DIY: Secondary Air Filter Removal

Just removed the secondary filter and installed a k&n air filter on my 4.0 v6. Noticed a 200 to 250 rpm decrease at 70 mph. Should help on the gas mileage but i havnt put a tank through yet so i'll let yall know when i do...

 

Anybody tried an underdrive crank pulley for more power and better mpg. Seems like a good idea? Might have a cooling prob when hot weather and towing hard, or maybe stop and go too? I don't thin the alt, p/s or a/c would be affected to much, maybe at idle a little? Anyone have experience?
Thanks
gearhead69

 

I removed the secondary charcoal filter and haven't seen any difference on my '09 V6. It did not look like the filter offered any resistance to airflow at all. Maybe they changed it to be less restrictive.

 

HOPS, I'm sorry but the secondary air filter is not related in any way to your gear ratio. But could help your mpg by uncorking your airflow.

 

When claiming that there are no measurable improvements to mileage or performance please keep in mind that there are two completely different engines and several different drive trains in these trucks. What might be unnoticable on a supercharged V6 4WD automatic driven enthusiasticly can make a noticable difference on a carefully driven 2.7L 2WD 5 speed.

 

Just not sure how air flow relates to lower engine RPM at driving speeds, it's not like you changed your transmission fluid to a thicker viscosity or locked the tranny or better, if you have a manual tranny... How can this corrilation be made. I would think they are not related at all and just reinforces my theory below.

After reading all this and other related threads (farmed out from this one), it looks that there may be a minor improvement in MPG, minor being the key word. Some of the larger MPG improvements (2 MPG or more) could be easily attributed to a lighter foot on the pedal. You may think you're driving the same but you are trying to strech that fuel and as a result get more MPG.

I hope this makes sense to everyone. With that in mind I'm going to replace my air filter with a dry high flow filter as most of my driving is freeway speeds. If I can squeeze a real 1 MPG more, I'm for trying it.

Joe

 

I just tore it out not thinking, do they check for the secondary filter? As long as its in there sealed around the edges blocking emmisions it will pass right or are you not allowed to tamper with it at all?

 

Youre fine. But before you tare at your car again, think.

 

Thanks, and will do

 

has anyone with the 4.0L noticed a difference either in MPG or power?

 

No increase in mileage AT ALL. I removed it and could just about see through it never mind air flow thru the thing. It is considerably more porous than a freaking sieve. Just leave it in place it offers absolutely no restriction to airflow. At least the one on my '09 I am not sure about any earlier models. I removed mine for no good reason...same as running super unleaded.

 

well roland has a point. my 4 speed automatic, when warmed up, runs at about 650 RPMs i can cruise all the way till I hit 50MPH at 1500 RPMs. so I wouldnt say that its totally not worth it. in my case it drastically helped with rpms and even MPG

 

I was prepared to do this mod but found that no secondary filter is installed in my truck. My build date was 1/2008. Could it be this secondary filter is not standard in the NH area...or have the engineers relocated the filter?

 

it should stil be there. right above your regualr paper air filter in the air box.

 

Ditto! No need to remove it. My MPG didn't improve. If you want better performance do the throttle body cleaning.

 

Did this last night, took 5 mins. Removed the K&N filter, took a flat head screw driver and popped the thick charcoal filter off... Checked to make sure there was no plastic bits in the housing, even though there is a metal deal that keeps crap like that out... put the K&N back in, no issues. Too early to tell about MPG, but throttle response is noticeable. Good little mod

 

Yeah, I guess people don't read the first post. This was really intended for the 2.7L 4 cylinder engine (which I no longer own).

I did not remove the secondary filter on my truck. However, my URD TCAI completely removes the filter housing from the truck. I have my original housing complete and in tact just in case I want to go back to stock.