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4th gen Coil on Plug mod (split thread)


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Does the 5th gen definitely use a CDI? I know the 4th gen is TCI. I was under the impression that most ignition systems using the COP's were CDI, and that we're trying to figure out how to use the COP's with a TCI.

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As far as I can tell, all the vfrs that we're trying to convert are cdi type.

I'm making this assumption based on tests outlined by Accel with regard to determining ignition type when replacing factory coils with their product. Since I've only been able to check primary resistance, and not the impedance rating of each coil, I have to assume that the cops will not work on the 4th gen.

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So the problem with the COP on a CDI system is that the COP does not have the required capacitor to hold the charge that fires the spark? I'm assuming this because of the size difference between the stock ignition coils for the VFR and the COP.

I just did a quick read of what a CDI system is here: http://en.wikipedia.org/wiki/Capacitor_discharge_ignition

I'm still trying to learn what all of this means... forgive the basic questions.

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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.

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.

When you 'twin-twingle' the V4, your pairing changes from across the bank to across the V... so you do in fact get both paired pistons at TDC at the same time. Whether this is relevant to the discussion I'm not sure - I am only about 80% up on the content here so far, but will learn more because I want to run a coil on plug set-up too :)

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Ok, well I could see how it would work like that. I wonder if this setup would cause some interesting vibrations... Kind of a poorman's biggish bang. Do you have any links to the one you've seen?

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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.

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.

When you 'twin-twingle' the V4, your pairing changes from across the bank to across the V... so you do in fact get both paired pistons at TDC at the same time. Whether this is relevant to the discussion I'm not sure - I am only about 80% up on the content here so far, but will learn more because I want to run a coil on plug set-up too :)

You really can't have two pistons at TDC at same time with a 90º V4 with a 180º crank no matter how you you turn the cams. The piston position depends solely on the crank and the v-angle. So I can't see how that would work without changing the crank to a 360º or 90º one (which doesn't exist to my knowledge).

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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.

Thanks for the picture, but being that I'm extremely electronically ignorant, I'm not sure how to interpret this. I can say from my own research that 2006 CBR cops are two coils. This may be something that I have my mechanic do, as he did say that it could be done, but I wasn't able to understand what he was explaining, his English is alot better than my German, but things still get lost in translation.

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VFR750 crank:

f30e_35.JPG

If we put a piston on each conrod, and then put those pistons into their respective bores, I believe we would have two pistons at TDC and two pistons at BDC, the angle of the V would have no bearing on this whatsoever.

RC45 crank, for reference:

300301472_f10330b1db_o.jpg

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Ok, well I could see how it would work like that. I wonder if this setup would cause some interesting vibrations... Kind of a poorman's biggish bang. Do you have any links to the one you've seen?

Not any more - it was done by a guy named Matt Wallace on the old VFR mailing list when John Perkins was running it. He rode it around like that for a while and said it sounded a little different but rode about the same, then switched it back to normal, IIRC simply because he could find no advantage to running it twin-twingled.

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VFR750 crank:

f30e_35.JPG

If we put a piston on each conrod, and then put those pistons into their respective bores, I believe we would have two pistons at TDC and two pistons at BDC, the angle of the V would have no bearing on this whatsoever.

RC45 crank, for reference:

300301472_f10330b1db_o.jpg

We're definitely going a bit off topic here with this. The V-angle definitely makes a difference as to where the pistons will end up in their respective bores. If you look at the first picture with the crank laying flat, and imagine two of the rods on the same journal are facing down and the other two are facing up, it would lead you to believe that one piston would be at TDC on each bank at the same time. The problem is that the crank is laying flat, which it wouldn't be in a V engine with one piston at TDC. The other crank journal would need to be pointing in the same direction as the bore, and the only way for it to do that is if the crankshaft journals were 90 degrees of each other, or V shaped if looking at it from the side as opposed to flat like the 180 crank or all inline like a 360 crank. Here's an awful pic of a 750 short block with one piston at TDC, and none of the others at TDC. I'm sure someone has a better one.

shortblock

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Ok, this may have been covered previously in this thread, but I probably didn't comprehend the data. Why can't I just take the 4 cops install them in the cylinder heads, and wire them like the existing coils are wired, i.e., basically run new wires to the cops from the orginitang point to the cops...something like what I've tried to depict below...

STOCK originating point>can coils>spark plug

MOD originating point>cop>spark plug

Like I've said before, I'm not really good with electronics, but all I want to do is swap the can coils for the cops, I really didn't think it would be a major modification, but hey, with these things, I really never know!!! Thanks for all the pateince, and repeated attemps to get me to comprehend all this data, as it is alot for me to take in!!!

The below thread has alot of useful info, especially on pages 2 & 3...they discuss how the mod was done, as well as voltage and resistance.

http://www.speedzilla.com/forums/honda-rc51/44187-removing-coils-wire-coil.html

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I didn't see anything written about resistance of the stock RC51 coils in that thread(kinda skimmed throught it), but Thorsten Durbahn mentioned on one page that the RC51 and RC30 use a CDI box instead of a TCI like our VFR's do. Apparently they've been using the stick coils on the RC51's with good success.

The concern is potential damage to the ignition box or coils over a long period of time. This may be one of those thing where someone is going to have to be the guinea pig and try it out. If my bike were together I'd be more than willing to try it.

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I didn't see anything written about resistance of the stock RC51 coils in that thread(kinda skimmed throught it), but Thorsten Durbahn mentioned on one page that the RC51 and RC30 use a CDI box instead of a TCI like our VFR's do.

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.

So our VFRs have a CDI or TCI ignition system? Or does it vary by generation?

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I actually didn't know the difference between CDI and TCI and had been viewing everything as TCI.

Checking into it though, since all the coils I've seen are 1.6 or 3.2 ohms I don't think they're CDI - those apparently have very low resistance (0.3 ohms or so). It's impossible to measure the resistance of the 6th-gen coils because they have the transistors inside the coil itself. I would guess that the 6th-gen is also TCI, as the coils are permanently fed 12 volts on one wire, have a dedicated ground wire and the third wire is the switch. This single wire should reasonably only be able to control a transistor that switched the 12 volt feed into the coil on (charge the coil), then off (collapse the field). So it's most likely TCI.

Another way of checking if a bike uses TCI or CDI is to look at the way the coils (2-wire coils anyway!) are powered. If they share a common +12 volt feed and have individual ground wires going back to the control box, then they're TCI. However if they share a common ground but have individual positive wires going to the control box, then they're CDI.

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Lookee what I found - a 4th-gen ignition diagram.

So it's definitely TCI, as all the coils share the same 12 volt feed from the engine stop switch. Same wire colour as on the 6th-gen too - Black/White. This wire colour is used as the common 12 volt feed for anything which needs a 12 volt source all the time the ignition switch is on and the Engine Stop switch is on.

post-380-0-31033400-1330651896.png

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

Untitled.jpg

That diagram tells me that the '86 VFR750 is also TCI, as it's shared +12 volt power for all four coils.

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Few more data points.

Not on Fireblades.org, but someone did it fairly simply on a Blade... no mention of how long it lasted though.

http://www.rrzone.co...72191#post72191

I found someone who switched to COP on a FZR600 and went on to rack up 15,000 miles on the bike with no problems:

http://www.fzronline.com/forum/viewtopic.php?f=8&t=3187

And his how-to:

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

Both of those write ups are for 4 cyl, 2 coil bikes. The vfr is 4 cyl, 4 coil.

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How does one measure the impedance value then?

You'd need to test and compare current flow of both coil types somehow.

Isn't this the one case where you can just measure the resistance across the terminals of the coil, and the result is indeed the impedance? I know all our talk about resistors in series wasn't right now, but isn't this measurement an exception?

No, there is more to it. Something about electromagnetic something or other. I wish Bernie would get back online to help out with this.

That might mean that the CBR stick coils - even though the measured resistance is wrong - could be just fine for our purposes...

Or not. I'm not willing to try it unless I understand it. If someone else wants to go ahead and guinea pig their 4th gen, I'll be the first to applaud good results. I also promise I won't laugh if it all goes horribly wrong.

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I'd definitely be up for experimenting with them, but its going to be awhile before my 4th gen is back together.

Its funny, I actually ran these same coils years ago on my Audi urS4 without doing any testing or comparing of the stock vs. stick coils. The car ran great on them right up until the day I sold it!

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I would like everyone to note this statement when discussing impedence and resistance. Oem's have been using resistor packs inline with injectors since the 80's (probably not anymore) and megasquirt users already know this trick to use low impedance injectors with the fairly low current stock drivers. Injectors have coils, too:)

I have been trying to figure out how to turn the stock cdi's sinking "output" to a sourcing one (at 5v for the bosch 4 coil ignitor, seen here http://www.microsquirt.info/Bosch_211.htm) but havnt spent alot of time at it tbh. If we could beef up the transistors in our stock ignition module this wouldnt be required. Obviously this statement only counts for the 3rd/4th gen.

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Ok, if someone can tell me how to wire this up in plain english, I'll buy the coils and wiring harness, and be the guinea pig. I just need to know how to make the changes...

I may be able to accommodate... I could take my F4i harness and coils and modify them so that you can plug them in on your bike and test them. If you don't explode and die, and nothing fails on your bike, then you can replace my parts.

Since we're starting with 4 coils and using 4 cops, we could just plug them in directly like the oem stuff. Changing from that is the part of this mod that I don't fully understand and as such am hesitant about.

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