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Discussion Starter #1
This is an off topic post.

Motor:
Single Cylinder from Yamaha XT600
Eaton M12 blower pushing 11 pounds of boost
Megasquirt ECU with oversized injectors, 100 octane fuel
All fuel requirements were met perfectly, timing was fine at 12 initial and 28 total.

The ring land between the first and second rings busted. No signs of detonation. No other signs of any damage or abnormal wear. Fuel was slightly fat. Any ideas?

Thanks in advance,
Propane Steve
 

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"Fuel was slightly fat"

What about fuel puddling if the combo was fat? I have read before that fuel puddling can be as destructive as detonation.
 

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Static CR?

What's the static CR of this engine?

What kind of ignition system are we talking about? Distributor/rotor/wires or coil on plug or what.

For comparison, on a V8 Ford with a 9:1 static CR engine on 100 octane with 11psi of non-intercooled eaton boost, I'd start around 18 total and would probably end up somewhere around 20-22 total. In addition, due to the high intake heat, you'd want to run the thing very rich...11:1.

Does this thing have a bypass valve? If not, be aware that your part-throttle intake temps are probably 230deg F or better; and the engine will probably suffer from incurable tip-in detonation when transitioning from part throttle to WOT due to the superheated air. A bypass valve is required equipment.

A 10:1 CR engine would be borderline untunable on 100 octane; the retard would be so extreme the exhaust temps would skyrocket possibly causing head/valve damage.

The total timing values will move around as much as 4deg depending on how much spark lead is required due to the type of ignition system.

I can't tell you how many 5.0L Mustangs came to me for help after killing engines with Ken Bell superchargers (autorotor screw type, similar to the eaton). More than 10...probably closer to 20. The early ken bell kits had no bypass valves and the ken bell chip ran 12:1 AFR with 24-26deg total advance on CA 91 octane fuel. Disaster for certain; I never saw one that didn't detonate. We would retrofit the system for a bypass valve, run about 8psi of boost on iron heads of 10psi of boost on aluminum heads, tune it for 11:1 AFR with about 18-22 total depending on the engine, drop the part-throttle advance in/around peak torque to avoid tip-in detonation, and they lived a long happy life. They're so arrogant down there, they wouldn't listen to anyone. They repeated their mistakes with the DOHC Cobra kits for the 32V engine and killed a lot of those as well. The failure mode was always shattered rings and/or broken lands...the cause was always detonation.

Hope that helps.
 
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