('14-'18) Cold air intakes - Subaru Forester Owners Forum
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post #1 of 12 (permalink) Old 06-07-2019, 04:53 AM Thread Starter
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Cold air intakes

Hey guys! I was considering getting the mishimoto cai for our cars. I was wondering if there would be any actual gains from it? Would love to hear your guys' thoughts!

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post #2 of 12 (permalink) Old 06-07-2019, 05:22 AM
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The largest gain would be in the noise level. Performance gains from CAI on a stock tune are questionable at best, especially on modern vehicles. It is my opinion that 'lite' modifications like this gained popularity before the 90's when cars started being much more efficiently designed, and today they are just a cash grab marketed to cool kids. Your 2.0L puts out nearly 300hp. The Grand National was a fast car in the 80's. It made about 240hp 3.8L turbo, however with further modifications and the help of McLaren they made it up to 300hp.

Your XT has decades of Subaru's engineering poured into it. It has roots in rally. I would put money on the idea that the intake system is exactly how it should be, and no aftermarket system will make a significant impact.

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post #3 of 12 (permalink) Old 06-07-2019, 05:25 AM
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Agreed with @RyanT comments. I'd also be very careful of companies saying the intake is safe with a stock tune. At a minimum, checking STFT and LTFT will be important to ensure your engine is operating safely. In the WRX FA20DIT land, they are running stock intakes on Stage 2/Stage2+ vehicles with no issues. There is a little additional power the tuner can extract, mainly due to increased airflow.
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post #4 of 12 (permalink) Old 06-12-2019, 05:10 AM Thread Starter
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The largest gain would be in the noise level. Performance gains from CAI on a stock tune are questionable at best, especially on modern vehicles. It is my opinion that 'lite' modifications like this gained popularity before the 90's when cars started being much more efficiently designed, and today they are just a cash grab marketed to cool kids. Your 2.0L puts out nearly 300hp. The Grand National was a fast car in the 80's. It made about 240hp 3.8L turbo, however with further modifications and the help of McLaren they made it up to 300hp.

Your XT has decades of Subaru's engineering poured into it. It has roots in rally. I would put money on the idea that the intake system is exactly how it should be, and no aftermarket system will make a significant impact.
Thanks man! I kinda figured it wouldn't be much of a gain in terms of power. I was looking into the mishimoto race intake which had larger diameter piping but does need to be professionally tuned. The only downsides is that it's not CARB legal in california so no shops are willing to sell them to me. But I want my car to sound like a race car! lol
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post #5 of 12 (permalink) Old 06-12-2019, 06:36 AM
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I would imagine intake on the XT 2.0DIT would also mean tune (even a Cobb stg1 OTS w/ intake)? Not sure it is a good idea to run a CAI on stock. I would imagine a CEL after some use.

I remember my STi days with intakes and the biggest gain was in the annoying (to me anyways) air intake audible increase, heh. After the cost of AP and intake, it was hardly worth it. Just my $.02. :)

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post #6 of 12 (permalink) Old 06-12-2019, 09:25 AM
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The OEM intake is already a CAI.

As with any aftermarket bolt-ons I'm quite skeptical that a few dudes with very limited resources can whip up something in a month better than an entire Subaru engineering team did after years of development.
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post #7 of 12 (permalink) Old 06-12-2019, 09:38 AM
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My understanding is that its a few guys with a Dyno. Its easy to make a new design that hits a peak power number, but they won't show you the bottom end loss or the noise increase. Subaru considered all of those things.
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post #8 of 12 (permalink) Old 06-13-2019, 06:47 AM
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The OEM intake is already a CAI.
Yeah, true. I'm just referring to aftermarket utilization though, like the Cobb SF intake for example. Same intake ducting, just flashier, more expensive filtering and plumbing for a louder WHOOSH on throttle, heh. :)

You can always look at the Compressive Tuning shroud. They claim better cooling and "performance gain". I've been waiting for guinea pigs to jump on this train and post results. Snake oil.... (?)

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post #9 of 12 (permalink) Old 06-13-2019, 07:17 AM
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Keep the stock intake, unless you want to go down the path of MAF scaling issues and horrific lean conditions.

Aftermarket intakes on the FA20DIT's are horrible unless you get a custom tune, as the MAF scaling and sensitivity are leagues different than the last-gen stuff. The Mishimoto and COBB intakes are by far the worst. If you don't believe me, pop on to NASIOC and read the FA20DIT section and how many people say the same thing.
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post #10 of 12 (permalink) Old 06-25-2019, 07:01 PM
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Agreed with @RyanT comments. I'd also be very careful of companies saying the intake is safe with a stock tune. At a minimum, checking STFT and LTFT will be important to ensure your engine is operating safely. In the WRX FA20DIT land, they are running stock intakes on Stage 2/Stage2+ vehicles with no issues. There is a little additional power the tuner can extract, mainly due to increased airflow.
Hi there, what would be the normal operating STFT and LTFT on a stock tune XT? Thanks

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post #11 of 12 (permalink) Old 06-25-2019, 11:34 PM
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Install a CAI, gotta tune it, aftermarket exhaust, Invidia q300, gotta get a tune, EGR delete, gotta get a tune. TGV delete, gotta get a tune etc etc. You install it you tune it, you drive it, you have fun. Stock? dont touch it. Install a new aftermarket head unit, gotta get a tune??
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post #12 of 12 (permalink) Old 06-26-2019, 03:06 AM
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An intake changes the way metered air passes over the MAF, the amount of air that passes through the tract, and changes the location of the MAF in relation to where it was from the factory. Unless you're making well past 350whp, there is literally no reason to change the intake anyway- the factory unit isn't choke point, it's a well-designed piece that provides excellent filtration and ease of filter changes.

Anything that alters metered airflow into or out of the FA20DIT needs to be accounted for properly. These are high compression, direct injected, cutting-edge engines that require care and tact to keep from scattering across the shop floor. These are not the engines of yesteryear with tons of room for error; they're prone to knock and this is compounded by being stuffed in a heavy chassis with a CVT that gives the rods no relief from the relentless hammering. A catback is far enough downstream that it's past where it will have any effect on anything, but anything closer than that requires an appropriate tune.

Don't like it? Stay stock. There's a reason why there are tons of modded WRX's listed with separate mileage for the shortblock and the chassis.

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  Subaru Forester Owners Forum > Technical Forums and Vehicle Assistance > Engine and Exhaust > FA20DIT - 2.0L Direct-Injection/Turbocharged (2014+)

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