Hydrocarbon Trap Filter

[JasonA]

I was looking for info on that hydrocarbon filter in the lids of our air boxes. It appears, at least from the text on this website (link) that it actually catches hydrocarbons ESCAPING from the engine after it's turned off, rather than further filtering INCOMING air:

Also, the TRD setup retains the California Air Resources Board's required hydrocarbon filter that appears in the factory filter system, so the TRD intake still captures polluting vapors that may escape when the vehicle is parked.

[TrdSpeed140]

but when the car is off the throttle is closed, there can't be much of anything getting out of the engine with it off. oh those wacky japanese engineers

[JasonA]

I happened across this this morning:

The "secondary filter" that you mentioned is probably the carbon filter located in the air cleaner housing cover. Its purpose is to trap hydrocarbons released from the PCV system and intake manifold.

[JasonA]

Interestingly, apparently some Fords also have a hydrocarbon trap. At least the Mustang does:

http://www.vividracing.com/catalog/k...8-p-11523.html

[JasonA]

It appears like this is just the "next step" in containing crankcase gasses. Back in the '50s, where were no PCV systems -- the crankcase was just vented to atmosphere. Then the PCV system recycled those gasses back into the engine, but that could only occur when the engine was running. I guess somebody identified the potential for gasses to escape when the engine is off, so they started installing these hydrocarbon trap filters into the intake systems.

I know they're staked into place, and are not meant to be removable. I'd like to remove mine, but I don't want to just butcher-cut it out. I'm going to see if I can figure a half-way clean way to remove the filter from the box, and maybe even make it "replaceable" if I want to put it back in.

[mikered30]

Anyone in CA that is thinking of removing it, keep it incase you have to reinstall it.

[JasonA]

I removed mine tonight. It's a rather thin "filter" of what appears to be small charcoal pellets in a fiberglass batting. I didn't cut it out, but I couldn't very cleanly remove it either. I used a small flat blade screwdriver against one of the sides of that "filter" and pried inward, and the plastic frame of the filter eventually cracked, and I could take the whole thing out from there. So I had to break it to remove it. But it's out now, and you unless you knew it was there, you'd never know anything was missing at this point.

Again, it was fairly thin, and I don't think it was much of a restriction, and probably wasn't worth removing. I'll see tomorrow, though, if there's any more pep.