiple coils sequentially, which provides for a very simple, yet very effective way to adapt multiple coils systems to older engines that were not originally equipped with multiple coils systems. The way the TFI system works is pretty simple. There is a toothed wheel (the Shutter Wheel) mounted to the distributor shaft. The wheel has eight teeth (one for each cylinder), one of which is narrower than the other seven. The narrow tooth represents cylinder number one. These teeth pass through a hall effect sensor. The sensor sends a signal to the TFI module, which in turn fires the coil. The ECU monitors the square wave pattern created by the shutter and hall sensor, and uses this to determine engine position and RPM. Simple...


The real trouble started when the aftermarket got involved. Aftermarket companies started making replacement hall sensors and TFI modules. The hall sensors are absolute garbage. If you buy a hall sensor from the parts store, you’ve got a very good chance it will not work right out of the box. The ones that do work will likely fail. It’s just a matter of when. They often fail when they get hot, and then start to work again when they cool, much like the old TFI modules. Because of this, people will often misdiagnose the problem, and replace the TFI module, only to find later that they are stuck on the side of the road again. Even the ones that do work often produce such a poor quality signal that it is difficult for the ECU to properly determine engine position.


Then the aftermarket started building replacement performance TFI distributors. While pretty to look at, these distributors actually represent a few steps backwards:


(1) They use the aftermarket hall sensors. The good news is that you can still buy an original Ford hall sensor and install it in any of the aftermarket distributors.

(2) The shutter wheels they manufacture are NOWHERE NEAR the quality of the originals. The original Ford shutter was held to a tolerance of one half of one degree. The aftermarket ones are so bad, you can often see the difference in the width of the teeth with the naked eye! The result of this will be an inconsistent spark advance from cylinder to cylinder.


These distributors DO NOT OFFER ANY INCREASE IN PERFORMANCE whatsoever. And now that you understand how TFI works, you understand why. They have not changed a thing that would do anything to improve performance. In fact, the poor quality components actually reduce performance due to the inconsistent spark advance! A better coil, increased primary voltage, and longer dwell times (the length of time the coil is charged) are the only ways to increase the output potential of your ignition system. These distributors do none of these things.


Some of these manufacturers claim that their TFI module has increased dwell times, and therefor produce a hotter spark. This is not possible:


(1) Every coil has an optimum dwell time at a given system voltage. When they sell you a TFI module, they do not know what coil you are using, and therefor do not know what that dwell time is, unless they sold you a coil too, however….

(2) Even if they do know what the optimum dwell is, there is not enough time between cylinder events to dwell the coil long enough to reach those dwell times! At least not with a single coil system, which is where multiple coil systems come in. More coils means more available dwell time, and a real increase in performance.


So what did we learn?


(1) If you want a better ignition system, buy a Coil On Plug system. Yes, you can use a CD box, but those are as unreliable as the aftermarket distributors. Learn about our C.O.P.

(2) If you own one of these aftermarket distributors, you probably have a junk hall sensor. Buy a new one from the Ford dealer and install it.

(3) If you have one of these aftermarket distributors, you likely have a junk shutter wheel. It is very easy to determine if yours is good or not. The proper tooth dimensions are below. Measure your teeth with a dial caliper or micrometer. If the dimensions are wrong, then change it. New ones are available from Pro-M Racing on this page.


Proper shutter wheel tooth dimensions for a V8 shutter wheel:


Large teeth — .398 to .400

Small tooth — .258 to .262

There should also be even spacing between the teeth, with the exception of the long space following the narrow tooth.


We should mention here that our Pro-M EFI engine management system employs a strategy to deal with the bad shutter wheels. Our strategy averages out the pulses generated by the shutter passing through the hall sensor. This provides a consistent spark at all cylinders. The Pro-M EFI system will also set a diagnostic code if the shutter or hall sensor is so bad that the ECU cannot make sense of the signal. Just one more feature of the advanced diagnostics in our ECU.

TFI Distributor Shutter Wheel

Double click on above image to view full picture

Zoom Out
Zoom In

More Views

  • TFI Distributor Shutter Wheel

* Required Fields

$49.99

Details

  The Truth About TFI Ignition, And Aftermarket TFI Distributors

The Ford TFI ignition system may best be known for the troublesome TFI module that would fail when it got hot. The engine would run for about half an hour, the TFI module would fail, and you’d be stuck on the side of the road. After some time to cool off, the engine would start back up, and you’d be on your way, but once it warmed back up again, you were again stuck on the side of the road.

It’s truly a shame that this is how TFI will be remembered. The truth is that the TFI ignition system was actually pretty ingenious. Yes, there were issues, but Ford did address them, and today a TFI system built with genuine Ford parts is actually a very good and very reliable ignition system.

The ingenious part of the Ford TFI system was that it allowed you to use the distributor as a camshaft and crankshaft position sensor, which allowed the ECU to fire the fuel injectors sequentially. Today, we actually use this same principal to fire multiple coils sequentially, which provides for a very simple, yet very effective way to adapt multiple coils systems to older engines that were not originally equipped with multiple coils systems. The way the TFI system works is pretty simple. There is a toothed wheel (the Shutter Wheel) mounted to the distributor shaft. The wheel has eight teeth (one for each cylinder), one of which is narrower than the other seven. The narrow tooth represents cylinder number one. These teeth pass through a hall effect sensor. The sensor sends a signal to the TFI module, which in turn fires the coil. The ECU monitors the square wave pattern created by the shutter and hall sensor, and uses this to determine engine position and RPM. Simple...

The real trouble started when the aftermarket got involved. Aftermarket companies started making replacement hall sensors and TFI modules. The hall sensors are absolute garbage. If you buy a hall sensor from the parts store, you’ve got a very good chance it will not work right out of the box. The ones that do work will likely fail. It’s just a matter of when. They often fail when they get hot, and then start to work again when they cool, much like the old TFI modules. Because of this, people will often misdiagnose the problem, and replace the TFI module, only to find later that they are stuck on the side of the road again. Even the ones that do work often produce such a poor quality signal that it is difficult for the ECU to properly determine engine position.

Then the aftermarket started building replacement performance TFI distributors. While pretty to look at, these distributors actually represent a few steps backwards:

(1) They use the aftermarket hall sensors. The good news is that you can still buy an original Ford hall sensor and install it in any of the aftermarket distributors.
(2) The shutter wheels they manufacture are NOWHERE NEAR the quality of the originals. The original Ford shutter was held to a tolerance of one half of one degree. The aftermarket ones are so bad, you can often see the difference in the width of the teeth with the naked eye! The result of this will be an inconsistent spark advance from cylinder to cylinder.

These distributors DO NOT OFFER ANY INCREASE IN PERFORMANCE whatsoever. And now that you understand how TFI works, you understand why. They have not changed a thing that would do anything to improve performance. In fact, the poor quality components actually reduce performance due to the inconsistent spark advance! A better coil, increased primary voltage, and longer dwell times (the length of time the coil is charged) are the only ways to increase the output potential of your ignition system. These distributors do none of these things.

Some of these manufacturers claim that their TFI module has increased dwell times, and therefor produce a hotter spark. This is not possible:

(1) Every coil has an optimum dwell time at a given system voltage. When they sell you a TFI module, they do not know what coil you are using, and therefor do not know what that dwell time is, unless they sold you a coil too, however….
(2) Even if they do know what the optimum dwell is, there is not enough time between cylinder events to dwell the coil long enough to reach those dwell times! At least not with a single coil system, which is where multiple coil systems come in. More coils means more available dwell time, and a real increase in performance.

So what did we learn?
(1) If you want a better ignition system, buy a Coil On Plug system. Yes, you can use a CD box, but those are as unreliable as the aftermarket distributors. Learn about our C.O.P.
(2) If you own one of these aftermarket distributors, you probably have a junk hall sensor. Buy a new one from the Ford dealer and install it.
(3) If you have one of these aftermarket distributors, you likely have a junk shutter wheel. It is very easy to determine if yours is good or not. The proper tooth dimensions are below. Measure your teeth with a dial caliper or micrometer. If the dimensions are wrong, then change it. New ones are available from Pro-M Racing on this page.

Proper shutter wheel tooth dimensions for a V8 shutter wheel:
Large teeth — .398 to .400
Small tooth — .258 to .262
There should also be even spacing between the teeth, with the exception of the long space following the narrow tooth.

We should mention here that our Pro-M EFI engine management system employs a strategy to deal with the bad shutter wheels. Our strategy averages out the pulses generated by the shutter passing through the hall sensor. This provides a consistent spark at all cylinders. The Pro-M EFI system will also set a diagnostic code if the shutter or hall sensor is so bad that the ECU cannot make sense of the signal. Just one more feature of the advanced diagnostics in our ECU.