Running without airbox lid?

[Space Fox]

Just finished install of the CarboProject plenum and really liking the look and additional induction noise running without the airbox lid on. Curious what the real negative effects of running without the lid are? I would assume heat soak could become a concern but as long as the car is moving there is still plenty of cool air being forced by the filter. Dirt/dust? Has anyone confirmed there is any real performance loss?

[roastbeef]

i think you'll be ok, but here are some things to ponder.

heat soak isn't going to be a concern from an engine health standpoint. on a naturally aspirated engine at sea level (i see you're in florida), you're not going to run into problems even on the hottest day. you might not make as much power if the engine retards timing a little, but you won't be knocking. forced induction is another discussion.

i had that same afe intake for a few years. i know the neck that the filter secures to is gloss carbon and it can slip off if you don't tighten it down enough, or try to get it too tight. without the lid, the only thing securing that carbon afe neck is the hose clamp at the plenum. the airbox lid helps secure the neck and reduce vibration. with that neck bouncing around, i'd worry about that filter bouncing off.

dust isn't going to be a major concern, its already exposed to the same dust.

[BayE30]

half carbon plenum, half an air box. seems logical.

[amrazM]

Originally Posted by BayE30

half carbon plenum, half an air box. seems logical.

youre gonna lose the exhaust effect from the back of the airbox as well as the function of the air coming in from the front.

[Space Fox]

Originally Posted by amrazM

youre gonna lose the exhaust effect from the back of the airbox as well as the function of the air coming in from the front.

All of the air coming from the front still passes by the filter as it normally would. I suppose you're right about any exhaust effect from the nostril at the back of the box (which I assume you're referring?) but again how much function does that really serve?

roastbeef I appreciate the thoughts. Good point about the filter, will be something to keep an eye on.
I think I'll run this set up for a bit and see if I experience anything negative. My next track day I'll add the lid back but for the time being just running around on weekends I think it'll be fine.

[M43S7RO]

So you are going for looks and sound at the expense of inhaling hot underhood air? Seems like a bad move to me, BMW (and every other manufacturer) would have left it without a lid if it was better.

By removing the lid you also lose the seal it creates which forces the intake to inhale the air coming through the front/rear inlets. Sure you'll still get some air coming through the front but I would think the hot air is gonna be the first in.

Like roast said, at worst your engine will just pull timing to compensate for a hotter, less dense air/fuel mixture. But why do this for looks sound? Isn't your plenum already and intake giving you more sound?

I'd be interested in data logs with & without the lid as opposed to butt dyno impressions.

Originally Posted by Space Fox

All of the air coming from the front still passes by the filter as it normally would. I suppose you're right about any exhaust effect from the nostril at the back of the box (which I assume you're referring?) but again how much function does that really serve?

roastbeef I appreciate the thoughts. Good point about the filter, will be something to keep an eye on.
I think I'll run this set up for a bit and see if I experience anything negative. My next track day I'll add the lid back but for the time being just running around on weekends I think it'll be fine.

[Space Fox]

Originally Posted by M43S7RO

So you are going for looks and performance at the expense of inhaling hot underhood air? Seems like a bad move to me, BMW (and every other manufacturer) would have left it without a lid if it was better.

By removing the lid you also lose the seal it creates which forces the intake to inhale the air coming through the front/rear inlets. Sure you'll still get some air coming through the front but I would think the hot air is gonna be the first in.

Like roast said, at worst your engine will just pull timing to compensate for a hotter, less dense air/fuel mixture. But why do this for looks sound? Isn't your plenum already and intake giving you more sound?

I'd be interested in data logs with & without the lid as opposed to butt dyno impressions.

I am not in any way claiming it is better, I absolutely believe the manufacturers got it right. I just believe any negative impacts are negligible.
The amount of clean air forced in from the duct in the front bumper is significant - enough to blow the excess oil off of my filter. Hot air rises so I would imagine this clean air forced in and past the filter would keep most of the heat coming from the engine itself at bay at least while the car is moving. While stopped or moving slowly yes, I could see the warm air from the engine mixing with whatever cool air is entering the filter box but again to what effect? I would love to see some data run on this but even on a dyno it would be nearly impossible to replicate the effects of a real life driving scenario even with fans, etc.

[Cyberdemon]

This is all conjecture, but opening that hole which is normally sealed now opens up all the crap falling in the hood vent to go wherever it wants in your engine bay, which I suspect will introduce dramatically more dirt/debris since normally that stuff just rolls into the bottom of the airbox.

As mentioned, unsealing that system likely just introduces more hot air (hurting performance) and hurts airflow which I'm sure was optimized with quite a bit of CFD analysis.

So I think in the end "the car will run and be just fine, but you're hurting everything else because it looks cool." I think that goes for pretty much every aftermarket intake at this rate - hurting performance for aesthetics and louder wooshing noises from the uncontrolled airflow.

If you wanted to actually validate this, logging your IAT with and without the cover across a couple of pulls would give you a quantified answer.

[Redd]

Why not just use some rubber moulding on the top edge of the airbox to seal it against up against the hood? You get the sound that you want while keeping most of the engine bay heat out of the airbox.

[SAMM3Y]

Originally Posted by Redd

Why not just use some rubber moulding on the top edge of the airbox to seal it against up against the hood? You get the sound that you want while keeping most of the engine bay heat out of the airbox.

Genius!!

[Space Fox]

Originally Posted by Redd

Why not just use some rubber moulding on the top edge of the airbox to seal it against up against the hood? You get the sound that you want while keeping most of the engine bay heat out of the airbox.

That would be ideal! I saw an e92 at the last cars and coffee I went to that had an aftermarket aFe air box that did just that. Unfortunately with the stock box I think it would need quite a bit of rubber molding to seat up against the underside of the hood.

[Redd]

Get a used airbox cover and cut a big hole on top.

https://www.ebay.com/itm/08-13-BMW-E...4AAOSwrxpd2aRR

[GORDON.M3]

Originally Posted by Redd

Get a used airbox cover and cut a big hole on top.

https://www.ebay.com/itm/08-13-BMW-E...4AAOSwrxpd2aRR

That's what some people did with plexiglass. Cut a big hole around it, install the glass on the inside of the cover with rivets if you want to see the filter so badly.

[SAMM3Y]

Do you get more sound with the stubby air filter? I think it would look better with a full size imho more beefcake plus it'd utilize the spring loaded doo hickey to better lock it into place. Engine bay looks great! Very nice

[SAMM3Y]

Originally Posted by GORDON.M3

That's what some people did with plexiglass. Cut a big hole around it, install the glass on the inside of the cover with rivets if you want to see the filter so badly.

Makes me think of the old band pass sub boxes we'd built in high school 😂.. two 12's in the trunk bangin' that chronic 2000.

If you were to do a plexiglass air box lid you could rig some leds in there with a switch that closes the circuit when you pop the hood. Add a little flavor at the car meet.

[M43S7RO]

Dont stop at the air box, plexi the plenum and wire some glow lights to illuminate the trumpets!

Originally Posted by SAMM3Y

Makes me think of the old band pass sub boxes we'd built in high school 😂.. two 12's in the trunk bangin' that chronic 2000.

If you were to do a plexiglass air box lid you could rig some leds in there with a switch that closes the circuit when you pop the hood. Add a little flavor at the car meet.

[DanMpower]

Originally Posted by SAMM3Y

Makes me think of the old band pass sub boxes we'd built in high school ��.. two 12's in the trunk bangin' that chronic 2000.

If you were to do a plexiglass air box lid you could rig some leds in there with a switch that closes the circuit when you pop the hood. Add a little flavor at the car meet.

Ahhh the good ol' bandpass box, I took my 12s out, flipped it around, and had a 10lb nitrous bottle hidden inside. I was hustling some people with my beat-up 3rd gen Prelude.

[Space Fox]

Lolol this took a turn for the worse..

[Space Fox]

Originally Posted by SAMM3Y

Do you get more sound with the stubby air filter? I think it would look better with a full size imho more beefcake plus it'd utilize the spring loaded doo hickey to better lock it into place. Engine bay looks great! Very nice

Sorry missed this. Thank you! I haven't tried using an OEM filter but I don't believe it would fit - the aFe elbow tilts the filter downward toward the bottom of the box and sits below the spring loaded doo hickey - hard to tell from the angle of the photo.

[zedtom3]

Some track heads in UK ran without it and confirmed minimal power loss.So I assume one everyday driving us ok.
P.S.Have the same set up.Waiting for a group buy on cf lid.One UK guy just started production and he will be shortly on here..