Ford TFI Basics...

All Megasquirt 1 support questions. See also the Documentation

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BoostedXD
MS/Extra Newbie
Posts: 2
Joined: Fri Jun 02, 2006 2:20 am
Location: Sydney - Aus

Ford TFI Basics...

Post by BoostedXD »

Hey guys, im getting everything together for a MSII install on a 79 Falcon running a TFI dizzy.

ive looked everywhere for a bit of information concerning the triggers from the hall effect sensors that feed the TFI module.

Now i understand the MS side requirements and mods to run the TFI, but just want to make sure i am understanding the TFI side of things. and see if the Australian modules are the same.

Now for the trigger angles, the hall sensor triggers from low to high (0.02V -> 0.3V) as the blade passes through the hall sensor. Now this occours at 60deg BTDC and the trigger exits at TDC. i also have a EST dizzy which is aimed at the hall sensor feeding directly into the control unit for a carby car, which has the same trigger angles, but triggers from high to low, i assume this makes no differance as i just set the trigger high or trigger low accordingly.

Now my main question is what does the TFI do with the signal at 60deg BTDC?? Does it process the signal, and in limp home mode send a trigger to the coil at 10deg BTDC, but in opperational mode, or when the signal is coming from MS, it signals as required.

So im after the appropriate rotor phasing for a TFI hall effect sensor, or an indication at to how to test it to ensure it will send a signal when it has to to MS. Are all TFI dizzys set up with triggers at 60deg BTDC and TDC???

Also, how do you set the base timing without MS attached, do you just remove the SPOUT and then set the timing to 10BTDC, then re-attach the SPOUT, assuming all the other wires are run to the TFI connector

Thanks

Jason
MegaScott
MS/Extra Guru
Posts: 1280
Joined: Mon Jun 14, 2004 9:35 am
Location: Chiang Mai, Thailand

Post by MegaScott »

You can look at the TFI setup as just a simple Hall effect sensor, with a dwell controlled high current driver.

The window in the dizzy triggers a low to high transition from 0v to 12v, that signal (PIP) is sent through the Module to the EEC or Megasquirt. The PIP has no delay to it and is sent at 10deg BTDC which is the Ford recommended dizzy position. In the absence of Spout, the Module will use the PIP to drive the internal driver, which charges and fires the coil. When Spout is present the module uses that signal to drive the internal driver to charge and fire the coil.

What doc did you read that said the TFI runs at 60deg BTDC?

The way the Megasquirt normally works with spark is this - When cranking, the Megasquirt takes the PIP and mirrors that signal to make the Spout, as the engine fires and crosses ~400rpm, the firmware switches into next cylinder mode, where the PIP is delayed a programmed amount derived from the Spark Map, calculated from the previous PIP and thus the next cylinders Spout signal is created to fire the coil at the appropriate advance angle..

To answer your question, just install the TFI dizzy at 10deg BTDC with the Spout disconnected from the Megasquirt, and then hook Spout back up for Megasquirt Spark control. When I install Megasquirt On my TFI equipped Fords I don't even really have to open the hood/bonnett except to hook up the Map hose.
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