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2G COP with built in ignitor

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okm12346

15+ Year Contributor
565
22
Dec 3, 2007
Chicago, Illinois
SO i have 4 coils that have the ignitor (power transistor) built in each one of them. They are 3 pin coils too . I have no problem with the harness, but Im not sure where to get the tach signal from since im gonna bypass the stock power transistor and the tachometer is sourcing its signal from it.

The options Im considering:

1. Get some sort of tach adapter that I have no idea which one.

2. Since stock power transistor is powered thru the coil, I'll just apply 12V to it and have it actually work w/o having the stock coils there, so all internals still operate and the COPs get signals directly from ECU

3. Do #2 and use the stock power transistor outputs to power the transistors in the COP. It would be like a transistor after transistor setup.
 
2) won't work because the stock power transistor needs to see the coil primary switching on/off to generate the tach signal. In order to make it work you'd need to add a tach adaptor back into the wiring on the transistor output, to make it think the coils are still there.

3) most likely won't work because you have to get the level right. Each transistor inverts the signal(more or less). So your coil would be dwelling when you want it to be off, and off when you want dwell. It'd fire at the wrong time too. You'd need to add another transistor stage in series.

1) will work. You may be able to use diodes, or more likely transistors to or the 2 coil channels together to create 1 output signal that is fed to the tach wire.

I assume you have checked that these coils are actually matched to the dwell that the stock ECM provides? What are these coils off of. It takes a little bit of work to get a good set of coils where you don't wind up doing more harm than good.
 
Not sure what ECU this is, but I know for a 2g:

1 - You can just connect the tach signal directly to the original two lines from the ecu into the PTU.
2 - You can do this too, but then you've got a PTU you don't really need
3 - You can do this as well, but you might not be getting the amps your coils need (do you know the specs?) in tandem with the dwell time used by DSMs and thus ultimately the wrong charge

Brads question about dwell is spot on. The dwell time for stock ecu's pretty long, in the 5-8+ ms range (been like half a year since I was thinking about this stuff) in the 12-14V range, and many coils need much less dwell time to charge up and you can basically fry them, or trigger a failure mode where they'll stop working until power cycled. So do you know if your dwell map will work will with the stock one?
 
Not sure what ECU this is, but I know for a 2g:

1 - You can just connect the tach signal directly to the original two lines from the ecu into the PTU.

If you just connect the two lines from the ECU together into the tach signal, you will be messing up the signals on the 2 lines from the ECU. You need to isolate them via diodes, transistors or something else, so that they are split when you feed them to the coils, and only combined at the tach wire.

#2 won't work either, without adding a dummy load/tach adapter to the PTU, like I mentioned earlier. That is why a tach adapter is designed into the ARC-2 plug in harness on the DSM :)
 
So then you haven't done it? I did it when I designed the ARC-2 ;)

If you are referring to the #1 solution, it should be painfully obvious why that wouldn't work. I've never shorted the battery terminals on my car battery together, but I know that isnt a good idea. Shorting together the 2 control wires for coils that are firing 180 degrees out of phase makes about as much sense. Diodes or a tach adapter to combine those is the way to go if that is the route to take.
 
i got it figured out, I'll post the solution soon when I finish the setup
 
Brads, after looking at what I wrote I wasn't clear in my description, and was actually a bit wrong in in what I remembered doing.

I was describing a wasted spark setup. You use the ECU's PTU inputs to the ignitor line inputs of the coils in the same fashion as originally, paired 1/4 and 2/3. You can then get a tach signal by taking tach output lines from one coil of each pair wired to the oem wiring harness's lines tach inputs, or if those aren't present use a tach adapter or wire those lines to the CAS outputs. I've only done the first option, and only read about the latter two.


edit - i just realized I might not have taken the ecu outputs, aka ptu inputs, and used them for the tach line. I'll defer to your comments about shielding those lines from each other like via the PTU, diodes, or a tach adapter. i.e. i'm a dumbass. I can't find any evidence I ever did that looking through my notes. I think I only ever had the PTU in its place. I do however have the ignitor tach outputs tied together successfully to create a unified tach signal like the one the oem ptu creates. Electronically why this is working I can't say because the internal circuit schematics are not published on my coils.
 
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No worries, it get a bit hard for me to remember all the details on the testing I did years ago as well.

I do remember the basics well enough though, that I know the tricks with the PTU and tach signal. I've had to use those "tach adapter" tricks on tons of different applications over the years.

I'd be interested in seeing the schematic of your coil/tach circuit, just to see how you merged the tach outputs. IF the tach outputs are a simple transistor to ground, with a resistor pullup, then you could just wire them all together and make the signal you wanted. That would make a really clean installation.
 
The tach outputs of the coils are just connected to each other and wired as one to the tach input on the ptu harness. With the two square wave pulses now on the line you get the tach signal expected (two pulses per revolution) and rpms will show correctly in the dash. Works nicely and easily.
 
Which coils are you using? Not all of them have a tach output, so it is definitely good to know one that does. Are you running a stock ECU with them, or something where you can adjust the dwell to work right?
 
Some denso ones from... a prius? camry? I'll have to look, Spoolinup (my sponsor) gave them to me but they're the same ones commonly used on evos. I just happened to notice the tach output line on a sheet I found a while ago for them and figured out what they were and how to use them because I wanted to get rid of the PTU altogether. I can't go into the detail on the dwell adjustment as it's something he may produce at some point.
 
SO im using coils from a Nissan Sentra. I got them for free a while back and I just found them in a storage bin. I do not know what the dwelling times of these coils are, really no idea.

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Now, I remembered there was difference, between 99-00 and 01-03 Galants, in the way they source the tach signal. Well the 99-00 models use this Ignition failure Sensor that provides the tach signal. So I went to the junk yard and got the whole harness with the sensor.

Here's the diagram:

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I'm still working on the setup and did about 90 % of the soldering right before it got so cold in the garage that the soldering gun refused to melt the solder...LOL.

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I'm not able to drill the holes in the aluminum plate, because my drill is too weak to drive the step drill thru. So I made one out of an old spark plug cover.

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SO im using coils from a Nissan Sentra. I got them for free a while back and I just found them in a storage bin. I do not know what the dwelling times of these coils are, really no idea.


Now, I remembered there was difference, between 99-00 and 01-03 Galants, in the way they source the tach signal. Well the 99-00 models use this Ignition failure Sensor that provides the tach signal. So I went to the junk yard and got the whole harness with the sensor.

Without a better idea on dwell, installing new coils is a real shot in the dark. Too short a dwell and the coils will not have much energy or work well. Too long a dwell, and you will cook the coils. Or worse, there are SOME coils out there that are designed to protect themselves by firing prematurely. So if your dwell is too long, you could actually cause the coil to spark at a very advanced timing.

The ignition failure sensor APPEARS to work by measuring the peak current to the coil, and using that to trigger the tach signal. If your dwell isn't long enough, it may show up as a tach signal dropping out. So at least that might help you do a little trouble shooting. But I am just guessing on the function, based on the way the circuit was drawn inside the sensor.
 
I use the same setup but with Hyundai coils.
 
^Thanks Jamie!

Here's a picture of the markings on the coil. I dont know if would say anything about the dwell times.
 

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The only info That I found was 1.5-1.8ms at 12V and 1.2ms at 14V.

From this picture I see the dsm dwell is around 6ms.

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The DSM dwell does drop a bit at higher RPM, but that still sounds like recipe for cooked coils. Too long a dwell is bad for the coils. If they go into a current limit mode, they will very quickly overheat. And some coils fire early instead of current limiting. Then you have a really advanced spark that the ECU is not truly controlling.
 
You can use Lancer (4G69 or 4B11) coils without problems, and so suzuki baleno, honda civic 1.7, etc but YES you must adjust the dwell setting.
About connection
signal from coil #1 #4 goes to pin 10
signal from coil #2 #3 goes to pin 23
ground obvious
12 v to leg 87 of a relay
 
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