45 Degree Air Box Intake Install - Finished = Feedback?

[wtdash]

In addition to upgrading my turbo, I decided to fab something w/the 45 degree air box.

I have 2 options: Impreza or Outback

Here's a pic of the fender-side hole differences. Impreza on the left; OB on the right. Guess which one I'm going with .



More to follow....

[Soul Shinobi]

Great, and pictures are always welcome. For the pickup location just bear in mind that a forward facing intake will not necessarily be best, locating the intake in a high pressure area is most important (ex. nearer to the vertical center of the front end, pressure is likely highest right at the bumper).

[wtdash]

Finished up the install.

Used a plumbing 3" to 2" adapter (closer to a 3.5"-2.25") between the MAF and my home-made CC mod/resonator delete.

Incorporated an old 90 elbow to connect to the JDM TD04 that is temporarily installed.

I also updated the fender well w/a bigger piece. I believe it's also from the same '98-ish Outback collection of intake parts I had. I cut the tube on the MAF end about 1 foot long and stuck it in the access hole. It's angled a bit down and toward the front.

The air box base will bolt into the stock holes - if the 'riser' is removed. Mine sits a bit @ an angle, and only one of the base 'feet' is bolted on. I also ran a screw into the back of the air box that connects to the fender well.

One issue is the top of the air box wouldn't fit over my K&N filter; but the same size paper filter did. I thought initially I had a Cali. Emissions model air box, which uses the newer style of filters, but turned out it was just the K&N, which I've heard mixed reviews on anyway.

After trying this, that, and the other, it finally started to come together.....I actually enjoy fabbing this type of stuff...just wish I knew whether I'm actually improving it over stock!

Certainly is NOT an improvement when it comes time to change the air filter...will have to remove the 90 from the turbo, as it's a very tight fit...albeit I could probably shorten something to get myself a bit of room....but that can wait.

If you're still awake , please take a look and give me some constructive criticism.....esp. on anything that looks like it may be unsafe for the EJ22T!

[Soul Shinobi]

Throw the K&N away. Not worth the potentially fouled MAF, IMHO. Of all the restrictions in an intake track the airfilter is usually around 2-5% of the total restriction (figures from the articles suggested below).

That white air director in the airbox probably helps (assuming it's an OEM bit).

You can measure the gains directly (assuming you go back and test the stock setup) by measuring air pressure right before the turbo at full throttle and peak torque. It's easier than you may think, read the Eliminating Negative Boost series on AutoSpeed.

http://autospeed.com/cms/search/index.h ... st&x=0&y=0

There is also another case study series using the same technique on that site called "Negative Boost Revisited."

They're real eye openers, not the best writing in the world but they'll show you how to measure the flow restriction of every part of your intake if you want to.

[93forestpearl]

I've run K&N filters for years and years for hundreds of thousands of miles without issue. And that was with sucking dirt and snow directly into the airbox. Fender completely full of snow, and the car ran great. Nasioc is funny sometimes.


That white piece is focusing a bulk of the air through a small portion of the filer. Fine with a new filter, not so fine after a while. There is no benefit to running it, more like a negative benefit.

[Soul Shinobi]

I wouldn't condemn it altogether without testing. Airflow can be very unintuitive. An example to illustrate:

The following picture is of an airbox with its belmouth inlet tube:


The owner tried to replace the inlet tube with one he made with hopes of better flow since the OEM one was so close to the airbox wall:


Looks like it should flow a lot better, but in reality after testing it turns out that the new design increased total intake flow restriction by a whole 15%.

Moral of the story is, don't think you can outsmart a professional automotive engineer based on how his design 'looks'; verify.

[SLODRIVE]

"Throw your K&N away"...Dude, that's a giant load of CRAP and I get tired of reading misinformation like this. If your K&N is properly oiled, it won't foul the MAF. Period.

Also, wouldn't it be way more accurate to measure airflow increases by logging MAF voltage at WOT?

[brand]

Moral of the story is, don't think you can outsmart a professional automotive engineer based on how his design 'looks'

...unless you're working on a British car

[Soul Shinobi]

"Throw your K&N away"...Dude, that's a giant load of CRAP and I get tired of reading misinformation like this. If your K&N is properly oiled, it won't foul the MAF. Period.

Also, wouldn't it be way more accurate to measure airflow increases by logging MAF voltage at WOT?

IMHO, and I do say IMHO, the minor flow gains from aftermarket filters aren't worth the hit to filtration performance. Again, standard air filters are large enough in surface area that the flow restriction is very small. Replacing a short corrugated section of intake tract would give flow benefits several times those from a K&N.

Pressure measurements are less subject to extreme change in the event of turbulent flow, unlike the MAF (I admit this is an educated guess). Also this measurement technique of intended for universal application, and allows measurements to give flow restriction measurements for individual parts of the intake track.

Moral of the story is, don't think you can outsmart a professional automotive engineer based on how his design 'looks'

...unless you're working on a British car

Give you that.

[SLODRIVE]

IMHO, and I do say IMHO, the minor flow gains from aftermarket filters aren't worth the hit to filtration performance. Again, standard air filters are large enough in surface area that the flow restriction is very small. Replacing a short corrugated section of intake tract would give flow benefits several times those from a K&N.

Pressure measurements are less subject to extreme change in the event of turbulent flow, unlike the MAF (I admit this is an educated guess). Also this measurement technique of intended for universal application, and allows measurements to give flow restriction measurements for individual parts of the intake track.

I'm afraid there's way too much real-world evidence to support the above claims. A high-flow air filter will make a substantial improvement in horsepower, normally 5-15 hp at the wheels. There's literally thousands of dyno sheets and dragstrip timeslips that prove this beyond a doubt. Also, to discount turbulence at the MAF is a huge tuning mistake on any engine. I think you'll find a couple of race engine builders and dyno operators who agree with this.

As far as the filtration thing...Yes, I have seen that link, it gets posted when these discussions arise on the Web. What it fails to acknowledge is that although a paper filter will normally filter smaller particles than a cotton gauze element, the difference in filtration doesn't significantly affect the engine's lifespan, again assuming the filter's in good shape and properly oiled. I have owned and worked on dozens of cars that had K&N filters for many, many thousands of miles with absolutely no loss of compression or oil pressure compared to cars running paper.

Engineers only partially design cars, ya know...the bean counters and lawyers do the rest. That's where the aftermarket comes in

[Soul Shinobi]

I don't doubt real world gains but I'm surprised it'd be that much outside of K&N literature--I am, however, inclined to trust your experience.

[Apex3]

IMHO, and I do say IMHO, the minor flow gains from aftermarket filters aren't worth the hit to filtration performance. Again, standard air filters are large enough in surface area that the flow restriction is very small. Replacing a short corrugated section of intake tract would give flow benefits several times those from a K&N.

Pressure measurements are less subject to extreme change in the event of turbulent flow, unlike the MAF (I admit this is an educated guess). Also this measurement technique of intended for universal application, and allows measurements to give flow restriction measurements for individual parts of the intake track.

I'm afraid there's way too much real-world evidence to support the above claims. A high-flow air filter will make a substantial improvement in horsepower, normally 5-15 hp at the wheels. There's literally thousands of dyno sheets and dragstrip timeslips that prove this beyond a doubt. Also, to discount turbulence at the MAF is a huge tuning mistake on any engine. I think you'll find a couple of race engine builders and dyno operators who agree with this.

As far as the filtration thing...Yes, I have seen that link, it gets posted when these discussions arise on the Web. What it fails to acknowledge is that although a paper filter will normally filter smaller particles than a cotton gauze element, the difference in filtration doesn't significantly affect the engine's lifespan, again assuming the filter's in good shape and properly oiled. I have owned and worked on dozens of cars that had K&N filters for many, many thousands of miles with absolutely no loss of compression or oil pressure compared to cars running paper.

Engineers only partially design cars, ya know...the bean counters and lawyers do the rest. That's where the aftermarket comes in

I don't know that I believe that 5-15 figure, it definitely depends on the car as well. With e30s it has been proven numerous times that a "high flow filter" will only gain you 1-2hp. The real gains you see are when you put in cold air intakes, which Subarus already have. Though I'm speaking in general, and I can't speak for what it does for our Legacys.

Filters is a thing that I generally do, K&N is all that I've used, and yes it does make things dirtier inside, that doesn't mean it is harmful to the engine, but you do need to clean throttle bodies and junk more often.

But +1 on the engineering thing, people always use that argument that engineers know better than you do, but engineers don't build cars based on performance alone, you may have different priorities than them, just look at the turbo resonator, it's just meant to quiet down the turbo, not important to you, but important to your average driver maybe. And really any performance mod is evidence of this as well.

[Legacy777]

What most aftermarket setups and home made setups fail to take into account is standing waves in the intake tract. This is why you see those oddly shaped devices on the stock intake piping. These are called helmholtz devices, and help eliminate these waves. I would think they tend to cause more issues with MAF based cars compared to MAP based cars.

[Soul Shinobi]

I don't know that I believe that 5-15 figure, it definitely depends on the car as well. With e30s it has been proven numerous times that a "high flow filter" will only gain you 1-2hp. The real gains you see are when you put in cold air intakes, which Subarus already have. Though I'm speaking in general, and I can't speak for what it does for our Legacys.

Filters is a thing that I generally do, K&N is all that I've used, and yes it does make things dirtier inside, that doesn't mean it is harmful to the engine, but you do need to clean throttle bodies and junk more often.

But +1 on the engineering thing, people always use that argument that engineers know better than you do, but engineers don't build cars based on performance alone, you may have different priorities than them, just look at the turbo resonator, it's just meant to quiet down the turbo, not important to you, but important to your average driver maybe. And really any performance mod is evidence of this as well.

In terms of power that sounds more realistic to me from things I've read, but I don't have any personal experience to share.

My original comment on engineers was somewhat of a blanket statement I admit. I do understand that longevity and ease and cost of manufacture are quite relevant too. Even so, air box and filter setups rarely have to compromise for anything but space.

What most aftermarket setups and home made setups fail to take into account is standing waves in the intake tract. This is why you see those oddly shaped devices on the stock intake piping. These are called helmholtz devices, and help eliminate these waves. I would think they tend to cause more issues with MAF based cars compared to MAP based cars.

This is very true and important, though difficult to account for. They do cause potentially major issues on NA MAF based cars. The definitive NASIOC thread: A Problem with CAI/SRIs and an Alternative (yes, finally)

[wtdash]

The definitive NASIOC thread: A Problem with CAI/SRIs and an Alternative (yes, finally)

That is a great link...@ least on 1st read.....and it sounds like it's a non-issue w/a turbo...hopefully I'm 'wave-proof'.

Thnx for the tech info!