This started a couple days ago..

At or maybe 100 RPM before I hear the VTEC engage and reach the engagement point (3500 RPM), I hear a metallic noise that sounds something like ripping tinfoil. It's very irritating and I'm very worried...anyone know what causes this? Is the piston that activates VTEC shot?

 

Vtec is engaged via solenoid, that could maybe cause a sound like that. And the fact that it happens 100RPM before you "hear" vtec engages, I'd entertain the possibility, that vtec could possibly be engaging before you hear it. That would make me troubleshoot the vtec system.

Also, maybe it is the oil windage sucking up more oil, right before vtec, or a semi blocked passage somewhere, and you're hearing a high pressure oil sound.

I'd consider: oil change, check for metal fillings. Maybe some new grounds if yours look shot, check wires for frayed spots. And then after all that, maybe pull the vtec solenoid, I hear there is a screen that you can clear out.

-PHiZ

 

Always look to the simple solution first. It's probably just something rattling at a particular RPM. The fact that it's around VTEC is likely more of a coincidence than anything serious.

Could be the exhaust manifold heat shield. Those are notorious for rattling. Something along those lines.

 

That's just like a canuck for ya, responding with a well-reasoned, sensible answer, while the american goes grasping wildy at straws proclaiming the sky to be falling.

You guys are such bastards.
-PHIZ