Turbo GpZ550 Ignition misfires starting above 10 lbs boost

Take a look at the Fuji datasheet again. The one with Japanese.
Look at the " Safe Operating Area" graph.

It plots collector-emitter current vs collector-emitter voltage for various Pulse widths
Depending on voltage and pulse width, it can handle short bursts higher than the 6 amp continuous rating.

I have a question about the "power dissipation" rating of 40W.
The igniter box is plastic but the back cover is an aluminum plate that functions as a heat sink for the transistor packages.
Unfortunately when mounted on the bike the ignitor is up against the plastic battery box and no free air can reach the aluminum plate.
The ignitor could be turned around to expose the aluminum plate and an additional heat sink attached if needed.
Do you think heat is an issue?

Good find on the Ic being a "continuous" rating. So it's more of a guideline on what to avoid long term rather than a strict limit.

I'm not sure what the safe-operation chart is exactly showing. The times shown are quite short. But again is supports the idea of going over 6A for short pulses.

Wattage is not usually a concern in a device used this way because the pulses are short and the device is used in "saturation". By device "used this way", in our case, I mean an ignitor that is a simply "on" or "off" like a switch (aka "in saturation" or "in cutoff"). We would worry about heat if the device was a current-limiting device (aka "active").

I included a bunch of detail below to explain the reasons why, for anyone interested, but it's not essential.

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Let's consider a "perfect" switch as a resistor that can be at infinite ohms, or 0 ohms. A transistor used as a switch is less than perfect. It can't quite be infinite, and it can't quite be 0. Notice in the english pdf it is described as having a low saturation output voltage. That is describing the condition of the transistor trying to be 0 ohms mode. Because it is not at o ohms, the voltage will not be pulled down to exactly 0 volts.

Darlington pairs, due to the "stacked" nature of the design has a drawback. That is that the device does not work as well as a "normal" transistor when acting like a switch. A normal transistor can act more like a short circuit (resistor with resistance close to 0). The darlington is slightly further away from 0. So that is one parameter that is always strived to be improved in the deigns... which is why it's advertised. But it's still not as good as a normal transistor.

The reason I mention all this is because this slight deviation from being a 0 ohm resistor is what causes the heat generation. When the transistor is turned on (acting like a closed switch), the voltage at the negative end of the coil will be close to 0v, but not quite. It is dependent on the current. More current means higher voltage drop.

Let's say the current is 6 amps.
Let's say the transistor can pull the voltage down to about 1.5 volts.

So that is 6 x 1.5 = 9 watts. But the average wattage is what generates overall heat. So let's assume a 50% duty cycle. That drops it to just 4.5 watts. So we are pretty safely in the 40w limit. However, that 40w limit is sometimes specified with a big heatsink and a fan blowing on it. So there is a lot of interpretation you have to take. Like you mention, being in a box does make a big difference. The aluminum plate on the back was a good idea.

I assume Kawasaki did many heat-related tests on the ignitor and they tend to way over-build their electronics.

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This was a very long-winded explanation of the wattage factor considering it's often not a consideration. Well the reason for all the detail is that wattage quickly comes to the top of the concerns when we talk about current limiting functions.

So in current limit mode, that switch model changes. When off the resistor is infinite, then when initially turned on, it's 0 ohms (saturation mode). But when we go to current limit mode, it suddenly jumps up to a larger value. That is called "active" mode. That is the mode when wattage becomes the utmost concern.

Let's say the coil is .5 ohm. Let's say we have 14v. Let's say we want to limit the current to 6 amps. What size resistor do we need the transistor to act like?

At 14v, and 6A, we need the total resistance to be 14/6 = 2.33 ohms. So we need a 1.83 ohm resistor in series with the coil. The transistor is that resistor. So what is the wattage on that resistor? It's current squared times the resistance. 6 x 6 x 1.83 = 65.88 watts. With a worst case duty of 50%, it drops to 32.94 watts. That is much higher than the 4.5 watts we had for the non-current limit example.

So it would still be in the spec range long term, but you are starting to creep up on the limit. I will say, in the box with no cooling fan I would not run that close to the wattage limit. It will be smoking hot. Plus you have two transistors side by side there so the actual heat dissipation will have to be doubled. Ignitors running without current limit don't really get hot. In current limit mode, they get untouchably hot.

Great stuff on transistor modes.
Thank you Lou

I know you can make your own inverter circuits but check out the MSD 6302 2 channel coil driver.
It's meant to go between an MSD ignition controller and MSD coils without internal drivers, but it seems to me it has everything needed to invert the signals from a zx550 ignitor AND provide high current control for some hot non MSD wasted spark coils.

It's $88 but no assembly is required.
Google and you can easily find a link

Should work. Right?

Sorry been bogged down in work.

I looked at the MSD 6302, and I'm not sure . I only looked briefly, but I didn't see any details on what the actual input to output function is, and what levels they are etc. It appears they are saying it's to be used with their MSD dis-2 or dis-4 module. Those things are like $800.

loudhvx wrote: Sorry been bogged down in work.

I looked at the MSD 6302, and I'm not sure . I only looked briefly, but I didn't see any details on what the actual input to output function is, and what levels they are etc. It appears they are saying it's to be used with their MSD dis-2 or dis-4 module. Those things are like $800.

Attached is the installation guide which shows the MSD 6302 inserted between an MSD ignition and a pair of MSD induction ignition coils.

On an MSD support forum a guy was using the 6302 with a pair of induction ignition coils and a Haltech ignition rather than an MSD. He was asking for details about the signal required to trigger the 6302. The 2nd attached file was the reply he received. It shows a falling 12V pulse of 2.5ms and it was characterized as an example of a general pulse. The 12V was rather interesting as it implies it could be used with points or the ZX igniter. Small current running through the ZX igniter

I did see that PDF in my searches, and the way I interpret it is that the 6302 is just an interpreter between the Ford car and the MSD DIS-2. The coils are powered and controlled by the DIS-2 (aforementioned $800). The 6302 just lets the DIS-2 talk to the Ford system. That would imply the 6302 has no coil drivers or related power circuitry.

Further evidence can be found by looking carefully at the wire colors. Notice in the drawing, the coils have their control wires labeled Brown/Green and Brown/White. While those colors are found on the 6032, those particular wires on the 6032 do not go to the coils. They go to the DIS-2. Then, presumably the coil control wires Brn/Grn and Brn/Wht go from the DIS-2 to the coils.

Notice the wire color chart is specifically for the DIS-2. In it you see the coil control wires Brn/Grn and Brn/Wht. While the green wire and white wire are input connections to the DIS-2. Those input connections are fed by the Brn/Grn and Brn/Wht wires of the 6032 in the harness diagram, implying the 6032 is only giving a low-power trigger signal as an output.

So basically, you would have to find out what kind of output the 6032 is giving to the DIS-2. Then you might possibly use it to control an HEI module or some coil-on-plug units with the Zx ignitor output. But that type of thing should cost about $5 to $10 max.

I have a schematic drawn up for the inverter. But I should be able to reduce the part count with some testing. I just haven't had time to slap it together yet. Normally, that is how the design process works. The first design uses a bunch of parts based on "best practices" for circuit design, but then you very quickly start eliminating the redundant parts and eliminate unnecessary parts based on actual tests. It takes more time, but you can sometimes get a circuit down to 1/4 of the parts originally used.

loudhvx wrote: I...
I have a schematic drawn up for the inverter. But I should be able to reduce the part count with some testing. I just haven't had time to slap it together yet. Normally, that is how the design process works. The first design uses a bunch of parts based on "best practices" for circuit design, but then you very quickly start eliminating the redundant parts and eliminate unnecessary parts based on actual tests. It takes more time, but you can sometimes get a circuit down to 1/4 of the parts originally used.

An inexpensive inverter circuit would be great for driving smart coils. Like the VW coil pack I was originally looking at. That would take all the "load" off the ZX igniter

Yes, exactly.

It wouldn't actually be much different from the points version, but I would eliminate the time-out circuit since that won't be needed.

No more ignition misfire under boost.
Finally got back to the bike and I started by testing the most simple solution to spark "blow out" under high boost.

I used a converter to step up the battery voltage to 19V (static) and fed that to the coils.
It solved all my misfire and for now I'm leaving the plug gaps at .022".
At some point in the near future I'll experiment and find the widest gap that won't blow out with the higher voltage.

Coils didn't seem to get warm at all and the ignitor is still tick'n.
In all honesty I've never checked the temperature of the coils before BUT I have checked the ignition coil in my MG. It gets very hot to the touch but has never failed.

Power is great. Especially with no ignition cut out. Once boost really kicks in it revs very fast and I'm seeing 12-13K on the factory tach.
Front wheel comes up easily in 3rd gear if you stay on the throttle into the higher revs. As long as you don't rev too far under boost it's easy to keep it down.
Haven't tried powering it up in 4th gear yet. Pretty sure it will lift without body English but it's going so fast I'm not comfortable trying it yet. Get there at some point.

Running on pump 93 octane ..... so far so good.

Converter is velcro mounted to the inside of the fairing

Another test ride today with no ignition miss.
Saw 13 lbs on the boost gauge for just a split second.
Boost signal is from the carb's vacuum line connection. It's on the engine side of the throttle plate so the gauge reads the actual vacuum and boost in the short intake manifold.

Before I test again I'm going to install the waste gate actuator and set it for 10 lbs.

Check out the Gearing commander image in the attachment.
"custom" is set for my back tire and sprockets.
Look at 12,000 rpm in 3rd gear. Under boost the bike wheelies at that speed.
I'm not going to try 4th gear.

That's great to hear that all you really need is the extra voltage.

Is that typical, to measure boost in the downstream side, rather upstream of the throttle plate? I always pictured upstream. If the the throttle position effects the boost signal, will that then effect the waste gate? Or will that detect boost at the turbo output?

loudhvx wrote: That's great to hear that all you really need is the extra voltage.

Is that typical, to measure boost in the downstream side, rather upstream of the throttle plate? I always pictured upstream. If the the throttle position effects the boost signal, will that then effect the waste gate? Or will that detect boost at the turbo output?

Taking the signal downstream from the throttle plate is" manifold" pressure. That's what you want to see on the gauge whether it's a vacuum signal or boost signal.
That's the actual pressure the engine sees from forced induction. The waste gate actuator gets it's signal directly from the compressor housing and it will be higher than what's downstream in the manifold. So when I saw an actual 13 lbs boost manifold pressure, the compressor was actually creating a bit more boost.
I have NOT been running a waste gate during testing. I have the gate wired shut and I used the throttle to limit boost.

Before any more testing I will begin using the waste gate actuator set to crack at 10 lbs. It will be interesting to see my actual manifold pressure. What I really want is 10 lbs in the manifold so I will be fine tuning the actuator adjustment to achieve that goal.