I have a 97 Outback wagon automatic. Since I can't get a cold air intake for the car, I was wondering if anyone here has had any experience replacing just the air filter -- performance, mileage, etc. In other words, will it pay for itself over time and is it worth it?
On a subaru? no. On several motorcycles -- yes On a drag car - yes on several race cars - yes.
The ONLY way to "improve it" is by altering the computer & exhaust as well. the computer compensates to bring everything back to "normal" (in it's eyes)
Improving intake does nothing if you do not improve the exhaust, typically an adjustment ot intake mixture is also required -- it really is a can of worms. I don't believe anyone that says "I put a k&n (or AFE) on my car and I get better throttle resonse & better millage" -- it's in their head. The same for "cold air intakes" Modern engines are SYSTEMS, everything is designed to work together -- and the brain will compensate to make it all play nice, typically to the effect of decreased performance.
Also; the K&N, unless properly maintainced (which most people do not do) will do one of two things: Let LESS air thru or MORE dust thru.
You cannot (as in normal oil changes) "clean your K&N" and "pop it back in" -- later than day? Maybe, the next day, probably -- it has to DRY completely after washing it, then you have to oil it -- most people screw up on the oiling, either too much, or too little -- or worse, oil it while it's still wet.
You have to be careful using these filters on newer cars. K&N's (or any filter that must be oiled) can foul the mass airflow sensors on some cars (Audi's in particular) leading to CEL's and driveability issues. Here is another view -
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Pet peeve: why are aftermarket intake systems called 'cold air intakes'? You're replacing a stock system that takes actual outside air with a system that doesn't - the air filter sits under the hood, sucking in nice hot air (regardless of whether there is a 'heat shield'.). Could never understand that terminology.
If the thing is designed properly, it will pick up air near the same point as the OEM airbox did, and the air should be cooler than the ambient eng compartment air.
They also make a 'deflector' for most intakes that helps scoop the air from the point where it comes into the eng. comp, helping to ensure the air is at the intake is cooler than ambient. Does it work? I dunno...
A *real* Cold Air Intake, like an Iceman, routes to just under the front bumper of the car, making sure the air coming into the intake is cooler than the eng comp air.
I put an 'intake' on a Tercel, and noticed 2 things right off the bat:
Throttle response was better. We're talking about a 1.5l engine here, so
*ANY* 'performance' gain would be noticable; but off the line, it was better.
Fuel economy. This car had an AT and managed 38 MPG combined City/Highway with my style of driving (rarely under 50, and 70 on the highway). After installing the intake, *COMBINED* fuel economy settled between 44-46 MPG!!!
Considering that's what a Prius averages, I'd say that's pretty decent!
On my Tercel, it was all in my wallet...a $50 Intake raised the fuel economy from ~38 MPG to ~45MPG.
And I keep records on all my cars. I have an '85 Corolla GTS in the back yard with a black notebook documanting every fillup the car has had since I owned it, along with a computation of the mpg.
21 YEARS worth of fillups!
In the Teercel's case, there were 3 months of fillups at 36~38 MPG, and after the installation of the intake economy ranged 43~46 MPG.
Another interesting note: there was NO variation for Hot/Cold weather. The fuel economy remained consistant for the three years I owned the car.
Well, we just out a deposit on a '99 Impreza RS2.5. It has a cold air intake! It is actually routed out of the engine compartment into the passenger's side fender area, behind the headlight, the stock location, apparently. It's a bigger tube - the brand is Injen. Looked very spiffy.
I see they have them for my 04 outback. A bit less than $300. I wish I knew of them when car was newer. If /i keep the car I may get one but I hope to get new vehicle next year. so who knows.
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