Finding knock

[Aubrey]

G'day
Recent dyno showed a lot of knock at WOT, E85 timing is coming off from 30deg to about 27deg, and so power is down.
I've taken off the JLT oil catch can, because it rattled and is not fastened anywhere, as well as the engine cover.
Any other areas to look for knock?
Thanks!

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[NoVaGT]

Have you considered that your engine is actually suffering from detonation, and there's no phantom "knock" to chase down?

 

[Cobra Jet]

What are the plugs gapped at (and how old/new are they)?

Are you N/A or forced induction - if FI, turbo or supercharger?

I mean you’re giving almost no info about your S550 and to diagnose or help, it’s needed.

 

[ChiTownStang26]

Did you test the corn in your tank? Maybe it's way lower than 85% ethanol.

 

[Bluelightning]

I'm assuming that since you are seeing 30 degrees of timing that you are NA? If that's the case, I would look at the e85 you are running especially if you are running an E85R tune. If you are boosted, 30 degrees seems like a lot even on e85, and if the ethanol content isn't 85% or higher, you are likely getting actual knock.

 

[Aubrey]

Thanks for the feedback, all good. I’ll get the spark plugs checked/replaced. The ethanol may need another refill to get all the other fuel out, although it was pumped dry.

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