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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 04 Feb 2020 08:21 #818529

  • garylbishop
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undiablo wrote: 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?


I don't have a build thread but I do have many pics that I can put together.
Here's a link to most of the pics. photos.app.goo.gl/6FgkjTfdVXuzb6T68
Some quick info:

T25 from late 90's Saab 900
CV32 carbs were from a ZX600 C model. Spacing will match IF you use the Zephyr 550 offset rubber carb spigots on Cylinders 1 & 4.
OR you move the outer carbs to match the ZX/KZ. Several mods needed for that.

Jetting for the CV's on NA motor with pod filters ; 12:1 pistons, 4-1 exhaust, long duration cams
1 size up pilot jets /screw at 1-3/4 turns out
raise needles with 3 shims
130 main jets.

For Turbo ;
1 size up pilot jet/ same screw setting
needles at stock height (no shims)
116 main jets. Size depends on the pitot tube signal /float bowls see boost pressure through pitot tube

High pressure electric pump with boost referenced fuel pressure regulator

Turbo oil outlet is below engine crankcase so it needs a scavenge pump. I copied the 750 turbo using a mechanical pump driven off the secondary shaft.

17" front wheel w/300mm brake rotors and Zephyr 550 calipers ( wheel from FZ600)
17" rear wheel w/ stock rear caliper and smaller Busa rotor. (wheel from Bandit 650)

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Last edit: by garylbishop.

Turbo GpZ550 Ignition misfires starting above 10 lbs boost 04 Feb 2020 09:20 #818536

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Turbo placement is smart. nice work
-Vic
_________________________________
'78 kz1000 LTD long term project

'80 kz750G project

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 04 Feb 2020 14:26 #818573

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I do have scope traces somewhere. I actually use an airmotor to run the pickups then use an audio recorder to record the traces. You can actually play them back on a computer and see and hear them. It's kinda like listening to the actual motor. I will try to find a way to post them when I get a chance.... just for the curious... it doesn't really show anything than the actual signal.

But to answer the question... I've only mapped out the dwell for the KZ type ignition, and only recall thinking the ZX was similar when I checked it briefly on a scope.
The KZ does not use a fixed dwell angle, but the angle does not vary widely. In the world of old-timey ignitions you can try to reduce the effects of wide ranging dwell time by either actually controlling the dwell time, or build in a safety margin to handle the excess heat created at low RPM. The KZ and I assume the ZX do a little bit of both. They make the coil big (considering it only fires two cylinders) to handle a lot of heat, and they designed a system that varies the dwell angle slightly.

As I mentioned, there are some design changes and/or manufacturing tolerances that effect the final dwell values, but for a rough average on KZ's, the idle dwell angle is about 100 deg (crank), and above 2000 RPM or so it stays around 120 deg (crank). The difference seems slight.

However, a slight change in dwell has a significant difference in heat. This is because in addition to reducing the amount of time heat is being generated, you increase time for cooling. So a small bit of dwell-angle variation is probably all that is needed... this is evidenced by the fact that these ignition are 40 years old and the majority are still working fine.

I think I still have a ZX igniter and pickups here at work. If I can rig up the air motor and a scope I'll post the hard numbers.

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 04 Feb 2020 22:26 #818624

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Ok so I was able to do a few runs at work. My buddy at work helped me get things setup, but we were still rushed so this is really only preliminary.

The ZX dwell is quite a bit more efficient than that of the KZ. At 1000 RPM the dwell is about 6 msec (quite a bit better than 17 msec). At 10,000 the dwell is the expected 2 msec.

However, below 1000 RPM, especially during startup type RPMs, the dwell is longer than 8 msec. I measured roughly 10 msec at 450 RPM. So that makes startup using an LS1 possibly problematic. Then again, maybe it won't matter. The spark will be coming about 2 msec early, but that's out of 120 msec for a rotation. Still, I'd rather not have early sparks during startup.

A couple side notes I noticed... unlike the KZ, the ZX ignition is not two independent ignition circuits in one box. Both pickups must be connected and functional in order for the dwell to work properly. With the other set of pickups not connected, the dwell drops to being very short. At times it drops well below 1 msec.

Also, unlike the KZ, the ground side of the pickups appear that they may be able to be swapped. That is, it appears the negative terminal of the pickups are simply hard-wired to ground.

I'll have to look back at the video (I'll post it after I edit it down hopefully with some screen shots) , but I think the igniter box alters the shape of the pickup signal. So how the pickup signal looks will depend on whether it's connected to the igniter or not.
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Last edit: by loudhvx.

Turbo GpZ550 Ignition misfires starting above 10 lbs boost 05 Feb 2020 03:42 #818627

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Awesome!
Thank you for doing that.

I suppose one could use a relay to insert a ballast resistor into the coil +B feed. That would limit coil current whenever the starter is cranking.

Just the opposite to what my MGB does. The MG uses a relay to remove the ballast resistor during start up in order to give the coil extra "juice".

Thanks again
P.S. My 750 Turbo ignitor came yesterday.

loudhvx wrote: Ok so I was able to do a few runs at work. My buddy at work helped me get things setup, but we were still rushed so this is really only preliminary.

The ZX dwell is quite a bit more efficient than that of the KZ. At 1000 RPM the dwell is about 6 msec (quite a bit better than 17 msec). At 10,000 the dwell is the expected 2 msec.

However, below 1000 RPM, especially during startup type RPMs, the dwell is longer than 8 msec. I measured roughly 10 msec at 450 RPM. So that makes startup using an LS1 possibly problematic. Then again, maybe it won't matter. The spark will be coming about 2 msec early, but that's out of 120 msec for a rotation. Still, I'd rather not have early sparks during startup.

A couple side notes I noticed... unlike the KZ, the ZX ignition is not two independent ignition circuits in one box. Both pickups must be connected and functional in order for the dwell to work properly. With the other set of pickups not connected, the dwell drops to being very short. At times it drops well below 1 msec.

Also, unlike the KZ, the ground side of the pickups appear that they may be able to be swapped. That is, it appears the negative terminal of the pickups are simply hard-wired to ground.

I'll have to look back at the video (I'll post it after I edit it down hopefully with some screen shots) , but I think the igniter box alters the shape of the pickup signal. So how the pickup signal looks will depend on whether it's connected to the igniter or not.

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 05 Feb 2020 08:40 #818651

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I forgot, I didn't include the pickup signal in this set of recordings. Their traces were distracting from the coil signal trace.

Notice the dwell is not exactly a function of RPM. That is, it depends on the dynamics of the RPM as well. The dwell at a given RPM may be longer or shorter depending on if the RPM is increasing or decreasing. However, this might not be so drastic on a real engine. The air motor can change RPM much faster than a real motorcycle engine.

I guess I should point out for anyone else coming across this post, the portion of the signal showing the dwell is the small horizontal section at the bottom of the trace. That is what is being measured. The dwell is the duration during which the coil's negative terminal is connected to ground. The rest of the time, it is floating up near battery voltage.

I should also mention, in case it matters, this was running from a 12v battery measuring about 12.5v. That's a bit lower than a running bike. If the supply voltage effects the operation of the igniter, that will have to be looked at more closely later.

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 05 Feb 2020 10:23 #818658

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Awesome scope video.

I can see the drivers on the Igniter circuit board but can't make out what the white rectangular area is.?

Well, too much curiosity.

I removed the board from an old module to take a look.
I will put it right back.

The white rectangle full of SM components has what looks like a microprocessor underneath it.
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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 05 Feb 2020 12:28 #818671

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Yeah, I didn't have the required enthusiasm to unsolder all of those standoff legs. :)

Not sure what's on the bottom side at all.

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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 05 Feb 2020 12:41 #818674

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loudhvx wrote: Yeah, I didn't have the required enthusiasm to unsolder all of those standoff legs. :)

Not sure what's on the bottom side at all.



Max current on those power transistors is 6A and 450V
Good to know the limit.
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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 09 Feb 2020 09:38 #818894

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I bought a used 750 Turbo ignitor off eBay to use on my bike.. Better for boost because It limits max advance to 30 degree.
I can confirm, the zx750 ignitor is a direct plug n play for the zx550.
It's up and running on my bike.

However the ignition rotor does need modification to match the ignitor. It needs to trigger max advance at 30 degrees BTDC.
Easy to do.

No time for test ride today but It should actually run stronger on boost with less advance.
And also less likely to detonate or ping on pump 93.

I've also switched to the 550's original TK carb rack which had been perfectly jetted for my pre-turbo engine.
Following what I had to do with the CVK carbs, I've made the equivalent changes to the TK jetting. With 10 lbs boost, carburetor size is not a concern.

Jetting should be right on but I can fine tune it as needed.
The TK carbs have a much better low speed circuit. They've always worked better than the CVK at low speed..
Cold start circuit too. In fact the small spark plug gaps (.022) don't cause any cold start problems with the TK carbs mounted.
Instant start and smooth running on and off cold start. Better fueling.

Testing this week.
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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 11 Feb 2020 12:33 #819049

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Test riding done..

Fuel metering is perfect with the TK carbs and the 750 turbo ignitor's 30 deg total advance is much better.
I'm running pump 93 with no problems.

Had a small problem yesterday on the first run.
The TK has a "choke" rod you pull out and the cold start plungers open on all 4 carbs.
It has a spring loaded detent to position it but it does not have a return spring. Nor is there a good place for a return spring.
It fully opened under boost. :ohmy: Pushed right open by the pressure. An oversight on my part.
I've since made a mechanical stop that keeps it closed. It has a spring loaded release lever to allow pulling out the rod and then automatically lock it down when you push the rod back in.

No problem after that.

With the new advance curve, power is less on-off.
Boost builds smoother and more predictably and it still builds just as much.

I was on a nice straight back road with 30 mph posted but no traffic and very few houses .
5th gear at 4000 rpm is 45 mph, then rolling on the throttle quickly had me at 103. That's when I shifted to 6th and backed off the throttle.
I'm using a GPS app for a speedometer and it captures top speed. I wasn't looking at the speedometer.

As a comparison..
I had an 07 Bandit 1250 that made 124 RWhp on the Dyno. with just a few mods. It had way more torque but this GpZ is quicker.
I ultimately added nitrous to the Bandit and ran a 25 shot which dyno'd at 150 hp. The GpZ is quick like that. The Bandit was much heavier.
I also ran the Bandit with a 50 shot. The Gpz isn't that quick.

I'd like to replace all the oil cooler and fueling lines with braided hose and AN fittings before I do any long rides far from home.
And the lower fairing needs to be mounted.

Taking a short break for now.

At some point I can video record a test ride.
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Turbo GpZ550 Ignition misfires starting above 10 lbs boost 13 Feb 2020 04:59 #819147

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As for ignition miss at high rpm and boost, I'm leaning toward the following solution.

I'm going to feed 19V to the coils but use a ballast resistor in series to limit current. That way the coils won't overheat/stress at low rpm when dwell time is high.
I'll also use an RPM window switch and relay to bypass the ballast resistor at high rpm.
At higher rpm, when dwell time is low, the coils will receive the full 19V. Coil current will be higher and it should produce a better spark under boost.

The simple solution would be to supply the coils with 19V without the ballast resistor and window switch.
If I knew the coils and ignitor could handle the extra current I would do that.

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