Hi all.

Any thoughts on modifying the airbox by drilling 4 or 5 .5 inch holes along the bottom with a "valve" on each (this could be as simple as a flexible rubber "flap" that is screwed down on one side)? The theory is as follows:

When the engine requires more air than it is getting from the stock intake, the vacuum pulls additional air in through the holes (the flanges flex open with the air being pulled into the airbox). When the car is at speed and presumably pushing enough air into the airbox, the valves are pressed closed and the positive pressure is maintained (I assume this is better for the engine since positive pressure means more air is forced into it).

With open-cone setups and open airboxes, there is no ability to establish positive pressure. This mod would be for increased performance/fuel economy and not sound as the latter is not my goal.

In any event, I know nothing about engine mechanics or design so all of the above may be complete bullshiznet. Any thoughts from those of you who actually know about this stuff?

P.S. I know about the DDM Works and the K&N Typhoon, etc. and I've read the other posts about the open cone option. However, I'm exploring an alternate theory/method and whether it would be preferable.

Thanks!

Dan

 

My guess is theyd open regardless.

But i can tell you on my S, a swiss-cheesed stock intake box = no difference in itself... probably pointless.

 

Thanks iwash.

So do you think even at speed the airbox is never at positive pressure (i.e. it will still pull extra air from the outside)?

I guess I'm narrowing my question down - is positive air pressure a factor in a naturally aspirated engine (i.e. will having an open airbox - and no positive pressure - affect engine performance negatively)? I'm guessing it doesn't since both the DDM and K&N are open CAIs and they report HP gains in their dyno tests.

Dan

 

I was just under the assumption that the factory tube or whatever, in itself would supply enough air. Those advertised power gains are probably way up in the WOT high rpm range too, where you dont (really) need it (most all of the time)... I think exhausts tend to do the same, but thats another thread.

Usually the benefit to at least changing the filter media is just to use something that stays cleaner longer than stock paper.

I did just realize the whole 'swiss-cheesing' of a stock airbox pretty much just makes it an open filter situation.... nothing like what you were initially asking about....

I think your always definately still pulling air from the outside. My vote is there is no positive pressure from a n/a cooper intake system

Your flap idea is kind of like the old "Ramcharger" scoops that could be opened up for more air when needed... though todays cars have computers that do that for us.

I also think im thinking of these valves the opposite direction as you, so they would open when MORE air is needed, not when EXCESS needs relieved (I dont think that would happen)

 

Nope, I think we're thinking the same way (I probably just explained it poorly). The flaps/flanges would be mounted on the inside of the airbox and would flex/swing inwards when more air is being used by the engine than the airtube can supply. So the same as you have in mind.

I just thought that if there was ever positive pressure (i.e. a lot of air being rammed down the tube at high speed), there might have been an advantage to having the flaps/flanges pushed closed sealing the airbox and maintaing the pressure rather than have it spill out of the drilled holes.

Doesn't seem like it though...

Thanks again.

 

Yeah youd need a very short ram intake with some giant scoop, and enough speed to make it plausible

 

Any intake on an MC won't really make much of a difference unless you're just going for sound. The open cone I ran with for about 10k sounded sweet but I doubt it made any more power than the stock air box.