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95 GC 371hp/355tq ej25 1.5xtr
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Discussion Starter · #1 ·
i was wondering if MPG is effected my air filters. like... now i have a ganzflow with a stock air filter, would MPG be increased if i get a K&N? do you think it will help my powerband as well?

what about regular cold air intakes. i want to get a Cobb but if that doesnt happen i will get a OBX cold air. how does OBX CAI vs ganzflow with K&N filter effect MPG? a K&N filter will go on the OBX intake too.

or does it not really matter? not a big enough different to matter.

if it helps the car too. i have all the N/A bolts on's. full catless exhaust, IM/TB spacer... ect.
 

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1998 Subaru Impreza RS - RBP
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Can't go wrong with a K&N. Most you will EVER see is 1-3 mpg increase and 3 is really pushing it.
 

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95 GC 371hp/355tq ej25 1.5xtr
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4,494 Posts
Discussion Starter · #4 ·
this is my contradiction. with a TB/IM spacers it really puts the torque box far back. it almost touches my strut bar. i have to stretch the vac lines but i like it because of the low end...etc. and the vac lines are easy to put on. but i want more top end, i want to hear my exhaust over my intake so thats why i have a ganzflow. so im stuck between

ganzflow with K&N (better low end for DD) or OBX cold air (better top end, and i hear the intake more than the exhaust)

:confused::confused::confused::confused::confused:
 

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1998 Subaru Impreza RS - RBP
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Keep the low end power IMO. If you want much high-end, get cams...
 

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JBCUSTOMS
2001 Impreza 2.5RS STM
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Keep the low end power IMO. If you want much high-end, get cams...
True Dat!

Plus obx is garbage compared to other intakes, look into cobb, AEM, or weapon r if you are gonna go CAI.

You dont gain gas milage by getting more air, your car balances the mixture... more air=more fuel...=worse gas milage.
 

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1998 Subaru Impreza RS - RBP
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You do get better gas mileage by putting in a more flowing intake system. He's not "getting more air" he's just make the air have an easier path to flow, which will make the car run better/easier. :)
 

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JBCUSTOMS
2001 Impreza 2.5RS STM
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2,486 Posts
You do get better gas mileage by putting in a more flowing intake system. He's not "getting more air" he's just make the air have an easier path to flow, which will make the car run better/easier. :)
Agreed. I misunderstood the second post. :blol:

Keep the ganzflow! Get a K&N panel filter... and you're set!
 

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2001 BRP RS Coupe 5spd
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I have been running a K&N Panel filter for about 6 months now.

I used to get 25 MPG average, but after changing the filter, tranny fluid, diff fluid (All Redline stuff), and fuel filter I now get a consistant 27-28 mpg.

I am not passing everyone on the road, or hammering the throttle around corners though. :burnout:
 

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'17 Impreza Sport, '15 OB 3.6R
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K&N is okay, I have one that's been there for nearly 8 years. I think the OEM STi replacement filter is better, though.
 

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1998 Subaru Impreza RS - RBP
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^^^^ You ever take it out and clean it...?
K&N is rated #1 in the world for a reason.
 

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It shouldn't. The air-fuel ratio stays the same anyways. The efficiency of the engine isn't affected, just the available airflow. More air + same A/F ratio = more fuel used. Even then, it will only happen at WOT near maximum RPM. Other than that, little or no change in the MPG should be expected...
 

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2000 Impreza Sedan
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It shouldn't. The air-fuel ratio stays the same anyways. The efficiency of the engine isn't affected, just the available airflow. More air + same A/F ratio = more fuel used. Even then, it will only happen at WOT near maximum RPM. Other than that, little or no change in the MPG should be expected...

that's the way I always though it
 

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'04 RS PBP w/ Black Tarmacs
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Here's my set-up...


It's a PDM intake which is like a Ganzflow, but one solid piece and a 3" elbow I grafted into the stock Airbox. I got the 3" elbow and coupling off ebay.

Anyway here's what my research has revealed. One... yes K&N's flow better than stock paper filters. Two... stock paper filters will filter better than K&N's. Since they're both surface filters they also both start to clog quickly. Three...the filter on the RS is oversized.

I ran a K&N on my RS for a while. I recently switched back to paper because I feel the size of the filter in plenty big enough to flow sufficiently regardless if it's paper or cotton-gauze and I wanted maximum filtration. It should be known too though that I live in a fairly dusty climate.

So my take on this. K&N's = more flow----- Paper = better filtration.

That said you want more air going in get rid of that stock elbow with a 2" opening and upsize to a 3".

On a different note. It's my belief that the best way to increase mileage is with a reflash such as I-speed's. I know my car runs way too rich as it is now. I'm waiting until my cams get a Delta regrind then I'll flash to the new SRS-30 reflash which has exactly my mods. It should be noticably more power, but I think my mileage will increase too.
 
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