Removing Air Box air horn, any gains?

[DaN]

I have an 85 325e with a 325i throttle body, afm boot and an 87 325is airbox.
It has a plastic airhorn inside it, that's easilly removable.

I was wondering if you guys saw any gains by removing it, it seems like it would restrict things a bit.

If it was warm out, I would have already yanked it, but I'm lazy and I want to know if my efforts are worth it.

Anyone?

[Jonathan M3]

I dynoed a 325is with and without it, the gains were neglidgible.

[DaN]

What do you consider negligable?
llike a 1-2 hp bump, or like a .2hp bump? OR a loss?

I figured it wouldn't be much, thats why I haven't done it yet.

[bimmerphile]

What do you consider negligable?
llike a 1-2 hp bump, or like a .2hp bump? OR a loss?

I figured it wouldn't be much, thats why I haven't done it yet.

varying across the power band from 0-1hp probably.

[Jonathan M3]

[DaN]

Word, thanks alot. :drink:

[OreoGaborio]

i've heard a guy on bf.c say that he ran w/o it for a while & his air filter got really dirty in one spot across the pannel.... so i THINK basically it's to even out the airflow to go through the entire filter, not a "hp robbing silencer"

[Jonathan M3]

i've heard a guy on bf.c say that he ran w/o it for a while & his air filter got really dirty in one spot across the pannel.... so i THINK basically it's to even out the airflow to go through the entire filter, not a "hp robbing silencer"

I had originally removed the airhorn from my M3 shortly after I bought it and my filters were always evenly dirty afterwards.
I think its there more to smooth out the air stream feeding the AFM.

Also, the M3 airhorns are only about half the length of the 6cyl. pieces, I'm guessing to help improve airflow volume possibly?

[DaN]

Is it possible to swap in the m3 air horn, onto a 325is airbox? lol
I'd cut mine, but then I would loose the outward flare at the end.

I suppose it would be a waste of time, but I have time to waste, haha.

[Jonathan M3]

Is it possible to swap in the m3 air horn, onto a 325is airbox? lol
I'd cut mine, but then I would loose the outward flare at the end.

I suppose it would be a waste of time, but I have time to waste, haha.

Yes they are swappable, in fact I'll get my friend to dyno his car with both and see which makes more power. :)

[E30/M30]

I don't know if you can modify your air box like mine(e34 535)but i bodged on some 4 inch pipe on mine.It's about double the size of the standard one so it's got to be less restrictive.

HTH

Andrew

[M3 Ryan]

that looks like a better setup...
once I do my Euro M30 I will have to figure out a better intake... I have an open K&N Cone now, but I am going to extend the pipe and make a heatshield for it to shield out the hot air, should be nice for my 230hp beast 8)

[Digitalwave]

Leave the air horn in. I had mine out for a while, and when I put it back in, I felt a smoother idle and stronger mid-range pull.

[E30/M30]

Leave the air horn in. I had mine out for a while, and when I put it back in, I felt a smoother idle and stronger mid-range pull.

If you didn't replace it with some thing then it whould have been sucking hot air from the engine bay ? So may be this caused it to run less well than before ?

Unless i'm misunderstanding you ?

Cheer's

Andrew

[Spaz]

Leave the air horn in. I had mine out for a while, and when I put it back in, I felt a smoother idle and stronger mid-range pull.

If you didn't replace it with some thing then it whould have been sucking hot air from the engine bay ? So may be this caused it to run less well than before ?

Unless i'm misunderstanding you ?

Cheer's

Andrew

sorry andrew but you are misunderstanding us,

the air horn is a piece of plastic pipe in side of the top half of the airbox, it connects to the afm with four bolts.
if you take off the top of the air box you'll see it and that will clarify everything up for you.