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1980 KZ13 Project 1 month 3 weeks ago #27643

  • biltonjim
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Divman - About that 10,800rpm - is that safe from a piston speed point of view? This engine has quite a long stroke. I'd be interested to hear your thoughts.

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1980 KZ13 Project 1 month 3 weeks ago #27644

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Kawboy wrote: I may be able to use 6 individual coils (D585's) in wasted spark.


Curious why you'd want to use a 'wasted spark' setup when running individual coils - you'd be cycling the coils twice as 'fast' as they need to be - could be an issue for the coils at higher RPM.
Hello from Canada's We(s)t coast.

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1980 KZ13 Project 1 month 3 weeks ago #27649

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Bucko wrote:

Kawboy wrote: I may be able to use 6 individual coils (D585's) in wasted spark.


Curious why you'd want to use a 'wasted spark' setup when running individual coils - you'd be cycling the coils twice as 'fast' as they need to be - could be an issue for the coils at higher RPM.

Currently, the bikes running wasted spark fire on every revolution (which is as you mentioned, twice as often). 2 spark plugs fire. The one on overlap fires at a reduced voltage compared to the one on compression stoke due to the ionization voltage. One plug fires center electrode to ground electrode, the other fires ground electrode to center electrode. By firing 2 individual coils simultaneous, both plugs fire center electrode to ground as they should although there is a "wasted spark" on the plug that is under overlap.. The only reason I would do this is because the Microsquirt only has 4 ignition outputs. The Megasquirt 3 has 8 ignition outputs which would run coil on plugs for up to 8 cylinders which i would prefer but the physical size and cost put it outside of reasonable. Now the Spitronic unit looks very promising since its Ultimate or the premium model has 8 ignition outputs and 8 injector outputs in a physical size that could be fitted under the seat or... and the cost is less than half that of the Megasquirt. Needs further investigation and I would really like to here from Divman about his experience with this unit and how he came to go this route. It's not a well known ECU on this side of the planet but maybe more well known over in Europe or Africa where its made. I'm not aware of any support in North America.

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1980 KZ13 Project 1 month 3 weeks ago #27654

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Hey there
Not too worried about RPM, with the new set-up she is still making power at 10K on the Dyno graph, hence the limit of 10800.
She still sounds and perform quite happily.
Bear in mind I don't ride her at the limit all the time, use RPM up to about 9K.

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1980 KZ13 Project 1 month 3 weeks ago #27655

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Hey Kawboy
In answer to your question re injectors - I;ve used 250cc injectors out of a Golf iv 1800 20 valve.
I run original coils with NGK BR8EG plugs and she runs fine at high RPM
I had to make up my own fuel rail for space under tank.
Bosch fuel pump with external pressure regulator set at 7 bar.

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1980 KZ13 Project 1 month 3 weeks ago #27658

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Divman wrote: Hey Kawboy
In answer to your question re injectors - I;ve used 250cc injectors out of a Golf iv 1800 20 valve.
I run original coils with NGK BR8EG plugs and she runs fine at high RPM
I had to make up my own fuel rail for space under tank.
Bosch fuel pump with external pressure regulator set at 7 bar.


So much to comment on here
6 - 250cc injectors will support 250 BHP @ 44 psi so these injector are oversized and you're running them @ 101.5 psi which is 2-1/2 times normal operating pressure. I'm surprised that you can control the injectors at low rpm's since the delta time would be so small.

BPR8EG's(which NGK.com show no reference to yet I remember the "G" series plugs) are 2 heat ranges colder than the stock plugs and you can get away with these without fouling plugs? These bikes are known for oil fouling and BPR6 seems to be a compromise that we manage to live with.

10,800 rpm and still pulling power. Almost all engines pull their highest power (torque) at about 3/4 maximum RPM which for the KZ should be around 6,000-6,500 RPM and highest BHP near valve float which usually happens near redline and you're pulling to 10,800 RPM so you haven't achieved valve float at 10,800?

10,800 RPM translates out to an average piston speed of 5031 Ft/min. Most engines are designed to not exceed 4,000 Ft/min and race engines to about 4500 Ft/min and the reason is lack of control of piston ring flutter.
Cut and paste from www.musclecardiy.com " The more power strokes per minute, the more power available to do work. Consider the 2000 Ferrari Formula 1 engine that has a stroke of 1.6-inch (40.64 mm). At 18,000 rpm that's a mean piston speed of 4,800 fpm and a peak speed over 7,536 fpm, or more than 85 mph at mid-stroke."
So you're pushing piston speeds higher than an F1 engine without catastrophic failure? With a redline of 8500 rpm and a stroke of 71mm on the stock engine, the average piston speed is 3960 Ft/min average and that's up there.

I would still like to hear which Spitronic ECU you chose (Mercury 2 or the Orion and which level Standard, Intermediate, Advanced or Ultimate) and if you are controlling the ignition coils it.

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