TFI Ignition Control Module w/stock points/distributor trigger

[GoMopar440]

Ok, I'll bite. I read the other thread "Pertronix (all points replacements) vs Points" and saw this post by Modok near the end. I'm not interested in fanning the flames in the whole Points vs Pertronix debate as that horse has been beat to death already. So please lets try to keep this thread off that track.

[ps2375]

[modok]

Yes the TFI ignition module is what you call "transistor ignition", the actual current being controlled with a transistor instead of mechanical switch.
BESIDES this, it also has a very simple dwell control. Below about 2000 rpm it starts to lower the dwell to prevent the coil overheating and reduce wasting power. Variable dwell is so conservative that you don't need to know about it, but it's neat to know, it won't require any special ignition coil or anything. In addition, there s a feature where if it does not receive a trigger pulse for a second it turns off power. You might have heard about "don't leave the ignition on" if you have petronix or compufire, because these will keep charging the coil until they overheat if you leave key on but engine off, THIS won't.

The module fires "going high", meaning uses a zero-12 volt signal, and fires when it goes to 12v. It will actually work fine as low as 8 volts(maybe lower) and as high as 16; it's not picky.


There are actually Four kinds of TFI module.
Grey(regular) and black(CCD), and distributor mounted or remote mounted, for four combos!
The distributor mounted ones have three pins coming out the side but actually are the same functionally.
Legend has it, in the the CCD ones are supposed to be black but the aftermarket didn't stick to the color codes. I collected three black ones so far and only one is actually CCD unit. THE CCD is computer controlled dwell if you haven't yet guessed.
CCD the coil fires going high, and charges going low, so the trigger signal controls the dwell also. These can be used with points too, but the points will control the dwell..........which is probably not as good, but sometimes good. I used one on a motorcycle. Controlling only one cylinder it made more sense to use the black one IMO.

[modok]

TFI can run any coil. It has "current limiting" at 6-8 amps.
This means once the coil ramps up(charges) to 8 amps then the module holds current at 8 amps by lowering the voltage to the coil as needed.

Our stock ignition usually runs a 3 ohm coil, to limit current to 4 amps.

TFI if you use a 2 ohm or 3 ohm coil it will not be using the current limiting.
I recommend a coil in the 1.5- 2 ohm range for a four cylinder.
The ford coil was 0.7 ohms, and will work too, but it may not be the best, I don't need a coil that charges fast enough to turn 10,000 rpm.

[modok]

You have to disconnect the condenser, OR run 40-50 ohms resistance from 12volts to points wire (#5 to #6)
MSD, DELTA, and other ignition boxes run 12 volts to the points through 40 ohms resistance, this allows you to keep the condenser connected, and also helps keep the points clean. It wastes 2 watts of power but it's so small you won't know

[GoMopar440]

From what I was told by the PO of my rail, the internals on my current engine are most likely going to be the stock VW parts. As a result I don't plan on revving the engine out past 5500 RPM at the absolute max. I'd rather limit it to 5000 for a little added safety factor. Would one of those rev limiting rotors do me any good when running a TFI conversion?
_________________
Homemade rail for street & off road: BJ front beam (bent), IRS rear (boxed/maybe bent), stock T1 DP 1600, 009, 34PICT-3 (soon to be dual 40HPMXs), 4-1 glass pack exh, T3 brakes (F disk, R drum & Dual MC), Bug trans (002, 5 rib going in soon).
Link to my rail (re)build thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=629493

[modok]

yes the rotors will work just fine. They short out the spark directly so will work with any system.

Points bounce can become a problem at high rpms.
With a used random set of stock points I found it began to bounce at 5500, at 6k it was still working but starting to wigg-out.
Where the RPM it will start to bounce IS depends on the particular distributor and points you have.

5500 rpm and below I think anything will be fine.

[raygreenwood]

Nice thread! I have been looking at the TFI system. Ray

[luvthemvws]

Modok, are you saying to put a resistor in the red wire (#6) going to the TFI module AND the yellow wire (#5) going to the points?

[modok]

One end of resistor to points wire, other side to 12 volts.

I should have put it in the picture........I knew I should have

[modok]

I have scrawled in the optional resistor

[GoMopar440]

I'm going to go poking around a couple of junk yards next week and see what I can find. I read on another web forum that the TFI modules can usually be found on Ford '90-'94 4 cylinder vehicles and '90-'97 8 cylinder vehicles. Can anyone suggest which Ford models I should be looking for specifically? Knowing that would help keep me from have to pop the hood of every Ford in those year ranges I come across in the JY.

I want to pick up a couple of the heat sink mounts as well as the remote TFI modules and the wiring plug that attaches to it. Is there anything else in particular I should be looking for while I'm out at the JY?

Is there a way to test these TFI modules while I'm out in the junk yard? I have a decent multimeter and know how to use it. What I don't know is the testing procedure for the TFI unit or the specific values I should be looking for.

The next question I had is about the difference between the (OEM Ford) black and grey TFI modules. Is one better than the other for a ACVW application? I've already heard that the aftermarket replacement units don't necessarily follow Ford's color coding policy for the plastic module housings.

I know the heat sinks can be modified to work with the distributor mounted modules, but you have to cut off a few cooling fins to do so. I'd much rather stick with using the remote modules and keep all of the cooling fins in place. If the heat sinks aren't perfectly flat and smooth where the module makes direct contact, I can take a skim cut with my milling machine on the heat sink to fix that. I have some CPU heat sink paste that I can use to get the best heat transfer possible between the module and the heat sink.

Sorry there's so many questions, but I figure this would be the best place to ask them. That way the questions and answers can all be found together in one thread.
_________________
Homemade rail for street & off road: BJ front beam (bent), IRS rear (boxed/maybe bent), stock T1 DP 1600, 009, 34PICT-3 (soon to be dual 40HPMXs), 4-1 glass pack exh, T3 brakes (F disk, R drum & Dual MC), Bug trans (002, 5 rib going in soon).
Link to my rail (re)build thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=629493

[modok]

90% of them are the "grey one" and that's the one you want.
You need a special tiny nut-driver to get them off a distributor. I don't recall the size. I had a miniature 4-way lug wrench for RC cars and it fits. LOL
If you steal a remote-mount unit then you can take the whole thing, wires, heat sink and all. and not need the tiny nut-driver. Check the bigger vans. Little pickups are all distributor mount it seems.

The OE heat sink is OVERKILL. But....better than underkill. The more you use the current limiting the hotter it gets, so, if you use a 2-3 ohm coil like stock then IMO you won't even need a big heat sink, just mount it to something metal with good contact, that will be enough to keep it cool.

I tested a half dozen initially on a test rig I made for testing ignition systems, which included a oscilloscope and variable drill to spin the distributor, but I didn't find any bad ones, so I don't have any input on how they fail.
Since it has a connector, if you suspect it's acting up unplug it and connect another one. That's my plan.

[GoMopar440]

So I should probably just grab the coil from the vehicle the TFI module comes from then. As long as it's still a factory coil on the vehicle that should mean it will work with the module as long as the coil itself is still good. I'll still bring my multimeter with me so I can check out the coils at least.

Without knowing what specs to check on the modules I should grab at least a couple or three in case I get a bad one in the bunch. That way I'll also have a spare to carry with me just in case one goes bad while I'm using it. They're fairly small modules so it won't be a problem finding a place to tuck one away on the rail.

I'd rather have more cooling than I need instead of just enough. Heat kills electrical parts easy enough already, so I'd rather keep it on the safe side for the sake of reliability. I'll also have more flexibility with having greater cooling reserves on hand if I need to use a less than optimal coil in a pinch in an emergency (away from home).
_________________
Homemade rail for street & off road: BJ front beam (bent), IRS rear (boxed/maybe bent), stock T1 DP 1600, 009, 34PICT-3 (soon to be dual 40HPMXs), 4-1 glass pack exh, T3 brakes (F disk, R drum & Dual MC), Bug trans (002, 5 rib going in soon).
Link to my rail (re)build thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=629493

[Fred Winterburn]

Actually points bounce starts just off idle, but it has no detriment to the actual dwell until the bouncing becomes a significant portion of the dwell period. If used to trigger the TFI it probably wouldn't be a problem at all but I have not tested this. Once the points start to float (which is significantly more severe and damaging to the points, than bouncing on closure) timing will be affected and no amount of fancy electronics can make up for that, but it takes an extremely high rpm for points float (not bounce) to start.
With regard to the 40 ohm resistor or removing the condenser. VW and Porsche applications with the Bosch distributors do not seem to suffer from the points crudding up as much as some other cars when the points current is very low. You could probably run without the optional resistor that Modok suggested. If you do use the resistor, make sure the connections are sound or it could affect the trigger and cause spurious firing of the TFI. Fred

[Frank Bassman]

You'll find the module on older F150 pickups and Econolines. I'm talking late 80's F150 and early 90's vans. On both the vans and the pickup they are located on the driver side of the engine bay bolted to the extreme side by the quarter panels. (Heatsink models, not distributor mount types.

If you find you need to take off the module from the sink you can buy the special tool from autozone. It is cheap and good to have. I also bought the module from autozone once, just to have , it was a bout 50 bucks wich I figured was cheap enough in itself with a lifetime warranty. I just have it as a spare. Never any problems with the junkyard one.

I will take pictures of my setup later, sorry I haven't posted them yet this has been one very busy weekend for me.

I do have one question though. I was running the module with a separate cable up until recently. But then I changed the whole dizzy with a worked over autostic DVDA and am niw just running it with the same cable that comes off the points and condenser. Works... Just fine or so it seems with the TFI this way. Why is it necessary to take out the condenser out from the circuit if all the points are doing is supplying an intermittent ground to the module for activating the ignition?

This is perhaps a stupid question but I can't seem to find any straightforward explanation.
Thanks in advance.

-Frank

[Fred Winterburn]

I would presume that if the condenser is left in place, the TFI will misfire. Modok knows the answer. Fred

[modok]

Leaving the condenser connected causes the ignition timing to retard as RPM rise. It still works, still runs,.... but if you check the timing with a timing light you'll see it's a little strange.

The TFI does supply 12volts to the trigger pin through a SMALL resistor, so, when the points open it takes a small amount of TIME for the condenser to charge up and let voltage rise high enough to reach the trigger point.

Using a much larger 40 ohm resistor to power the trigger circuit the condenser charges up quick and makes this delay moot.

[Fred Winterburn]

Modok, I think you meant large resistor for the TFI internal circuit, and small resistor for the external 40 ohm circuit (although physically larger due to the higher watt rating). Thanks for the correct answer, that I guessed incorrectly, Fred.

[modok]

Ah yes, you are correct. I was thinking in physical terms.

The TFI has a small resistor with a very large resistance.