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1G ARC-2 CDI Questions

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RT-AWD

15+ Year Contributor
396
1
Apr 28, 2007
Norristown, Pennsylvania
Spark notes:
Installed arc-2
Tach not working
Car breaks up really bad
Its a 1991

Hello all,
Last night i spent a solid 3 hours wiring up this CDI box to hopefully fix an occasional breaking up issue (spark blowout). I got everything wired correctly and noticed right away my tach wasnt working?! Figured, ah screw it lets go for a spin and see if the car performs better.. its MUCH worse. Car breaks up at about 15psi now (used to be at 25psi at around 6k). I have my setting on the box to crank, rising edge, and restrike.
I did not use the launch control, timing retard, or tach wire. The diagrams didnt even show these and i have all that stuff (besides tach) setup on DSMLink, so i thought i didnt need them.
What do i need to do? Also, i have a sparktech COP that i didnt put in.. would that be beneficial or no? Seen mixed opinions on COP with CDI
 

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Spark notes:
What do i need to do? Also, i have a sparktech COP that i didnt put in.. would that be beneficial or no? Seen mixed opinions on COP with CDI

I have actually heard the opposite, COP without CDI does not run the best, CDI combined with COP however is really good, that is what I currently run in mine..
 
ARC 2 compliments a COP setup, mine ran pretty smooth until some wires wore bare and started arcing. I'm running the ARC-2 hooked up to the stock coil and its working pretty good for me, did idle a bit smoother with COP but that's about it. I can't remember what mine is set it. if the tach isn't working its because that small tach adapter box is bad.. if you did any searching you'd notice that's the first thing people complain about.
 
Did you use the install harness that was designed for DSMs? It looks like you didn't, since you posted that wiring diagram.

The install harness is designed to give a tach signal back to the PTU, so that the tach works correctly. If you don't use the install harness, you have to wire the tach output from the ARC-2 in as well.

Do you have a timing light? I suspect you have something miswired on the install. This should be obvious when you try to check your timing.
 
All, so an update, i installed the wrong harness. Last night i got the new correct harness and installed it. Tach is now working and car runs better however still hitting what feels like fuel cut at 20psi and building and about 6k rpm. I didnt remove the little black box capaciter on the coilpack and havent put in the COP yet. Im going to put in the COP and see if it improves.

Settings are
Restrike
Crank
Rising edge
Rpm limiter i have off and timing ret i have off
All this i have setup on dsmlink
 
Last edited:
All, so an update, i installed the wrong harness. Last night i got the new correct harness and installed it. Tach is now working and car runs better however still hitting what feels like fuel cut at 20psi and building and about 6k rpm. I didnt remove the little black box capaciter on the coilpack and havent put in the COP yet.

That capacitor is on the 12V wire on the stock ignition. When you wire the ARC-2 up with the plug in harness, that should change that 12V wire to a ground wire, so the capacitor is basically grounded on both sides. It shouldn't affect things, but it can't hurt to remove it anyhow. On some of the early cars(90 I think), I think there is a tach adapter on the coil signal side, and that definitely does have to be removed.

New plugs and wires? Have you tried lowering the plug gap to see if it gets better?


I would shut the restrike off, mine ran like crap with it on.

Restrike really shouldn't cause it to run worse, unless you have some other issues, probably wiring. All it does is add a few more sparks after the main one, which can be good for lean running/idle/cruise.
 
That capacitor is on the 12V wire on the stock ignition. When you wire the ARC-2 up with the plug in harness, that should change that 12V wire to a ground wire, so the capacitor is basically grounded on both sides. It shouldn't affect things, but it can't hurt to remove it anyhow. On some of the early cars(90 I think), I think there is a tach adapter on the coil signal side, and that definitely does have to be removed.

New plugs and wires? Have you tried lowering the plug gap to see if it gets better?




Restrike really shouldn't cause it to run worse, unless you have some other issues, probably wiring. All it does is add a few more sparks after the main one, which can be good for lean running/idle/cruise.
It caused it to run poorly at idle, Im not alone in that though, I have known others with the same issue, the wiring is new so I know its not a problem, and it runs fine with the cdi bypassed, I of course run full standalone and can log anything and everything and theres nothing notable going on, I dont think the 4g63 does well with restrike for some reason, it might be a flame propagation issue or something.
 
It caused it to run poorly at idle, Im not alone in that though, I have known others with the same issue, the wiring is new so I know its not a problem, and it runs fine with the cdi bypassed, I of course run full standalone and can log anything and everything and theres nothing notable going on, I dont think the 4g63 does well with restrike for some reason, it might be a flame propagation issue or something.

The successive sparks on the ARC-2 at idle are several degrees apart, almost a full millisecond between them. I would be surprised if the second spark that much later made a big difference.

Your standalone is logging timing, correct? Does it actually monitor the output from the ECU? Or is it logging the timing value it calculates? Even if it did actually monitor the output, it wouldn't see anything past that, unless you have additional logging monitoring the output of the CDI. As an example, if you wired in the timing retard on the ARC-2 and activated it, would you see any difference in the ignition timing value shown in your ECU? What I am getting at is that anything going on in the ignition wiring past the ECU is largely invisible to the ECU. Logging would catch problems with stray noise affecting other sensors though.
 
Got everything hooked up and put in my COP noticed a sputter accelerating just at a cruise. Popped the hood and the led was not on. Switched to restrike and the led came on... bad box?
 
Got everything hooked up and put in my COP noticed a sputter accelerating just at a cruise. Popped the hood and the led was not on. Switched to restrike and the led came on... bad box?

Did you purchase this new or used? There have been some issues here and there, I purchased mine brand new from Extreme PSI, no issues yet..
 
That doesn't sound like the way the LED should operate. But it's been a long time since I worked on that project, and the LEDs may operate differently now. Contact Dynatek and ask them.
 
The unit was purchased brand new from extremepsi. I was cruising home and came across a buddy and while playing in mexico, the car could not go above 4500 under heavy throttle and boost. It voilently breaks up each time. Im going to call them tomorrow
When i got home the LED was on but flickering. I have my idle set to 750
 
With the ARC-2, do you still need the stock power transistor? Or can you eliminate that and run straight from the ecu to the ARC-2?
In the ARC-2 install manual it says "If installing on a vehicle with a power transistor, you have 2 choices. You can install the ARC-2 between the power transistor and coil, and set it up like a standard coil. Or you can remove the power transistor, and wire the ARC-2 directly to the ECU and coil, and set the ARC-2 up as if you were replacing a coil w/driver."

But I wonder which way works better on our cars.


Also, if the ARC-2 really does output something like 500 volts to the coil, how can that be OK with a stock coil pack? Doesn't the coil pack normally only get 12 volt pulses from the PT?
 
Last edited:
With the ARC-2, do you still need the stock power transistor? Or can you eliminate that and run straight from the ecu to the ARC-2?

If you want to install it the way I designed the ignition to be installed, you leave the power transistor in place. You use the plug in harness that plugs in right at the coil pack, and make installation a breeze.

In the ARC-2 install manual it says "If installing on a vehicle with a power transistor, you have 2 choices. You can install the ARC-2 between the power transistor and coil, and set it up like a standard coil. Or you can remove the power transistor, and wire the ARC-2 directly to the ECU and coil, and set the ARC-2 up as if you were replacing a coil w/driver."

But I wonder which way works better on our cars.

I say that it works better to leave all stock stuff in the car. Other people say to remove the power transistor because it isn't reliable. But the transistor should help to isolate the ECU from some of the electrical noise during firing/charging. and it should provide a stronger signal to the ARC-2 to fire.


Also, if the ARC-2 really does output something like 500 volts to the coil, how can that be OK with a stock coil pack? Doesn't the coil pack normally only get 12 volt pulses from the PT?

With a standard ignition, the coil pack generates a voltage spike of up to 400V on the coil negative when it fires. That is how inductive ignitions work. The CDI is just generating that spike from the ignition, instead of inside the coil. I think if you can find a copy of the ARC-2 manual, you can see a description of that.
 
If you want to install it the way I designed the ignition to be installed, you leave the power transistor in place. You use the plug in harness that plugs in right at the coil pack, and make installation a breeze .................

OK thanks for the good info!
I looked for the plug-in harness on the Dynatek web site and couldn't find it. In fact the oldest DSM they let you even search for there is 1995. (My car is a 1990).
Anyway, I would like to see a good pic of the harness if there is one made for 1990. I mean, my coil pack, PT, ecu, engine wire harness, and instrument panel are all 1990 in my 1990 Talon.
But if I do an ARC-2, I probably would want to do it together with a COP setup.

Are you one of the original designers of the ARC-2 unit?

"if you can find a copy of the ARC-2 manual" LOL, yeah, I wasted about 15 minutes trying to find one on the Dynatek web site and could not find one.
But I have one, "DARC-2 NEW INSTALL.pdf" that I got in 2014 via email from Larry Nelson at Dynatek Tech Support.
 
Yes I was one of the original designers, left there a little after it was released. My car was the one in the install pics, I don't know if they ever updated that. Larry isn't there anymore either.

IIRC, the 95-99 kit includes the mounting bracket for the unit, and a harness. The harness will work on the 1991-94, no changes needed. It plugs in at the 3 pin coil connector and gets all the signals there. It has a small tach adapter built in. This makes it so that your tach should work, and everything should plug in no splicing needed.

It works on the 90 too, with just a little change to account for the 4 pin connector on the coil(the 91-99 all use a 3 pin connector). There have been a few people on here who have done it and posted threads on it that would have all of the specifics.

The Dynatek website never was easy to navigate to get to the instructions. I have had better luck pulling them off the RoadRace Engineering website when I need to find them.
 
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