Thoughts on Stock Air Box Filters

[Fiat_Phil]

How many of you have replaced your stock air box filter with a after market one? Thinking of getting a Sprint Filter any feedback is appreciated. Thanks.

[reedbri]

I had swapped mine out for a BMC filter. I ran with it for about 2 years, and it definitely made a difference. I'm sure it didn't add any horsepower, but it did seem to pull a bit better. I just changed it out for my AFE intake a couple of months ago, so it's sitting on a shelf.

[Oli]

I have also the replacement filter in mine, combined with a dual air intake. Pulls better and makes also a little louder intake noise.

[KellyfromVA]

Purely placebo effect. No different than feeling like your car runs better after it's been washed.

Aftermarket air filters have little nor any performance benefits. In fact, they can easily do more harm than good.

Here is a pretty good side-by-side tests of aftermarket air filters. As you can see in the video, the amount of air needed is directly proportional to the actual horsepower capacity of the engine, not the other way around. Putting a "low restriction filter" on just means there is a better chance of passing more dirt along with air:

[ice445]

Purely placebo effect. No different than feeling like your car runs better after it's been washed.

Aftermarket air filters have little nor any performance benefits. In fact, they can easily do more harm than good.

Here is a pretty good side-by-side tests of aftermarket air filters. As you can see in the video, the amount of air needed is directly proportional to the actual horsepower capacity of the engine, not the other way around. Putting a "low restriction filter" on just means there is a better chance of passing more dirt along with air: https://www.youtube.com/watch?v=GS69owXpGdY

Normally correct but this engine runs a deficit when it comes to airflow. The more air you can shove in it, the more top end power you will see. It's slight, but 10HP is 10HP. Obviously a drop in filter is going to give the smallest amount of gains compared to a full intake replacement, but this has been dyno tested.

[KellyfromVA]

10HP on a 100HP (down hill with a tail wind) engine is a huge increase. I don't see just an air cleaner or aftermarket air box ever generating that sort of gain, unless the stock air filter it replaced had 100,000 miles on it, so the engine was only producing 80HP to begin with.

[Oli]

I think it´s always the whole concept. Installing a cotton-filter makes no sense, if you don´t also remove the restrictors, that come OEM....I´m not sure of what engine you are talking (I was thinking this is the N/A section), but cutting off the intake hose that is sticking in the air-box right after the narrowing, is surely no disadvantage....

[ice445]

10HP on a 100HP (down hill with a tail wind) engine is a huge increase. I don't see just an air cleaner or aftermarket air box ever generating that sort of gain, unless the stock air filter it replaced had 100,000 miles on it, so the engine was only producing 80HP to begin with.

Sorry, I'm only talking about the turbo ones. On a NA motor you probably wouldn't see any changes.

[KellyfromVA]

Sorry, I'm only talking about the turbo ones. On a NA motor you probably wouldn't see any changes.

Okay understood. That said; generally manufacturers will take superchargers or turbochargers into account when designing the intake path. Sure, I get the whole wanting to hear the cool side of the turbocharger spool up and down more clearly, but I still believe based on tests I've seen that there is little benefit to "low restriction" air filters with an engine that produces less than 500HP.

[Fabio13]

I think it´s always the whole concept. Installing a cotton-filter makes no sense, if you don´t also remove the restrictors, that come OEM....I´m not sure of what engine you are talking (I was thinking this is the N/A section), but cutting off the intake hose that is sticking in the air-box right after the narrowing, is surely no disadvantage....

Looks to me like you're losing intake air velocity by cutting. Bernouli's Principle.

[Oli]

Looks to me like you're losing intake air velocity by cutting. Bernouli's Principle.

But that´s not a carburetor....for what do I need air velocity, when the air, after passing the narrowing, will enter the plenum in front of the air filter, then passing the filter entering the plenum after the filter and then finally will go through the throttle body...
No this thing is simply an air restrictor to reduce intake noise.

Or do you think these are also inserted due to the positive effect of high air velocity...?

http://www.speedhunters.com/2010/06/car_feature_risi_competizione_ferrari_430_/

risi19.jpg