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Old 06-08-2009, 01:47 PM   #1
tazswing
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Default AEM CAI review: 08STI

In the process of adding power to my 08STI some tuners have reported gains with intake systems in addition to turbo upgrades (the exhaust goes without question). The turbo tuning will be poster elsewhere at a later date. Basic mods: DW850, Perrin two-cat DP (heat wrapped), Wal255 pump, HTA68 turbo, one step colder.

The AEM system is very well engineered; both product quality and fit to the contours of the engine compartment of the 08'STI. Additionally, it is a dry cotton cone design which in theory should help keep the MAF sensor cleaner in the long-run (short-run?). So over-all it looks like a great addition to a power building process.

But now comes the trouble: Heat, and lots of it.

-Testing conditions-
Weather: 62 degree F, cloudy
Humidity: 72%, damp roads
Roads: Highway, 8-10 miles of continuous cruising 50-65mph. Street, stop and go along with 2-3 miles continuous cursing around 35mph. Same route driven in all testing conditions.

Monitoring device: Accessport V2 Live Data

1) AEM Intake as designed: In stop and go traffic, intake temps would peak around 130 degrees and would stay around 115-125. Upon moving from a light, intake temps would start to drop very slowly and would take just under 3 mile of continuous driving to drop below 105 degrees.

After sitting at a light on to get on the highway, it would take about a mile of highway driving to see the temps drop below 105 degrees and after 3 miles the intake temp stabilized around 95 degrees. The lowest temp I got on the highway was 93.

The temp would also climb very quickly back up (so 95-120 degrees while waiting for a 25 second light…yes, I timed it…yes, I am that neurotic).

2) AEM intake without heath shield: Basically the same as with the heat shield, only slightly lower peak temps all around with slightly quicker temp drops and slower increases upon stopping.

3) AEM intake as designed with fog light cover removed: Removing the cover opens a direct path to the well where the intake sits. With the cover removed (heat shield on the intake mind you) highway running temps were only ~8 degrees above ambient air temps.

Peak temp in stop and go traffic stayed below 105 degrees. Intake temps would rise after coming off the highway at a rate of about 1 degree every 4 seconds (before it was 1 degree per second). Best yet, the drop in temp. was very fast and instantaneous upon moving again even on the street.

Conclusion: The well the cone sits in has very little airflow and is isolated enough from the rest of the engine that even taking off the heat-shield did not help. But given a fresh charge of air on a nice cool day like the day of testing, the AEM intake performs very well indeed.

I am going to test out some other intake and see if a short ram, so a “cone” that does not stick down into that well, can get the air it needs. Other options would be to see if somehow that well can be vented without exposing the cone to direct water-flow if driven in the rain. Also, if I had fog-light opening that challenge to the intake would not have been feasible.

I would love feedback and questions. Also, has anyone else taken the time to run around data-logging intake temps?
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Old 06-08-2009, 02:28 PM   #2
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My Perrin Bigmaf CAI cruises at about 2-4 degrees warmer than ambient temp. At a traffic light, it would jump 10-15 degrees warmer than ambient temp. Difference is, I have an 06 STI, so CAI design is different. Just trying to give you an opinion.
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Old 06-08-2009, 02:35 PM   #3
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Originally Posted by 06mattsti View Post
My Perrin Bigmaf CAI cruises at about 2-4 degrees warmer than ambient temp. At a traffic light, it would jump 10-15 degrees warmer than ambient temp. Difference is, I have an 06 STI, so CAI design is different. Just trying to give you an opinion.
that is a short ram style, right? 2-4 above ambient is rather nice!
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Old 06-08-2009, 02:54 PM   #4
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No, I have the cold air extension.
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Old 06-08-2009, 03:45 PM   #5
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No, I have the cold air extension.
So it sounds like it is getting much more free air. I am going to try and Perrin CAI on my ride but I am not expecting much difference since I trailed the AEM w/out the heatshield and got little improvement.
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Old 06-08-2009, 03:47 PM   #6
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Well don't forget, your filter goes straight down whereas mine routes through the fender well. So its a little different design.
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Old 06-08-2009, 03:48 PM   #7
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Well don't forget, your filter goes straight down whereas mine routes through the fender well. So its a little different design.
Right, and there I think inlies the problem. I think the Perrin for the 08sti sits in the same location as the AME; the heat-well of death!
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Old 06-08-2009, 04:03 PM   #8
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You can always fab up something better, or have a shop do it.
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Old 06-08-2009, 04:18 PM   #9
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You can always fab up something better, or have a shop do it.
Yeah, i might do some cutting this week....however, i would rather not after paying an AEM price. R&D these days seems to fall very short once something seems to "fit."
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Old 06-08-2009, 04:48 PM   #10
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I still have the stock air scoop and air filter box but here are some numbers I got for comparison... http://forums.nasioc.com/forums/show....php?t=1780099
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Old 06-08-2009, 09:28 PM   #11
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While we love reviews here, yours means nothing without A/F testing as your post may lead lemmings to the cliff of a lean motor.
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Old 06-09-2009, 12:43 AM   #12
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when i had my CAI it read the same as what my outside temp read.... thats while driving.... and thats using the AP and assuming my thermostat on my car is working right... while driving there was no more than a 3 degree difference.... im not sure exactly how different ur sti sits compared to my lgt.... but i would assume its pretty similiar....
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Old 06-09-2009, 10:33 AM   #13
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While we love reviews here, yours means nothing without A/F testing as your post may lead lemmings to the cliff of a lean motor.
Ok, so can you give me some direction? Should I log intake temp and A/F against each other and then post that? And if A/F is then an important variable can I assume that the temp being read at the intake really does not matter for over all performance where on the same day Tingtang would be running +3 degrees and I would running +20 from ambient? B/c by saying my review means nothing you are then implying that temp difference may not be a big deal which might lead lemmings of the other side of the cliff.
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Old 06-09-2009, 06:41 PM   #14
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Thanks for moving this. My first real review
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Old 06-15-2009, 01:18 PM   #15
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I got a chance to sit and chat with a great tuner who schooled me on intake issues (this is what I can remember of the conversation). He has done hundreds of hours of tuning on his 08sti on which he runs a Perrin CAI that sits as does the AEM and a FMIC. I am now running the AEM without a heat-shield like the Perrin runs.

Basically he feels that two things are happening: One the MAF sensor is getting soaked as a product of sitting on an aluminum arm and therefore the air-temp once moving through is lower that the MAF is reading since the metal take longer to cool down then does the actual temp change in the tube. Ideally yes, there would be a more direct path of fresh air to our intakes, but absolute outside air temp is generally a greater factor.

Second, the different in 10 degrees on intake temp. is nothing compared to the heat added to the air at the turbo. The statement above about absolute air-temp comes into play here since an intercooler is an air-to-air heat exchanger.

The final picture then seem to be that what becomes more important is how well the intake flows air second to the intake temp. Lower intake temps are still a good thing, but the intercoolers ability to drop the air temp trumps. The issues at the MAF in terms of temp I am still fuzzy on, meaning what the car does in relation to it.

Next step is to try and wrap the intake arm and modify the fog-light cover to flow air but not water.
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Old 06-15-2009, 01:40 PM   #16
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Yes that's all basically true, BUT when the IAT get up to about 140*F+ at the MAF sensor the ECU starts to pull timing at least thats the way I undersand it... So the colder the air going into the turbo, the better.
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Old 06-17-2009, 10:58 PM   #17
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^^^
That hood would shoot some more air over the intake
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Old 07-01-2009, 01:21 PM   #18
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Fog-light covered modded. 3/8" drill bit and wala, the CAI temps respond nearly as fast as with the cover fully off. would have been nice not to drill the cover, but they are $15 if I get sick of the holes...which i can't really see readily.
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Old 07-06-2009, 12:34 AM   #19
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Could you post some pix??
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Old 07-06-2009, 10:22 AM   #20
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Could you post some pix??
Thanks for asking, i really need to. No one has noticed them until I point them out. I will make myself a reminder.
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