Are CAI's a big no-no?

[Mr. Electric Wizard]

Based on tons of reading over the years I've gathered that CAI's on the Legacy platform aren't necessary until you go over like 350HP, and most people add them for the sound alone.

I have a friend that is offering me a Perrin CAI for my '06 OBXT because I have a Cobb turbo inlet and it's causing a kink in the stock elbow to the stock air box.

Should I go ahead and "upgrade" to a CAI, or no?

[Infosecdad]

If you do, you'll need a tune.

I don't know what the Perrin brings, but the Grimmspeed intake is approx 12% increase in airflow.

[Mr. Electric Wizard]

If you do, you'll need a tune.

I don't know what the Perrin brings, but the Grimmspeed intake is approx 12% increase in airflow.

 

Trying to get as much stuff done before the e-tune.

I really like the GrimmSpeed stuff.

I might just do that. Thanks!

[shralp]

Yup correct. No need to go CAI until your nipping at about 350HP, or more appropriately, until your moving enough air that that stocker can’t keep up, typically anything larger than a VF52 with supporting mods

[Mr. Electric Wizard]

Yup correct. No need to go CAI until your nipping at about 350HP, or more appropriately, until your moving enough air that that stocker can’t keep up, typically anything larger than a VF52 with supporting mods

 

Exactly what I was thinking. I'd be doing it more (at this point) to alleviate the kink in the stock elbow.

When I pick the car up this weekend I'll get a picture of it.

[utc_pyro]

I sent a stock intake off to get tested a few years back, it's actually fairly restrictive over ~200g/sec. If I remember correctly it was almost 2PSI of restriction around the 300g/sec airflow mark (VF52 ish).

 

THAT SAID: changing it wont gain you much on the stock turbo, and you MUST tune it at the same time to correct the MAP scaling. Otherwise congrats, you need a new motor (ask me how I know....). The intake will basically let your turbo run a lower boost ratio, requiring less drive energy from the exhaust, which really isn't a huge factor until you start choking out the exhaust housing/turbine.

Edited March 14, 2022 by utc_pyro

[Pleides]

Also something to keep in mind is that an upgraded intake will introduce boost creep that you wouldn't have had to the same degree without. Opening up the exhaust will introduce the most boost creep, of course, but might as well mitigate what you can and leave the intake stock for as long as possible.

[Pleides]

I sent a stock intake off to get tested a few years back, it's actually fairly restrictive over ~200g/sec. If I remember correctly it was almost 2PSI of restriction around the 300g/sec airflow mark (VF52 ish).

 

THAT SAID: changing it wont gain you much on the stock turbo, and you MUST tune it at the same time to correct the MAP scaling. Otherwise congrats, you need a new motor (ask me how I know....). The intake will basically let your turbo run a lower boost ratio, requiring less drive energy from the exhaust, which really isn't a huge factor until you start choking out the exhaust housing/turbine.

 

300 g/sec is usually anything that flows more than a VF52 if we're going by this old thread.

[Mr. Electric Wizard]

I usually have that thread open all the time in my browser, lol!

[utc_pyro]

Keep in mind the values Les used in that thread were "typical" values. It's not unusual to see VF52/VF48's pushed into the low-mid 300's with enough supporting mods. The "bang for the buck" isn't there though, it's more money efficient to follow the recommendations he lays out and just go with a bigger turbo.

[Scubaboo]

I sent a stock intake off to get tested a few years back, it's actually fairly restrictive over ~200g/sec. If I remember correctly it was almost 2PSI of restriction around the 300g/sec airflow mark (VF52 ish).

 

THAT SAID: changing it wont gain you much on the stock turbo, and you MUST tune it at the same time to correct the MAP scaling. Otherwise congrats, you need a new motor (ask me how I know....). The intake will basically let your turbo run a lower boost ratio, requiring less drive energy from the exhaust, which really isn't a huge factor until you start choking out the exhaust housing/turbine.

 

I remember your intercooler scoop airflow thread, very informative! Do you happen to have a writeup on the intake test, or any other tests you did?

[utc_pyro]

I went digging for it the other day, but I cant find the write up I though I did here.

 

I'd send the intake to the "My Audi S4" guy, here is his writeup on testing it: https://myaudis4.com/2018/02/04/subaru-airbox-maf-flow-testing/

 

He also did a pressure test, but didn't publish that. Then I did some addition testing with some differential pressure sensors wired up to the TGV position sensors. I think those are buried in one of Covertrussian's threads, but I cant find them.

Edited March 18, 2022 by utc_pyro

[boxkita]

my wagon dynoed at 369 hp on stock intake & exhaust. ymmv.

 

Trying to avoid a tune usually is a recipe for a new engine. The tune, at least on an old car car, should be your starting point not ending point.

[Mr. Electric Wizard]

A friend has this CAI that he will give to me for free.

Would you replace a janky stock box:

 

 

With this:

 

I’m know I’ll need a tune and I’m about to get one as soon as I get this wideband and AFR gauge installed.

[JoeInOregon]

A friend has this CAI that he will give to me for free.

Would you replace a janky stock box:

 

 

With this:

 

I’m know I’ll need a tune and I’m about to get one as soon as I get this wideband and AFR gauge installed.

I would but purely for the sound, it could be augured you may even get lower air temps with the stock box and that would translate to more power.

 

Even with the potential loss in power I would still put the aftermarket on, the loss is negligible and I like the noise.

 

I bought a cob for mine knowing full well stock would be better, but my car came without a stock box and the Cobb package deal with accesport made it only slightly more expensive than a stock replacement.

 

Again I would do it but only for looks and sound , even provided I may lose a little power.

 

My car is not going to be super high power or a racecar and I like a little bling and dat woosh pshh

 

Sent from my Pixel 3a using Tapatalk

[Mr. Electric Wizard]

Right on, thanks!

[MoleMan]

After spending thousands of dollars on CAI's for my cars I can give you your answer.

 

On my American Muscle cars that I have put CAI's on I generally made power. However Most of my Muscle cars also were fitted with exhausts and headers. So the gain was minimal if best.

 

On the Subarus I have put CAI's on it was more of a "cool noise" but no real benefit that I could feel. But i always was able to negotiate an SPT intake into the sales with install so the cost factor was nothing.

 

With my Infinitis I placed a Stillen Gen 3 on my G37 and that did make power gains of 4 HP on a dyno. Now this type of setup is different and had the filters in front of the radiator. I did notice fuel economy go up about one MPG when everything is clean.

 

At the end of the day when all is done you may make one HP with a cool sound factor.

[Mr. Electric Wizard]

I guess what I would like to know is that are there any downsides? The lower intake temps is one thing the stock airbox has going for it. M

[shralp]

Downsides are it may throw your MAF scaling off and with no airbus around it, it may be more like a HAI, a "hot air intake" I get it, it looks cool and all but I'd still recommend going stock airbox unless your pushing over over about 325HP. the snorkel off the bottom of the stock airbox

if you want a bit more turbo noise.

Edited March 27, 2022 by shralp

[Mr. Electric Wizard]

Dumb question but just because mine are missing.

Does the front of the stock air box connect to the body with one nut on the top (what size? 12mm) and two bolts on the bottom? All of mine are missing.

[MoleMan]

Dumb question but just because mine are missing.

Does the front of the stock air box connect to the body with one nut on the top (what size? 12mm) and two bolts on the bottom? All of mine are missing.

 

 

If I recall it’s one with a rubber bushing between the body and the airbox. I have not really looked in a long time to be honest as the EZ30 I kept stock. The EJ25 I bought new and it has stayed stock ever since.

 

For reference take a look a the Stillen gen threes and pay attention to the setup. This is the type of intake you really want. I will say one thing however. Make sure you either clean the filter on a regular cycle or buy a new one. These filters get dirty regardless of what K&N says.

[Mr. Electric Wizard]

Thanks! I found the parts diagram from Subaru and ordered the stock air box nut and bolts from them. I think for now, I’m going to stay with the stock box and the Perrin Afta-MAF pipe as suggested earlier.

[MoleMan]

Thanks! I found the parts diagram from Subaru and ordered the stock air box nut and bolts from them. I think for now, I’m going to stay with the stock box and the Perrin Afta-MAF pipe as suggested earlier.

 

 

Just some advice just in case lol.. Clean the MAF before you put it back in. Just some advice.. however I am sure you probably are aware lol.

[Mr. Electric Wizard]

The MAF that is on the car is really new so it should be good.

[MoleMan]

The MAF that is on the car is really new so it should be good.

 

 

The MAF being new is a huge plus. What I do is clean the MAF every other oil change when I change the air filters. I think cleaning every 10k is good preventative maintenance.