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Stock Air box vs Cone Filter

19238 Views 37 Replies 20 Participants Last post by  darmawaa
Hey All,
I decided to test out the Cone Air filter install today, and more importantly, compare some data points to try and separate myth from fact. The first thing I wanted to validate was whether or not IAT (Intake Air Temperatures) change much, since a cone style filter does not draw air from outside, but from inside the engine compartment. Secondly, I wanted to compare the flow rates at the MAF and see if it made any changes to MAP. For my data logging, I used an Actron CP9185 Auto Scanner. This is a nice tool, and allows for all sorts of fun when you don't have access to tuning software.

First up was to take a look at the stock setup, and see what it does. I did runs in both 3rd and 4th gear, but the results were pretty much the same. From here on out, all my testing is done in 3rd gear.

What I found was the following with the stock box. Air flow at a 100% ECU load flows around 34lb/m (average) for full out runs, with MAP peaking at 73.8in /Hg (full boost) and settling to around 66in/Hg towards redline. The IAT stayed equal to the exterior temps, which is a good thing. Means we weren't sucking in any air that was warmer then the outside air.

Next up was the standard cone filter you can buy at any auto parts store. I went with a K&N air cone filter to ensure it had high flow rates. This is what I found with the cone filter.

First things first, the IAT was not noticeably effected by the filter. I left the snorkel on, so this may be providing enough cool air to ensure that the engine is still able to draw in cooler then engine bay air. This is a good thing. Air flow at 100% ECU load also went up by an average of 2lb/m across the board. However, this did not equate to more manifold pressure. For whatever reason, MAP was down 2in/Hg across the board. I find this interesting because this was reporting exactly what I was seeing in the car. I was having a harder time building boost. My boost gauge showed some eradicate behavior that I did not get with the stock box. To verify that the cone filter was causing this, I put the stock components back on, and the issue went away. Not sure why this is happening, since I am using a MBC, its not an ECU thing. Something to play with more in the future.

On a good note, I noticed that timing was advancing a lot faster with the Cone then with the stock air box. This may have something to do with the load cells being different, since with the stock box I was getting an ABS load of around 222 peak, but with the cone I was only getting into the 215 range. The car also felt slower to me, and a lot less linear. This may change over time, so I am going to put the cone filter back in and see if it changes over the next few days. But, right now, I am losing power with this thing, not gaining. This may be fixable though with some boost adjustments.
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I don't know if this works, makes sense to me, but will resetting the ECU after the changes help it adjust to the new found air?
I don't know if this works, makes sense to me, but will resetting the ECU after the changes help it adjust to the new found air?
ekkk so many technical details. for me if it increases the hp/tq it means better than the airbox. and it did in some dyno test. there are some diy heat shield too no need to worry about heat.
I'm not using a reverse conical filter just the standard K&N. I think I can feel it build boost a little slower but its much stronger in the top end. It pulls harder till red line unlike before where it was awful past 6k. Also how would I go about resetting the ECU? And if I did would the dealership be able to see that I reset the ECU and cause warranty problems?
Resetting the ECU would just get rid of your LT and ST fuel trims. It may get rid of stored performance data too, but I am not sure. Its possible that I picked up horsepower, but lost torque. Hard to tell. All I know is that I am hitting lower load cells in the ECU, because I am getting lower MAP. I will play with this more next weekend.
Just disconnect your battery for a few minutes and it should reset your computer. That is what I did. I have had the cone filter on my car fora about 900 miles and it feels better than the stock air box. But I have not proof just my butt dyno.
^ does it seem to take your turbo a little longer to spool up? Also would resetting the computer for just a new air filter do anything. Won't the computer react to the new airflow and adjust itself?
How does this mod compare to one of those drop in air filters which is suppose to increase air flow in the standard air box? I know it's cheaper, but I'm wondering about performance similarities/differences.

@PDX - It's not abnormal for a freer-flowing air filter to cause you to boost less. I have seen your results on other cars before.
How does this mod compare to one of those drop in air filters which is suppose to increase air flow in the standard air box? I know it's cheaper, but I'm wondering about performance similarities/differences.

Not sure Dan. I couldn't find a drop in filter that fit, so I was not able to test this.
Apparently there are a few AEM air filters that are supposed to fit the X
Ouch, $130 for a filter?!?! No thanks. A drop in filter generally doesnt do anything negative for your MAF. All the MAF issues are caused by turbulent flow that is caused by air coming in from a multi-directional setup. The stock air box is usually designed to have all the air flow in a single path that is the least turbulent to the MAF. Changing to a drop in, keeps this flow design, and allows you to increase your flow rate without getting jumpy MAF signals, which are difficult to tune and are very inconsistent.
I'd like to get a drop in for now but not 130 bucks! First time I heard that it pissed me off. K&N where are you dammit. No way can I morally spend 130 on a drop in. I hate it when some of the vendors gouge owners
yea, that drop in filter is definitely overpriced. however, i believe i read on EvoM that drop in filters worked better for the Evo IX's than the cone filters. i'm thinking that maybe it would be the same for the X's
That drop in is cleanable and reusable, not sure if that adds any value to it or not.

having taken apart my airbox recently, i dont see manufactures are gonna be able to make the product much cheaper.

its not just a filter like it was before that is inside of an enclosure, its part of the actual box itself so the sides need to be a bit more reinforced.

its more like a sandwhich.

i dont see the k&n one being the $49 or whatever it was before, it put it at more like $89.

just my view.
I have a k&n cone filter. I installed it last friday and I could notice the turbo spooling up later. I decided to give resetting the ECU a shot by disconnecting the battery. It made a big difference. The turbo spools up a good 500-700 rpm earlier. Before it really didn't start pulling till almost 4 now its back to around 3 again and it still pulls a lot harder to redline. If you install a cone filter make sure you reset your ECU.
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