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6,618 Posts
Discussion Starter · #1 ·

F2 (black) and AEM

- Fits both MTX and ATX (original version only fits MTX)
- Fits both 2.0L and 2.3L engines
- CAI intake diameter = 3.0"
- CAI diameter is reduced by a removable 5" long urethane reducer in the MAF section to give the ECU a better voltage reading
- CAI tubing is connected by a 3.0" coupler
- CAI connects to the TB via 3.0"-2.75" reducing coupler (original version only came with 3.0" couplers)
- Mounted to the frame via vibration mount
- Tubing normally comes in Black powdercoat
- Comes with ASPEC dry filter (blue in color; dry meaning it's not oiled)
- Outerwear Pre-Filter (black) is an option

Here is the breakdown for the current (03/07) group buy:

(Note all prices include shipping to the US only, canada will add $12.00)
$185.00 w/AEM Dryflow airfilter
$185.00 w/K&N airfilter
$170.00 w/dry airfilter and outer wear
$155.00 w/dry airfilter only

outerwear is $15 or $20 extra (F2 will verify pricing on that)

Special powder coating colors please add another $10.00


Do you need to go through the splash shield to take off the filter, or can you do it up from the top of hood?
Go through the splash shield and the wheel well cover. I only had 1 screw holding the left splash shield and 1 clip holding the bottom section of the wheel well so checking and replacing anything if needed only took <5mins.

Is there a difference between "outerwear" and "pre-filter"?
Both are the same. It's also called intake condom by some members. Outerwears is the company that makes them and they make pre-filters. Here's their website:

"Outer wear" is what, exactly?
It looks like a very fine water repellent net that keeps dirt particles from touching the the filter. The outerwears are hydrophobic, though my small tests reveal that they can resist droplets of water, a very minute amount passes through. Further testing shows that 15mL poured from 1ft 5 times would have about 10ml passing through. 15mL poured from 6" away 5 times showed less than 5mL passing through. If that isn't hydrophobic for a pre-filter, I don't know what is. If you still want the most resistant, get an hydro shield and be done with it.

Where can I buy the outerwear pre-filter for my F2 if mine didn't come with one? or

How much extra is the outerwear for the K&N filter
Should be around $15-$20

Was wondering as to the difference between AEM dryflow and the K&N and I DEFINATLY want AEM synthetic dryflow now. Should you still have outerwear w/ the AEM? I'm really liking the maitenance, or lack thereof, for the AEM dryflow, also looks like it should filter better. Is there a lack of flow w/ the AEM? If they end up giving us the AEM what model filter would we need?
Here are K&N's and AEM's info pages: & Bottom line: AEM will not outflow K&N. Outerwears are there for extra protection and to keep of the bigger particles from getting stuck to the filter.

Why get the K&N filter instead of the normal ASPEC dry filter?
K&N will offer better filtration because it's oiled and should have the same amount of flow

How is the dry filter different then the AEM Dryflow?
It outflows the AEM Dryflow and does not filter as well

So the a-spec is basically a K&N filter right? The others that are dry-flow I take it are paper? I just want to make sure I am selecting the optimal option.
Filtration: STOCK (paper) > AEM Dryflow (polyester) > K&N (4-6 layer cotton gauze + closed or open top) > ASPEC (4 layer cotton gauze + open top)
Flow: K&N > ASPEC > AEM Dryflow > STOCK

Does the K&N or AEM Dryflow need the outerwear?
A-spec is like K&N: cotton gauze. The AEM dryflow is synthetic and does not seem to flow as much as the a-spec. I tried the AEM dry-flow on my F2 and posted it up on the FS section a few minutes later: I like K&N, but I don't like the washing and oiling maintenance required (i've oiled a ton of them before I got a 3). K&N + the outerwear = less maintenance, good filtration and flow.

Is ASPEC a good company like K&N?
Aspec makes "general" items (filters, piping, knobs, spoilers, etc), while K&N specializes in filters and intakes.

Any other members with AEM Synthetic Dryflow experience?

Where's the cheapest place to get a splash shield? $17.99 (pic of it installed, below)

So what filter would you get?
I've had no problems with the ASPEC filter. I got the outerwear almost a year later when i got another F2. Since you have the option, i say go with the K&N. Its cheaper to get it now then buying it later, and you can clean it with the $10 Recharger Kit if it ever gets really dirty. If I had to buy this again, I'd probably still get it with the ASPEC and outerwear.

I just want to get the one that's the most water resistant. I have the sedan and I've read the thread about water collection and dripping on the filter and eventually CEL. I don't need a $200 part destroying a $2000+ engine.
The 2 sedan owners that have had the F2 longer than anyone else is Chibana [I've haven't heard a peep of a CEL from his F2] and myself. My daily driven 3 was never garaged and has been through several days in the rain- even the horrible thunderstorms we had last year and has also been driven as hard as possible in the rain. I've never gotten a CEL from it.

Hydrolock/dripping concerns will only be permanently eased by buying an SRI. If you want the F2 CAI, then buy a splash shield like the Injen's . A filter is just an air filter, not a water filter. It's going to be wet no matter what press release you read or what mesh it's made out of: cotton, steel, urethane, paper, polyester, etc. It doesn't matter if it's oiled or not.

Yes, the filter will get wet in the rain, so does AEM's and Fujita's being that the filter is so close to the wheel well. It's up to the owner's best judgement whether to drive hard or not knowing full well what can happen. If the filter is wet and he accelerates hard in an onramp and the intake sucks water/droplets into the MAF sensor, the ECU will panic, throw a cel, and the car will jerk. And while you have that CEL, your car sometimes wont' let you rev above 4k until you dry up everything. From trbab's F2 scare: "...and merging on to 45, i hit the gas, the car jolts, and the infamous CEL comes on." Anyone with a CAI can easily reproduce the same CEL by going to a carwash, and flooring to redline it as you leave. Anyone who've ever had CELs from a wet MAF sensor will think nothing of it and just wait till everything dries up. Those who haven't had that much experience with it, will say "oh shit, i might need a new engine".

[quote author=thebeansoldier's "Twin Charger Review" link=topic=64756.msg1110329#msg1110329 date=1166343537]
This is great for warm/summer weather, but you have to be really careful during rainy days. I triggered a CEL going on an onramp during the rain- twice. It's no big deal since it didn't go into limp-home mode, and the CEL went away the next morning on both occasions. The CEL was MAF high input. That happens when a local wash doesn't know you have a CAI and sprays the bottom of the car hard and/or you create enough suction to have a mist cool your MAF's hotwire (ecu then thinks there's way too much air than normal, then triggers a cel). I suggest purchasing a pre-filter/outerware instead of a metal splash shield so you don't cover any of the cold air being pulled from the ducting. I put my F2's pre-filter on it and went through that same wet onramp to redline hard with no CEL.

After reading the right up in the NA stage 2 upgrades is it really necessay to have a prefilter with the F2? Sounds like the filter might be in a good location to avoid hydro lock.
Not only is it an extra protection against water droplets/splashes and dirt, it saves you from cleaning the crap from your filter after several thousand miles of use. It repels water very well while still being breathable. From the pics on the SCI website, it doesn't look like much, but when you actually see it up close, you'll see why it's a nice piece- and it doesn't even block air flow.

Are these CAI CARB (California Air Resource Board) legal?
They don't have a CARB sticker, but if you need to have the car smogged, it only takes 5mins or less to put the stock box back on. The CAI does not affect any of the emissions equipment of the 3, so it can pass smog testing. Also, as long as you retain the breather hose and not use a breather filter, you're smog legal.

What 'special colors' are availible? I've seen pictures of the red and blue, is that it?
No confirmation yet, but powdercoated colors besides black is an extra $10.

Are the dynos I see floating around with the K&N or a ASPEC dry filter?
They are from the ASPEC filter and the original 3.0" TB coupler. It will have better low-end #s if I used the newer 3-2.75" couplers as shown in my last dynos. Pics below.

Is F2 better than AEM/Mazdaspeed?
When I originally got the intake (before the new TB couplers were released), AEM had a better throttle response and low-end torque while F2 picked up after 3K rpm and had a better top end. Once I switched to the 3-2.75" TB coupler, throttle response and low-end torque improved and on par with the AEM and top end was as good as it was before. I had to wind up the AEM to 5K to hear it over my exhaust while I could easily hear the F2 below 4k. One thing I couldn't stand is during low throttle cruising, I'd hear the ticking sound of a butterfly valve which would make me throttle in or downshift.

Is F2 better than Injen?
No known user who has switched yet.

Is F2 better than Simota?
Note: dmention7 had the original 3.0" TB coupler
[quote author=dmention7 link=topic=44791.msg745107#msg745107 date=1149040699]
The first thing I felt was ashamed for ever thinking that the Simota SRI sounded kinda good. :oops: This thing has such a nice growl, I couldn't stop grinning! And when I was heading up a freeway ramp, it was the first time I'd ever been able to chirp my tires in 2nd gear on a straight smooth road, without power shifting.

I can tell that some of the low-end torque and response of the SRI is missing (or it could just be that the ECU needs to do a bit of learnin'), but once you get your revs up, it just pulls harder and harder--whereas the Simota felt like it plateaued around 6500, the F2 feels like it wishes there was another 500rpm past the rev limiter. Plus, when your engine sounds this nice, it's a treat to really wind it out!

Is F2 better than F5?
Note: NKKNIGHT Had the 3-2.75" TB coupler.
[quote author=NYKNIGHT link=topic=50605.msg1190360#msg1190360 date=1170796724]
just as a quick reference, I have the F2 on my car now for a few days and had the f5 on for a few months. Besides the CEL probs with the F5, so far I feel that it pulled slightly harder throughout the band. Not by much, however I have not reset my ecu so that may be the reason. Still waiting for my ECU to adjust to the F2. One more difference is now I have a ms exhaust with the F2 whereas before it was F5 only. I had went through 3 different pipes with Fujita because they were all throwing CEL's so they where changing the bend and the length of pipe at the end. My car was there test dummy. I gave them results, bitched a bit, they changed until it was good. The F5 had a very aggressive sound and the whistle has a louder pitch, it whistled all the time. The F2's whistle is the best, sounds really good when the air is flowing through and at the right time. To be honest I can't tell which one had a deeper tone because of the exhaust however I feel it was the F5. Going back to power, the F2 is more powerful at the end of the band whereas the F5 was more linear through the band and at the end gave a lil extra oomph. That difference is what makes me like the F2 better. It explodes and makes my car rocket off. Either way you can't go wrong. F2 is cheaper, but F5 has good Customer service. The guy from F5 "Brian" was actually apart(parital owner) of Injen and bounced from them due to differences. He really stands behind his product and is very honorable. I have not dealt with anyone from SCI or F2 however I have not heard the greatest things, however thats for you to judge. I cannot say anything bad about them. So far no CEL with the F2 and boy what a big pipe it has. Kinda bogs low end but makes up for it big time later on. In the end I would lean towards the F2. I am very pleased with this product. Forgot to add one more thing, the F2 needs to have a better filter like the Fujita's.

Is F2 better than stock?
Note: Mayoke had the original 3.0" TB coupler.
[quote author=mayoke link=topic=44791.msg751064#msg751064 date=1149353955]
Butt dyno says: Of course I'm aware that the computer will need a day or two to adjust to the new amount of airflow. Lowend torque feels slightly lower however the engine appears to rev a little free'er. Throttle response is more noticeable now. Actually, I should say that it's much easier to notice the delay between the time you hit the peddle and the time the throttle responds. I hate fly-by-wire now more than ever. Above about 3.2k there is a noticeable increase in torque and most likely hp as well. The car definitely pulls harder and sounds meaner. I can't hear my exhaust at all now over 3k which is funny but expected.(That is if you're "into" it. At a cruise, it's just a mild mannered black hatchback.) Chirped 2nd everytime without really trying and chirped 3rd when I wanted to. I'd say the gains are good. Good vs. the competitor? Well, the dynos here have proven that. There's no way in HELL that I'm pulling this thing back off and putting a DIFFERENT one on.


ASPEC filter close-up

F2 vs AEM tubing width:

F2 Intake Filter A-SPEC

F2 Intake Filter A-SPEC macro shot ;)

F2 vs AEM

Filter sat close to my Toyota horn... no problems with rain and the car was never garaged




Reducer close-ups



Dynos were taken at 4500ft, AEM taken at 57° ; F2 at 68°
F2 was taken with 3.0" TB coupler. Low end should be better with the 3-2.75" TB coupler.


F2 3.0” vs AEM 2.5” 3rd gear:
@3.5k: 1hp, 1tq
@4.5k: 0hp, 1tq
@5.5k: 0hp, 0tq
@6.0k: 1hp, 1tq
@6.5k: 1hp, 1tq

F2 3.0” vs AEM 2.5” 4th gear:
@2.0k: -1hp, -2tq
@3.0k: -1hp, -2tq
@3.5k: 0hp, 1tq
@4.0k: 2hp, 3tq
@4.5k: 1hp, 1tq
@5.5k: 2hp, 3tq
@6.0k: 5hp, 4tq
@6.3k: 3hp, 3tq



135 Posts
+50 for that prefilter, ive driven through some nasty hard rain without a hiccup or CEL.

and, IMO, there is no debate over cai's. The F2 is king and anyone wanting a cai needs to GET ON THIS GROUP BUY! Those gains are against an AEM!

Great Post Bean!

5,817 Posts
my only problem with your posts is that you claim that the "low end will be improved with the reducer" but don't mention that this will hurt the top end (you claim that it doesn't, based on butt dyno claims only).

People start to yawn when I preach about fluid mechanics, so I will spare you all the explanation I have made before on this (PM me if you want the full version), but lets just say that theory dictates that it will aid low end and hurt top end. I know theory and dynos have butted heads before, and I will concede to a real dyno (you are actually quite good in controlling your dynos to give meaningful comparison results), but a butt dyno compared to theory, I'll take theory as "butt dyno" variance is much larger than the effects we are talking about with adding this coupler (note, I'm saying in comparing the F2 with reducer versus F2 without, where hp variances are 1-2 hp at most).

I don't want to turn this into an intake war thread, so let me make it clear that all I wanted to point out is:

the statement that the throttle response being improved by the reducer is valid (as no more precise measurement method exists)

but, the claim that the low end of the F2 w/ reducer would be as good as the AEM and that the high end wouldn't suffer any losses requires dyno backing to be as valid as the other statements in this faq (which are all very soundly backed by "bean" testing procedures)

897 Posts
Excellent synopsis of the F2 GB questions. Thanks for all your effort thus far Bean :-D

5,817 Posts
edit: short answer, yes.

Long answer: well, it all depends on orientation.

Sedans have an issue of water dripping down the hoodline onto the filter, so Mazdaspeed added a sheet metal "Drip shield" to the filter, which just covers the top of it. This piece also serves as a "heat shield" I suppose, as it makes the intake draw more air from underneath the car and less from the engine bay side of the filter, although its questionable as to whether such a shield gains any hp, the main reason is to protect your filter from getting soaked while your car is sitting out in the rain. This is what you need to add a similar shield to your AEM/F5/F2/K&N CAI:

6,618 Posts
Discussion Starter · #8 ·
[quote author=rubyred3 link=topic=73013.msg1291504#msg1291504 date=1174919817]
my only problem with your posts is that you claim that the "low end will be improved with the reducer" but don't mention that this will hurt the top end (you claim that it doesn't, based on butt dyno claims only).

Nope, because the reducer in question is the silicone coupler that connects the CAI to the TB. Not the urethane reducer inside the tubing, but the coupler that connects the CAI to the TB. This is what I mean:

Members with the original 3.0" coupler can easily do this mod to their existing coupler by adding a worm gear clamp in the middle of the coupler and tighen until the diameter of the tightened area is the same as the TB end or in the middle of the CAI and TB.

5,817 Posts
ah, I see, I thought you were talking about when you were just putting cut pieces of urethane in there to bring intake velocity up. Smoother transitions are always a good thing, for high end AND low end. Applying similar principles to the MAF reducer could probably net even further gains.

20 Posts
hey quick question i put my F2 CAI on about 2 weeks ago and about a week ago i noticed a clicking sound when im n 4th and 5th gear at around 2250-3000rpms. its not a loud clicking and it only really happens when i kinda floor it, is this a sound coming from the CAI or is it somthing else????

5,817 Posts
its the butterflys from the VTCS, nothing to worry about, its normal.

312 Posts

I've read that lag & near stalling at low RPM's is an issue with the F2, is that so?

I'm interested in this intake & I hear the lag can be worse depending on what type of tranny you have. I have the 5ATX.

5,817 Posts
the complaint is more that the throttle response isn't as quick as with some other intakes. With an ATX, I doubt you'd notice the difference though, most people have been quite happy with it. The only person I know who complained of the poor throttle response was ag_bullet when he switched from AEM to F2 on his MTX hatch. On an MTX, you can notice throttle response more than on an auto, the torque conveter takes a while to lock up anyways.
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