Thread: Cone filter vs Air box

I am going through the process of redesigning my intake tubing and had a few thoughts.

Would adding a large box with filtered inputs be better than putting a cone filter directly on the velocity stack? What i am thinking is that the filter has some effect on the air coming into the velocity stack and piping. Thoughts? In the end I can actually test this on the dyno, and i may end up doing this, but i thought i would get some input first. This would also completely isolate the incoming air from the engine bay.

My guess is that when all of the aftermarket intake systems come with a cone filter that it is the best way to go and i should not go through the trouble of making anything. But in my case i have a rather large area for such a box, where in most cars there is very little space, thus the small stock intake boxes.

My setup now. I could make the area even bigger by not putting the angle in and have it go straight from the headlight to the shock tower. I am guessing i could get 2-3 cubic feet of space.

i reckon theres maybe slight gains from doing what your thinking if your maf was closer to the air filter, but maybe not much difference where it is there now.i remember reading about air turbulence (affecting maf readings) is less with a panel filter rather than a cone filter. that said, you also want the air filtered, and theres extra power if the airs cold (ie sucking from outside the bay) so an airbox setup is a good idea.

I will be getting rid of the MAF and going to speed density so i have more flexibility. I will need to make sure i can get enough air into the box, i might cut out more of the metal that goes into the cavity behind the bumper.

I think you should try it and see. As long as the air flow isn't restricted in any way, there shouldn't be any issues with the setup, other than making sure that the box is properly sealed so that unfiltered air or debris doesn't enter the chamber. I don't think the gains would be huge in the end but that's just a guess on my part. I also have plans to do a very similar thing in the future.

If you do decide to do it, I would do do some research on flow stack placement. In an intake manifold setup, you ideally want the trumphets to be raised off of the manifold floor. This is done for two reasons. First, the air moves slower along the walls and floor versus in the centre of the plenum or just slightly away from the walls. Second, it is usually ideal to have the tops of the trumphets/bellmouth in line with the centre of the throttle-body entrance. When you relate this to an open-style air box setup, the same or similar theory might be able to be applied here. In my theory, if the box is designed properly, you may be able to take advantage of this same phenomena to some degree. More specifically whether or not you put the end of the flow stack flush with the side of the box or make it so that it juts out into the box a bit. Another consideration would be to design the box so that it tapers or is formed to meet the flow stack in a way that lengthens the flow stack but yet continues the taper. I hope the last part made sense...

Interesting food for thought though. I like when people thinnk outside of the box (pun intended). Even if the experiment proves fruitless, usually something is learned along the journey that may be applied elsewhere at a later date.

I found that out of the hole acceleration is better with an air box on my car, as compared to just a cone filter on the end of a tube.
An airbox creates a slightly pressurized envelope of air around the filter. Air entering the box slows, so pressure is slightly increased.
Box volume, shape and opening size need to be experimented with, unless you have the engineering chops to do the math

I totally wouldn't mind if you sent me that divider if you don't want to use it

My thought is to make some boxes to bring to the dyno of various volumes. They would not have to fit in the car and i could test tubing length, position of the velocity stack in the box, and box opening size. I would also test just the velocity stack with and without the cone filter and different tubing length. I know Payu says the longer the better, but how long is too long or too short. I will have no MAF to deal with so it should be fairly easy, i will need to find some cheap 3.5" piping that i can have various lengths of.

The first series of tests would be the velocity stack with no filter and just change the length of the tubing. This would be the best case scenario, everything after that would be compared to those numbers. Then i would add the filter to the best length and see if there are any gains or losses. If no or minimal losses there would be no need for further testing. The only other variable would be to plot IATs with the divider vs a box.

I can look at IATs from this fall and see but they were pretty cool with my divider in from what i remember, i never did compare without the divider as i had planned, but i can do that in the spring.

for the first few runs i would run the OE air box with an aftermarket panel filter and move on from there. i would say the OE set up with cold air feed, will be the best all rounder.

I would be willing to be that the stock air box does not have the flow capacity for what i need. It was designed for a DE making 140 HP at the crank, and not designed for high flow at that. The inlet to those boxes is ~2.5", no where near the 3.5" i will be running, it would be a choke point. Also the volume is quite small, i would like as much volume as i can get to help tip in throttle response.

The idea is that this box will have a large volume to have air on demand that does not have to go through a filter, ie less resistance, then once a vacuum is created in the box it will draw air through a large filter or filters, effectively increasing the area of the filter to reduce resistance. And also hoping that by not having a filter on the velocity stack increasing the flow there as well.

The best case scenario is running just the velocity stack with cold inlet air. If i can replicate a large enough volume box to where the air flow is not restricted it should be just as good. My question that i will hopefully answer is just how big the box needs to be. Or at what point the gains are diminishing.

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90mm will do the stock box.