Another Ignition Coil Option - 4 coils

[socrace]

Recently installed a 4 coil ignition system on the GL1100. It’s been running well for a few weeks now, so time to do a write-up.

coilR50.JPG

First off, it should be said that the stock GL1100 ignition gets the job done 99.99% of the time, so this mod will address, at most, the remaining .01%! That being said, the overall goal was to gain some additional ignition energy, loose the high voltage spark plug wires, reduce electrical interference, and free up some space under the shelter.

The basic method used here is not new, it’s been done before by BMW and several British twins and triples going back to the 50s and 70s, and by many other waste fire engine owners more recently. After the change, the basic ignition is still waste fire, but with one coil per plug. Major advantages are that each coil fires only one plug (instead of 2), and that all 4 plugs have the same polarity (instead of 2 reversed).
Here is a diagram showing how the 2 coil and 4 coil systems are wired:

ford coils.gif

The modified ignition system is still all stock Honda, other than the four coils and ballast resistor.
The coils used are Ford late model “mod motor” COP (coil-on-plug) and usually sell for around $7 each used. One source for them is a 2003 F150 (all models). As seen in the photo, they connect directly to the stock Honda spark plug terminals (with some rework with the bench grinder). Here’s another description of the method: http://www.diyautotune.com/tech_article ... ustang.htm

As a rough test of effectiveness of the system, I decided to create a problem by forcing a rich mixture misfire. After adding about 40% global fuel, the motor misfired badly above 4000 rpm, and would not rev to 6000. Then switched to the 4 coil system and took the bike back out. This time no misfire, even up to 6000 rpm. The 4 coils seemed to be doing something, and was at least worth a closer look.

Decided to collect some objective data showing the energy input to the coils under the two systems. Waveforms for both systems were measured using an oscilloscope, and the energy available to each plug calculated. The energy units are in millijoules, which is a smaller version of kilowatt-hours, if that helps to visualize things:

Dwell @ rpm, GL1100 stock reluctance triggers, for both systems:
0350 9.5 ms (cranking)
1000 8.3 ms
3000 3.6 ms
6000 2.0 ms
9000 1.7 ms

Energy per plug, GL1100 stock system, 2 Stock coils, 1.5 ohm ballast:
0350 64 mj
1000 59 mj
3000 27 mj
6000 12 mj
9000 08 mj

Energy per plug, GL1100 stock system, 4 COP coils, 0.5 ohm ballast:
0350 100 mj
1000 093 mj
3000 043 mj
6000 019 mj
9000 013 mj

As can be seen, the calculated energy gain is pretty substantial, in line with the rich-running misfire test.

Here is one of the scope traces, this one taken across a .5 ohm ballast resistor powering 2 Ford COP coils in series. Scale is 5ms H and 2v V. It basically shows a smooth 6mh charge curve with no evidence of saturation. This means that the current could probably be increased some more, although it’s already approaching 10 amps peak. Fourteen gauge or larger wire is best to wire up the coils.

BitScope.6.png

Also did some additional energy calculations, this time for the GL1000 stock points system with Honda 2 ohm coil and 3 ohm ballast. Also did calculations for the Dyna electronic ignition points conversion system, using the same Honda coils and 1 ohm ballast. Then, also looked at using 4 Ford coils and 2 ohm ballast with both systems.

The dwell numbers below are different than the GL1100 because they are based on a point’s system constant 88 deg camshaft dwell. Honda does not specify dwell, but 88 deg is about the largest possible given that the ignition system will stop working correctly at 90 deg and above.

Dwell @ rpm, constant 88 deg, for both points and Dyna systems:
0350 42.2 ms (cranking)
1000 14.8 ms
3000 04.9 ms
6000 02.5 ms
9000 01.6 ms

Energy per plug, points, stock 2 ohm coils, 3 ohm ballast:
0350 70 mj (3 ohm ballast bypassed while cranking)
1000 11 mj
3000 10 mj
6000 07 mj
9000 05 mj

Energy per plug, points, 4 COP .5 ohm coils, 3 ohm + 1 ohm ballasts:
0350 82 mj (3 ohm ballast bypassed while cranking)
1000 13 mj
3000 12 mj
6000 08 mj
9000 06 mj

The energy gain is still there with 4 coils but not as great. The current capacity of the points and condenser is not a good match to the Ford low inductance coils.

Finally, did an estimate for the Dyna S (model DS1-3) conversion, using a stock 2 ohm coil, and using their supplied 1 ohm ballast:

Energy per plug, Dyna S with stock Honda 2 ohm coils, 1 ohm ballast:
0350 77 mj (1 ohm ballast bypassed while cranking)
1000 34 mj
3000 24 mj
6000 12 mj
9000 07 mj

Energy per plug, Dyna S with 4 COP .5 ohm coils, 1 ohm +1 ohm ballasts:
0350 91 mj (1 ohm ballast bypassed while cranking)
1000 40 mj
3000 29 mj
6000 15 mj
9000 09 mj

As shown, the Dyna S does a great job in increasing energy as compared with the points system. And the 4 coil system is worth some here as well.

[JBz]

WOw. What a test and a Great write up. I read that the COPs were better and Honda has used them on their CBRs. Also less IFR I believe that's the terminology. Does it have a different exhaust sound than the wasted spark?? Thanks JB

[sunnbobb]

Nice write!

[jimmyz3286]

I am was already looking for coils to do the same thing I already have plated to mount them on top of the plug. This is how I have planning mine sunnbobb. Thanks for the write up. I was going to debut mine but you beat me to it. lol

Like!

[Red2trike]

Nice job. Clean job. Can I get one for my 1985, GL1200 Aspencade trike????????? PLEASE????????

Great to have the pics and all this info. Maybe my buddy (electrician/Street Rodder) and I can figger this out and put it on the trike.....mmmmmmm. He'll like this set-up........mmmmmmm, maybe he could use it on the 41 Willy's street rod.....with the blower and get rid of those carbs!!!!!!! Now that would be nice as well.

RT2

[Fred Camper]

Very clean solution. Thank you for all the experimental data, very helpful.

[socrace]

Thanks all, JBz, sunnbobb, immyz3286, Red2trike, Fred Camper!

[jdvorchak]

WOw. What a test and a Great write up. I read that the COPs were better and Honda has used them on their CBRs. Also less IFR I believe that's the terminology. Does it have a different exhaust sound than the wasted spark?? Thanks JB

Looks like dyslexia got ya there JB... It's RFI or Radio Frequency Interference.. Hey you only had 2 letters in the wrong place!

[JBz]

WOw. What a test and a Great write up. I read that the COPs were better and Honda has used them on their CBRs. Also less IFR I believe that's the terminology. Does it have a different exhaust sound than the wasted spark?? Thanks JB

Looks like dyslexia got ya there JB... It's RFI or Radio Frequency Interference.. Hey you only had 2 letters in the wrong place!

close 2 out of 3 aint bad .............jb

[Roady]

Excellent.

This is going into ShopTalk and How-To 4 Wings.

[Brant]

And it's fuel injected? Did I miss something? Pretty impressive.

[Brant]

Aw, just read the efi thread. All I can say is very impressive. Thanks for all the sharing of knowledge.

[silverbullit]

Just what I was lookin 4.


This will be the first real mod that should be done to any 1000

it has always been a weak point.

[ericheath]

Wire in an adjustable rpm window switch at perhaps 5k RPM to trigger a relay and bypass the ballast resistors, (like when starting the bike) and you would get big spark at upper rpm as well.

[silverbullit]

This is what I need to do.

I'm letting it sink in and drawing the plan in my head.

Won't be a copy visually but inspired and electronically

similar.

Total investment including the pieces that will loose

their smoke less than $100.

Something that would have cost $2000 just a few years ago.

and I did put EricHeath Kit but that is mostly due to A DD

Used to be A D H D but the hyper went.