Built motors and detonation
08-01-2013, 01:28 PM
#182
Saw this thread during my build and thought I would luck out with my setup. Well, obviously no one is immune 
Figured I'd share my latest disaster.
Check out the pics for the carnage. The cylinder scoring wasn't horrible since I shut the engine off as soon as I heard things going to hell, lol. #1 had a portion of the crown removed, and #1 and #4 had severely cracked skirts. #1 spark plug was mechanically crushed from the debris.
No wideband or datalog readings, unfortunately. The engine was running rock solid for 4 months on this tune, but the day that this happened it was about 90 degrees out so I'd imagine the IATs were sky-rocketing thanks to my small-ish Mishimoto z-line intercooler and in addition to running at 20-22psi daily through a GT2871R.
Always used 93 octane and BKR8E-11 plugs. I don't remember what the p2w clearance was, but it was within spec when I measured it according to the Miata workshop manual.
Machinist said 100% severe detonation, likely from too aggressive timing. Bottom-end assembly looks OK - crank and bearings still good, and pistons were starting to melt in intake valve relief cuts (cats tongue feel). I'm going with 83.5 (+.020) Wiseco 8.5-8.8. Also looking into Meth injection for throttle>70% & over 10psi. I was also thinking of upgrading intercooler and being more aggressive with IAT dependant retard and fueling.
Figured I'd share my latest disaster.Check out the pics for the carnage. The cylinder scoring wasn't horrible since I shut the engine off as soon as I heard things going to hell, lol. #1 had a portion of the crown removed, and #1 and #4 had severely cracked skirts. #1 spark plug was mechanically crushed from the debris.
No wideband or datalog readings, unfortunately. The engine was running rock solid for 4 months on this tune, but the day that this happened it was about 90 degrees out so I'd imagine the IATs were sky-rocketing thanks to my small-ish Mishimoto z-line intercooler and in addition to running at 20-22psi daily through a GT2871R.
Always used 93 octane and BKR8E-11 plugs. I don't remember what the p2w clearance was, but it was within spec when I measured it according to the Miata workshop manual.
Machinist said 100% severe detonation, likely from too aggressive timing. Bottom-end assembly looks OK - crank and bearings still good, and pistons were starting to melt in intake valve relief cuts (cats tongue feel). I'm going with 83.5 (+.020) Wiseco 8.5-8.8. Also looking into Meth injection for throttle>70% & over 10psi. I was also thinking of upgrading intercooler and being more aggressive with IAT dependant retard and fueling.
Last edited by JustinOMGWTF; 05-26-2020 at 11:12 PM.
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08-01-2013, 03:12 PM
#193
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Intake cam retarded 7 degrees!?
Also, Im surprised at xenocron, I thought they would be a little better than that.
Although its a bit weird it held together for so long before popping. Whats your fuel system like BTW? You running used injectors?
Also, Im surprised at xenocron, I thought they would be a little better than that.
Although its a bit weird it held together for so long before popping. Whats your fuel system like BTW? You running used injectors?
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08-01-2013, 03:45 PM
#198
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They work, they just have poor atomization compared to modern injectors.
The tune is going to have to be re-worked anyway, it shouldnt be a big deal to offset the fuel table for different injectors.
The tune is going to have to be re-worked anyway, it shouldnt be a big deal to offset the fuel table for different injectors.
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