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Intake Silencer Delete Concerns

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GHott

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Discussion starter · #1 ·
I've searched and read several threads about the intake silencer delete mod...including the 6-page how-to. I also read this thread: http://www.iwsti.com/forums/showthread.php?t=94763&highlight=silencer which talks about aftermarket intakes.

The thread above is where my concerns are.

It is stated that with an aftermarket intake, the engine is being given more air...yes, no brainer, thats what aftermarket intakes are all about....so the ECU may need tuned for such a modification. A/Fr is a concern in any car...more air than fuel = lean (detonation), more fuel than air = rich (not soo good performance). This makes sense.

But, with the free intake silencer delete mod, the car is now pulling air from two places...the intake, and the fender, which means more air is entering the combustion chamber...correct? I could be wrong here, but it seems as if tho this is the way it works.

So, if one completes the intake silencer delete on an '07 STI (which is known to run lean from 0-4,000 RPM from the factory anyway), couldn't this cause the car to run even leaner, and possibly hurt performance and longevity of the engine?

I've searched this subject pretty thoroughly, and this is the best conclusion that I can draw.

Someone school me. :p
 
#2 ·
More air in yes, but the MAF g/s measurement will hopefully increase as well ;) Your car will add more fuel correspondingly. The major issue with after market intakes is that they do any combination of the following.

1) Suck in hot air from under the hood.

2) Modify the MAF signal, and even worse, not in a linear manner which makes tuning the modification out a pain in the arse. This can mess with the AFRs.

A silencer removal won't mess with your AFRs.

I've done some simple investigations into how best to get the stock airbox to flow better. Have a look. AFRs were stable.


http://www.enginuity.org/viewtopic.php?t=2257
 
#3 · (Edited)
Sounds good, but I feel like the entry point of the air does not grow when the silencer is removed.

Here is my oversimplification that seems logical...

If you put a straw into a cup of water and sip, or put a straw into the ocean and sip, despite the ocean being a bigger body of water, the straw size stays the same, and so does the amount of fluid, or in this case air, being pulled through.

Now if you use a bigger straw (a CAI for example) then you get more water (or in this case air).
 
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#4 ·
^ makes sense to me.

you might have more area to draw air from after removal but that does not mean you are drawing more air in alltogether.
 
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Discussion starter · #5 ·
StylesJim said:
Sounds good, but I feel like the entry point of the air does not grow when the silencer is removed.

Here is my oversimplification that seems logical...

If you put a straw into a cup of water and sip, or put a straw into the ocean and sip, despite the ocean being a bigger body of water, the straw size stays the same, and so does the amount of fluid, or in this case air, being pulled through.

Now if you use a bigger straw (a CAI for example) then you get more water (or in this case air).
Click to expand...
As always, great info...thanks!
 
#6 ·
Why dont you just seal off the hole you made by sawing the silencer thing off. That way it's just an elbow like the GP Moto elbow. Duct Tape it or if you want to get crazy use fiberglass. That way it wouldn't be sucking any air from the fender well.
 
#7 ·
the sensors would compensate. people wouldent be running bolt on intakes if the issues were that bad, and you would hear about it. if you are really worried, just cover the hole with tape as stated above. :)
 
#9 ·
JD_STI said:
Why dont you just seal off the hole you made by sawing the silencer thing off. That way it's just an elbow like the GP Moto elbow. Duct Tape it or if you want to get crazy use fiberglass. That way it wouldn't be sucking any air from the fender well.
Click to expand...

Then it becomes a funnel for water in heavy rain, right into the airbox.
 
#10 · (Edited)
Szumita said:
the sensors would compensate. people wouldent be running bolt on intakes if the issues were that bad, and you would hear about it. if you are really worried, just cover the hole with tape as stated above. :)
Click to expand...
The issues can be that bad with after market intakes. I've seen the SPT a few times over change the maf signal to read more air than whats really being ingested by the engine. The result was an overly rich AFR. Other intakes like the k&n can cause the maf reading to read less air than whats really be ingested, with a corresponding lean condition. And with the k&n its been speculated that this lean condition is where most of the power gain comes from. The stock map is too rich to start with.
 
#11 · (Edited)
StylesJim said:
Sounds good, but I feel like the entry point of the air does not grow when the silencer is removed.

Here is my oversimplification that seems logical...

If you put a straw into a cup of water and sip, or put a straw into the ocean and sip, despite the ocean being a bigger body of water, the straw size stays the same, and so does the amount of fluid, or in this case air, being pulled through.

Now if you use a bigger straw (a CAI for example) then you get more water (or in this case air).
Click to expand...
With a CAI that has a larger inner diameter you need to scale your maf table. Depending on the intake it can be a real pain. Of course then you have those not so awesome hot air intakes to choose from. Under hood air ftw.

You can make the *straw* bigger with the stock airbox. You could go as far as making the airbox hole that mates with the fender the size of the hole in the fender.

Here is my setup.

Before
Image


After
Image


Sealing things off with the foam kept the IATs in check (cold air from fender).
Image

Image


Measured increase in air flow. No filter vs stock filter vs modded airbox and k&n panel
Image


All the data is in my first post link.
 
#13 ·
Tgui said:
You can make the *straw* bigger with the stock airbox. You could go as far as making the airbox hole that mates with the fender the size of the hole in the fender.

Here is my setup.

Before
Image


After
Image


Sealing things off with the foam kept the IATs in check (cold air from fender).
Image

Image


Measured increase in air flow. No filter vs stock filter vs modded airbox and k&n panel
Image


All the data is in my first post link.
Click to expand...
one word, ghetto.
 
#20 ·
KarlSTI said:
Deleting the silencer and leaving the elbow open to pull from the snorkle and from the wheel well will not draw in water per my high speed testing in a Florida deluge. ;)
Click to expand...
I never wanted to test. Then again I'm sure you don't speed through white out rain conditions. After seeing water drip out of my stock snorkus thing I decided to go all rain man on my setup.

I like my ghetto rain man setup. :D
 
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