DIY: Secondary Air Filter Removal

It doesn't make the cylinders have any more volume, but it will allow more air to flow into them allowing for complete combustion instead of rich combustion

 

thats volume.
"more air" is more air, less restriction means less work to acquire volume of air.

 

Sorry I read your first statement wrong. So yes, more volume of air in the cylinders, which is a good thing. And if the fuel injector does in fact give the exact amount of fuel needed for stoichiometric making it a useless mod, how do I describe 1+ mpg bump? The only reason I can think of is that the fuel injectors are only accurate to a certain point, and if they have to burn lean or rich, they're going to burn a little on the rich side, therefore wasting a small amount of gas. So my reasoning is that I'm getting a little more air in there which is completing the combustion, making it so that I'm not burning rich and leaving any unburned fuel

 

+1 gain can be atmospheric condition's and ECU tuning on that day. If your management system is in range of the ECU's files for adaptive long term fuel trims then you're not going to run rich, if you were/are a CEL would be flagged as the range either low or high would be exceeded.

An Engine is simply a pump, if you make the restriction of air going in and out less work then you have made the pump more efficient not necessarily more power. Granted if you make Major change you will not only achieve better RPM response but will undoubtedly pick up HP.

 

I'd agree with that. I never really claimed to have more power, and I wouldn't have noticed anyways because I was driving conservatively and keeping it under 2k rpm. We'll see if I can keep up the same mileage, but 19.9 mpg city driving in a high elevation city is pretty damn good for a truck

 

Everyone should get better mpg at high altitude. Thinner air = less power = less gas.

More reason that your intake doesn't matter, your flowing less mass of thin air.

Still your throttle plate is the bigger restriction no matter what intake you have at 2000 rpm.

Not magic, just inconsistencies between tanks, a little extra wind a few days, cooler or warmer temperature, better driving, seems you are now hyper conscious of your mpg.

Here is a graph of every tank since my truck was new, usually a few mpg difference between tanks and different time of year.

 

It's not 1972.
A restricted intake will not drag more fuel from a carb's bowl.

Read the PDF on the link that wads posted.

ZERO difference in fuel economy.

0.6 seconds difference in 0-60 times on a Dodge Charger.
The comparison is between a new, clean filter, and a filter that is so blocked that it causes the intake vacuum to distort and destroy the filter.

 

I removed mine today. After looking at it the one obvious observation that I made was that it could (and most likely does) restrict air flow. Take a vacuum hose from a shop vac and try drawing air through BOTH filters, then try drawing air through the air filter alone. I guarantee that you will notice a difference. Just my two cents.
Ken

 

You are making some wild speculations that aren't accurate. The fuel injectors are getting information from the MAF which is after the air filter and before the throttle plate. You got rid of something that is not a restriction at all at 2000 rpm because the throttle plate is the greater restriction so you are absolutely NOT getting "a little more air in there" that the fuel injection brain doesn't know about and therefore a leaner mix.

I estimate I get minimum 15% better mpg at 5300 ft than at low altitude after driving from Boulder to Mississippi and back.

 

You're guaranteeing something based on an assumption and passing false information. I ran tests with and without the charcoal filter and the maximum airflow didn't change. Not that a shop-vac would prove anything, but the filter is so free-flowing a vac won't even hold it up.

 

At low throttle the filter restriction isn't measurable and even removing the entire intake tract above the throttle body wouldn't change the volume of air entering the engine. Even if removing the filter allowed more air into the engine, the sensors would detect it and add more fuel anyway. If you did add more air to the cylinders without adding more fuel it would run too lean to make complete combustion and you'd loose mileage.

 

Did the removal the other day and installed the AFE oil free filter. My truck now gets 31 mpg and hauls ass!! OK, I made all of that up (except I did remove the secondary air thingy and install the AFE filter). I can totally see that the little charcoal thingy could definitely restrict air flow. It was super easy to remove and is definitely worth a try. Thanks for the write up, MUCH appreciated!!!
Ken

 

Super easy to remove? Yes
Worth a try? No

I saw no difference in MPG, power, or throttle response on my 2.7.

 

Then explain why some people say they do?

 

People say that magnets on their ass makes their arthritis feel better.

 

6 coffee enemas a day show positive results too.

 

I've found it does nothing for a 4.0L, I wish I had never taken that charcoal filter out. All it does is mess the ecu up cfm wise. The bottom end torque has disappeared a bit. For some reason the mass air flow and the ecu are picky about mods done to the intake. You can do what you want to the intake, but without tunning the ecm for the mods you have done; I'm afraid you're kicking a dead horse.
From all the other threads I have read concerning fuel air/ratio and changing the OE engine set up you need a tunner to get the most out of the mods done to the engine.

Right now I'm running a stock air filter and no charcoal filter, it runs a bit rich.
Sure if you could get more cfms rammed into the cylinders you would have more efficiency, but what's going to force the air? A supercharger maybe?

I don't know anymore, it takes far too much money to try and outsmart some thing that is already enginenered to do something specific .

 

I don't know that I would say that it is not "worth a try". If some people are getting positive results, why not give it a try, especially if you have a 4.0L?
Ken

 

Some people want to believe they are getting positive results based on 1 tank. Look through this thread, was a time lots of people repeated "does nothing for 4L, works for 2.7L" but there is no evidence.

It can't help mpg, it is as simple as that.

 

It takes like three tanks of fuel before you can get a more accurate idea on fuel mileage. The injectors have to learn the fuel
Consistency before you get a good reading.
Like I say I think our ecm systems don't have much room for change without out tunning it.
I had my charcoal filter off for some time now, it revs a bit quicker but that's it. Try adding a k&n filter or afe without the charcoal filter, all I found was bottom end torque loss and fuel consumption not to mention fine dirt penetrates the afe filter.

I understand why this mod is done, it's not worth it on 4.0L.