AEM Dry Flow vs. Cotton Filter (w/Pics)
08-19-2006, 02:02 AM
#1
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Join Date: May 2006
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Posts: 700
AEM Dry Flow vs. Cotton Filter (w/Pics)
Practically everyone on this board seems to have a CAI and a tune. It's the modification that most of us make to our Mustangs. With good reason, too! A good tune and a CAI can produce at least 20 hp and even a 87 octane tune plus a good CAI might net you 10 or so. Now that's good bang for your buck.
Anyway, like many of you I think waaaaaay too much about my Mustang. I also have a technical background and anything I do to my car always makes me wonder: Why didn't the engineers do this way first?
In this spirit, I decided to look into cotton air filters that come with all of our CAI's. They definitely flow freely, but at what cost? How well do they filter dust and dirt?
Long story short, I did some searching and heard about the Dryflow filter from AEM. They claim it filters out more dust, INCREASES air flow, and doesn't need to be oiled. You just clean this one. The last point really attracted me to the filter. I don't like the idea of messing with oil: too much oil and I can mess up my MAF sensor, too little and I'm not filtering dirt properly.
I ordered a filter from JEGS and it arrived yesterday. I immediately installed it on my Steeda CAI. The first thing I noticed, I should have order AEM Part 21-209DK, with a six inch diameter and five inches tall. That would have been shorter than the Steeda filter by about 2.5 inches...I got a filter that's about 2.0 inches longer than the original. Whoops! I just didn't want to downsize...It touches the side of the car just a little and the end cap makes contact with the hood, but air doesn't flow through the sold plastic end cap, so I think I'm ok. The diameter isn't really much larger, it's just a lot longer.
Back to the story, today I take the car out and it feels like I've lost a little bit of power. Throttle isn't quite as responsive. (Ok, I may have an automatic, but I know the feel of the car and every single sound this thing makes, I pride myself on it!) The car was definitely quieter, too.
I decided that a test was in order. I took it to my brother's and drove the car. First with the Steeda, then with the AEM. Again, I noticed that Steeda felt a little more responsive, not by a lot, but I could tell. Next, I took my brother and had him drive the car. I told him absolutely nothing about what I did. He took it along the same route. We stopped and I changed the air filter and we travelled with the same route again. I asked him his impression. The same result. He said the car felt a little "smoother", but not as responsive (he actually prefered the feel of the AEM). By the way, gas mileage IMPROVED quite a bit WITH the AEM and DROPPED noticable with the Steeda as measured by the computer.
I also have a XCAL2 SF with SCT canned tunes preloaded. The 93 octane tune looses a little bit of power at around 1,500 or 1,700 RPM (somewhere around there), just a slight dip for a split second. With the Steeda CAI installed it smoothed out, with the AEM installed I felt that slight loss again, like a brief hesitation. My brother also noticed it without me telling him, but only because I made him pay close attention to everything about the car. It really isn't much of an issue.
Ok, so why did the AEM underperform? I believe it has to do with air flow through the filter. I don't care what their marketing says, below is my own unscientific research. I held each filter up to a light so that it would shine through. Tell me what you think!
I know the filter is a bit oversized, but I think the drop in horsepower is due to filter material. Light from the bulb in my garage will easily penetrate the Steeda, but not the AEM. That tells me the AEM synthetic material is much more dense.
I'll admit, it looks a little funny with the larger air filter. However, I'm expecting my Steeda Inlet elbow any day now. That should look much better.
Bottom line. I believe the AEM just doesn't flow as well. How could it?! Did you see all of those tiny holes in the Steeda filter? That's letting in air...pollen, dust, and whatever else might be out there, too. The AEM filter is obaque. That's probably why AEM recommends a cleaning every 10k miles and Steeda recommends a cleaning ever 30k to 50k. More dirt collected = greater cleaning frequency. In this case, I think I'm willing to live with the slight horsepower loss and take the better fuel economy / filtering performance.
I wonder, though, how much of a gain would someone with say an AEM Brute Force with the Dryflow filter experience if they replaced it with say a K&N or another cotton filter?
[IMG]local://upfiles/37741/6E63461499CC4059B58ADB0C3F0D99A1.jpg[/IMG]
[IMG]local://upfiles/37741/CD48B7E777BE4FDEB5F88DB4DE8309CA.jpg[/IMG]
[IMG]local://upfiles/37741/9C44FF8EE6174C639535127BE2747C72.jpg[/IMG]
[IMG]local://upfiles/37741/37B43D3CD66446E8AECB8275D8FF9808.jpg[/IMG]
Anyway, like many of you I think waaaaaay too much about my Mustang. I also have a technical background and anything I do to my car always makes me wonder: Why didn't the engineers do this way first?
In this spirit, I decided to look into cotton air filters that come with all of our CAI's. They definitely flow freely, but at what cost? How well do they filter dust and dirt?
Long story short, I did some searching and heard about the Dryflow filter from AEM. They claim it filters out more dust, INCREASES air flow, and doesn't need to be oiled. You just clean this one. The last point really attracted me to the filter. I don't like the idea of messing with oil: too much oil and I can mess up my MAF sensor, too little and I'm not filtering dirt properly.
I ordered a filter from JEGS and it arrived yesterday. I immediately installed it on my Steeda CAI. The first thing I noticed, I should have order AEM Part 21-209DK, with a six inch diameter and five inches tall. That would have been shorter than the Steeda filter by about 2.5 inches...I got a filter that's about 2.0 inches longer than the original. Whoops! I just didn't want to downsize...It touches the side of the car just a little and the end cap makes contact with the hood, but air doesn't flow through the sold plastic end cap, so I think I'm ok. The diameter isn't really much larger, it's just a lot longer.
Back to the story, today I take the car out and it feels like I've lost a little bit of power. Throttle isn't quite as responsive. (Ok, I may have an automatic, but I know the feel of the car and every single sound this thing makes, I pride myself on it!) The car was definitely quieter, too.
I decided that a test was in order. I took it to my brother's and drove the car. First with the Steeda, then with the AEM. Again, I noticed that Steeda felt a little more responsive, not by a lot, but I could tell. Next, I took my brother and had him drive the car. I told him absolutely nothing about what I did. He took it along the same route. We stopped and I changed the air filter and we travelled with the same route again. I asked him his impression. The same result. He said the car felt a little "smoother", but not as responsive (he actually prefered the feel of the AEM). By the way, gas mileage IMPROVED quite a bit WITH the AEM and DROPPED noticable with the Steeda as measured by the computer.
I also have a XCAL2 SF with SCT canned tunes preloaded. The 93 octane tune looses a little bit of power at around 1,500 or 1,700 RPM (somewhere around there), just a slight dip for a split second. With the Steeda CAI installed it smoothed out, with the AEM installed I felt that slight loss again, like a brief hesitation. My brother also noticed it without me telling him, but only because I made him pay close attention to everything about the car. It really isn't much of an issue.
Ok, so why did the AEM underperform? I believe it has to do with air flow through the filter. I don't care what their marketing says, below is my own unscientific research. I held each filter up to a light so that it would shine through. Tell me what you think!
I know the filter is a bit oversized, but I think the drop in horsepower is due to filter material. Light from the bulb in my garage will easily penetrate the Steeda, but not the AEM. That tells me the AEM synthetic material is much more dense.
I'll admit, it looks a little funny with the larger air filter. However, I'm expecting my Steeda Inlet elbow any day now. That should look much better.
Bottom line. I believe the AEM just doesn't flow as well. How could it?! Did you see all of those tiny holes in the Steeda filter? That's letting in air...pollen, dust, and whatever else might be out there, too. The AEM filter is obaque. That's probably why AEM recommends a cleaning every 10k miles and Steeda recommends a cleaning ever 30k to 50k. More dirt collected = greater cleaning frequency. In this case, I think I'm willing to live with the slight horsepower loss and take the better fuel economy / filtering performance.
I wonder, though, how much of a gain would someone with say an AEM Brute Force with the Dryflow filter experience if they replaced it with say a K&N or another cotton filter?
[IMG]local://upfiles/37741/6E63461499CC4059B58ADB0C3F0D99A1.jpg[/IMG]
[IMG]local://upfiles/37741/CD48B7E777BE4FDEB5F88DB4DE8309CA.jpg[/IMG]
[IMG]local://upfiles/37741/9C44FF8EE6174C639535127BE2747C72.jpg[/IMG]
[IMG]local://upfiles/37741/37B43D3CD66446E8AECB8275D8FF9808.jpg[/IMG]
08-24-2006, 09:21 PM
#2
Join Date: Aug 2006
Posts: 2
RE: AEM Dry Flow vs. Cotton Filter (w/Pics)
Interesting experiment. I think your feeling of power loss is right on. AEM is trying to play up the misconception that oiled cotton filters cause issues with MAF sensors. They have put all of their eggs in one basket trying to scare people from using oiled cotton thereby creating a market for their new product. I think it was a stupid marketing ploy that could backfire on them. They infer that oil from cotton filters cause problems but they never come out an make that statement as fact. If they did they would have to ofter proof. For more on this topic see K&N's website on MAF sensor testing at http://www.knfilters.com/MAF/massair.htm. AEM also infers that their filters flow better and provide more power but they don't. Their filters are much more restrictive than a K&N or a K&N style filter. More restriction means less air (oxygen) to your engine which means less power and torque. AEM filters do filter dirt much better than OEM requirements but that's overkill at the expense of power. I've heard these new filters are a pain to clean as well. Has anyone cleaned one of them that can comment?
Tom
Tom
08-25-2006, 12:40 AM
#3
3rd Gear Member
Thread Starter
Join Date: May 2006
Location:
Posts: 700
RE: AEM Dry Flow vs. Cotton Filter (w/Pics)
Tom,
I did some additional reading on the AEM filters on their website. I had to read very carefully, but:
"AEM's DRYFLOW Synthetic filter flows almost as well when it is dirty as it does when it is clean, and flows over twice as much air than is required for large displacement engines in vehicle applications covered by BRUTE FORCE intakes. Many of our competitors emphasize flow as a primary means of power production in intakes, stated Chief Engineer John Concialdi."
Translation:
1) AEM filters provide more than enough air for your engine.
2) Reading between the lines: AEM filters don't flow as well.
You're spot on, they definitely imply that it flows better, while at the same time telling you it doesn't! If you read their engineering data, you'll find it is absolutely does not flow as well. Compare the graphs of the airflow in the report on cotton filters and on the Dry Flow filter. It doesn't flow as well per their own testing.
So, what's the real advantage to Dry Flow? Well, there are always tradeoffs and from what I can tell the cotton filters just do not collect dirt as well.
From K&N's site (http://www.knfilters.com/faq.htm#10)
"Our testing has demonstrated that on average, K&N air filters have an overall efficiency rating of between 97 and 99%. With proper cleaning K&N air filters will protect your engine for the life of your vehicle."
I think I'm getting part of the story. The AEM engineering tests put a K&N filter efficiency at about 96.13% cumulative efficiency that's pretty close to 97%. AEM tests seem to validiates K&N's overall (cumulative) filter efficiency.
Cumulative efficiency is measured after the dust test, as the filter collects dust holes are plugged and the filter actually filters dust better. Makes sense!
However, the initial efficiency (how well it filter works when it's clean) of the K&N filter was 93% in the AEM tests. Yikes. Dry flow's cumulative and initial were up around 99%.
We're also not considering dust size. With all that light streaming through my Steeda filter, my guess is the filter collects large particles, while the smallest pass right through. AEM claims that Dry Flow traps particles down to 1 micron in size. I obviously can't measure it myself, but it makes sense at least after a cursory inspection.
It turns out these small particles can do quite a bit of damage, perhaps more so than larger particles. Consider this article:
http://www.noria.com/learning_center...inationControl
The air filter makes a difference both in terms of protection and power. That makes me wonder, how much difference would we see in these CAI's if they all used the same filter material?
Here's what I consider the bottom line from my research.
1) Dry Flow filters produce less horsepower than cotton filters. They are more restrictive.
2) Dry Flow filters appear to be better at filtering out small particles.
3) Small particles can cause engine wear, possibly more so than large particles.
Like all things in life, there is no free lunch. A free flowing filter will let more air in, but to do that it needs to make a compromise, it doesn't filter as well. A restrictive filter won't produce as much horsepower (it's noticable in my Mustang!), but it filters small particles well.
In the end, I actually decided to keep the AEM filter on the Mustang. I decided to play it safe, either way the 93 octane tune, larger MAF, and bigger intake have improved peformance enough for me, at least for now.
I did some additional reading on the AEM filters on their website. I had to read very carefully, but:
"AEM's DRYFLOW Synthetic filter flows almost as well when it is dirty as it does when it is clean, and flows over twice as much air than is required for large displacement engines in vehicle applications covered by BRUTE FORCE intakes. Many of our competitors emphasize flow as a primary means of power production in intakes, stated Chief Engineer John Concialdi."
Translation:
1) AEM filters provide more than enough air for your engine.
2) Reading between the lines: AEM filters don't flow as well.
You're spot on, they definitely imply that it flows better, while at the same time telling you it doesn't! If you read their engineering data, you'll find it is absolutely does not flow as well. Compare the graphs of the airflow in the report on cotton filters and on the Dry Flow filter. It doesn't flow as well per their own testing.
So, what's the real advantage to Dry Flow? Well, there are always tradeoffs and from what I can tell the cotton filters just do not collect dirt as well.
From K&N's site (http://www.knfilters.com/faq.htm#10)
"Our testing has demonstrated that on average, K&N air filters have an overall efficiency rating of between 97 and 99%. With proper cleaning K&N air filters will protect your engine for the life of your vehicle."
I think I'm getting part of the story. The AEM engineering tests put a K&N filter efficiency at about 96.13% cumulative efficiency that's pretty close to 97%. AEM tests seem to validiates K&N's overall (cumulative) filter efficiency.
Cumulative efficiency is measured after the dust test, as the filter collects dust holes are plugged and the filter actually filters dust better. Makes sense!
However, the initial efficiency (how well it filter works when it's clean) of the K&N filter was 93% in the AEM tests. Yikes. Dry flow's cumulative and initial were up around 99%.
We're also not considering dust size. With all that light streaming through my Steeda filter, my guess is the filter collects large particles, while the smallest pass right through. AEM claims that Dry Flow traps particles down to 1 micron in size. I obviously can't measure it myself, but it makes sense at least after a cursory inspection.
It turns out these small particles can do quite a bit of damage, perhaps more so than larger particles. Consider this article:
http://www.noria.com/learning_center...inationControl
The air filter makes a difference both in terms of protection and power. That makes me wonder, how much difference would we see in these CAI's if they all used the same filter material?
Here's what I consider the bottom line from my research.
1) Dry Flow filters produce less horsepower than cotton filters. They are more restrictive.
2) Dry Flow filters appear to be better at filtering out small particles.
3) Small particles can cause engine wear, possibly more so than large particles.
Like all things in life, there is no free lunch. A free flowing filter will let more air in, but to do that it needs to make a compromise, it doesn't filter as well. A restrictive filter won't produce as much horsepower (it's noticable in my Mustang!), but it filters small particles well.
In the end, I actually decided to keep the AEM filter on the Mustang. I decided to play it safe, either way the 93 octane tune, larger MAF, and bigger intake have improved peformance enough for me, at least for now.
08-25-2006, 02:47 AM
#4
Join Date: Aug 2006
Posts: 2
RE: AEM Dry Flow vs. Cotton Filter (w/Pics)
The Noria information is intesresting. I don't know if engines are getting better than they used to be but it seems they go for many more miles than they used to. My old SUV has 135,000 miles with no engine work and 20 years ago that would have been incredible. There's a story on the K&N site about a guy who drove over a million miles in his Chevy Pickup without any engine work (http://www.knfilters.com/news/news.aspx?ID=157). One thing that goes against what most people think is how bad some paper filters are at filtering dirt as low as 93% and you can't see holes in it. All paper isn't the same either.
08-25-2006, 06:01 PM
#5
3rd Gear Member
Thread Starter
Join Date: May 2006
Location:
Posts: 700
RE: AEM Dry Flow vs. Cotton Filter (w/Pics)
I agree and I have no idea the initial efficiency, cumulative efficiency and size of the particle filtered by the stock airbox. Heck, for all I know the Steeda filter isn't much worse than the stock air filter.
I think you're right, new cars last longer and are built better than they ever have been. I think the average car on the road is now about ten years old...and I don't think most people maintain theirs properly. There aren't too many things that we can buy that will last ten years, even under harsh use.
I was comforted to see my Steeda / Ford Racing CAI on the soon-to-be released Shelby Mustang GT (Not to be confused with the GT-500!). So, someone at Ford thought it wasn't such a bad idea to put it on a stock vehicle...air filter and all.
I never realized how complicated it was to design an air filter. That makes me wonder about all of the CAI's out there on the market for our cars. How efficiently do they filter out dust? I bet at least a few of them cut corners by using cheap air filters.
I think you're right, new cars last longer and are built better than they ever have been. I think the average car on the road is now about ten years old...and I don't think most people maintain theirs properly. There aren't too many things that we can buy that will last ten years, even under harsh use.
I was comforted to see my Steeda / Ford Racing CAI on the soon-to-be released Shelby Mustang GT (Not to be confused with the GT-500!). So, someone at Ford thought it wasn't such a bad idea to put it on a stock vehicle...air filter and all.
I never realized how complicated it was to design an air filter. That makes me wonder about all of the CAI's out there on the market for our cars. How efficiently do they filter out dust? I bet at least a few of them cut corners by using cheap air filters.
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