LT8 and FC vs. FD coils
 

im getting an LT8 that is set up for FC coils, but i am using FD coils on my motor. should this matter?

wich ignitor should i go with? im guessing the FD one, but im looking for some insight here.

thanks.

It matters greatly. FC tailing uses a single trigger channel and a toggle. FD uses two triggers. You need to either use FC coils or send the Microtech back for reprogramming.

theres no other way to wire it?

cause im using the FD apexi on my FC with FC coils. i just had to modify the trailing coil. or i could have used the FD ignitor. its all on banzai-racing.com website.

so there must be a way...m just no wiring expert. its my downfall

The Microtech is always going to output the same signal, so the only way for you to get around it is to use the FC trailing ignitor and then use it to trigger your coils. However I don't think you can trigger the FD coils this way. They probably fire on rising and not falling.

The leadings should be as simple as connecting the trigger wires together and then connecting to the Microtech's trigger. I think the leadings trigger the same as the FC except the FD uses two while the FC uses a dual ended coil.

I am not an FD guy however, so check with someone else before you take this at my word. :)

To use FD coils you need to use the FD igniter. The FC igniters are integrated into the coil packs where as the FD uses a remote igniter.

The Microtech does not need to go back for reprogramming. However if you are not good with wiring then you may not want to tackle this, you will have to make a custom harness from the igniter to the FD Coil pack with shielded wires for it to function properly.

It would be far easier the wire up the FC coils, besides the FC leading coil is an upgrade for FD, when the OEM one fries.

so taking into consideration from both of your posts, i should just use the FC coils? would it be a bad idea to use two leading coils instead of one leading and the two single post trailing. im trying to keep it compact and nice looking. this was the major choice for me when picking the FD coils.

damn...i just made this custom bracket for the FD coils. whats the diffacult part with wiring the FD coils and igniter up? i have the original harness that comes off the FD coils.

You can not use two leading coils, the trailing coils are two coils the leading is only one coil with two outputs that fire at the same time. The trailing coils fire at different times.

It is not overly difficult you just need to know how to solder and read a wiring diagram. We are using the FD coils on our 13b-re vert with the FD igniter.

Here is a how to that we did for using the FD igniter with the FC coils, you can use it to help you wire up the FD coils. Obviously the FD coils have their own harness so all the cutting for the FC coils explained in the how to is unnecessary.

http://www.banzai-racing.com/fd_igni...all_how-to.htm

You should take a look at the FD FSM electrical section, and use the microtech wiring diagrams. If you are not good with wiring this is going to be difficult.

why are you so insistent on using fd coils?
they are no were near as good as the fc coils.

Just be done with it and use FC coils.

thanks. this is a big help.

and its not that im horrible at wiring. im just no pro. but i've always been able to handle what i needed done in the past. im sure with your write up and some heavy thinking. i can get it done...

thanks again

I think you mixed that up. The FC coils are bolted to the igniters.

The FD uses the same toggle setup for the trailing as the FC? I had always thought it was a separate channel for each trailing coil.

Nothing mixed up about it at all. The FC uses two seperate igniters that are integrated into the coil packs, yes bolted to it....integrated. The FD uses a remote mounted igniter that is no where near the coil pack.



Both FC and FD have three triggers from the ECU, one leading , two trailing. The voltage for the T2 coil igniter trigger is higher then the T1 this is what causes the "toggle" in the trailing igniter. The FD uses one igniter to accomplish what it takes the FC two to do, so it is "toggling" between all three coils. Take a look at the FSMs they both have three ECU controls, the FC just has a confirmation signal. The FD ECU uses the same voltage for both trailing, the Microtech doesn't care if it is a FD igniter or two FC igniters, it still has three outputs for triggering the igniters.

Sen2two-
One thing to keep in mind is that the FD igniter does not have a tach signal out wire like the FC. We cover that in the previously posted how to.

Ah, I see.


Wait...something about that doesn't seem right. The FC has two trailing channels: trigger and toggle. Hold toggle low and hit trigger and you get T1, hold toggle high and hit trigger and you get T2 (or vice versa, I forget). I just checked the FC FSM and training manual (page 5 of engine electrical) on this to make sure I was not crazy.

I'm a bit confused on the FD side. The FSM shows two lines from the ECU to the ignitor. Are you saying that the ECU tells the ignitor to fire based on the amplitude of the signal on the "trigger" line and the 2nd connection is for the ECU to know that the ignitor fired?

If so that would mean that a Microtech set up to fire FD coils can't be connected to fire FC coils without a FD ignitor.

What am I missing?

You obviously do not understand how the ignition system works. Both FC and FD have two outputs from the ECU for trailing.

I do understand how the FC ignition works quite clearly, but it's the FD I'm not clear on.

The FC trailing uses two outputs from the ECU, a trigger and a toggle. Trigger tells the coils to fire, toggle tells the ignitor which coil to fire.

My post above says the same thing, just a bit differently.

What I'm asking is how this relates to the FD system. I am really not an FD guy and it's likely I'll never own one, but I am curious as to how the trailing system differs from the FC. I've not been able to find the FD training manual, only the FSM. The FSM doesn't really cover things in the same detail the training manual does.

The FD igniter doesn't need to see the a difference in voltage for it to toggle between trailing coils, both T1 and T2 are 0.8V , where as the FC has different voltages at the ECU 0.8V and 2.2V this is what causes the FC trailing igniter to toggle. These are just grounds like anything else the ECU does, so wiring a Microtech to an FD igniter it is still going to ground the proper portion of the circuit and the igniter will fire the coil.

Understand?

I was never really concerned with the voltages, only the functions of the two channels.

So the FD uses a trigger and toggle like the FC, but just uses a different signal voltage. That makes sense.

I had always thought the FD used two trigger channels and no toggle. That's where my confusion is.

They are both two trigger, sounds like you are confused at how the FC works. The .8V is T1 the 2.2V is the select signal for T2. When the igniter sees the higher voltage ground it fires the T2 coil. If the igniter sees .8V at both triggers it fires the T1 coil twice. This is why we developed the dual igniter trailing coil setup for the PFC install.

http://www.banzai-racing.com/FC_coil_install_how-to.htm

No, I get it. A high signal tells one coil to fire, a low signal tells the other coil to fire. We're just saying the same thing two different ways. I'm coming from an electronics perspective but you're coming from an automotive perspective.

I've never heard the toggle line referred to as trigger though by anyone but yourself. Everyone else calls it "trailing select" or "trailing toggle", which I think is where some of the confusion is coming from.

You can actually hold the toggle low and then pulse the trigger line with 2V to 12V and it will fire one coil. Then connect the toggle high (to greater then 2.2V as you indicate, but most standalones use around 5V) and then pulse the trigger line and the other coil will fire.

See post #17

the 2.2V is the select signal for T2

There is no confusion. What is your problem, you can't deal with being wrong? Honestly, give it a rest. You told the guy it couldn't be done, read post #2. You have then been trying to prove me wrong since post #5. Just because you have 18,xxx post does not mean you know everything......maybe you should stop posting up bad info and try learning something from the people that are actually making this stuff work.

I am approaching it from the automotive electronics perspective, I have no clue where you are approaching it from. You start out by saying the FC and FD are completely different (post #2), I prove they are almost the same, then you say we are saying the same thing... Not even close.

Both of you guys should get over it. Have a beer.

Come on man, it's pretty clear that we are both right and we're saying the same thing just differently. There's no reason to get hostile and start to attack me just because I'm asking a question. Asking you how the FD ignition differed from the FC was exactly because I made a mistake in my first reply in my understanding of the FD system. I know the FC system quite well. We are saying the same thing and we both understand how the FC system works. You're turning this into an argument for no reason because there's nothing to argue.

I'm not going to reply further to this thread. I'm sure it's clear to anyone else reading now what's happening. You may go on thinking that I don't know what I'm doing as this doesn't bother me. :)

OK, I think I figured out where we are miscommunicating.

There's the problem! I'm saying that regarding the FC ignition system, we are saying the same thing about how it works. Nothing to do with the FD system at this point. I've not been talking about the FD system since post #15.