How-To: Dual Coil Mod

Started by Johnnyfive · Jul 13, 2004 · 102postsSMF 2010–26

KeithFeb 1, 2008, 5:33 pm · #51

Long Shot My question is what does having two coils offer over have one. and would it work for my 86 200sx xe?

You already have 2 coils in there.....thats how it came from Nissan. One coil fires the intake side(primary), and the other fires the exhaust side(secondary), The exhaust side shuts down after 4k pms at wot.....the "coil mod" allows both coils to fire all the way to redline.
But to answer your question.....no you don't need 2 coils.....you can remove the secondary coil, and exhaust side plug wires, and the car will run perfectly fine.....

Long ShotFeb 1, 2008, 5:52 pm · #52

KeithYou already have 2 coils in there.....thats how it came from Nissan. One coil fires the intake side(primary), and the other fires the exhaust side(secondary), The exhaust side shuts down after 4k pms at wot.....the "coil mod" allows both coils to fire all the way to redline.
But to answer your question.....no you don't need 2 coils.....you can remove the secondary coil, and exhaust side plug wires, and the car will run perfectly fine.....

So will this better performance then out of the engine or will i be getting some kind of power gain? Also does it affect gas mileage?

ArroFeb 1, 2008, 5:59 pm · #53

These are old cars; as such, they often are suffering from weaker spark. Part of this is because the spark plugs may be old. Another reason can be old plug wires. Both of which are easy to correct.

But another reason can be old coils. So replacing them with these helps restore power that has been lost over the many years. What is more, it boosts the signal a bit.

So between new plugs, new wires, and better replacement coils, you get a cleaner, brighter spark. Meaning you get back any power lost over the years, as well as fuel economy. So the answer to your two questions is yes and yes.

That's why this is such a good mod.

Long ShotFeb 1, 2008, 6:06 pm · #54

ArroThese are old cars; as such, they often are suffering from weaker spark. Part of this is because the spark plugs may be old. Another reason can be old plug wires. Both of which are easy to correct.

But another reason can be old coils. So replacing them with these helps restore power that has been lost over the many years. What is more, it boosts the signal a bit.

So between new plugs, new wires, and better replacement coils, you get a cleaner, brighter spark. Meaning you get back any power lost over the years, as well as fuel economy. So the answer to your two questions is yes and yes.

That's why this is such a good mod.

thanks, I think i'll give it a try when i get the money, My car opnly has 67K miles on it so i don't know how bad things are but i'll change em anyways. I just need to follow the dual coil installation on the main page correct?

IggyEGuanaFeb 1, 2008, 7:31 pm · #55

Empedocles99On MK1 I have found a simple way to get dual coil all the time when planning my megasquirt install. I have no idea how the mk2 works, I have no manuals and no interest in finding out.

I don't believe that these approaches risk frying out your coils trigger transistors by trying to trigger both coils off of the same one, as the other methods of 'dual coil mod' may be doing.

I have tried this on my ca20e and it seems to work. I have not tried the ca18et, but I am relatively sure it would work. Make sure you have a way to reverse the changes in case you don't like the outcome

On the ca20e it seems to get rid of some hesitation around 3000-3500 rpms.

Ultimately, you are responsible for mods you make to your car. This mod may make your car break, or kill you. You have been warned.
ca20e

Simple version

Cut the wire from the ecu that goes to the distributor IC, pin 17 on the 20 pin connector, the Green/Red wire.

Explanation version

The distributor has a chip in it that the ECU sends a signal to when it wants only one spark. If you sever this connection, then you get dual spark all the time.

The diagram from the Factory Service Manual (in the 85 version) on page EF & EC 30, under 'Spark Plug Switching Control (CA20E engine)' shows the decision tree for when to choose 1 vs. 2 spark system.

It only switches to 1 spark when under heavy load and 'Drive' which I assume means 'Not in neutral' for manual, or 'D' is selected for auto.

Note that the 'Heavy Load' signal also advances timing on Automatic Transmission models, so this mod may not increase performance for Autos because of this, I really don't know.

Either way, the wire to disconnect is pin 17 to the ECU, G/R (I believe this is Green/Red) wire.

Or, if you look at the engine wiring harness, and look at the plug end that goes to the distributor on the engine harness, the wire to disconnect is labeled as x in the ascii chart below:

x G/R Pin/Wire to disconnect
a B/W Coil (+)
b L/W Exhaust Coil (-)
c L Intake Coil (-) and Tach Output
_ Tab on the plug

x a
b_c
ca18et

Simple Version

Use the intake coil trigger signal to trigger both coil transistors. Sever the wire on the ecu's pin 14. Splice the transistor side of pin 14's wire in to pin 5's wire.

Explanation Version

Pin 5 (Blue/White near ECU, Blue near distributor) is the intake coil transistor trigger.
Pin 14 (Blue/Red near ECU, Blue/White near distributor) is the exhaust coil transistor trigger.

Near the distributor, on the engine wiring harness, there are two plugs, one for each coil transistor. On these plugs, do the following:
Cut the Blue/White (exhaust transistor trigger wire) and splice it in to the Blue (intake transistor trigger wire).

Essentially, the blue wire will send the trigger signal to both transistors.

That's it.

Now we're talkin! This is the tuner's approach. Love it!

Long ShotFeb 3, 2008, 7:29 pm · #56

87S12NotchI just finished this mod and it made a world of difference to my tired engine. It revs soo much freer through the rpms and now it doesn't seem to fall off as bad over 4k. I did what Indecisive said to do as I have an 87 and it worked perfect the first time.

this mod gets 5/5 in my books.

If your engine is an '85 and older you can just do a jumper wire between the two coils black with white tracer wires and you're done.

Here's how it was done since no one has a detailed write up on it posted anymore...

First you need to remove your air box (or filter if you have an after market one like me). Take the rubber elbow off as well that connects from the MAF to the metal pipe that runs over the rad. I disconnected the MAF sensor from the harness (just 2 plastic connectors) to get it out of my way so I had a little more room, you don't have to do this but I like to have room to work.

Next, on the 86 and newer (if I'm wrong please correct me) CA20E's you can't just simply bridge the 2 positive (black with white tracer) wires as they have a built in transistor. What you'll have to do is cut the black with a white tracer on the secondary coil (secondary coil is the one closest to the engine mounted vertically), then run an extention from that wire to the black with a white tracer on the primary coil. Don't cut the wire on the primary coil, just strip the shielding back to expose the wire. Now tie the extended wire from the secondary coil to the now stripped back primary wire.

Soldering is the best way to seal all your splices but if you can't don't worry. I used crimp connectors and they work great. Just make sure that after you're done that everything is sealed up good and tight. I used electrical tape and made sure everything was covered well.

Now just put everything back together and take it for a test drive. You may or may not feel the difference but now you'll have all 8 plugs firing at all times and at all RPMs.

Thats all there is to it.

Well I followed this with my 86 and now it wont start. I really need help on this one. I cut the secondary black/whit wire, then attached an extension from the plug end( shoud i have connected the extension to the transistor end instead), When i go to fire it up it'll try to turn over a few times and then just stop.

Can someone please help me?

IggyEGuanaFeb 3, 2008, 8:52 pm · #57

Long ShotWell I followed this with my 86 and now it wont start. I really need help on this one. I cut the secondary black/whit wire, then attached an extension from the plug end( shoud i have connected the extension to the transistor end instead), When i go to fire it up it'll try to turn over a few times and then just stop.

Can someone please help me?

IDK much about the mod first hand cuz I haven't done it but be sure that everything is mounted up the way is was before (that is, if you even undid them). The transistors are grounded through thier bodies. As for it not wanting to crank, maybe the battery got worn down?

Long ShotFeb 3, 2008, 9:19 pm · #58

IggyEGuanaIDK much about the mod first hand cuz I haven't done it but be sure that everything is mounted up the way is was before (that is, if you even undid them). The transistors are grounded through thier bodies. As for it not wanting to crank, maybe the battery got worn down?

i don think the bat is worn down because it started perfectly 15min before i did this. I was looking at the wiring diagram of the coils in the FSM and both black/white wires are already tied together to pos. could it be the other 2 that need to be connected.

demonic s12Apr 16, 2008, 5:05 am · #59

someone repost the how to on this... it was lost in the crash...

Abunai S-12 DrifterApr 25, 2008, 12:57 am · #60

id be interested in a thread about how to convert a ca20e duel coil into 1 coil. im this already exists for the love of all s12 gods please link me.

XanoApr 25, 2008, 2:02 am · #61

Abunai S-12 Drifterid be interested in a thread about how to convert a ca20e duel coil into 1 coil. im this already exists for the love of all s12 gods please link me.

put shitty plugs in one side and dont connect the wires, wire 1 good coil to the other side.

David BApr 25, 2008, 3:51 am · #62

alright, i tried the dual coil mod
im a noob like shit, dont hate
i did not even know exactly what a ignition coil was until today to be very honest

but, i read this forum, and messed around with some wires and tabs
this si what i did, my car runs.... i can tell a difference in a good way, i just wanna make sure i did it right.

so i made a diagram. its very crappy i know

BEFORE
posted image
AFTER

so i made a diagram. its very crappy i know

BEFORE

AFTER

Abunai S-12 DrifterApr 25, 2008, 3:55 am · #63

im confused.

David BApr 25, 2008, 3:59 am · #64

dont be confused! i am. and im trying to figure this out!

Abunai S-12 DrifterMay 4, 2008, 6:20 am · #65

ok let me know when ur done. i need to know.

Umai NaaMay 4, 2008, 1:04 pm · #66

All you need to do is run a wire between both positive terminals.

No disconnecting, just a short length of wire, and an eye terminal crimped onto each end.

It's hardly rocket science.

Abunai S-12 DrifterMay 4, 2008, 4:29 pm · #67

^^
well CallaroSX blew his ecu doing it. *having the vg30e motor in a ca20e car but the passengerside harness *where the coil plugs in* was from the ca20e. i really wanna make sure i get this right because i im extremely afraid of blowing my ecu. are you sure it'll be fine?

jeffwins24May 10, 2008, 4:26 am · #68

1986.5-1995 Nissan ECU Flash Codes(all engines)
11 Crank Angle Sensor/Camshaft Position Sensor.
12 Air Flow Meter/Mass Air Flow Sensor.
13 Engine Coolant Temperature Sensor.
14 Vehicle Speed Sensor.
21 Ignition Signal.
22 Fuel Pump.
23 Idle Switch.
24 Throttle Valve Switch.
25 Idle Speed Control Valve.
28 Cooling Fan Circuit.
31 ECM.
32 EGR Function.
33 Heated Oxygen Sensor.
34 Knock Sensor.
35 Exhaust Gas Temperature Sensor.
36 EGR Control-Back Pressure Transducer.
37 Knock Sensor.
38 Right hand bank Closed Loop (B2).
41 Intake Air Temperature Sensor.
42 Fuel Temperature Sensor.
43 Throttle Position Sensor.
44 ECCS Normal Operation.
45 Injector Leak.
47 Crankshaft Position Sensor.
51 Injector Circuit.
53 Oxygen Sensor.
54 A/T Control.
55 No Malfunction.
63 No. 6 Cylinder Misfire.
64 No. 5 Cylinder Misfire.
65 No. 4 Cylinder Misfire.
66 No. 3 Cylinder Misfire.
67 No. 2 Cylinder Misfire.
68 No. 1 Cylinder Misfire.
71 Random Misfire.
72 TWC Function right hand bank.
73 TWC Function right hand bank.
76 Fuel Injection System Function right hand bank.
77 Rear Heated Oxygen Sensor Circuit.
82 Crankshaft Position Sensor.
84 A/T Diagnosis Communication Line.
85 VTC Solenoid Valve Circuit.
86 Fuel Injection System Function right hand bank.
87 Canister Control Solenoid Valve Circuit.
91 Front Heated Oxygen Sensor Heater Circuit right hand bank.
94 TCC Solenoid Valve.
95 Crankshaft Position Sensor.
98 Engine Coolant Temperature Sensor.
101 Front Heated Oxygen Sensor Heater Circuit right hand bank.
103 Park/Neutral Position Switch Circuit.
105 EGR and EGR Canister Control Solenoid Valve Circuit.
108 Canister Purge Control Valve Circuit

taking silver's quote and putting it up for info. just thought it should be posted incase anyone doesn't have a FSM or hayens

David BMay 11, 2008, 8:06 am · #69

alright. this has 2 be why ihave my rev problem! its because my 2cnd coil positive coil is unplugged. there were like 5 write ups so igot messed up. when i wake up ill try it out

sideways_s12May 11, 2008, 8:27 am · #70

Abunai S-12 Drifter^^
well CallaroSX blew his ecu doing it. *having the vg30e motor in a ca20e car but the passengerside harness *where the coil plugs in* was from the ca20e. i really wanna make sure i get this right because i im extremely afraid of blowing my ecu. are you sure it'll be fine?

I have this done on my turbo car and it's fine and has been fine since I've done it so you should n't have a problem

Abunai S-12 DrifterMay 12, 2008, 12:54 am · #71

neh i wanna be safe. i think its a little different when ur hooking one up to a 4cylinder coil harness to a v6 motor.

KustamogenMay 12, 2008, 1:47 am · #72

I have msd blasters in now.....and my tach is no longer working....from my search on here I see theres a couple things I could do....but most just say "its the green wire" haha......so find the green wire and do what?

XanoMay 12, 2008, 2:56 am · #73

KustamogenI have msd blasters in now.....and my tach is no longer working....from my search on here I see theres a couple things I could do....but most just say "its the green wire" haha......so find the green wire and do what?

lol, i dont have any problems with my tach, and i use a blaster SS. but it could be because the VG you have to reuse the transistor (i think its a transistor) that is just before the coil in the circuit.

KustamogenMay 12, 2008, 3:05 am · #74

all I did was rewire the blue and black (w/ white tracer) into the blaster SS and ta da.......dont get why my tach would stop working

KeithMay 12, 2008, 8:29 pm · #75

Kustamogenall I did was rewire the blue and black (w/ white tracer) into the blaster SS and ta da.......dont get why my tach would stop working

Is the primary transistor still hooked up? The tach feed is on that....the primary transistor is the one with 3 wires

KustamogenMay 12, 2008, 10:46 pm · #76

pretty sure it is.....Im gonna take all my IC stuff off today and get a good look again.....maybe clean the grounds

xbcoupeAug 13, 2008, 6:31 am · #77

where do i find number 23 the idle switch as my car wont idle but thats one code that keeps coming up and how do i checked if its working.

thanks lee

soapdudeAug 21, 2008, 2:01 pm · #78

Does this mod work and is it effective on vg30e? It's an 88 s12.. Thanks!

XanoAug 21, 2008, 3:00 pm · #79

soapdudeDoes this mod work and is it effective on vg30e? It's an 88 s12.. Thanks!

your VG30E only has a single coil, so its not effective, HOWEVER, it is effective to swap in a single MSD Blaster SS and bigger plug and coil wires.

no need for dual coils, vg30e's only have a single plug per cylinder, where as the 4 cyl versions have 8 plugs total, two in each cylinder.

soapdudeAug 21, 2008, 6:38 pm · #80

That's crazy... Thanks..

I am ordering an MSD Blaster SS today... What do you mean by bigger plug and coil wires?

XanoAug 22, 2008, 4:24 am · #81

soapdudeThat's crazy... Thanks..

I am ordering an MSD Blaster SS today... What do you mean by bigger plug and coil wires?

Plug wires, and coil wires. Go with a set of 8.5MM or larger wires (you'll need 7 total)

1 for each cylinder, and 1 for the coil to the distributor....stock wires are either 7mm or 8mm wires. Theres companies that sell 10mm wires, but imo thats overkill.

soapdudeAug 22, 2008, 5:58 am · #82

Where do I get these wires? Are they made for these cars...? So I shouldn't go NGKs??

XanoAug 22, 2008, 6:14 am · #83

soapdudeWhere do I get these wires? Are they made for these cars...? So I shouldn't go NGKs??

NGk's would work too, they have a better core inside the 8mm wires, which makes up for the smaller size. You'd have to get a set of NGK's made for the V6 model, not the 4cyl though.

The other wires are make to fit, meaning you have to cut them, crimp and solder connectors on, and put the boots on yourself and all that.

with the larger wires, you just get a spool of wire, and boots.

soapdudeAug 22, 2008, 12:32 pm · #84

Gotcha... Thanks!

soapdudeAug 24, 2008, 5:29 pm · #85

I just put NGK Iridiums on my car and a set of NGK wires made for the 300z ($50 bucks cheaper!), and man what a difference!!!

LupichAug 26, 2008, 10:38 am · #86

This sounds like something I'd love to do but is super confusing without pictures.

Can you help me out?

silver_s13Sep 14, 2008, 5:50 am · #87

Okay since this thread is all about converting your dual(primary/secondary) coil setup to what is what is pretty much considered a "waste spark" type ignition system, lets make this a little bit easier for everyone to understand. The factory coil configuration on your four cylinder 200sx operates by creating a spark for the intake(primary) spark plugs and a separate spark(which is why you have two coils) for the exhaust(secondary) spark plugs. This allows the engine to run at optimal efficiency at low(below 4000) RPMs. to maintain this efficiency at higher RPMs you simply have to feed the secondary coil with the primary coils positive signal. There are a few arguments as to the proper wiring for this but it can be done. Another option to consider that has been totally over looked is to use a GM dual tower coil. These coils do exactly what our other members are trying to achieve but without the meesiness of wiring harness modification.They produce an equal spark from both towers of the coil at the same time through a single feed. This will allow the dual spark to take place exactly like the other method.
posted image
The connection to power this wonder of engineering is a simple + and - located at the bottom of the coil. use your imagination and you'll be able to make the required connection without any harness modification. The connector for these coils are small blade type prong that simply slides into to base of the coil(Kinda like a home outlet). It is mounted by two centrally located screws on each side. If someone was able to mount this on a small piece of plywood with prongs fastened to it with some type of threaded post to connect the factory primary coil connector they could mount this coil and isolate it from a short circuit condition at the same time. This in theory will still allow you to run all spark plugs and there corresponding wires as designed from the factory and still allow the dual spark condition you are looking for. The best part of this method is that there is no cutting/splicing of the factory harness so the original equipment could be reinstalled at any time. I apologize for the length of this post but this (to me) would be the easiest method to achieve this. Well what do you guys think? I know it's "outside of the box" but it should work.

IggyEGuanaSep 16, 2008, 1:00 am · #88

On NICO theres a lot of info about converting the CA18DET ignition system from COP to GM waste spark coils. In it they say (if using stock ecu instead of standalone) you have to eprom and rewrite the ignition values to be compatible with the coils.

No real point to me sayin this. Just be aware of the possiblity of this not working.

silver_s13Sep 17, 2008, 2:32 am · #89

Contacted MSD about this and still waiting for a reply. I'll probably try it anyway and see.

200sxkitcarSep 18, 2008, 8:22 am · #90

Jesus, this thread is full of mixed and often off information.

The BLACK/WHITE wire is the positive feed from the fuse block. The same wire has a splice and feeds both coils.

The BLUE and BLUE/WHITE are the computer-controlled ground sides.

If you are jumpering the black/white wires, you are simply adding another splice. The black/white wires are already connected.

If you want both intake and exhaust side plugs to fire, you would need to jumper the blue and blue/white wires together.

This information applies to all model years of CA20E and CA18ET per all the FSM manuals that I have.

The S12 does NOT have a waste-spark system, and the dual-coil mod does NOT convert the system to waste spark. When you jumper the system, it is like running two entirely independent spark systems simultaneously. There is no waste-spark action.

If you disconnect the coil and transistor assembly completely, you can measure the voltage present at the connector. You will find with the key in the 'ON' position there will be 12V at the black/white wire's terminal. Feel free to check this before you do this mod.

If you jumper the blue and blue/white wires, I would do it before the transistors.

I personally don't care too much for this mod, I don't think its particularly necessary or a good idea, but if you want to do it, do so at your own discretion. Several people have done it without issues.

Once I have some time, I'll put together some pics and diagrams, unsticky this thread, and put the info in a new one and sticky that, to clear up the confusion. I will also add all the technical reasoning and logic behind these statements.

Please refrain from discussing the V6 motor in this thread, seeing as its aimed at the cursed 8 plugged 4cyl cars

alundraSep 18, 2008, 12:17 pm · #91

Nice thread but what about detonation?
Is there any electronic device to test our det sensor?
A multimeter is it sufficent? A computer?

silver_s13Sep 20, 2008, 6:59 am · #92

The definition of a waste spark ignition system in case there is any confusion according to wikipedia

A wasted spark is when in an ignition system in a four-stroke cycle internal combustion engine spark plugs fire in pairs, on both the exhaust and compression strokes. The extra spark on the exhaust stroke has no effect and is thus "wasted".

Are you saying that both plugs fire at the exact same time?
The contact on the rotor for the intake side is larger then the contact on the exhaust. I assume the intake fires BTDC and the exhaust fires either at TDC or ATDC. If thats wrong then I stand corrected and this would be considered standard system. Otherwise if they are sequential and fire at BTDC and TDC/ATDC it is in fact a waste spark system and only in place to reduce emissions.

toytoyMay 22, 2009, 8:08 pm · #93

Hi guy !

sorry for this question but one member for my clubS12france has a problem with his silvia !

Be macking a chek ecu he obtaint this !

http://www.youtube.com/watch?v=JZgFAW-3NJE

The car no longer starts !
What do you think please ?

PS : sorry for my bad language

raid_650Aug 2, 2009, 1:57 am · #94

ok so i read thru this like 5 times and just want to clear something up, i have a 84 mk1 and so i can just jump the postive terminals on the coils right and then all the spark plugs will fire? Or will this not work?

chris1986Sep 4, 2009, 2:55 pm · #95

to Raid 650

as in post #71

The black/white wires are already connected.
If you want both intake and exhaust side plugs to fire, you would need to jumper the blue and blue/white wires together.

i have another question:

what is the ignition signal the black/white wire or the bleu wires?
i need to know that for the bee-r rev limiter

thanks, chris

YvesdouleacDec 29, 2009, 9:55 am · #96

I found the ECU, however I can't get the plastic cover of it, nor can I find any 12mm bolts. I have a FJ20E engine, here's a picture of what I mean:

posted image

It's located left from the clutch pedal. It's fitted with two screws, I removed them but I can still not get it loose. What did I do wrong? Thanks in advance!

BattleFairyMay 13, 2010, 6:36 pm · #97

haha digging out old stuff

a t2/t25 from the Z IS NOT A direct BOLTON!

Some Z31 300ZX's have T25's (I think 86-88?), some of them have T3. The Z31's with the T25's will bolt right on without any changes. T25 can take you to 15 psi before it starts to get too hot, so I'd say it gives you about 5 psi more potential over your stock T2.

the downpipe is unique and only found a the Z, you could use the OEM t2 downpipe if you dont mind that only 2 bolts holding it

sideways_s12May 13, 2010, 7:10 pm · #98

I said this in your other thread lol

BattleFairyMay 13, 2010, 7:14 pm · #99

yeahh but right now
i have all possibel combos on my table LOL

i was thinking its a good thing to inform others bevor they make the same mistake

s-chassis_onlyNov 15, 2010, 1:58 am · #100

what are the benefits from doing this and a diagram would be handy if anyone has one