10W 2.2 Ohm cement resistor + COP 0.7 Ohm

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one2dmax

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You are in experiment phase. Give it a try. All you can do is fry your CDI if it's overloaded or burn down the bike if it catches fire.
 

DreamV4

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I installed 7.5A fuse instead of 10 A to save my new module. 2.2 Ohm should be fine, I don't ride faster than 5k RPM, which means twice less current than at 10k
 
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02GF74

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I don't ride faster than 5k RPM, which means twice less current than at 10k

You've said this before and I am not convinced that is correct, and will explain why I think that.... but I don't know the answer.

In old points based ignition systems, the current is switched by points that are pushed by a lobed cam. As the engine speed increases, the points open/close faster but the mark/space ratio (dwell angle) is the same so the average current remains the same, as below. Lower trace is the current at twice the rpm of the top trace.
1631086933178.png

The ignition coil is an inductor which means that it takes finite time for current through the coil to reach its maximum. I would expect that circuit parameters are chosen so that at all RPMs, the coil will have reach its maximum (saturation current) so that the power for the spark is the same, else the spark would get weaker at higher RPM due to the coil not having enough time to reach saturation current.

The red line shows the current ramp.
1631087266212.png

At at higher RPMs, there is not enough time for the current to reach saturation:
1631087491468.png

I would need to do the math, but pretty sure that because the current is not a square wave but has the ramp at the beginning, the average current decreases as RPM increases.

Now the question is, does the ignition unit in the Vmax operate like that or has it been programmed so that the time the coil is saturated is the same regardless of RPM? The advantage being that power consumption is reduced and there is less stress on the coil, and indeed, in this case, average current would rise with RPM. Without putting a 'scope onto the coil, I don't know.

1631087892660.png

To answer you question, give it a go as Sean said, but keep an eye out on the resistors, if they start to smoke or glow red hot, then the power rating is too low. Hopefully they will burn out before the transistor in the output stage of the CDI.

Also you probably want a fuse between CDI and each resistor for best protection, if all goes well, you can remove them.
 
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DreamV4

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There is no need for you to flex your brain, because bulbs (resistors), which I have now, glow brighter when RPM increases. I have it on one of my videos, but you can trust me w/o video(maybe). I got your idea about contact ignition, where current % is not changing.
You can use clamp ampermeter to check.
 
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02GF74

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I believe you.

Makes sense to use the computing power of the microprocessor /microcomputer to turn the power as needed.
 

DreamV4

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I installed resistors, they are getting hot!!! I need to figure out how to attach them. Any ideas? Power=amps square x resistance. I will check current with clamp multimeter.
20210911_203156.jpg
 
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DreamV4

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It seems like attaching to frame pipe is the best place with hose clamps. Last thing to figure out is some kind of gasket(?) between resistor and pipe. I really hope to ride my bike first time today.
 

Screwloose

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It seems like attaching to frame pipe is the best place with hose clamps. Last thing to figure out is some kind of gasket(?) between resistor and pipe. I really hope to ride my bike first time today.
Sorry mate, had to watch the first few laps of F1.
without a mock up, i do this.
1. Tin both your resistor wire and the wire you are attaching. Bring them together and with a spare strand wrap that around both. Solder the 2 wires and the strand all together.
2. Use your heat gun (or hair dryer etc) on shrink wrap to cover the connections.
3. if you are using stress relief on your wires then you can loop the cable and shrink wrap that too.
4. for attaching the hot resistor to something else like a piece of steel, remember that you really want to sook that heat from the resistor as fast as you can, hence attach the resistor to a piece of metal like aluminium first. Do not use silicon to attach the resistor. There are products such as heat carrying pastes but you will probably not have them.

i have an additional write up for mechanical crimp advantages if anyone wants it.

hope that helps.
 

Screwloose

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I should have mentioned also but got caught up on the Hamilton Verstapen crash.
Attaching something hot to painted/anodised surfaces can slow down the heat dissipation process.
 

DreamV4

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Sorry mate, had to watch the first few laps of F1.
without a mock up, i do this.
1. Tin both your resistor wire and the wire you are attaching. Bring them together and with a spare strand wrap that around both. Solder the 2 wires and the strand all together.
2. Use your heat gun (or hair dryer etc) on shrink wrap to cover the connections.
3. if you are using stress relief on your wires then you can loop the cable and shrink wrap that too.
4. for attaching the hot resistor to something else like a piece of steel, remember that you really want to sook that heat from the resistor as fast as you can, hence attach the resistor to a piece of metal like aluminium first. Do not use silicon to attach the resistor. There are products such as heat carrying pastes but you will probably not have them.

i have an additional write up for mechanical crimp advantages if anyone wants it.

hope that helps.
thanks.
I need crimp advantages info, please.
 

Screwloose

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thanks.
I need crimp advantages info, please.
I've had a look for the write up I done, but cannot find it straight off, although I do admit it was very long winded.

So off the top of my head, aerospace have a standard that prefers mechanical crimps, where down-hole drilling solder and go through laborious methods of attaching items together. What is best I'm not sure myself as they both put up good arguments, and drilling takes a constant hammering sometimes up to about three weeks non stop.

Aerospace consider that screwed down connections (even torqued) to manufacturers specifications do not consider the following (this is not exhaustive, but includes):

1. A torqued screwed connection cannot accommodate movement of cable wire strands, if movement occurs the strands flatten out and the torque on the screw becomes less, and even loose.
2. Current overload (I see you understand current squared produces allot of heat with even a small rise in current), meaning wire strands expand and contract, again pushing against screw contacts and flattening out the wire strands, hence again loose connections.
3. Points 1 & 2 therefore mean that maintenance must be considered to periodically check all screwed down connections.
4. Consider point 3 where a gap between the wire strands and the screw now exists. If a home can attach an arc welder that would bond 1/4 inch steel plates together without popping the main household fuses, then we now know that arcing is generally not detected in circuits and can easily burn a building down if it catches fire to something. ( As an aside; there are fuses called Arc Fault Detection Devices that can be installed in homes to detect arcing, but I do not know one person who has them fitted as they are very expensive). So moving on.
5. Crimps, and most of them are spring loaded to a certain point, will allow expansion and contraction and are quicker to assemble. As the heat goes down the crimp closes again slightly to keep what is known as a 'gas tight connection' meaning no air is in-between causing a possible arc between two items of differing voltages.

As another aside; maintenance free connections that are spring loaded (crimps on equipment side) are becoming more the norm in households to try and reduce the arcing effect (that you especially see behind light switches). It is not unusual for an electrician to have to tighten all the connections on a home fuse board after a few years of use due to heat expansion and contraction.

I think the above captures the mechanical crimp scenario, and an understanding of what it can help to achieve.

Hope your bike runs good. 🏍
 

02GF74

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I installed resistors, they are getting hot!!!
What temperature are they getting to

They may get so hot you cannot keep a finger on them, nothing to worry about a long ad there is nothing nearby that can be affected by the heat.

I refer you to the 5th post in this thread.

The resistors I recommended have mounting holes in the heat sink and can be further bolted to metal, such as another heatsink to dissipate the the heat.
 

DreamV4

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What temperature are they getting to

They may get so hot you cannot keep a finger on them, nothing to worry about a long ad there is nothing nearby that can be affected by the heat.

I refer you to the 5th post in this thread.

The resistors I recommended have mounting holes in the heat sink and can be further bolted to metal, such as another heatsink to dissipate the the heat.
Thanks, but I found perfect resistance 2.2. Do they make 2 ohm resistance like yours? do you sell them or it is from some website? which one?
 

02GF74

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An alternative to try is 2 pieces of 1/4 in. aluminum plate, credit card to playing card size and sandwich between them 2 of the resistors, using silicone thermal adhesive. Then clamp the plates together with 1 or 2 bolts. Don't worry if the clamping action squeezes the thermal adhesive out the way, that will give the best thermal contact between the plates and resistors

You can use a metal bracket to mount the sandwich to the bike frame.
 

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