Joe Hooper (Pit Stop Performance) recommendations for camshaft tuning.

It’s quite possible that installing a second spark plug would help. As I mentioned to Zed 1015, I’m currently running a Dyna S and an MSD MC-3. I suppose I *should* be using an MSD MC-4 instead... but unfortunately, that’s not an option for me right now. By the way, why aren't you considering the Suzuki ignition system? Judging by the description, it ought to perform quite well, especially in the mid-range and during acceleration. Plus, the reliability of factory ignition systems is far superior to that of the Dyna.

It’s the later GPZ system I am using. Back in the day tuners adjusted the advance curve by changing the springs on the advancer - stiffer springs slow the advance

Never tried the Suzuki ignition.
I run Dyna S 's on all my zeds except the turbo.
On my supercharged one i'm running twin spark and Dyna with new springs on the advancer and the stops built up to retard full advance whilst maintaining a static figure of 10 degs.
I had severe detonation on hard acceleration which i mostly cleared by gradually retarding the timing to it's current 20 degs full advance and tuned the rest out on the mixture.
On the blowers current gearing ( around 1 to 1 in relation to the crank ) it runs very well but if i change the gearing to speed up the blower and increase the boost the detonation reappears and i have to recalibrate the timing and the mixture.
This is on premium pump gas and for the higher gearing ( which is supposedly for racing ) i really should run a Dyna 2000 ( or fit my spare BHP hei with boost retard but lose the twin plug as it only runs a 4 lead dizzy )  and some proper VP C16 race fuel. 
Either way it's down to the octane rating of the fuel you want to use and whether you want the convenience of filling at any gas station or just do trips within the range of a full tank of high octane from your home and back.
Even with dual plug and an all singing all dancing ignition you are still likely going to have to drop the compression into the 10's to run pump gas.
As for the Dyna S reliability, I'm on 27 years with the one on my Z1R, 18 years on the Supercharged Z and 12 years on my Zeph1r cafe with no problems.
 


 

Thanks, I actually did that on a car a long time ago. It takes a lot of time and is a real headache.))) Plus, you need to know exactly which springs to use as replacements and what they come from.

Да, я действительно сейчас пытаюсь перейти на обычный бензин с заправки; наше топливо с октановым числом 95 эквивалентно американскому 91. У вас большой опыт и терпение — настройка момента зажигания — действительно сложное дело. Я раньше занимался этим на гоночных автомобилях, и это всегда компромисс. В дрэг-рейсинге мы использовали системы зажигания от GSX1100 на двигателях KZ, и они, казалось, работали довольно хорошо. Dyna S надежна; я имел в виду Dyna 2000 — она внезапно вышла из строя, поэтому я перешел на Dyna S. Я действительно не хочу тратить еще 400 долларов. Я смирился с тем, что мне придется снизить степень сжатия, но здесь возникает интересный вопрос. Допустим, впускной клапан закрывается при 65° с распредвалом Andrews X3, тогда как с распредвалами GPZ1100 1983–1984 годов он закрывается при 70°. Следовательно, динамическая степень сжатия будет выше с распредвалами от GPZ, даже несмотря на то, что продолжительность открытия клапанов значительно короче. Тем не менее, для большинства владельцев GPZ, использующих поршни Kawasaki (степень сжатия 9,5:1), распредвалы от сторонних производителей работают хорошо. Что вы думаете о динамической степени сжатия 8,25:1? Или мне следует снизить её ещё больше? Спасибо. Кажется, переводчик работает не совсем корректно. Извините за это.

Curious as to what this person said, I used google translate.....

Yes, I’m actually trying to switch to regular pump gas right now; our 95-octane fuel is equivalent to the American 91. You have a lot of experience and patience—dialing in ignition timing is a really tricky business. I used to do this on race cars, and it’s always a compromise. In drag racing, we used GSX1100 ignition systems on KZ engines, and they seemed to work pretty well. The Dyna S is reliable; I was referring to the Dyna 2000. — it suddenly failed, so I switched to a Dyna S. I really don't want to spend another $400. I’ve resigned myself to having to lower the compression ratio, but an interesting question arises here. Let's say the intake valve closes at 65° with the Andrews X3 camshaft, whereas with the 1983–1984 GPZ1100 camshafts, it closes at 70°.  Consequently, the dynamic compression ratio will be higher with the GPZ camshafts, even though the valve duration is significantly shorter. Nevertheless, for most GPZ owners using Kawasaki pistons (9.5:1 compression ratio), aftermarket camshafts work well. What do you think about a dynamic compression ratio of 8.25:1? Or should I lower it even further? Thanks. It seems the translator isn't working quite right. Sorry about that. 

Most aftermarket street piston kits come at a advertised compression ratio in 10.00 or 10.25:1, some specialty racing pistons up to 13:1 off the shelf. Some blank or custom pistons are capable of 16:1 for all out NA racing, Turbo use pistons at 8:1 ratio or lower.

The street pistons are targeted for pump gas use using stock combustion chambers and mild lift cams. The drag versions at higher compression will work with stock chambers but they need to be check fitted. All of the higher dome drag pistons have deeper valve pockets for high lift cams. Pump gas will start to detonate at around 11:1 depending on setup variables.

Some of the pictures you posted of aftermarket pistons had very large domes so I suspect they were drag racing versions.

All of the drag pistons I have seen converted for street use will have the dome top milled down. Conventional wisdom says you need to maintain a piston dome thickness of .150" for NA engines and .300" for turbo engines when milling the tops to decrease compression. You can also deepen the valve pockets to gain additional volume removal.

You can also reduce compression by modifying the combustion chamber edges or plunging the valve pockets but this is a more permanent solution whereas pistons can easily be replaced back to a higher compression version.

If there aren't any piston to valve issues currently isn't the easiest and least permanent solution a spacer under the barrels (or is there a reason for not doing this ?)

You are absolutely right about the piston crown thickness and the various ways to lower the compression ratio—thank you. However, the specific question I have concerns the target dynamic compression ratio. The intake valve closes at 65° ABDC. Previously, I had a static compression ratio of 10.5–10.6, resulting in a dynamic compression ratio of approximately 8.5–8.6; I was able to drive normally using 100-octane fuel. I want to lower it to run on 95-octane fuel. So, what dynamic compression ratio is required for 95-octane fuel?In a car with a less-than-ideal wedge-shaped combustion chamber, the engine performed and drove very well with a dynamic compression ratio of 8.25. However, on the Kawasaki—which features a Hemi-style combustion chamber—the tendency toward detonation is higher; consequently, the compression ratio must be lower when using commercial-grade gasoline...

If the goal is to achieve higher power and efficiency, then theoretically, the squish effect within the combustion chamber should be minimized. Specifically, the piston should stop 0.2–0.3 mm short of the cylinder block deck; when combined with the cylinder head gasket thickness, this results in a total clearance of 1.2–2.3 mm, which is the optimal range for this gap.

For 95 octane you want up to 8.2 to 1 dynamic.
You can retard the intake cam timing ( and/or advance the exhaust ) to reduce Dynamic compression without changing the static compression .
This also shifts power further up the rev range.
High lift cams may allow up to 11 to 1 static comp due to the later intake closing point which reduces the Dynamic compression.

Zed, thanks! So, I guess I'll go with 8. Especially considering I might try installing cams from a GPZ Uni-Trak later on... By the way, if the GPZ really does have a valve closing point of 70°, then its dynamic compression ratio is 7.2.)))