Aftermarket air filters on modern engines?

[Dirtman]

If it has worked since the truck was new it should work after you have the engine all apart.

IMO check for leaks.

First rational post... i never checked the numbers with the old stock filter cause I only had it about a month before putting the k&n on. The truck has always run a k&n and since the first time I checked fuel trims they were in the +8 range. If you read some of my other post i suspected a vacuum leak and went nuts sealing everything.

My fuel trims now stay 10.2 at idle, 9.8 cruising at 65, and lowest is 5.5 full throttle up a hill. Long term. Thats a fairly good ratio of high vacuum to no vacuum so I'm not seeing a vacuum leak being an issue anymore. If im wrong correct me...

 

[Dirtman]

Am i being scientific or just over thinking numbers and need to put the scanner down... i checked a jeep i worked on and those numbers were like 23% idle 0 at 2500rpm... i was like damn thats a leak... but wasnt my problem to fix.

 

[85_Ranger4x4]

If it runs ok and isn't setting a CEL I guess I wouldn't worry about it too much.

I thought it was running rich after you got it back together.

 

[97RangerXLT]

You people are worthless...

not really... we can all serve as a bad example.

AJ

 

[Dirtman]

If it runs ok and isn't setting a CEL I guess I wouldn't worry about it too much.

I thought it was running rich after you got it back together.

It was running on the border of a CEL... a normal person wouldn't care. I do... +20 or -20 sets a code. I was at +17...

 

[G8orFord]

Isn't that what the MAF is for? The PCM should compensate and adjust trims based on the MAF readings. I'm relatively certain that when I install the M90, I'll be pulling more air than the stock system alone ever could, but, according to ModBoxx, the base setup does not require any tuning. It does require a better fuel pump though.

 

[Dirtman]

Maf reads airflow. Computer is set from the factory to know grams per second at certain ranges and it adjusts fuel trims up and down as airflow changes with maf and o2 readings. So yes it compensates but that is fuel trims... more air = higher fuel trim from factory settings. Get too high or too low and CEL goes on.

 

[adsm08]

The computer would be able to compensate things to a degree, however on an EFI system the computer's ultimate goal is to make 14.7:1 air/fuel ratio. So if you add more air you add more fuel, end of story. More air + more fuel = more power.

Now an engine that is making more power doesn't have to work as hard to do it's job.

 

[Dirtman]

The computer would be able to compensate things to a degree, however on an EFI system the computer's ultimate goal is to make 14.7:1 air/fuel ratio. So if you add more air you add more fuel, end of story. More air + more fuel = more power.

Now an engine that is making more power doesn't have to work as hard to do it's job.

But that compensation is the positive fuel trim?

 

[sgtsandman]

The only negative I've seen from different articles and so on with oiled, gauze filters like the K&N is the potential of increased engine wear due to their lower filtration ability compared to a standard engine air filter. Meaning they let in more dust that leads to to more engine wear. I have no proof to provide one way or another on the subject. So it may all be considered anecdotal. To me, it makes sense, so I stick with a good quality paper filter.

 

[adsm08]

But that compensation is the positive fuel trim?

Well, more air requires more fuel. More fuel would be reflected in a positive fuel trim, but the fuel trims grow to the positive for other reasons as well.

Engine wear, injector wear, lower fuel pressure, worn O2 sensors, these will all drive fuel trims to the positive.


The computer is told to "weigh" the air coming in and add one pound of fuel for every 14.7 pounds of air that come in. It isn't told why, just to do it. Then it is given a table of other compensations to make in response to the input from the oxygen sensors. The short term fuel trims are driven 100% by the signal from the oxygen sensors, the long terms are a sort of rolling average of the short terms. If short term fuel trims are positive the long term will go up until the short term begins to level out. You can see this with clearing the KAM. The long term will react very quickly right after the memory is reset, and as more data is gathered they settle down.

 

[Crosscut_Drifter]

I only use OEM air filters. They get the job done and no risk of messing up your MAF from the filter oil.

I used to be into "free flow" intakes and exhaust for a couple of my projects, followed by a custom chip as a first stage mod. Yeah, I'm dating myself.

 

[85_Ranger4x4]

The only negative I've seen from different articles and so on with oiled, gauze filters like the K&N is the potential of increased engine wear due to their lower filtration ability compared to a standard engine air filter. Meaning they let in more dust that leads to to more engine wear. I have no proof to provide one way or another on the subject. So it may all be considered anecdotal. To me, it makes sense, so I stick with a good quality paper filter.

Extra dust really seems to be a bigger issue on boosted engines and/or high dust enviroments.

Lots of Power Strokes have been dusted from open element/oil type air filters.

 

[G8orFord]

Exactly, more air in will require more fuel to keep the balance, but less "foot" makes it work out in the end.

 

[8thTon]

If the only thing you changed was the filter and the fuel trim moved more negative, then the K&N must flow more air because the computer had to add more fuel to keep the mixture correct. I don't know if that was a long or short term trim though.

However, you're going to use your foot on the gas pedal to get the power you need at any given moment, so the fuel use will be the same under every condition but wide open throttle - where the engine is open loop anyway. You're controlling the mechanical energy output and it takes a certain amount of fuel to create that.