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TOPIC: Turbo GpZ550 Ignition misfires starting above 10 lbs boost

Turbo GpZ550 Ignition misfires starting above 10 lbs boost 01 Feb 2020 09:35 #818359

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ZX550 A1 with factory 2.3 Ohm coils and ZR550 ignitor

Plug gaps are at .022" in order for it NOT to misfire at 7-8 lbs boost.

Current misfire begins above 10 lbs boost which doesn't come until over 9k rpm.

From reading other posts I understand the ignitor only provides the coil with 2 msec of dwell at high rpm.

Not much current is reach in so short a time.

What IF?

I was able to deliver 19V to the ignition coils (ignitor still gets 13) but ONLY when boost is over 7 -8 lbs.
That would be over 7500 rpm. and triggered by boost
High voltage should not require as much dwell. to create the magnetic field.

Would the coils and ignitor be OK with 19V for such a short dwell?

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 01 Feb 2020 11:27 #818362

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does a 550 igniter not have too much dwell built in for a turbo application? I thought 20 degrees would be around max?

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 01 Feb 2020 14:02 #818369

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rangeroy wrote: does a 550 igniter not have too much dwell built in for a turbo application? I thought 20 degrees would be around max?


thanks for your reply

If you're referring to ignition timing:, the ZR ignitor has about 23 degrees of advance on top of around 12 degree base timing for total timing of 35 degrees.
More than desirable.

My problem and question have to do with high speed ignition misfire under high boost.
At high rpm, the factory ignitor doesn't provide enough "on" time for the coils to store enough energy for the turbo application.
Plugs do not fire under high boost even with tighter plug gaps.

Since dwell is not adjustable, and running lower resistance coils could damage the ignitor, I thought I might try raising the coil supply voltage at high rpm under high boost.

If I had a scope and a coil tester I could run a 2.3 ohm coil with 19V and 2 msec of dwell. Find out if the resulting current would be safe for both the coil and the ignitor.

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 01 Feb 2020 15:53 #818376

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I replied to your PM before seeing this post. In the PM I was referring to a KZ ignition. I assume the dwell for ZX and ZR will likely be similar.

Yes, the dwell is only around 2 msec as you approach 10,000 RPM. The coil, with only 13v will only reach about 2 amps. With 19v applied it will be more like 3 amps.

As you suggest, the 19v boost should work fine to get a little more coil current at high RPMs.

The coil under normal mid-range RPM condition will get to around 4 amps. So you even have a little more room to go with the current, but there are other limitations... most notably high-tension breakdown of the coil insulation, and high-tension breakdown of the igniter.

With 10PSI boost, are you still using 10:1 compression? I would think that high pressure would be beyond the reliable capability of the stock igniter and coils.

Typically for such a high-pressure application you would want to go to MSD or some other CDI based ignition. It can more reliably produce the higher voltages needed to strike an arc at such high pressures. (You want MSD for lower-rpms to ensure a good idle.)

When I ran Accel 3-ohm coils (which charge slower than stock coils) , and neglected the plugs for 10 years allowing them to get to almost 50% wider gaps, the ignition cut out entirely above around 6000 RPM with large throttle openings. Simply replacing the plugs with normal gaps fixed the problem. The symptom was like someone turning the ignition off. If I rolled the throttle back, or waited for the RPMs to drop, the engine would come back to life.

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Last edit: by loudhvx.

Turbo GpZ550 Ignition misfires starting above 10 lbs boost 01 Feb 2020 17:25 #818379

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loudhvx wrote: I replied to your PM before seeing this post. In the PM I was referring to a KZ ignition. I assume the dwell for ZX and ZR will likely be similar.

...
With 10PSI boost, are you still using 10:1 compression? I would think that high pressure would be beyond the reliable capability of the stock igniter and coils.

Typically for such a high-pressure application you would want to go to MSD or some other CDI based ignition. It can more reliably produce the higher voltages needed to strike an arc at such high pressures. (You want MSD for lower-rpms to ensure a good idle.)

....


Thanks Lou
I'm actually running the 12:1 forged pistons and long duration cams. Same pre turbo engine build I've used for a few years. Late intake valve closing and considerable overlap so the high "static" compression pistons make sure it's not a turd down low.

Last test runs included boost to between 10-11 lbs and that was with an approximate 94 octane mix of pump 93 and leaded 110. No misfire at or below 10 lbs with the tighter .022 plug gaps. I ended up at that gap through trial and error. I took a look at the 750 turbo supplement manual and Kawasaki specs those plug gaps at .5-.6mm. Same as what I ended up with.

The ZR ignitor uses 1 trigger coil and has total timing of 35 deg. It run's fine now but I believe it will run stronger and definitely safer with less timing. I bought a used 750 turbo ignitor off eBay. It uses 2 trigger coils and has the same pin out as the ZX550 ignitor. I just need to modify a 550 trigger rotor to match the turbo ignitor's 30 deg. of total timing and put the 2nd trigger coil back on. Should be an easy swap.

Blowing through CVK32 carb rack with on-boost A/F between 11 and 11.5
The bike is insanely quick right now but it has a bit more in the tank.
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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 01 Feb 2020 20:54 #818383

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Wow! That does look insane! Do smaller motors somehow deal with that high pressure better than larger motors? I always thought people generally run lower boost when using a turbo or super charger.

When I was playing around with spark gap, the motor definitely seemed livelier with the larger spark gap. But it seemed to get tad bit more knock under lugging conditions.
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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 01 Feb 2020 21:14 #818385

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I was surprised at the 12:1 compression pistons. I thought when using boost one used lower rather than higher compression pistons. Notice in the article linked to below it mentions:

"Low Compression Pistons - Turbochargers increase pressure in the combustion chamber, making the mixture more prone to detonation. High compression pistons also increase the detonation potential, which makes engine compression the primary limiting factor where boost is concerned. One good rule of thumb is to drop compression by about one point for every 15 pounds of boost. However, keep in mind that dropping compression too far will reduce engine power when off of boost, increasing turbo lag and decreasing driveability."
Ed

itstillruns.com/pistons-use-turbo-7682654.html
1977 KZ650-C1 Original Owner - Stock (with additional invisible FIAMM horn)

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 02 Feb 2020 03:45 #818391

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loudhvx wrote: Wow! That does look insane! Do smaller motors somehow deal with that high pressure better than larger motors? I always thought people generally run lower boost when using a turbo or super charger.

.


It all has to do with dynamic compression as apposed to static compression.


.
2002 ZRX1200R
81 GPz1100
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78 KZ650sr
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76 KZ400/440 Fuel Injected

www.dotheton.com/forum/index.php?topic=39120.0


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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 02 Feb 2020 05:37 #818401

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650ed wrote: I was surprised at the 12:1 compression pistons. I thought when using boost one used lower rather than higher compression pistons. ...

itstillruns.com/pistons-use-turbo-7682654.html



If you lower the compression you'll be able to run higher boost and make even more power. However, when the motor is OFF boost, lower static compression kills your low and mid range power. Cam/cam timing that closes the intake valve later also kills low end.

Boost only builds with large throttle openings (under load) and in my case, higher rpm.. Starting at 4500 rpm I see boost of 1 to 2 lbs and at 7500 it's making 6 to 8.
Lugging the engine between 2500-4000 is no problem because there's no boost.. No fear of detonation or ping.

The only time I would get any ping out of this 12:1 (static) engine was when I ran it with the stock ZX cams set with 104 LCA. On pump 93 I could not use full throttle below 5000 rpm in any gear above 2nd. Too much cylinder pressure and load As rpm climbed the problem went away.

With the longer duration cams, also set at 104, there's absolutely no problem with full load at low rpm. Pump 93 is all it needs.
In general, as rpm climbs high, worries of ping go away. Of course you must maintain proper A/F under all conditions.

Small displacement high revving motorcycle engines are much less susceptible to the problems found adding turbos to passenger cars.
But since the GpZ ISN'T water cooled, I moved the oil cooler up high for more airflow. It sits where the headlight bucket used to be.
I'm also running a copper head gasket to handle the high cylinder pressure.and to conduct heat from the head to the cylinder block.
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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 02 Feb 2020 08:49 #818411

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The only thing that worries me is that if you are already having to reduce the plug gap to get reliable spark, and then have to increase the voltage at higher RPMs to get reliable spark, I think you are already well into the margins on what a factory ignition can do.

I'm a fan of the factory ignition (over other makes) but I would be afraid of entering into a condition where the spark intermittently fails and you get a series of violent backfires in the exhaust.

I apologize that this post is not very helpful since I'm not offering any solutions, but I would hate to see that motor get damaged. In my mind MSD was always the solution, but it is a huge box and not exactly cheap either. I just haven't dealt with much more than stock compression.

Some have used a Dyna 2000 or maybe it was 3000, but I've heard some reliability complaints on those. They(not sure which one exactly) have a fully digital dwell structure which allows for using the mini-coils. That is, the dwell time is constant so the coil gets what it needs, and only what it needs every time. That may work, plus it would be nice to be able to adjust the timing digitally.

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 02 Feb 2020 09:42 #818415

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loudhvx wrote: The only thing that worries me is that if you are already having to reduce the plug gap to get reliable spark, and then have to increase the voltage at higher RPMs to get reliable spark, I think you are already well into the margins on what a factory ignition can do.

I'm a fan of the factory ignition (over other makes) but I would be afraid of entering into a condition where the spark intermittently fails and you get a series of violent backfires in the exhaust.

I apologize that this post is not very helpful since I'm not offering any solutions, but I would hate to see that motor get damaged. In my mind MSD was always the solution, but it is a huge box and not exactly cheap either. I just haven't dealt with much more than stock compression.

Some have used a Dyna 2000 or maybe it was 3000, but I've heard some reliability complaints on those. They(not sure which one exactly) have a fully digital dwell structure which allows for using the mini-coils. That is, the dwell time is constant so the coil gets what it needs, and only what it needs every time. That may work, plus it would be nice to be able to adjust the timing digitally.


All great advice and I ultimately may have to go with an expensive ignition system with more versatility.

With the stock ignition coils powered with 19V (only under higher boost) I won't need to run the small plug gaps. Should be able to run .030" without a problem.
That being said I may end up limiting the engine to 8 lbs boost in which case I won't need to upgrade at all.

My original upgrade idea was to run 4 LS1 coils fired in pairs. The LS1 coils have their own drivers however they need a 3-5V + pulse to turn them on. The Kawasaki factory ignitor would still be used to control dwell and ignition timing but an adapter circuit would be needed to invert the logic and provide the 3-5V pulse to the coils. The LS1 coils should have plenty of spark energy with only 2msec of dwell but an ideal dwell would be 4 or 5msec. At low rpm the Kawi igniter may provide too much dwell but the LS1 coils have internal current limiting of 8 amps. The Kawi igniter wouldn't see any of that current. Only the few dozen mA needed to turn on it's output drivers and that would be provided by the adapter circuit.

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 02 Feb 2020 10:37 #818417

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An inverter to drive LS1 coils can be easily made with a transistor and maybe a resistor or two.

However, when you go to a current-limiting feature, you have to start considering heat. Current-limiting means the current gets held at a steady level. This is done by a transistor acting as a variable resistor. When the coil reaches the desired hold-current, the transistor jumps up in resistance. This works fine when the dwell time is just a little bit longer than desired. But the transistor is acting as a load and is dissipating a large amount of heat to do this. It is the excess heat the coil would have been destroyed by if the transistor wasn't there. So if the transistor goes into current-limit mode for too long, it can also eventually be destroyed by heat.

( On the HEI ignitions, if you use a high-resistance coil such that the current-limit is never reached, and thus you never go into current-limit mode, you don't really even need to heat-sink the module. )

So current-limit mode should only be used sparingly unless the system is designed specifically for heavy current-limit use. I would expect the LS1 to be driven by a computer which would be programmed to only use the current-limit sparingly.

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 02 Feb 2020 10:52 #818418

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loudhvx wrote: An inverter to drive LS1 coils can be easily made with a transistor and maybe a resistor or two.

However, when you go to a current-limiting feature, you have to start considering heat. Current-limiting means the current gets held at a steady level. This is done by a transistor acting as a variable resistor. When the coil reaches the desired hold-current, the transistor jumps up in resistance. This works fine when the dwell time is just a little bit longer than desired. But the transistor is acting as a load and is dissipating a large amount of heat to do this. It is the excess heat the coil would have been destroyed by if the transistor wasn't there. So if the transistor goes into current-limit mode for too long, it can also eventually be destroyed by heat.

( On the HEI ignitions, if you use a high-resistance coil such that the current-limit is never reached, and thus you never go into current-limit mode, you don't really even need to heat-sink the module. )

So current-limit mode should only be used sparingly unless the system is designed specifically for heavy current-limit use. I would expect the LS1 to be driven by a computer which would be programmed to only use the current-limit sparingly.




I believe the LS1 coil's internal driver handles the current limiting independent from an ECU. The bike's 18 amp charging system wouldn't be able to keep up with 4 of them all maxed at 8 amps:) . The idle speed dwell from the Kawi ignitor is probably too long.

NOTE . The LS1 coil internal "intelligence" limits dwell to 8 mSec even though the ECU, or in my example the Kawi ignitor, is providing more. Not sure how it does that. It can't simply be cutting off the coil early. That would cause early spark. So it must be operating 1 or more cycles behind the ECU. That way it knows what it needs to do BEFORE it has to do it.

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 02 Feb 2020 14:38 #818430

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I checked Megasquirt's site. The dwell time limit on the LS1 igniter is simply a safety limit so the driver doesn't melt down. It's really more of a time-out function. After 8 msec the coil shuts down. If there hasn't been a fire signal after 8 msec, it assumes an ECU malfunction and overrides the dwell signal of the ECU.

They recommend sticking to a designed dwell of about 5.6 to 5.8 msec. It does take longer for the coils to reach current-saturation than 5.8 msec, but they must be reaching magnetic-saturation sooner since they report no increased spark energy when going above 6 msec.

So it is likely a simple current-limit circuit much like the old HEI modules. This works well as long as the ECU knows to use short dwell in the first place.

The problem in the case of using a ZX igniter to drive the LS1 is that the ZX igniter doesn't use a short dwell. It uses a steady dwell angle with varying dwell time, or at the very least uses a steady long dwell time for the much slower ZX factory coils. Simply using an inverter to drive the LS1 units will result in the LS1 units running much hotter than designed because it will be using the current limiter much longer than designed and/or worse, it will simply time out and possibly create a spark way too early.

At 1000 RPM, a ZX will be sending very roughly a 17 msec dwell signal. This will steadily drop to about 2 msec by 10,000 RPM.

www.megamanual.com/seq/coils.htm

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 02 Feb 2020 14:47 #818432

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loudhvx wrote: I checked Megasquirt's site. The dwell time limit on the LS1 igniter is simply a safety limit so the driver doesn't melt down. It's really more of a time-out function. After 8 msec the coil shuts down. If there hasn't been a fire signal after 8 msec, it assumes an ECU malfunction and overrides the dwell signal of the ECU.

They recommend sticking to a designed dwell of about 5.6 to 5.8 msec. It does take longer for the coils to reach current-saturation than 5.8 msec, but they must be reaching magnetic-saturation sooner since they report no increased spark energy when going above 6 msec.

So it is likely a simple current-limit circuit much like the old HEI modules. This works well as long as the ECU knows to use short dwell in the first place.

The problem in the case of using a ZX igniter to drive the LS1 is that the ZX igniter doesn't use a short dwell. It uses a steady dwell angle with varying dwell time, or at the very least uses a steady long dwell time for the much slower ZX factory coils. Simply using an inverter to drive the LS1 units will result in the LS1 units running much hotter than designed because it will be using the current limiter much longer than designed and/or worse, it will simply time out and possibly create a spark way too early.

At 1000 RPM, a ZX will be sending very roughly a 17 msec dwell signal. This will steadily drop to about 2 msec by 10,000 RPM.

www.megamanual.com/seq/coils.htm



Great info
thanks

17 msec dwell at idle kills that idea.

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 04 Feb 2020 05:01 #818515

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Question for Lou

Have you had a chance to scope a full electronic ignition to confirm the 17 sec dwell at idle?

120 deg of dwell would give 2 msec on-time at 10000 rpm and 17 msec at idle but it's hard to imagine the ignitor would use a fixed angle.

It should have been simple to adjust dwell based on rpm. I believe spark is delayed based on rpm.

The ZX reluctor has the single long totally flat ramp with leading edge timed at max advance and the trailing edge at min advance.

When the leading edge aligns with the trigger coil, the ignitor would need to calculate an appropriate spark delay based on rpm.

Zero delay if rpm is high enough and max delay if rpm is low enough. That would adjust timing based on rpm.

If it can do that, it should be able to delay turning the coil back on.

Zero delay would theoretically approach 360 deg which would maximize dwell time for high rpm.

Max delay would limit dwell time at idle. Only enough on time for coils to reach max energy.

How would delay be calculated? A timer circuit?

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 04 Feb 2020 05:16 #818517

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Maybe someone at 750turbo.com have a solution for your ignition Problem.

www.750turbo.com/forum/index.php

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 04 Feb 2020 06:02 #818519

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Garylbishop, do you hjave a thread on your bike build? Seems pretty awesome. We want more pics :silly:
What turbo are you running? CV32s are from a ZR7S or Zephyr? Jetting?
Kawasaki KZ 750/4 LTD 1981
Kawasaki KLR 650 2011
Argentina - Buenos Aires

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 04 Feb 2020 06:10 #818520

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May be this ignition can help:

www.c5ignitions.com/
Kawasaki KZ 750/4 LTD 1981
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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 04 Feb 2020 06:44 #818522

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Scirocco wrote: Maybe someone at 750turbo.com have a solution for your ignition Problem.

www.750turbo.com/forum/index.php



Thanks for the link.

I'm searching the site and can't fine any reference to the very real problem of misfire at high boost.

Many who raise boost above 15 lbs but no mention of ignition misfire. Some raise it higher than 15.

There appears to be a "race" mode.

The ignitor may be controlling dwell which would be great.

I have a used one coming

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