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Guest Message by DevFuse
 

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What's with a the plastic on the Air intake?


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11 replies to this topic

#1 abubailey

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Posted 05 April 2005 - 01:02 PM

Do I really need all the plastic air filter tubing that came stock on my '04 Subaru Legacy? Anyone have any suggestions on generating more horsepower from my 2.5L?

#2 cannonball

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Posted 05 April 2005 - 02:03 PM

From my research here and yonder it appears that unless you want to spend some serious cash there's not much you can do except possibly a CAI with a K & N type filter. This supposedly will cause you to lose some hp at lower rpms, but increase to top end. I personally have no desire to try it out.

#3 SevenSisters

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Posted 05 April 2005 - 06:47 PM

Why does everyone buy a Subaru and then want it to run like a 'Vette?

God I must be getting old.

#4 cblwilson

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Posted 05 April 2005 - 10:20 PM

Maybe cuz they have more power than people think? My '90 Legacy wagon seems to have some serious get up and go for a Subie.

#5 Gnuman

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Posted 05 April 2005 - 11:47 PM

Maybe cuz they have more power than people think? My '90 Legacy wagon seems to have some serious get up and go for a Subie.


Well, it needs to, in order to keep up with mine, just south of you. . . :brow:

#6 subie94

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Posted 06 April 2005 - 07:20 AM

Do I really need all the plastic air filter tubing that came stock on my '04 Subaru Legacy? Anyone have any suggestions on generating more horsepower from my 2.5L?



cold air intake or k&n filter that goes in stock location,cat-back exhaust for starters.of course you mpg is gonna go down

#7 friendly_jacek

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Posted 06 April 2005 - 09:11 AM

The intake in 2000+ subs was optimazed at factory for more torque at low to mid RPM; drive older subaru and you will see a difference. If you don't like that extra torque, go ahead and take it off.

#8 wkoepp

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Posted 06 April 2005 - 10:47 AM

Having experimented with Miatas, in my opinion there's nothing you can do to the torque unless you can alter the timing; the air intake and any attendant nodules put there to quiet the sucking sound is restictive because of the length ( just try attaching 50 foot of hose to your shop vac and see what the added friction does for the power). Adding or keeping the cold air intake is important as colder air is a denser air/fuel charge to each cylinder.
I tried a cold air intake out by first running a set course ( no cold air intake) on a hot day and the thermocouple recorded 90 degrees inside the filter box, then I hooked up a cold air intake, ran the same course immediately and recorded 80 degrees in the box, a denser air/fuel charge. A K&N air filter helps as it's less restrictive, it cannot change the engine torque, only timing can do that in a home shop. An engine builder can alter the torque by changing the cams or using adjustable cam gears which are available for some makes like Mazda.
If you want more hp, incease the air/fuel charge with a turbo or add cubic inches.

#9 friendly_jacek

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Posted 06 April 2005 - 11:34 AM

Having experimented with Miatas, in my opinion there's nothing you can do to the torque unless you can alter the timing; the air intake and any attendant nodules put there to quiet the sucking sound is restictive because of the length ( just try attaching 50 foot of hose to your shop vac and see what the added friction does for the power). Adding or keeping the cold air intake is important as colder air is a denser air/fuel charge to each cylinder.
I tried a cold air intake out by first running a set course ( no cold air intake) on a hot day and the thermocouple recorded 90 degrees inside the filter box, then I hooked up a cold air intake, ran the same course immediately and recorded 80 degrees in the box, a denser air/fuel charge. A K&N air filter helps as it's less restrictive, it cannot change the engine torque, only timing can do that in a home shop. An engine builder can alter the torque by changing the cams or using adjustable cam gears which are available for some makes like Mazda.
If you want more hp, incease the air/fuel charge with a turbo or add cubic inches.


Quoted from http://www.cobbtunin...m/tech/airflow/

"Lets start with the intake manifold which is designed with long runners branching off of a relatively small plenum chamber in the center. The long, small diameter piping works well to provide low-mid range torque by improving cylinder filling at low RPMs. At high RPMs though, this long tube design can eventually become a restriction and would need to be addressed. Don't necessarily think you need to go out and spend your hard earned money on a new intake manifold quite yet though. The cylinder heads are still the biggest restriction in the intake system so you're better off addressing that first before swapping over to another manifold. If and when different intake manifolds become available, be sure they are part of a system which also includes a matched cylinder head and cam. Otherwise, you might end up with a intake manifold designed to work at high RPMs and a cylinder head and cam designed for low RPM torque. Unfortunately, there is no one manifold design perfect for every application and be wary of manufacturers who claim otherwise."

#10 Scottbaru

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Posted 06 April 2005 - 09:15 PM

The intake in 2000+ subs was optimazed at factory for more torque at low to mid RPM; drive older subaru and you will see a difference. If you don't like that extra torque, go ahead and take it off.

A guy down the street has a '96 Legacy L wagon and an '03 OBW, says the '96 seems faster. Bought both new.

#11 Setright

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Posted 07 April 2005 - 12:57 AM

Yes, but that's cause they have the same engine, but the 03 weighs 300kg more!!

#12 abubailey

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Posted 08 April 2005 - 03:15 PM

Having experimented with Miatas, in my opinion there's nothing you can do to the torque unless you can alter the timing; the air intake and any attendant nodules put there to quiet the sucking sound is restictive because of the length ( just try attaching 50 foot of hose to your shop vac and see what the added friction does for the power). Adding or keeping the cold air intake is important as colder air is a denser air/fuel charge to each cylinder.
I tried a cold air intake out by first running a set course ( no cold air intake) on a hot day and the thermocouple recorded 90 degrees inside the filter box, then I hooked up a cold air intake, ran the same course immediately and recorded 80 degrees in the box, a denser air/fuel charge. A K&N air filter helps as it's less restrictive, it cannot change the engine torque, only timing can do that in a home shop. An engine builder can alter the torque by changing the cams or using adjustable cam gears which are available for some makes like Mazda.
If you want more hp, incease the air/fuel charge with a turbo or add cubic inches.



That's exactly what I thought. I likened all the extra tubing to trying to breath underwater through a 50 foot garden hose instead of a one foot snorkel. I took it off and didn't sense a difference at all in the low end torque. If anything, the tubing was there to reduce the engine noise when the throttle is wide open. My car sounds like it had a $1500 intake and exhaust job done on it. Pretty cool actually, and it has a little more giddyap, especially when it is sucking hard on the the high end.




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