Have been playing with the adjustable cam sprockets on a B18C1 here, and I am realizing that I may have been overly aggressive with my dialing in. Even on cool gray overcast days, going up hill at low RPMs produces a steady faint tinking of detonation. It's not loud, but it's constant, so I assume that the ECU is getting the word from the knock sensor and is pulling spark timing back as far as it can.

Part of this problem is that I'm in California, where $2.50/gal buys you an absolute maximum of 91 octane. Effing dishwater. Don't get me started on bitching about our crappy fuel. Anyway, I'm stuck with 91 until I decide to move to a saner place, and the engine isn't happy with that.

Whenever someone asks me about detonation, I always tell them they have a few options:

(a) switch to higher octane, if available;
(b) detune the engine by retarding timing, etc;
(c) cool the intake charge if possible.

I can't do (a) easily without spending a fortune (100-octane unleaded is available but for $6/gal, and nowhere close to me). I don't want to do (b); the engine is right at a sweet spot for the powerband right now.

That leaves (c). The engine compartment is pretty well cooled and I have no real signs of heat dissipation being a problem. But the underhood air that the stock intake is pulling in is still warm, to say the least.

I am wondering if a CAI like an Icebox would give enough of an improvement on intake temperatures as to hold back this last annoying bit of rattle. Has anybody got any anecdotes, or better yet, real data?