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2008 Forester XT Auto
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148 Posts
Discussion Starter · #1 ·
I'm running a catted DP, sti TMIC, vf43, walbro 255, sti cat back exhaust.
I'm using a stage 3 cobb tune, and the car makes pretty impressive power!

I want to order an E-tune from Torqued Performance, as Eric states that his tune will reach a max boost of 18.5, compared to the 15.5 that the cobb tune delivers.

This thread isn't going up to ask if I should not E-tune, as I've already paid eric, and Im getting it done.

The main question is, is if getting an aftermarket CAI will help my performance at all, and or spooling characteristics of my turbo? People all say that gains are minimal to a stock engine, but I'm in the 300 flywheel horsepower area now, and I'm going to have an increase of some type with going with a custom tune from torqued performance.

I don't care about the noise factor, or the novalty of the aftermarket intake, I'm only curious about actual power gains and if I'm 'feel' the difference or not.

I'm currently running a stock fram paper filter in my airbox. AFE makes a nice reusable paper filter, but it'll cost $80. A CAI will run about $200. Should I bother, or keep my stock intake?
Thanks
 

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07 FXT
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828 Posts
I previously had my car setup with a VF43 and tuned to about 280 whp. Added an AEM cold air intake and retuned to about 300 whp. Torque came in quicker, and more of it, across the whole rev range.
 

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07 FXT
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You gained 20 wheel horsepower? That much? Did you dyno it? How did you know? And did the car feel a lot faster?

http://www.subaruforester.org/vbulletin/f87/mythbuster-stock-intake-good-enough-up-400-whp-88927/


There will be people that discount the gains because they were not a perfect same-day comparison, but I think the conditions were pretty similar. The fact is that it was noticeably faster at the end of the day, with better throttle response. The boost comes on quicker, holds flatter further out in the rev range. What is not to like?
 

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2008 Forester XT Auto
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148 Posts
Discussion Starter · #5 ·
This is true, and Im pretty much convinced that I'm going to buy one. I've narrowed the search down to buying a short ram with heat shield. I'm not interested in a true cold air intake due to possible problems with weather like heavy rain and snow. (I live in canada). The 3 I like the most seem to be the cobb short ram, the k and n typhoon, and the spt... they all seem to cost identical, come with a heat shield box, and have a matched ID of piping near the MAP sensor to prevent CEL's. The cobb and K&N have a reusuable oil based filter, and the spt uses a non reusuable filter....
Which one would work best? I'm using an access pro economy map for winter time, and a custom e tune for my summer map. Cobb says the economy map will work with their intake, but don't guarentee their map with any other maps...

what do you think?
 

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Premium Member
2008 FSXT 4EAT
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4,143 Posts
Between the two you listed, I'd go for the Cobb SRI. The SPT unit is metal (cast aluminum, I think), which will absorb heat. The Cobb unit is plastic/resin, which won't absorb as much heat. The Cobb intake also has air-straighteners to produce a more accurate MAF reading by reducing turbulence...I don't know if it actually works, but it sounds fancy. :)

I'd try to find a used Cobb intake, throw away the oiled filter, and replace it with an AEM dry-flow filter. I've been using Cobb intakes for the last few years with zero complaints.
 

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2001 Forester 4EAT
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842 Posts
Another less popular, yet cheaper, option is the snorkel-ectomy with a high flow panel filter.
It requires some very minor fab work but it utilizes the factory cold air induction, costs under $50, gives you a little intake noise and the higher flow element reduces restriction a bit.

GP moto used to make a plastic elbow that replaced the snorkel but I haven't been able to find them in years. For my Baja, I just cut the bottom part of the snorkel off and resealed the elbow at the cut. Reinstall with your OEM ducting and Voila, OEM "cold air" intake.
FYI-I'm currently on the stock air box in my forester as well (making 330awhp). BUT, I do have a 'true' CAI ready to go on the Fozz as that is still optimal for HP/spool etc... when water/snow isn't a concern.
Redirect Notice
 

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2004 Forester XT Premium 4EAT
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Between the two you listed, I'd go for the Cobb SRI. The SPT unit is metal (cast aluminum, I think), which will absorb heat. The Cobb unit is plastic/resin, which won't absorb as much heat. The Cobb intake also has air-straighteners to produce a more accurate MAF reading by reducing turbulence...I don't know if it actually works, but it sounds fancy. :)
Agree on the material. The SPT SR has some of the best flow characteristics (low turbulence), but even on a mild (70 degree) day and after only 30 minutes or so of freeway driving, I've seen intake air temps in excess of 120 degrees. A heat shield is a must-have.
 

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07 FXT
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the Cobb intake with the box looks alright, I wouldn't count on getting the same performance increase as a true cold air intake though. Will make it easier to service your filter, so there is that. As far as having a filter in the fender, I live in Seattle which is known to get a little moisture now and then, and I haven't had a problem with it in the several years I've been using it.
 

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2007 Forester XT 4EAT-VTD
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2,138 Posts
My first tune with a VF48, Maddad TB, STi TMIC, stock turbo inlet and stock air box produced 244 WHP/315 ft.lb.

Second tune (same dyno and tuner) added AEM CAI, Perrin TMIC and Samco turbo inlet produced 261 WHP/310 ft.lb. The net effect of a complete intake system and monster, low restriction TMIC vs. a totally stock intake/STi TMIC was +17 WHP and a loss of 5 ft. lbs. After talking with the tuner, we speculated the CAI contributed to maybe half of the 17 WHP gained.

After adding an Aquamist water/meth system on top of those mods I ended up at 274/360.

A CAI can make a contribution, but it really depends on the rest of the mods in terms of how much it will contribute to the overall gains. I think most of the bottleneck in the stock air box system is through the snorkus and inlet fitting. Remove those, run a hi-flow panel filter and I'd have to believe you can gain as much as a dedicated CAI.

BTW, I removed my CAI and am running the stock intake again (Samco inlet remains). I'm not sure I'm missing any full-throttle ponies after doing so, but I'm surely not missing the constant induction noise.

Final note - the AEM CAI is a really nice piece, well constructed and fit my Foz perfectly. In the end, what ever gains it did give at full throttle didn't seem worth the noise and risk of freezing the filter in winter storm conditions.
 

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My experience with the CAI in these cars creates too much turbulence for the MAF and the rest of the system. The Snorkel-ectomy always is safe and my opinion , more stable for tuning purposes.
 

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2008 FSXT 4EAT
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4,143 Posts
My experience with the CAI in these cars creates too much turbulence for the MAF and the rest of the system. The Snorkel-ectomy always is safe and my opinion , more stable for tuning purposes.
I think it depends on the style of the intake. Some intakes locate the MAF close to bends, which can cause some issues. For making power, a CAI/SRI is almost always better than the stock airbox.
 

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I think it depends on the style of the intake. Some intakes locate the MAF close to bends, which can cause some issues. For making power, a CAI/SRI is almost always better than the stock airbox.
I have tried different setups , SR, CAI ,Snorkel,etc , the best setup I found was a Turbo inlet upgrade , stock box , Snorkel.
Since the air will be heated up from the turbo going into the motor, the CAI temp difference will not make a significant difference, hence not worth the hassle or problems on these car/trucks IMO. Unless you really like the WHOOOSH sound:Banane02:
 

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2006 Forester XT Limited 5MT
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I'm running a catted DP, sti TMIC, vf43, walbro 255, sti cat back exhaust.
I'm using a stage 3 cobb tune, and the car makes pretty impressive power!

I want to order an E-tune from Torqued Performance, as Eric states that his tune will reach a max boost of 18.5, compared to the 15.5 that the cobb tune delivers.

This thread isn't going up to ask if I should not E-tune, as I've already paid eric, and Im getting it done.

The main question is, is if getting an aftermarket CAI will help my performance at all, and or spooling characteristics of my turbo? People all say that gains are minimal to a stock engine, but I'm in the 300 flywheel horsepower area now, and I'm going to have an increase of some type with going with a custom tune from torqued performance.

I don't care about the noise factor, or the novalty of the aftermarket intake, I'm only curious about actual power gains and if I'm 'feel' the difference or not.

I'm currently running a stock fram paper filter in my airbox. AFE makes a nice reusable paper filter, but it'll cost $80. A CAI will run about $200. Should I bother, or keep my stock intake?
Thanks
I'd run an Amsoil absolute efficiency panel filer and keep it clean at each oil change (blow off using air hose) and use it a couple years.
I trust Amsoil for their overall R&D (check their website out about this).

No oil to mess with your MAF, and does it's job of filtering the air (search used oil analysis for free flowing oiled filters and there's all kinds of stuff winding it's way in to your engine).

As far as CAI's go, watch this;
Cold Air Intakes Mythbusted - YouTube

Mighty car mods guys busted that a while back.

If you want more noise do the snorkel delete or add a CAI but fwiw unless you have a fully built race car I'm not sold on the need.

P
 

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07 FXT
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As far as CAI's go, watch this;
Cold Air Intakes Mythbusted - YouTube

Mighty car mods guys busted that a while back.

If you want more noise do the snorkel delete or add a CAI but fwiw unless you have a fully built race car I'm not sold on the need.

P
You can't test one type of car and make a generalized conclusion for all cars. To get gains from a mod it needs to address a weak link in the chain, some cars will have inherently better stock intakes than others. The Mighty Carmod guys put a big long corrugated tube as a "custom" intake, that is just a horrible idea.

With the Subaru there are gains to be had, you can choose to ignore them if you want.
 

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04 Forester XT
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145 Posts
Let me step in here and help dispel a few myths and a lot of untruths here.

1)a CAI will give you more power in a turbo motor: NO! The reason a CAI helps power in a NA car, is a cooler load of air flowing in. However, in a turbo motor that air is compressed in the turbo process, it heats up to the same temperature +/- a few degrees no mater what you do. Hence why we have intercoolers. Please don't make me post all the math about air compression and flow people.

2)The reason a "CAI" will give you a little more control/better spool, is it helps fight overboost. Running a SAI or short ram, has the side affect of letting the turbo draw air faster, this can result in a overboost, especially if you are running the stock/OEM boost control solenoid and without a proper tune.

The key here folks, is a PROPER TUNE, and get rid of that damn stock BCS. However, please remember if you do switch to a 3 way BCS you MUST get a tune as it will cause a very unsafe and engine killing overboost situation.
 

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2008 FSXT 4EAT
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4,143 Posts
1)a CAI will give you more power in a turbo motor: NO! The reason a CAI helps power in a NA car, is a cooler load of air flowing in. However, in a turbo motor that air is compressed in the turbo process, it heats up to the same temperature +/- a few degrees no mater what you do. Hence why we have intercoolers. Please don't make me post all the math about air compression and flow people.
IAT timing compensation tables...
 

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07 FXT
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828 Posts
Let me step in here and help dispel a few myths and a lot of untruths here.

1)a CAI will give you more power in a turbo motor: NO! The reason a CAI helps power in a NA car, is a cooler load of air flowing in. However, in a turbo motor that air is compressed in the turbo process, it heats up to the same temperature +/- a few degrees no mater what you do. Hence why we have intercoolers. Please don't make me post all the math about air compression and flow people.

2)The reason a "CAI" will give you a little more control/better spool, is it helps fight overboost. Running a SAI or short ram, has the side affect of letting the turbo draw air faster, this can result in a overboost, especially if you are running the stock/OEM boost control solenoid and without a proper tune.

The key here folks, is a PROPER TUNE, and get rid of that damn stock BCS. However, please remember if you do switch to a 3 way BCS you MUST get a tune as it will cause a very unsafe and engine killing overboost situation.
You need to check your facts, you are spouting more myths and untruths than anyone else here.
 

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Premium Member
2009 Fozzie XT Ltd 4EAT
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553 Posts
my tuner recommended the cobb cai on my SH, since the OEM airbox is "small"

mods are vf52, cobb cai, Crawford aos, grimmspeed ebcs

seems to be running great
 
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