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4th gen Coil on Plug mod (split thread)


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She rode better today. Felt pretty much normal with the coil sticks.

I suppose this means the Viffer has a closed loop ignition dwell system then. Keep us posted.

Would this closed-loop thing apply only to FI bikes, or apply to my carbed 4th gen as well?

Reviving this thread because the topic came up in another - and I'm still curious. Will try and dig up those F4i coils today.

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Located my F4i coils. Turns out I only have 3. DVM set to ohms, two of them slowly came up to 1.1/1.2ohms, the third spiked up to 1.4 then settled at 1.1ohms.

I'm going to think up a prize to offer to the first person to figure out how to make these work on a 4th gen...

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Some other notes for everyone's benefit...

615803df-1.jpg

The blue wire fires the coil going to 1/4. The yellow wire fires the coil going to 2/3. The black/white wire provides the switched 12volts +.

There is no real polarity on the coils. Just a black/white and a color to each.

The one plug fires positive the other negative. So interchanging the location on the coil just interchanges which plug is firing positive.

You can wire it whatever makes the wires "reach" best. Coil location on the bike whatever is unimportant. Blue is 1/4,yellow is 2/3,is the only important info.

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Located my F4i coils. Turns out I only have 3. DVM set to ohms, two of them slowly came up to 1.1/1.2ohms, the third spiked up to 1.4 then settled at 1.1ohms.

I'm going to think up a prize to offer to the first person to figure out how to make these work on a 4th gen...

That's easy - run them in series as wasted spark. It's already a dual-coil (rather than quad-coil) setup isn't it? If it's wasted spark 3.4 ohms each coil with dual coils you just wire two 1.6 ohm stick coils in series. (1 & 4 and 3 & 2).

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Located my F4i coils. Turns out I only have 3. DVM set to ohms, two of them slowly came up to 1.1/1.2ohms, the third spiked up to 1.4 then settled at 1.1ohms.

I'm going to think up a prize to offer to the first person to figure out how to make these work on a 4th gen...

That's easy - run them in series as wasted spark. It's already a dual-coil (rather than quad-coil) setup isn't it? If it's wasted spark 3.4 ohms each coil with dual coils you just wire two 1.6 ohm stick coils in series. (1 & 4 and 3 & 2).

***Please disregard the following, I was being an idiot***

Yes, 4th gen is dual coil. Come to think of it, my 83 750F is dual coil as well, but I've already spent a bundle on Accel coils and wires and such for that bike. And my CB900F is dual coil as well, but just yesterday I installed CBR900RR coils and Accel wires on that one!

So, I wire it up like these then?

http://www.fzronline.com/forum/viewtopic.php?f=43&t=6316

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So, I wire it up like these then?

http://www.fzronline...php?f=43&t=6316

Yep that's the way it's done. It only ever works if one of the new coils is half the resistance/ohms of the oil dual coil pack. So even though some of your other bikes will be dual-coil they may not be 3.2 ohms.

If the original dual coil packs are much lower than 3.2 ohms, you will overcharge the new coils (too long a dwell time) and blow the coils/wear the plugs out fast, or undercharge the coils (too short a dwell time) and get poor spark. Unless your CDI has closed loop dwell control of course, in which case pretty much anything should work.

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So, I wire it up like these then?

http://www.fzronline...php?f=43&t=6316

Yep that's the way it's done. It only ever works if one of the new coils is half the resistance/ohms of the oil dual coil pack. So even though some of your other bikes will be dual-coil they may not be 3.2 ohms.

If the original dual coil packs are much lower than 3.2 ohms, you will overcharge the new coils (too long a dwell time) and blow the coils/wear the plugs out fast, or undercharge the coils (too short a dwell time) and get poor spark. Unless your CDI has closed loop dwell control of course, in which case pretty much anything should work.

Well, in that case, I just need to get my hands on one more coil. I have 3... dunno what happened to the 4th. I have the harness for them as well, so that will be simple to cut up and run new wires to the old coil spades(will create a new connection with more suitable hardware).

Of course, I should probably get the bike running in "stock" trim first... heh!

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So, I wire it up like these then?

http://www.fzronline...php?f=43&t=6316

Yep that's the way it's done. It only ever works if one of the new coils is half the resistance/ohms of the oil dual coil pack. So even though some of your other bikes will be dual-coil they may not be 3.2 ohms.

If the original dual coil packs are much lower than 3.2 ohms, you will overcharge the new coils (too long a dwell time) and blow the coils/wear the plugs out fast, or undercharge the coils (too short a dwell time) and get poor spark. Unless your CDI has closed loop dwell control of course, in which case pretty much anything should work.

Well, in that case, I just need to get my hands on one more coil. I have 3... dunno what happened to the 4th. I have the harness for them as well, so that will be simple to cut up and run new wires to the old coil spades(will create a new connection with more suitable hardware).

Of course, I should probably get the bike running in "stock" trim first... heh!

Running would be good!!! If you do the coil conversion, please take picks ofr us individuals that aren't so electrically inclined, as I'm seriously debating on doing this mod prior to my track day at Spa in April, as I really haven't done anything to my VFR this winter, running out of things to mess with I guess...

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4th gens have four individual coils that are fired by 4 separate ignition drivers. IIRC my NC30 had two coils running wasted spark, each coil fired both paired cylinders since it was a 360 degree motor and they were adjacent.

I would think it's possible to pair up the four ignition drivers(each pair firing two stick coils wired up in series) in wasted spark configuration, at least on a 4th gen.

I think I read somewhere that the 5th gen had specific ignition maps for each cylinder, or at least different maps front to rear, so it might run funky if you were to pair up a front and a rear cylinder(which you would have to do since its a 180 motor) to one driver meant for either a front or rear cylinder. Or it might run just fine.

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4th gens have four individual coils that are fired by 4 separate ignition drivers. IIRC my NC30 had two coils running wasted spark, each coil fired both paired cylinders since it was a 360 degree motor and they were adjacent.

Wow, yeah. I totally spaced on that one. Insert facepalm here!

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4th gens have four individual coils that are fired by 4 separate ignition drivers. IIRC my NC30 had two coils running wasted spark, each coil fired both paired cylinders since it was a 360 degree motor and they were adjacent.

I would think it's possible to use two of the four ignition drivers(each one firing two stick coils wired up in series) in wasted spark configuration, at least on a 4th gen.

I think I read somewhere that the 5th gen had specific ignition maps for each cylinder, or at least different maps front to rear, so it might run funky if you were to pair up a front and a rear cylinder(which you would have to do since its a 180 motor) to one driver meant for either a front or rear cylinder. Or it might run just fine.

Umm, ok, ahh...what does all this mean??? I'm really good with nuts and bolts and aircraft, and aluminum, but not electricity. Someone needs to draw me a pretty picture, because I'm just not getting this, and could really use the visual assistance!!!

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well, my ms paint skills are pretty lacking. I'll try to draw a picture(artistic skills also lacking) when I get a chance, scan it and post it up. In the meantime, if you look at a 4th gen ignition wiring diagram, you'll see two wires going to each coil. One wire is switched ignition, the other is the "ground" circuit which is controlled by the ignition driver in the TCI. There are 4 drivers, one for each coil/cylinder that are actuated in the firing order of the engine, which I can't remember off the top of my head.

The reason you want to wire them in series is so that you add up the resistance of the two "stick" coils so that it equals the same amount of resistance of the original factory coil. To do this, you're going to have your switched ignition wire going into one terminal of the paired coils, then on the other terminal of the same coil, you'll run a wire to the other coil, then you run your ignition driver wire to the other terminal on this coil... Ok, a pic would definitely help here.

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here's a good pic stolen from another site that should explain it pretty well, you just have to ignore how the wires are labeled in this pic. Basically the green negative wire going to cylinder 3 would go to the cylinder #2 and #3 ground/driver wire on the VFR harness, and the negative yellow wire going to cylinder 4 in this pic would go to the cylinder #1 and #4 ground/driver wire in the VFR harness. That is assuming cylinder's 1 & 4, and cylinders 2 & 3 are companion cylinders on the VFR engine, which I'm pretty sure they are.

stickcoilsinseries

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Some other notes for everyone's benefit...

615803df-1.jpg

The blue wire fires the coil going to 1/4. The yellow wire fires the coil going to 2/3. The black/white wire provides the switched 12volts +.

There is no real polarity on the coils. Just a black/white and a color to each.

The one plug fires positive the other negative. So interchanging the location on the coil just interchanges which plug is firing positive.

You can wire it whatever makes the wires "reach" best. Coil location on the bike whatever is unimportant. Blue is 1/4,yellow is 2/3,is the only important info.

so implementing this setup (which I think is a late 90's CBR600 setup would convert the 4 coil system on a 4th gen to a 2 coil, wasted spark system, essentially doubling the number of sparks in each cylinder per revolution?

This could be really useful for those of us fightering our VFRs to reduce the number of coils to relocate. Of course figuring out the COP option would be even better.

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Some other notes for everyone's benefit...

615803df-1.jpg

The blue wire fires the coil going to 1/4. The yellow wire fires the coil going to 2/3. The black/white wire provides the switched 12volts +.

There is no real polarity on the coils. Just a black/white and a color to each.

The one plug fires positive the other negative. So interchanging the location on the coil just interchanges which plug is firing positive.

You can wire it whatever makes the wires "reach" best. Coil location on the bike whatever is unimportant. Blue is 1/4,yellow is 2/3,is the only important info.

so implementing this setup (which I think is a late 90's CBR600 setup would convert the 4 coil system on a 4th gen to a 2 coil, wasted spark system, essentially doubling the number of sparks in each cylinder per revolution?

This could be really useful for those of us fightering our VFRs to reduce the number of coils to relocate. Of course figuring out the COP option would be even better.

Yes, you should be able to in theory.

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Some other notes for everyone's benefit...

615803df-1.jpg

The blue wire fires the coil going to 1/4. The yellow wire fires the coil going to 2/3. The black/white wire provides the switched 12volts +.

There is no real polarity on the coils. Just a black/white and a color to each.

The one plug fires positive the other negative. So interchanging the location on the coil just interchanges which plug is firing positive.

You can wire it whatever makes the wires "reach" best. Coil location on the bike whatever is unimportant. Blue is 1/4,yellow is 2/3,is the only important info.

so implementing this setup (which I think is a late 90's CBR600 setup would convert the 4 coil system on a 4th gen to a 2 coil, wasted spark system, essentially doubling the number of sparks in each cylinder per revolution?

This could be really useful for those of us fightering our VFRs to reduce the number of coils to relocate. Of course figuring out the COP option would be even better.

Yes, you should be able to in theory.

Didn't we already establish that I was wrong, the 4th gen uses 4 coils?

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here's a good pic stolen from another site that should explain it pretty well, you just have to ignore how the wires are labeled in this pic. Basically the green negative wire going to cylinder 3 would go to the cylinder #2 and #3 ground/driver wire on the VFR harness, and the negative yellow wire going to cylinder 4 in this pic would go to the cylinder #1 and #4 ground/driver wire in the VFR harness. That is assuming cylinder's 1 & 4, and cylinders 2 & 3 are companion cylinders on the VFR engine, which I'm pretty sure they are.

I don't think this could work with the VFR's 180º crank as there is there are no two cylinders that are in TDC the same time as with a 360º crank you can pair 1&3 and 2&4. This connection only allows to run to 2 different timing advances which is fine for conventional I4 or a 360º crank V4 engine but with a 180º crank the other cylinder would be in BDC with a fresh air/fuel mix while the other cylinder is ignited. I think this is the reason 3rd and 4th gen have 4 coils and 4 coil drivers with individual timing. If you'd pair 1&2 and 3&4 the other cylinder would be half way to exhaust or intake stroke while igniting the other depending on the cylinder to be ignited. Is that a problem I don't know but I have doubts. Also the paired coils would have to get signal from both coil drivers and this connection does not do this. I think the same goes to 5th and 6th gen also as they have 180º cranks also.

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^ Well on a 750 you can lift one cam on each bank, rotate it laterally and reinstall it. That way each bank fires at the same time so you could in effect have both cylinders in each bank at TDC simultaneously.

The bike will run just fine like this, it's been done before.

Came across this diagram from the 1986 VFR750 F-G microfiche, don't know if it helps...

Untitled.jpg

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^ Well on a 750 you can lift one cam on each bank, rotate it laterally and reinstall it. That way each bank fires at the same time so you could in effect have both cylinders in each bank at TDC simultaneously.

The bike will run just fine like this, it's been done before.

The "Twin Twingle" project.

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Yeah, but I think Jeremy was asking if it were possible to use a two coil waste spark setup like the one you posted a picture of to eliminate two of the factory coils.

That's correct. The idea of either eliminating half the coils or moving the coils to the plug should appeal to the Streetfighter guys as we try to eliminate clutter that is normally hidden under fairings... b/c we don't have fairings.

I think I would prefer to do a nice COP mod, if that's an option, because it should keep the factory timing and power consumption... I think.

I'm still learning about all this stuff... I love VFRD because there is so much knowledge being shared and lots of collaboration between members.

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^ Well on a 750 you can lift one cam on each bank, rotate it laterally and reinstall it. That way each bank fires at the same time so you could in effect have both cylinders in each bank at TDC simultaneously.

The bike will run just fine like this, it's been done before.

Came across this diagram from the 1986 VFR750 F-G microfiche, don't know if it helps...

Untitled.jpg

I don't see how this would work on any of the 180 degree motors as one piston will always be at BDC when the other is at TDC per bank. I could see how it would work on a 360 degree motor though.

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