Just wondering, has anyone ever actually done a dyno comparison with the stock air box vs a cone filter?
I know they don't make much of a difference at all, but I'm curious to see if anyone got actual whp out of one.

BTW this is really directed at N/A guys, so I'd really rather hear from them.

 

been done... about a 6 (well 5.9) HP increase when used with cold air box and a cone filter of at least 5.5 inches tall and 6 inchs round.

Any smaller than that for the filter and you would be smaller than the stock filter.

 

is that to the wheels?

 

yeah, wheel or crank hp?

What about a stock box with a cut off top?

 

I don't remember if it was at the wheel although I imagine it was since it was the car on the dyno and not just an engine.

You may wish to search and find the thread... it was about a year or two ago.

 

Sorry Icemark, but I find those statements misleading. I would like to clarify some things so that the casual reader doesn't get the wrong impression.

1) The stock filter is not necessarily a restriction due to its size.
2) You cannot compare filters by exterior dimensions alone, as the material, design, and pleating will also determine its effectiveness.
3) Once you get to a certain point, increasing the size of the filter no longer increases the airflow or the performance, although it may take longer to get dirty.
4) The performance increase due to a high-flow filter is geometric, not arithmetic. Therefore, higher-horsepower engines will gain more horsepower from a high-flow filter than will stock engines. K&N states a 2-4 percent increase in horsepower.
5) LOL, you don't need a 5.5 x 6" cone filter to gain performance over the stock air box. For example, a K&N filter 6" long 6" dia tapered to 4.63" is good for 400 bhp.

 

I was wondering if the increased flow capacity of the cone outweighed the cooler air you get with the stock box. The restrictiveness of the stock box comes from the shape and the number of turns the air has to make, rather than the filter element. Looking at the two side by side, I'd bet anything that my stock filter element has more surface area than the cone filter, but the air has a straighter path when going through the cone.
It really seems like mazda put a lot of effort into getting cool air to the engine, so I can't imagine a cone filter sucking in hot air making any difference.

 

actually you can... for example if you were to compare the K&N panel fliter vs the a smaller cone than mentioned you would find the filter panel less restrictive.

Quote:

3) Once you get to a certain point, increasing the size of the filter no longer increases the airflow or the performance, although it may take longer to get dirty.

I would agree with that 100%

Quote:

4) The performance increase due to a high-flow filter is geometric, not arithmetic. Therefore, higher-horsepower engines will gain more horsepower from a high-flow filter than will stock engines. K&N states a 2-4 percent increase in horsepower.
5) LOL, you don't need a 5.5 x 6" cone filter to gain performance over the stock air box. For example, a K&N filter 6" long 6" dia tapered to 4.63" is good for 400 bhp.

Your 6x6/4.63 would be larger than the area from a 5.5x6 and that is the point. A small 3x5/3 cone filter would be considerably more restrictive than the stock panel filter if the filtering materials are the same.
But thank you for helping clairify my remarks, I wouldn't want to be misunderstood on this.

 

Um, so what do you get when you solve for the lateral surface area of a conical frustum of those dimensions? (Feel free to get help from a math whiz if you like). So how do those filters compare now?

That would depend on the design of the intake, the airflow under the hood, and the requirements of the engine. This SAE J1349 formula calculator may help to understand the general relationship that pressure and temperature have on engine performance:
http://wahiduddin.net/calc/calc_hp_dp.htm

 

The surface of a typical cone filter is actually a rectangle. When it's pleated & rolled up the pleats are closer together at the small end..

 

So in other words, 2) You cannot compare filters by exterior dimensions alone, as the material, design, and pleating will also determine its effectiveness. Wow, so not all pleats are the same, even from the same manufacturer. That's a great point.