The other day I was looking under the hood of one of my friends. The *cough* civic *cough* had a small air filter on the back of the head that resembles a miniture air intake but without the pipe. He said it releases hot air from recirculating into your intake. If anybody has one of these would you suggest it and could you give a proper discription of what it does because im sure his explanation was scewed.
Thanks

 

Crankcase filter.

Basically all it does is vents the blow-by into the atmosphere. Normally its a "closed" or "sealed" system and what it does is vents the blow-by into the intake charge to be burned off in the combustion chamber. It is supposed to help with emissions but the blow-by is so minimal that it does more harm to the engine than good (Kind of like the EGR Valve).

All you do is pull the hose that runs fromt he back of your valve cover off and remove the other end from the intake tube. Plug the hole on the intake tube with something (I used silicone) and then get a small filter which is called a Crankcase filter (I believe on the Neon it's either 3/8" or 1/4" and stick it on the nipple that comes off the valve cover.

Viola, you've just vented your crankcasse.

Keep in mind though the car is supposedly going to take a little longer to warm up in the winter but it'll supposedly stay a little cooler in the summer because instead of recirculating hot gases you are just venting them to the outside.

 

Engines have now been running them for so long that they do no real harm to the engine and yes it is an emissions concern. While blow by has been reduced these days it still occurs and probably more than you might think. It is why CARB legal CAI's have that tube connection. The car is calibrated today to handle the air flow and won't really gain anything by venting it other than show car looks!