CBX Z Ignition power Circuit


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Kool_Biker
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CBX Z Ignition power Circuit

Post by Kool_Biker »

There's this issue which has been bugging me for some time.
The potential impact of the original Honda wiring on the performance of our bike's ignition system. So I got out my trusty analogue scope ...

On the pic below, taken at idle, the top osciloscope beam probe is connected directly to the bike's battery.
The lower one is connected to the coils positive. Both probes are set at 2V/div and 0V (Gnd) is the very bottom grid line.
P1060971.jpg
So here it is! Routing of the original (puny - ish) wiring, feeding the three big coils via the ignition & kill switches plus few spade connectors along the way, leads to a sizeable voltage drop across the coils. Indeed at idle (when battery voltage is at its lowest), the peak voltage across the coils does not exceed 9.3V, a whopping 2.5 V below battery voltage.

Battery voltage does rise rapidly with RPM, of course. And I'm sure all CBX's can and do live with this reality; they have done so since time immemorial.

But due to Ohm's law the coils voltage will always be below battery voltage and as battery voltage rises with RPM so does current, so the 2.5 Volts difference from the battery voltage what ever the latter may be, will ALSO increase, if by a little.

My coils are stock. And I wonder how all this pans out when we spend good money to replace the OEM coils with expensive 'high energy' ones. Of course these work. But if anything, their increased current requirements further worsen the above voltage drop, possibly in part negating the extra benefits they are supposed to bring. On top, the increased current requirements will eventually play havoc with the ignition and kill switches reliability.

Wouldn't it be better to first optimize what ever is already there? To check this I connected the coils +ve, direct to the output of the battery (starter relay terminal) with a beefy cable I had lying around. And presto, matters improved significantly. Practically all battery voltage was now available to drive the coils (harder).
P1060915.jpg
So the addition of a small, high quality relay, feeding directly from the battery fuse to the coils +ve can improve the above. ON TOP, freed from all these ignition amps they have to carry continually, our ignition and kill switches will thank us every single day of their ... extended lives.

I will certainly do this mod to my bike, when I find a bit of time.
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Aris Hadjiaslanis
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Re: CBX Z Ignition power Circuit

Post by daves79x »

Excellent Aris! Your conclusions are further bolstered by another post here about wiring new ignitors and optionally providing a direct feed to the coils via a relay. This might solve a whole host of problems, from an erratic idle to easier carb syncing, to eliminating a high-speed miss a few CBXs exhibited from when they were new (I solved this problem on a couple by exchanging coils, but this might have been the problem all along). Maybe, as you hint at, the Honda coils aren't so bad after all.

Dave

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Re: CBX Z Ignition power Circuit

Post by Larry Zimmer »

Hadn't given that one consideration, Aris. GOOD 'stuff'. And, if my simple understanding of sparktronics is correct, with a 20% voltage drop through the wiring, that would represent a power loss into the coils of approximately 35%! Definitely something to be considered at the high end when spark strength is most critical. A considerable gain to be had for much less $$ than a set of high-end aftermarket coils. Easier install, too.
Thanks, again.
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Re: CBX Z Ignition power Circuit

Post by Kool_Biker »

I have not looked into the output energy side of this yet. It will be what it will be, definitely somewhat better and very welcome as it is so easy and cheap to get.
The proposed wiring mod is also 100% reversible (need to think of originality at all times).
On top, only those who had an OEM ignition or kill switch overheat and fail on them (don't ask), can understand the importance of (substantially) reducing current flow to these ageing parts of our bikes.
BTW, as an extra bonus, the above mod in itself will somewhat reduce the bike's endemic (wiring inflicted) voltmeter error, see: viewtopic.php?f=21&t=8137
Aris Hadjiaslanis
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Re: CBX Z Ignition power Circuit

Post by Kool_Biker »

daves79x wrote: ... This might solve a whole host of problems, from an erratic idle to easier carb syncing ...

Dave
This is so interesting and wish I knew more.
Everyone's focusing at the performance of ignition systems at the top end of the RPM scale. And rightly so.
BUT, I've also wondered at times how tough it must be at idle and on transition (as the throttle is opened at low RPM) with an (as yet) less than stellar spark and cylinders full of charge.
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Re: CBX Z Ignition power Circuit

Post by herdygerdy »

This is so interesting and wish I knew more.
Everyone's focusing at the performance of ignition systems at the top end of the RPM scale. And rightly so.
BUT, I've also wondered at times how tough it must be at idle and on transition (as the throttle is opened at low RPM) with an (as yet) less than stellar spark and cylinders full of charge.
On the weekend I took my CBX-Z for it's first ride after fitting a new set of 3x Procom ignitors and the 12 volt relay to provide battery voltage directly to the coils.

I literally could not believe the change in the way the bike now runs - it feels like it just came off the showroom floor.

And, as you can see below, it starts from stone cold with just key on, choke on and a brief touch of the starter.



It also runs much, MUCH smoother at idle, responds far more crisply to throttle, and is just so very smooth on the road.

Did this demo of engine smoothness just for a bit of fun...... (worked fine till a gust of wind came in the garage!)



It also seems to have a whole heap more torque in the mid range, as evidenced by it being only too happy to loaf around at just 60 kph (I'm in Oz remember) in top gear. And pulls both very smoothly and like a freight train from that speed just by turning up the wick.

I have a suspicion, and it is JUST a suspicion, but I think if you have a large voltage drop across the stock ignition power circuit, then this may be an indication your igniters are not as healthy as they could be. Reason I say this is because on another CBX-Z I worked on recently, it was only presenting a little over 9 volts to the coils. But on fitting the new Procom ignitors, voltage went back up to 12 volts. And this bike had only done 300 kms from brand new!

An easy way to measure the actual voltage drop to the coils, (when compared to the battery voltage) is to take your multimeter (set to measure volts) and put the +ve lead from the meter on the ignition coil 12V input (Black/White lead that loops between all three coils) and the negative meter lead onto the +ve terminal of the battery. With ignition and kill switch on, the number shown is the no. of volts being 'lost' between the battery, through the loom, switchgear and connectors, and back out to the coils (see below for full path).

For those interested, the FULL path of the (hopefully) 12 volts that finally arrive at the coils on the black/white wire in absolutely stock form, as the CBX came straight from the factory, goes something like this.....

a) From battery + to Solenoid terminal
b) From solenoid terminal to (probably 36 year old) fuse holder
c) From fuse holder to wiring loom connector
d) From Wiring loom connector to ignition switch connector
e) From ignition switch connector, through Ignition switch and back down to RH handlebar connector for kill switch
f) From RH handlebar connector through Kill switch and back down into RH handlebar connector
g) From RH handlebar connector to wiring loom
h) From Wiring loom to brown 2P connector on side of battery box.
i) From brown 2P connector on side of battery box down to Ignitor for, say, Cyls 1-6
j) From Ignitor for Cyls 1 & 6 to Ignitor for Cyls 3 & 4
k) From Ignitor for Cyls 3 & 4 to Ignitor for Cyls 2 & 5.
l) From Ignitor for Cyls 2 & 5 to 4P connector to coils at rear of tank on RH side
m) From 4P connector to Ignition coils under the tank. (It then loops between each of the three coils, and ends on the ignition coil for Cyls 1 & 6 - LH coil when sitting on the bike.

When everything was factory fresh, the above worked just fine and was reliable. But given the age of our bikes now (mine was built in NOV '78, so it is now 36 years old), the likelihood in the very long path above for corrosion inducing voltage drop to occur due to old terminals or flakey wiring connections is pretty high.

With an Ignition coil relay installed, as Kool Biker suggests, the trigger for the relay is taken from the brown connector in h) above and then the path of power to the coils simply becomes:

a) Battery + through (the very important) inline fuse holder to relay.
b) Relay output direct to the first ignition coil, which then loops between the other two coils.

Far, far simpler and less chance of failure, esp with the modern reliable relays available.

Next steps for me is to install a set of Dyna coils I have then re-synch the carbs and see if it gets even better - if that's possible !

Cheers...Tony

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Re: CBX Z Ignition power Circuit

Post by herdygerdy »

Hi Aris,

Thinking some more about your coil input voltage drop issue over night, here is a suggestion to find out precisely where it is occurring - because inquiring minds need to know, right? :ugeek:

a) Suggest measuring and recording the voltage across the black/white and green wires found at the brown 2x position connector located on the side of the battery box under the RH side cover. This is your "input" positive (black/white) and negative (green) into your three igniters. Lets call this Measurement A

b) Then measure and record the voltage between the black/white wire and frame ground at the 4x position connector that also sits on the RH side of the bike mounted high on the airbox, just below and behind the rear of the tank. This connector has not only the 3x coil wires from the igniters, but, as you have found, also the black/white wire which is the (in your case not quite) 12V input to the coils. Voltage in this black/white wire is always 'hot' when the ignition is on. Let us now call this Measurement B.

Pic below shows the connectors, connector for Measurement A is in the middle of the pic and connector for Measurement B is top right.

Image

The path of the black/white wire from Measurement A to Measurement B simply "transits" through each of the three igniters.

If you find that A measures within 1 volt of battery voltage and B is still just over 9 volts (ie; as you found when you first started this investigation) , then the problem clearly lies in that path from the brown connector down and through the igniters and up to the coil connector. I would almost bet the house you will still have very close to battery voltage at Measurement A - ie; little or no voltage drop from battery, through wiring loom, ignition switch, kill switch and all related connectors.

If you now grab a dressmakers pin or needle and carefully pierce the insulation of the black/white wire that goes to each igniter and measure the voltage there, you may find an individual one that is causing the problem. You may have to dig around in the black goop found underneath the "Gang of Three" igniters. This may be quite difficult, esp. if the first igniter in the 'chain' is causing the issue, which will ensure the remaining ones "downstream" also receive less than 12V. And working out which one is wired in which position in the loop may be difficult. Also, FYI, the green earth wire also does "the loop thing" through each of the three igniters.

If one is found to be out, it would be worth seriously considering replacing all three, esp. given the age of our bikes. FYI, Procom have individual igniters available for US$79 per pair at the moment, but to use these you will need to fabricate an interface 'harness' as has been done by myself and others. If you want to go down that path, PM me. I will also be posting instructions on how to do this, but it is not for the faint hearted. But as you know your way around an oscilloscope (Oh, hw I wish!), I am sure you are more than equal to the task!

But.....if you find you are getting just over 9 volts at Measurement A, then the problem definitely lies "upstream" from the igniters in either:

a) the wiring loom itself; or
b) the ignition switch and its connector; or
c) the kill switch; or
d) the RH switch assembly connector inside the headlight shell.

And one last thing.....have you replaced the flakey old stock fuse holder with a modern one? (I am doubtful those old OEM fuses are readily available in your local garage!)

Let us know how you get on Aris.

Cheers..Tony

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Re: CBX Z Ignition power Circuit

Post by Larry Zimmer »

FYI Tony and all, I believe you can get those flat fuses from Bill Brint at TIMS.
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Re: CBX Z Ignition power Circuit

Post by Kool_Biker »

Hi Tony
I forgot to state in my previous entry: my ignitors are new Dyna-S units and my coils OEM Honda.
So yesterday I got some time and actually implemented my proposed mod. I think you will agree, results have been very satisfactory:
1. You can see below a rough sketch of the mod, shown on the original 79 CBX circuit (hence you need to allow for the fact that I do not have the standard ignition - Functionally there is no difference, if anything the inclusion of the Dyna-S ignitors simplifies the circuit:
IC-408978.jpg
2. See below the before and after oscilloscope shots, they speak for themselves. At idle (worst case) the previous ~2.5V drop between battery and the coils +ve, is now down to ~0.2V!
P1060971.jpg
P1070007.jpg
3. You can see below a shot of my electrics. The ignition circuit relay is clearly visible. It is not very clear in the picture, but power to it is taken from the output of the battery fuse (original).
P1070002.jpg
Bottom line: I believe this is a very worthwhile mod, which is in any case 100% reversible (originality is important to many of us).
It will certainly pump more energy into the coils BUT EQUALLY IMPORTANT, will take a big current load off our ailing switches and circuitry.
Finally, it will improve somewhat the endemic inaccuracy of the OEM Voltmeter.
And BTW, if I were to decide to replace the OEM coils with high performance units, I would deem the mod as mandatory.
Hope this helps, Aris
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Re: CBX Z Ignition power Circuit

Post by daves79x »

"FYI Tony and all, I believe you can get those flat fuses from Bill Brint at TIMS"

Or your local Honda dealer. If you replace those fuses(both the active one and the spare) every few years, you won't have any trouble THERE. Trouble comes with the couplers overheating from bad connections.

Dave

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Re: CBX Z Ignition power Circuit

Post by Larry Zimmer »

Just a thought regarding connectors: Minimum maintenance might be to just pull them apart and slide them together a few times every couple years. This will, at least, scrape a bit of corrosion of the contact paths. Better, certainly, to clean them well and lube with a good di-electric grease. This applies particularly to the high current and voltage sensitive circuits. But, good for all. Even more-so for those whose bikes live in humid climates and/or near the 'beach'.
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Re: CBX Z Ignition power Circuit

Post by herdygerdy »

Dave & Larry, thanks for the heads up for folk re sourcing the OEM fuses and to be on the regular lookout for corrosion occuring on all connectors.

Aris, thanks for your update and I agree, the relay install is absolutely a VERY good thing to do. Your measurements of full 12 volts going straight to the coils undeniably back this up.

I have to say in my case, installation of the new ignitors, ignition coil relay and Iridium plugs have totally transformed the way the bike runs and rides.

Just so I am crystal clear, you are saying that the Dyna S pulser unit replaces BOTH the OEM pulsers (loctated under the cover at 2:00 o'clock on the clutch cover) AND also those pesky leaky stock igniters? From looking at the pic of the RH side of your bike, this definitely looks to be the case, esp. as the brown connector from the wiring loom (bringing earth & 12 volts from kill switch) appear to be turned around 180 degrees and is now connected directly to the Dyna connector from the pulsers.

Assuming yes, it may be worth measuring the voltage across the brown connector and see if that too is considerably less than 12 volts (ie; similar to what you had at the coils on first measurement). If it is low, then this confirms the loss is in the wiring loom somewhere from battery to the brown connector. Could there be any concern if the Dyna pulser/igniter unit is also getting less than the full 12 volts input into their components ?

But if measurement across the green earth and black/white wires on the brown connector is actually showing close to 12 volts, then to my way of thinking the drop MUST be occuring somewhere in the path from the brown connector and on through Dyna ignition and up to the ignition coils? Pls understand I am not suggesting anything bad whatsoever about Dyna ignition (I have never even seen one in the flesh), but there just must be a good reason for the drop to occur. As they say in the classics....enquiring minds need to know.

And then again.....if she now runs very sweetly with the Dyna ignition and the relay mod in place (ie; much better than before), then if it ain't broke, don't fix it ! Your call.

Cheers..Tony

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Re: CBX Z Ignition power Circuit

Post by NobleHops »

Tony or Aris, would you post up a link to a nice compact relay for this purpose please?
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Re: CBX Z Ignition power Circuit

Post by daves79x »

NAPA stores have really tidy ones right on the shelf. PICO brand, part number 5590PT. 12 volt and 30-40amp depending on wiring and application.

Dave

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Re: CBX Z Ignition power Circuit

Post by NobleHops »

Nevermind Tony, I found where you posted it prior, and if you don't mind, I'll repost it here:
herdygerdy wrote:
Jebbysan wrote:Where in the heck do I get some of those slick flat Relays like Tony is showing.....
I looked for 30 minutes on Digi-Key and Allied electronics and nothing.....

Jebby
Here you go Jebby, http://www.cycleterminal.com,

Part No. MR20-N-5 for the relay, and Part No. TE250 for the base.

http://www.cycleterminal.com/accessory-relays.html

And relay pinouts here, image from http://www.cycleterminal.com. I have found these guys really great to deal with, fast service, reasonable prices and OEM Japanese very high quality products. Love their stuff.

Image

Cheers..Tony
Nils Menten
Tucson, Arizona, USA '80 CBX, sort-of restored :-)

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