- cop coils
- coilR50.JPG (61.93 KiB) Viewed 1352 times
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 (28.92 KiB) Viewed 1352 times
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 (6.07 KiB) Viewed 1352 times
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.
