I just installed a K&N air filter on my 2007 prius, and noticed there is a secondary air filter in the lid of the air filter housing. Do you think I could remove that secondary filter? Thanks
I don't have Gen. II so I am curious to see what this secondary filter is? Could you post a picture? Is it before or after your Engine Air Filter Element in the airflow? If it is before it could be a pre-filter did not know autos had those. If it is after it is probably an activated charcoal filter that is part of the vehicles emissions controls and you would not want to remove it.
Since you have already installed a K&N which passes 4 or 5 times more dirt than a paper filter, why not remove the secondary filter and pass even more dirt.
xs650 - I'll assume you work for one of the paper filter companies. Take a look at the reviews. The K&N filter in my pickup has way more dirt embedded in it when I clean it than I've ever seen on a paper filter.
Data is not the plural of anecdote. Compare K&N's own filter efficiency numbers with paper filter numbers.
06' I didn't(remove the secondary filter), love my K&N Take it out twice a year and clean it, stick it back in, just like the cabin filter... Listen to the motor when accelerating(didn't know there was one), couldn't hear it with the stock filter, need one for my nostrils, to much dirt in the atmosphere I also love the Nitrogen in my tires(no need to add more air every three weeks, after checking pressure)
The "secondary air filter" is a charcoal filter and its purpose is to prevent HC from rising out of the throttle body and into the atmosphere. Yes, you could remove that but then your Prius will pollute the atmosphere needlessly.
with do respect we already had this discussion. Yes the paper filters more efficient then oiled gauze in trapping particles. There was a study which found that using paper filters will increase interval btw engine rebuilds by ~20%. Little known that the study was done on open pit mining equipment, and use of paper vs oiled gauze air filters increased operational time from 18,000 to 22,000 hours, while costing about 30,000USD in filters. For records 20,000 hours at nation avg 35MPH is ~700,000mi. One can only hope there arn't many Prii which operate in such harsh environment as open pit mine.
The oil in the K&N air filters can be picked up in the inlet air stream and foul Mass Air Flow sensors. This provides incorrect air flow rates to the engine management system. I would not use a K&N air filter on a computer controlled engine.
Re: Pic for DustOff Cool thanks I have not opened mine up yet and was too lazy to go out and investigate. That is a charcoal filter and part of the emissions control system as stated in post #2 by me and post#7 by PW.
