Topic: Ignition Analysis: Honda's coils

[HondaMan]

Several of you have asked me about my "opinions" on the topic of Dyna S and Martek "points replacing" ignitions, and why I don't like them with the stock Honda coils. Here's the analysis, from an engineering standpoint, of what happens when you install a Dyna S or Martek trigger, just replacing the points, and keep the stock Honda coils. The sheet below is the notes and graphs from those analyses (the other pix is the oscilloscope waveform of the Honda coil, showing it's characteristic 1.5mS discharge time). While the image is too small here, if you want to see it better, e-mail me and I'll send you a full-size scan of it. This analysis is the summation that urged me to develop the now-popular, transistorized "Hondaman Ignition" that makes the most of Honda's original design.

The "bottom line" here is: a Dyna S or Martek trigger, if simply installed in place of the original points, will cause HV spark droop, starting at 3000 RPM. The stock points will not let the spark droop until in excess of 12000 RPM. The Honda coils' discharge time is 1.5mS, fixed. If the coil is allowed a full discharge before recharging, the droop will not occur because the magnetic field stays at max flux. If, however, the OFF time of the "points" is too short, the discharge is not complete, which will cause a strong resistance to the current reversal when the trigger "closes" again, and the resulting coil flux is lower (about 40% lower at 6000 RPM) than normal, which makes the HV begin to droop.

I first noticed this issue in my test setups at the beginning of this "Hondaman Ignition" project. The OFF time of the Dyna S is determined by the width of the magnet that is embedded in the advancer's "cam". This is a mere 27% of the equivalent points cam's OFF dwell, in physical degrees (Martek is similar). This causes a very short OFF time for the coil's discharge, especially acute as the RPM rises. This is probably the reason that the Dyna S manual states that you will receive "about the same spark voltage as the stock setup". If measured below 3000 RPM, as these graphs show, this is true. But, the droop at 6500 RPM is almost 40% and it gets worse above that. If the Dyna III "amplifier" module is added, this problem gets better, because that amplifier stretches the OFF time somewhat. Dyna's answer, of course, is to use their coils also, which actually generate about 25% more spark voltage at 8000 RPM than the Honda coils. But, that's a whole system, and that sort of performance should be expected in an expensive "set" like that!

The "Hondaman" Transistorized Ignition simply lets the points switch the coils through transistors, letting some additional electronics absorb the back-emf ("kickback" of the coils)  that would normally arc the points and cause their wear. But, in addition, the Hondaman unit also switches these spikes much faster (600% faster) than the open points and stock condensor, so the coil's discharge voltage remains at the full 100% value all the way to 20,000 RPM (should you be so lucky!), reducing spark droop considerably in everyday driving. This allows for a longer spark at all RPMs than the Dyna S can provide.

It's not so much that I don't LIKE the Dyna S, I actually do like them, in the right application. But, that's not on my bike, anymore. 

[Jonesy]

Facinating stuff!

I have a Dyna S with stock coils on my K3. I'm seriously thinking about changing to Dyna 5 Ohm coils. Since the Dyna coils are more "matched" to the module, would there be any improvement? And, if I purchase the coils, would you want to borrow them as guinea pigs for a comparative analysis?

[HondaMan]

Facinating stuff!

I have a Dyna S with stock coils on my K3. I'm seriously thinking about changing to Dyna 5 Ohm coils. Since the Dyna coils are more "matched" to the module, would there be any improvement? And, if I purchase the coils, would you want to borrow them as guinea pigs for a comparative analysis?

I could run them across my test setup to see how they perform: I have never seen a pair of the 5-ohm units.

[sbc1320]

My newly acquired (3 months) 76 K has the Martek 440 in place of the points. I think it has Martek coils. The coils are green and a little bigger than the stock ones. Seems to be working OK as in bike runs real well after getting carbs right,

[GammaFlat]

Have you had a look at how factory electronic ignitions (on newer bikes) stack up to your hybrid system?  Are they similar to a Dyna-S in performance? 

If you have a notion that improvements could be made in ignition performance over factory electronic ignitions, I have an 85 Aspy to test on   I can only guess at the complicating factors.  I would assume you'd need to wrestle control of the duration of the open and closed states. 

[Soos]

Ok...
If i am understanding all this right...
On a 750, using an aftermarket points plate results in a loss of performance due to timing differences between the new and stock timing plates.
But that may(will?) increase performance back to that of a stocker setup if not more than the stock setup.


Out of curiosity, what would be the situation you have when using a STOCK timing plate and a aftermarket set of coils?


l8r

[HondaMan]

Have you had a look at how factory electronic ignitions (on newer bikes) stack up to your hybrid system?  Are they similar to a Dyna-S in performance? 

If you have a notion that improvements could be made in ignition performance over factory electronic ignitions, I have an 85 Aspy to test on   I can only guess at the complicating factors.  I would assume you'd need to wrestle control of the duration of the open and closed states. 

The newer factory electronic units have short-dwell coils, similar to automotive coils. They do use quite a bit more current, so the new alternators have more poop, to support these systems. Using 180-degree points-like setups with these has no negative impact on the coils, but does improve the overall amperage situation, especially on bikes like the CB500/550/400/350 group.
For example, putting a Dyna S on a CB500, then switching to coils from, say, a CBX, would result in approximately the same current consumption overall as if it were stock points-and-coil, or Hondaman module with stock 500 coils. The spark would be better than used stock points, but not as good as with the Hondaman module. The CBX coils generate about 8 kV with a 1.8-amp current draw, while the stock coils generate 7.5 kV with a 2.2 amp draw. The difference is: the points-and-coil module draw charge current for only 180 crank degrees, while the "trigger" types draw charge current for about 330 degrees, or nearly twice as long. This long charge draw increases the overall current load on the bike, hence the subtle, but significant, problem.

[HondaMan]

Ok...
If i am understanding all this right...
On a 750, using an aftermarket points plate results in a loss of performance due to timing differences between the new and stock timing plates.

Pretty much: it's the very short OFF time of electronic triggers that produces the problem. The coil can't fully discharge, which results in lower spark voltage for the NEXT spark. That's why the problem shows up as RPM increases, but not at low engine speeds.

But that may(will?) increase performance back to that of a stocker setup if not more than the stock setup.

In the case of a Dyna S or Martek trigger with stock Honda coils, you will net LESS spark voltage, especially above 3000 RPM. It's a nearly 50% loss at 7000 RPM, and proportional loss from there down to 3000 RPM. At 10,000 RPM, for reference, it's a 66% loss, as measured on the bench.

Out of curiosity, what would be the situation you have when using a STOCK timing plate and a aftermarket set of coils?

This is the Dyna Coil scenario, where the 3-ohm coils from Dyna's high-performance systems just get substituted into the bike. It makes more spark, but eats the points quickly with the higher coil currents (nearly twice the stock currents) and higher back-EMF spark when the points open. With Dyna and Accel coils like these, the best you can hope for is to add a 1-ohm resistor, like your car has, in series with the coil's +12 lead. This limits the charge current to about 3 amps, which helps the points live a little longer and reduces the alternator's load, while still giving about 25% more spark voltage than stock coils.
One version of the Hondaman ignition is designed to handle the abuse from the Dyna/Accel coils, and on a 750 this all works out well, with or without the resistors, with higher spark and very long points life, and RPM into the stratosphere, with better MPG, according to several users. In the 500/550/400/350F, though, the amperage increase is too much for the bike's alternator, and low system voltage results from these coils. Dyna came out with their 5-ohm coils to help solve this situation, and the combo of their Dyna S and the 5-ohm coils works well on the smaller bikes.

I don't know, though, what the spark voltage is on their 5-ohm coils. I've never seen one, so far. If it's better than 7.5 kV, then these would improve the overall performance on the smaller Fours, especially if used with the Hondaman module.

Update 9/09: I now have the Resistor Packs available, which removes the requirement to use the "Dyna-capable" Hondaman Ignition module with low-ohm coils. You just use the Resistor Pack with the "Basic" Hondaman module (or points, or Dyna S triggers) to limit the current to an appropriate value for these bikes. See the post in the "For Sale" section with the other Hondaman Ignition stuff.

[750essess]

Hey Hondaman, I am in the process of setting up my ignition on a cb750 with 3ohm dyna coils, triggered by dyna 2000 hall effect sensors, controlled by a microsquirt ECU. The ECU has the ability to control the max dwell and and max spark duration. The instruction have directions to calculate these values, but requires a scope (have) and signal generator (dont have). Can you make a recommendation what these should be set to in milliseconds? I curentlly have the dwell at 3 Msec and don't recall what  the spark duration is.

[HondaMan]

Hey Hondaman, I am in the process of setting up my ignition on a cb750 with 3ohm dyna coils, triggered by dyna 2000 hall effect sensors, controlled by a microsquirt ECU. The ECU has the ability to control the max dwell and and max spark duration. The instruction have directions to calculate these values, but requires a scope (have) and signal generator (dont have). Can you make a recommendation what these should be set to in milliseconds? I curentlly have the dwell at 3 Msec and don't recall what  the spark duration is.

Those Dyna coils require a minimum discharge time of 1.2mS. Longer is better. Their charge time is about 3 ms or a little more. They are pretty much a scaled-down automotive coil, like those found on a 4-cylinder distributor. If you add a 1 ohm resistor in series with the coil, the charge time is a little less, because the flux doesn't build up so fast that it fights back at the incoming current.

[750essess]

Thank you very much, just what I needed to know.

[HondaMan]

Thank you very much, just what I needed to know.

Let me know how that fancy sparker turns out! 

[750essess]

Well, I tried to get it running over the weekend. Got it to spark at the right time with the light, but it won't run??? doing some more reading now...too many settings you can mess up LOL

[HondaMan]

Well, I tried to get it running over the weekend. Got it to spark at the right time with the light, but it won't run??? doing some more reading now...too many settings you can mess up LOL

Don't let the old 1&4  vs.  2&3 switcheroo sting you. Timing lights can be downright unhelpful on a twin-firing system when just 1 wire is out of place.   

...just a thought...

[750essess]

Yeah, I already tried that, its got me before too. There seems to be a problem with the firmware, it doesnt set both channels to the same settings. They are looking into it now. I am apparently the first to try dual tach inputs. Most people use a trigger wheel. It throws a nice fat spark though. I'm also having problems getting a reliable signal with the timing light(inductive pick-up). The plugs are firing but sometimes I dont get a flash. I guess its the dyna wires causing it.

[eldar]

Ok so here is my question. I installed the dyna-s and my warmup time is decreased.Ihave greater power over all rpm ranges,at least it feels that way, and my plugs burn pretty clean,especially in the high end. Idle is rich but that is cause of carb adjustment. The dyna has been an improvement over points in every way it seems. Stock engine and coils and electrics.

How old is the unit you re using for your test? I got mine last year. Maybe there have been changes?

[Terry in Australia]

Nah, it's just because it's a K8 Eldy, anything you do to one of them is an improvement.............. 

[Jonesy]

I've noticed the same differences in my K3 as well...

[Terry in Australia]

I've noticed the same differences in my K3 as well...

Is "I've noticed the same differences as well" a "double entendre"? 

[eldar]

oh SNAP! and terry gets OWNED by Jonesy!

Jonesy, how old is your dyna S?

[dusterdude]

Nah, it's just because it's a K8 Eldy, anything you do to one of them is an improvement.............. 

bwahahahahahaha 

[eldar]

Yeah you laugh but secretly you want an answer too! It is impossible to hide the K8 envy you and terry have!

[Terry in Australia]

Er, what was the question again? K8 envy? That'd be like "small penis envy", I reckon!;D

[eldar]

Small penis? Oh I get it. Out of your shame, you ride a K1.Terry, I may not be licensed for the help you need but you should not worry. Them sheep will never talk!

[Terry in Australia]

Hey Eldy, do you live near Fargo? I love that movie!