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DIY denso COP (no CDI required)

So you want to ditch your 30 year old coils and plug wires for something cleaner, but don't want the issues that come with running 300m coils in wasted spark, or the problematic CDI's that tie in with the 300m COP.

The EVO community has been using Denso coils for COP with great success in 800+ hp setups with no CDI required. They're a cheap, reliable and comparatitvely powerful coil to the stock DSM coils, however these can eliminate the factory ignition control module, factory coil packs, and the spark plug wires all in one.

If you're looking for an ignition improvement over the factory DSM coil packs, chances are these are not going to improve over good OEM coils.

There are a few guys that have been successfully running these in DSM's, but I have yet to find a good guide on wiring them and having proper tach functions as you will be eliminating the PTU at the same time. I like the cleanliness of COP and I will say in comparison they are a better setup all around, I run a sparktech kit using the same coils on the 2.3/FP black in my EVO and have had zero issues with it the past 8 or so years it's been on there.

The reason these work so much better than the 300m coils is due to the fact that the 300m coils have to be wired in series to be properly fired by the factory PCM. Wired in parallel has too much load due to their resistance and will either blow up the PTU or blow up the driver in the ecu. Wiring them in series however drops their output way lower than they would be if fired sequentially. The Denso coils have a built in igniter so the computer doesn't carry any of the load of the coil firing, which allows us to wire them "sequentially" but still fire them as a wasted spark coil like stock.

Into the guide, what you'll need:

4x Denso coils - Prius coils are what SparkTech uses for their Evo COP, however almost any 4 wire Toyota coil will work fine as long as it's the same style as the Prius coils. In my pictures I'm using some random Toyota coil packs that I had laying at work. You're looking for this style ideally
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Next you need 4x matching connectors- Spoolin Up used to sell these as pin your own kits, you can also find these online from various vendors. I pulled mine from a junkyard Toyota. Just make sure they're 4 wire and you'll be good to go.
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Next you'll need a small length of wire or if you're cutting out junkyard connectors remove as much of the harness as you can with them.

Next on the list is either a junk 2g MAF, like I used, or if someone knows where to get a male PTU connector as a pin-it kit I'll gladly edit that in. I asked ECMTuning, Ohm Racing, and a few other manufactures on obtaining a male either 2g MAF connector or the PTU connector and none of them got back to me on it. The 2g MAF uses the correct connector and they aren't too hard to gut out of the MAFs housing.
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You'll need to figure out a mounting plate for hold the coils. I traced a plug wire cover onto a sheet of aluminum and cut mine out with an angle grinder. The plate is setup for Prius coils, however, since I didn't have Prius coils on hand when I assembled it for testing I had to put some nuts under the coils to mount properly. As far as I know no one makes a plate for these off hand.

Wiring for these is fairly simple, we'll go back to the picture posted above of the connector to start.
On the Coil Connector:
Pin #1 is the 12v feed.
Pin #2 is a tach output signal.
Pin #3 is the trigger to fire the coil.
Pin #4 is the ground.

On the MAF/PTU connector: (you'll have 8 male pin slots in the connector itself, but only 7 legs on the back side. The 2g MAF doesn't use pin 8 so go to the side of the connector with the missing pin and mark it so you know which side is pin 8.)
Pin #1 - Combine Pin #3 for Denso coils 2 and 3, these 2 wires will run to Pin #1 of the MAF connector. Trigger B
Pin #3 - Combine all of Pin #4 wires off the Denso coils, they all run to Pin #3 of the MAF connector. Ground
Pin #4 - Combine Pin #2 from Denso coils 1* and 2*, these 2 wires will run to Pin #4 of the MAF connector. Tach Output
Pin #6 - Combine all of the Pin #1 wires off the Denso coils, they're all going to be run to Pin #6 of the MAF connector. 12v coil feed.
Pin #7 - Combine Pin #3 for Denso coils 1 and 4, these 2 wires will run to Pin #7 of the MAF connector. Trigger A

*Note: These wires are the tach output, if you combine all 4 coils together you'll have double the RPM reading on your tach. We combine 1 and 2 as they're on opposite banks of the firing order. You can combine 1/2, 1/3, 2/4, or 3/4 and still get the same accurate RPM reading, 1/2 are just closest to the connector and require the least amount of wiring. If you don't have these combined properly you're tach will not work properly.

I used crimp on connectors and then solder them to the MAF connector. This isn't the most ideal way to do this and where a pin kit would be much nicer. It is solid and works fine though for now.
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Loom the wiring, plug everything in, test to make sure it runs on all 4 cylinders and the tach is reading accurate. Then you can remove both the stock coil packs and the ignition module and enjoy the new COP setup.

I'm currently using these on my 91 galant with a 210K mile stock 6 bolt with an FP red and supporting mods. I didn't have any issues with my original coils, but I like that I was able to ditch a couple fail points of the stock ignition system. There's definitely cleaner ways to orient these, but the angle on these specific coils made it a pain.

This should work on a 90 as well, however, you'll need a different male connector and the wiring is slightly different. My 90 is currently still tore apart in the back corner of my garage, but I do plan to update this guide with the proper 1990 wiring specs.

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TSiAWD666

Supporting Vendor
2,647
883
Aug 15, 2003
Herndon, Virginia
So how much have you tested this setup? My experience with some specific Denso coils similar to these is that this wiring setup can fail in unexpected ways. If you haven't tested this then I strongly suggest everyone take caution with this approach. Here's why.

My experience with similar Denso coils from some year Camry (I'm drawing a blank right now, but they look very similar to these) is that their maximum charge time is almost half of what a DSM ECU is hardcoded for (with exception of the black box ECUs as I think you can edit the dwell table there). My specific coils I found at 12V really could only tolerate a charge time around 3.2ms per their tech sheets, compared to the stock DSM charge time of I think 6.8ms? I forget, I have the dwell table somewhere.

What I found was when wiring my coils directly like you're describing let the car idle, and even drive at very low RPM, but as I started driving the coils stopped working (they completely stopped firing), yet would work after a power cycle (again, only idling, would crap out if I revved the engine). In the technical documents on my coils I found they had a failure mode that triggers when the coils are overcharged to prevent destruction/damage to the coils. What I realized was happening was as car RPM went up my voltage went up and coils were overcharging as my alternator voltage output was jumping above the idle voltage, and the dwell map was mapping out a dwell time way too long for these coils to tolerate at the given voltage. The stock dwell map as I pointed out is already way using a dwell time across the voltage range that is almost double what my coils are spec'd for, and honestly I'm surprised they even idled considering how far off spec this configuration was.

My solution was to develop a dwell reduction circuit, one that would intercept the firing trigger signal and delay it appropriately to map to the desired dwell times for the coils. This fixed my problem, and I've raced successfully on this setup for a few years now. Not something everyone is capable of doing and I turned over ownership of it to Spoolinup that produces Evo coil-on-plug systems as he sponsors me and provided the coils and wiring for me to play with.
 

talonman1200

Supporting Member
37
25
Mar 23, 2018
Potterville, Michigan
I've driven roughly 4k miles on my setup. 2009 yaris coils directly wired like the post reads. Not one issue so far. But if you would like for curiosity sake I can measure the dwell tomorrow morning.
 

Tyeler18

Proven Member
2,475
204
Dec 16, 2008
Casa Grande, Arizona
What is the capability of these coils vs 300m with ARC2 box? I currently am on the 300m/arc 2 train at the moment.
I've never had good luck with the 300m coils and ARC on any customer car.
So how much have you tested this setup? My experience with some specific Denso coils similar to these is that this wiring setup can fail in unexpected ways. If you haven't tested this then I strongly suggest everyone take caution with this approach. Here's why.

My experience with similar Denso coils from some year Camry (I'm drawing a blank right now, but they look very similar to these) is that their maximum charge time is almost half of what a DSM ECU is hardcoded for (with exception of the black box ECUs as I think you can edit the dwell table there). My specific coils I found at 12V really could only tolerate a charge time around 3.2ms per their tech sheets, compared to the stock DSM charge time of I think 6.8ms? I forget, I have the dwell table somewhere. What I found was when wiring my coils directly like you're describing let the car idle, and even drive at very low RPM, but as I started driving the coils stopped working (they completely stopped firing), yet would work after a power cycle (again, only idling, would crap out if I revved the engine). In the technical documents on my coils I found they had a failure mode that triggers when the coils are overcharged to prevent destruction/damage to the coils. What I realized was happening was as car RPM went up my voltage went up and coils were overcharging as my alternator voltage output was jumping above the idle voltage, and the dwell map was mapping out a dwell time way too long for these coils to tolerate at the given voltage. The stock dwell map as I pointed out is already way using a dwell time across the voltage range that is almost double what my coils are spec'd for, and honestly I'm surprised they even idled considering how far off spec this configuration was.

My solution was to develop a dwell reduction circuit, one that would intercept the firing trigger signal and delay it appropriately to map to the desired dwell times for the coils. This fixed my problem, and I've raced successfully on this setup for a few years now. Not something everyone is capable of doing and I turned over ownership of it to Spoolinup that produces Evo coil-on-plug systems as he sponsors me and provided the coils and wiring for me to play with.
I've run this same setup in my evo for 8 years with zero issues, along with the evo guys that run the sparktech and spoolinup kits. The prius coils share the same dwell as mitsubishi. Couldn't tell you on the dwell of these random denso coils but I can tell you they've held up fine to 24lbs of boost on my FP red. The normal prius coils have been used by many people over the years without issue on dsms, I'm by no means the first to do this, I just made a guide to do it since no one seems to know you can use these on dsm's for whatever reason.
 
Last edited by a moderator:

TSiAWD666

Supporting Vendor
2,647
883
Aug 15, 2003
Herndon, Virginia
Spoolinup's coils do not match the DSM non-blackbox ECU hardcoded dwell times.

I know this because we are good friends, my coils came from him, and we together worked on this little project of mine (he lives like 15 minutes from me). Also the Evos can adjust dwell times in their ECU to match and so any such issues are moot. That said, the fact that your coils work just fine on a DSM platform is great, and a wonderful simplification.

Wish I'd known before I dicked around so much with that dwell reduction circuitry. Thanks for sharing!
 

Tyeler18

Proven Member
2,475
204
Dec 16, 2008
Casa Grande, Arizona
Spoolinup's coils do not match the DSM non-blackbox ECU hardcoded dwell times. I know this because we are good friends, my coils came from him, and we together worked on this little project of mine (he lives like 15 minutes from me). Also the Evos can adjust dwell times in their ECU to match and so any such issues are moot. That said, the fact that your coils work just fine on a DSM platform is great, and a wonderful simplification. Wish I'd known before I dicked around so much with that dwell reduction circuitry. Thanks for sharing!
All the prius coils (as far as I know spoolin up is still using prius) are 3.5MS at 12v and will alter some with RPM and voltage. DSM dwell varies from 3.5-6MS as modeled by ARC with their box. The evo guys aren't altering dwell when installing spoolin up or spark tech coils. I can't say why yours didn't work but the prius coils have been used in quite a few dsms. The evo uses the same dwell time as a DSM does, so I don't know what would've been different with yours.
 

brads

DSM Wiseman
852
95
Oct 24, 2002
Alta Loma, California
What I found was when wiring my coils directly like you're describing let the car idle, and even drive at very low RPM, but as I started driving the coils stopped working (they completely stopped firing), yet would work after a power cycle (again, only idling, would crap out if I revved the engine). In the technical documents on my coils I found they had a failure mode that triggers when the coils are overcharged to prevent destruction/damage to the coils. What I realized was happening was as car RPM went up my voltage went up and coils were overcharging as my alternator voltage output was jumping above the idle voltage, and the dwell map was mapping out a dwell time way too long for these coils to tolerate at the given voltage.

Some of the LS coils people use in custom ignitions have a similar issue. If the dwell current is too high, they will fire prematurely to save the coil. The dwell reduction circuit you made is a good way to fix it. Lowering the voltage to the coils or a ballast resistor could do it too.
 

brads

DSM Wiseman
852
95
Oct 24, 2002
Alta Loma, California
What is the capability of these coils vs 300m with ARC2 box? I currently am on the 300m/arc 2 train at the moment.

Keep in mind that apparently several people are improperly installing the coils nowadays. Comparing it to an improperly installed system isn't very meaningful.

There are a few threads where people talk about using 300M coils as COPs and wiring them in parallel. That is absolutely NOT the way to do it. And will cause misfires at even moderate boost levels. I tried to point it out in those threads, but they don't get it. The old COP kits were wired in series, and they worked fine.
 

Tyeler18

Proven Member
2,475
204
Dec 16, 2008
Casa Grande, Arizona
Now if you want a COP setup that's comparable to OE (if not slightly better) and doesn't require a junk CDI, these denso coils work great. If you're at the performance level of needing better than OE coils you're standalone computer should be capable of running coils better than any of these options anyways.
 
Last edited by a moderator:

jed344

Supporting VIP
1,175
276
Jan 10, 2008
Waterville, Iowa
Wow haven’t been on this thread in a while. I missed a lot. Personally I have been using 300m coils not in parallel with ARC 2 box’s for years. I have used them up to and above 40psi of boost without issue. My car currently uses NGK branded 300m coils I wired myself with ARC 2 box. Well north of 30psi on a 62mm and 10:1 motor on e85. I also prefer to use BR8EIX for plugs and gap them down to .017. With this combo I have never had spark blow out issue again. Even as high as 40psi and north of 70lb/min logged. I am interested in these coils as a alternative when still using Ecm link sense dwell time is not adjustable with it.
 

brads

DSM Wiseman
852
95
Oct 24, 2002
Alta Loma, California
Now if you want a COP setup that's comparable to OE (if not slightly better) and doesn't require a junk CDI, these denso coils work great. If you're at the performance level of needing better than OE coils you're standalone computer should be capable of running coils better than any of these options anyways.

Whether they are slightly better or worse than OE is probably going to depend on the application and condition of the existing components. But getting them to match the actual firing voltage of any of the available junk CDIs will be tough. Junk CD ignitions of all brands do a great job of creating high voltage. And the energy from these Denso's is going to be less as well. A junk CD spark will be more intense. So you should still be able to run larger plug gaps and have a stronger combustion start with the junk CD ignitions out there.

You should also check the wire seals on the brown connectors on the galant install. Looks like they were mostly likely improperly installed, they shouldn't be sticking out of the connector that much. Fortunately that isn't high voltage, but that could cause a misfire if it was. The pic posted by talonman1200 looks right.
 
Last edited:

Tyeler18

Proven Member
2,475
204
Dec 16, 2008
Casa Grande, Arizona
Wow haven’t been on this thread in a while. I missed a lot. Personally I have been using 300m coils not in parallel with ARC 2 box’s for years. I have used them up to and above 40psi of boost without issue. My car currently uses NGK branded 300m coils I wired myself with ARC 2 box. Well north of 30psi on a 62mm and 10:1 motor on e85. I also prefer to use BR8EIX for plugs and gap them down to .017. With this combo I have never had spark blow out issue again. Even as high as 40psi and north of 70lb/min logged. I am interested in these coils as a alternative when still using Ecm link sense dwell time is not adjustable with it.
Using these on the 2.3 stroker/FP black in my evo with stock dwell times for years. I run .024 gap on e85 with BR7ES copper plugs. Couldn't tell you logged airflow as I honestly have never cared to check it but no issues with no CDI and just these. My galant is an FP red car on pump gas at 24lbs currently and BR6ES plugs at .028 gap. Same mileage as stock coils, no break up, were going to turn it up more here soon but I wont have issues i know that. Richard montalvo with the summit van has been running these on a 35R at over 40psi without issue for a few years as well, but he's on a haltech. I know he's done a few installs on cars as well as he was selling them on facebook for a bit.
Whether they are slightly better or worse than OE is probably going to depend on the application and condition of the existing components. But getting them to match the actual firing voltage of any of the available junk CDIs will be tough. Junk CD ignitions of all brands do a great job of creating high voltage. And the energy from these Denso's is going to be less as well. A junk CD spark will be more intense. So you should still be able to run larger plug gaps and have a stronger combustion start with the junk CD ignitions out there.

You should also check the wire seals on the brown connectors on the galant install. Looks like they were mostly likely improperly installed, they shouldn't be sticking out of the connector that much. Fortunately that isn't high voltage, but that could cause a misfire if it was. The pic posted by talonman1200 looks right.
You'll have to talk to toyota on those brown connectors since those came straight off a prius in the junkyard like that, they suck so bad I still have no issues with these junk densos.
 
Last edited by a moderator:

Car Cannibal

Proven Member
455
23
Jun 7, 2003
Chicago, Illinois
I'm looking to jump to this on my 1G, Spoolinup setup.

How much psi are you running on this without spark blow out?

Spark plug gap?
 

mark curtis

Proven Member
7
0
Jan 23, 2005
austin, Arkansas
So you want to ditch your 30 year old coils and plug wires for something cleaner, but don't want the issues that come with running 300m coils in wasted spark, or the problematic CDI's that tie in with the 300m COP.

The EVO community has been using Denso coils for COP with great success in 800+ hp setups with no CDI required. They're a cheap, reliable and comparatitvely powerful coil to the stock DSM coils, however these can eliminate the factory ignition control module, factory coil packs, and the spark plug wires all in one.

If you're looking for an ignition improvement over the factory DSM coil packs, chances are these are not going to improve over good OEM coils.

There are a few guys that have been successfully running these in DSM's, but I have yet to find a good guide on wiring them and having proper tach functions as you will be eliminating the PTU at the same time. I like the cleanliness of COP and I will say in comparison they are a better setup all around, I run a sparktech kit using the same coils on the 2.3/FP black in my EVO and have had zero issues with it the past 8 or so years it's been on there.

The reason these work so much better than the 300m coils is due to the fact that the 300m coils have to be wired in series to be properly fired by the factory PCM. Wired in parallel has too much load due to their resistance and will either blow up the PTU or blow up the driver in the ecu. Wiring them in series however drops their output way lower than they would be if fired sequentially. The Denso coils have a built in igniter so the computer doesn't carry any of the load of the coil firing, which allows us to wire them "sequentially" but still fire them as a wasted spark coil like stock.

Into the guide, what you'll need:

4x Denso coils - Prius coils are what SparkTech uses for their Evo COP, however almost any 4 wire Toyota coil will work fine as long as it's the same style as the Prius coils. In my pictures I'm using some random Toyota coil packs that I had laying at work. You're looking for this style ideally
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Next you need 4x matching connectors- Spoolin Up used to sell these as pin your own kits, you can also find these online from various vendors. I pulled mine from a junkyard Toyota. Just make sure they're 4 wire and you'll be good to go.
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Next you'll need a small length of wire or if you're cutting out junkyard connectors remove as much of the harness as you can with them.

Next on the list is either a junk 2g MAF, like I used, or if someone knows where to get a male PTU connector as a pin-it kit I'll gladly edit that in. I asked ECMTuning, Ohm Racing, and a few other manufactures on obtaining a male either 2g MAF connector or the PTU connector and none of them got back to me on it. The 2g MAF uses the correct connector and they aren't too hard to gut out of the MAFs housing.
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You'll need to figure out a mounting plate for hold the coils. I traced a plug wire cover onto a sheet of aluminum and cut mine out with an angle grinder. The plate is setup for Prius coils, however, since I didn't have Prius coils on hand when I assembled it for testing I had to put some nuts under the coils to mount properly. As far as I know no one makes a plate for these off hand.

Wiring for these is fairly simple, we'll go back to the picture posted above of the connector to start.
On the Coil Connector:
Pin #1 is the 12v feed.
Pin #2 is a tach output signal.
Pin #3 is the trigger to fire the coil.
Pin #4 is the ground.

On the MAF/PTU connector: (you'll have 8 male pin slots in the connector itself, but only 7 legs on the back side. The 2g MAF doesn't use pin 8 so go to the side of the connector with the missing pin and mark it so you know which side is pin 8.)
Pin #1 - Combine Pin #3 for Denso coils 2 and 3, these 2 wires will run to Pin #1 of the MAF connector. Trigger B
Pin #3 - Combine all of Pin #4 wires off the Denso coils, they all run to Pin #3 of the MAF connector. Ground
Pin #4 - Combine Pin #2 from Denso coils 1* and 2*, these 2 wires will run to Pin #4 of the MAF connector. Tach Output
Pin #6 - Combine all of the Pin #1 wires off the Denso coils, they're all going to be run to Pin #6 of the MAF connector. 12v coil feed.
Pin #7 - Combine Pin #3 for Denso coils 1 and 4, these 2 wires will run to Pin #7 of the MAF connector. Trigger A

*Note: These wires are the tach output, if you combine all 4 coils together you'll have double the RPM reading on your tach. We combine 1 and 2 as they're on opposite banks of the firing order. You can combine 1/2, 1/3, 2/4, or 3/4 and still get the same accurate RPM reading, 1/2 are just closest to the connector and require the least amount of wiring. If you don't have these combined properly you're tach will not work properly.

I used crimp on connectors and then solder them to the MAF connector. This isn't the most ideal way to do this and where a pin kit would be much nicer. It is solid and works fine though for now.
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Loom the wiring, plug everything in, test to make sure it runs on all 4 cylinders and the tach is reading accurate. Then you can remove both the stock coil packs and the ignition module and enjoy the new COP setup.

I'm currently using these on my 91 galant with a 210K mile stock 6 bolt with an FP red and supporting mods. I didn't have any issues with my original coils, but I like that I was able to ditch a couple fail points of the stock ignition system. There's definitely cleaner ways to orient these, but the angle on these specific coils made it a pain.

This should work on a 90 as well, however, you'll need a different male connector and the wiring is slightly different. My 90 is currently still tore apart in the back corner of my garage, but I do plan to update this guide with the proper 1990 wiring specs.

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Did you ever get the 90 wiring worked out? I have a 90 and want to do this.
 
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