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TFI Ignition Control with MegaSquirt-II
Thick Film Ignition (TFI) modules were used on Ford vehicles with distributors from the early 1980s to the mid-1990s. It was used on a number of Ford's engines, the EFI 5.0 engines in particular. The TFI module is a gray box fitted to the side of the distributor. It is about one inch wide, and about four inches long. The distributor itself uses a Hall effect sensor.
The TFI modules are available as Holley 891-105 or Accel 35368 (~$46), as well as from a number of aftermarket sources.
Installing the Ford TFI System
The connections are:
- GND: Ground.
- TACH: Coil control wire.
- PWR: Battery voltage input with ignition switch in run position.
- STRT: Battery voltage input with ignition switch in start (cranking) position.
- SPOUT: The timing control signal from your controller to the module goes on this wire.
- PIP: This signal provides the crankshaft position.
The other three pins on the side of the module are for the distributor's sensor. These pins are:
starting from the pin closest to the 6 pin external connector.
Note: this information is tentative. The MS-II/TFI setup has not been 100% verified yet.
First, be sure to use MegaSquirt-II code version 2.1 or higher. This code has the appropriate algorithm for the necessary 'trigger return' cranking parameter. Get the code here.
To install TFI with MegaSquirt-II, you connect:
V3.0 main board:
- Use the Hall/optical/points input circuit, in step #50 of the V3 assembly guide, but:
- Use a 1k resistor in series with the ignition input coming from the TFI. Do this by pacing a 1K Ohm resistor in the main board location marked "D2" (instead of the jumper you would normally put there), and
- Install the high current ignition driver circuit (step #65 of the V3 assembly guide). Note: do NOT install R57. Use a 100 Ohm, ¼W pull-up resistor on the coil output of the MegaSquirt® EFI Controller, and drive this directly to the TFI's SPOUT input. You can do this by connecting a 100 Ohm, 1/4W resistor from the IGBTOUT jumper on the main board to the via immediately below the "S12" making on the silkscreen (near Q19).
Leave the jumper from IGN to IGBTOUT in place, just solder the resistor to it (see the red lines in the diagram below).
Note that the jumper goes to the via marked S12 on the top side of the board. Some PCBs may have a slightly different layout, in all cases you should check for 12 volts (nominal, actual voltage depends on the power supply voltage) at the end of the resistor that doesn't connect to the IGN/IGBTOUT jumper.
The PIP signal comes into MegaSquirt-II on DB37 pin number 24, the SPOUT goes out on pin #36.
Then in MegaTune, set:
- Trigger offset = 10° (this will vary, depending on the distributor orientation),
- Ignition Input Capture to 'Falling Edge',
- Cranking Trigger to 'Trigger Rise',
- Coil Charging Scheme to 'Standard Coil Charging',
- Spark Output to 'Going High (Inverted)', ('Going High (Inverted)' for MicroSquirt).
Then set the maximum dwell duration to 8.0 milliseconds with no battery voltage compensation (set the five 'Duration at Voltage X' to 0.0 under 'Dwell Settings/Battery Voltage Compensation' in MegaTune.).
MegaSquirt® and MicroSquirt® controllers are experimental devices intended for educational purposes.
MegaSquirt® and MicroSquirt® controllers are not for sale or use on pollution controlled vehicles. Check the laws that apply in your locality to determine if using a MegaSquirt® or MicroSquirt® controller is legal for your application.
©2005, 2007 Bruce Bowling and Al Grippo. All rights reserved. MegaSquirt® and MicroSquirt® are registered trademarks. This document is solely for the support of MegaSquirt® boards from Bowling and Grippo.