My $2 air box plug - The Unofficial BMW M5 Messageboard (m5board.com)

P97 · 29th February 2008, 20:12

Other air box plug kit mounts in the air box itself, thereby reducing effective volume. My version is cheap and allows 2x the amount of volume to be used. This in combination with the RPI ram air kit, it should help with top end HP loss when compared to the smaller volume air box plug kit.

[Pic 1] There's an outlet on the bottom of the airbox that vents down towards the wheel well. The amount of volume between this distance is significant. Why not just put a plate and block this vent off?

[Pic 2] View of the vent from behind the fender linning.

[Pic 3] Take a water carton (or any plastic sheet for that matter) and cut a 4"x6" rectangle; secure/seal with a hot glue gun

[Pic 4] Final result

Great thing about this is if you're caught in the rain, the water can still run down to the bottom vs. accumulating w/in the airbox itself.

ThisFlyGuy · 29th February 2008, 20:47

but aren't you blocking the air that normally would be cooling the rotors/calipers?

550Chris · 29th February 2008, 20:52

Quote:

Originally Posted by P97

Other air box plug kit mounts in the air box itself, thereby reducing effective volume. My version is cheap and allows 2x the amount of volume to be used. This in combination with the RPI ram air kit, it should help with top end HP loss when compared to the smaller volume air box plug kit.

[Pic 1] There's an outlet on the bottom of the airbox that vents down towards the wheel well. The amount of volume between this distance is significant. Why not just put a plate and block this vent off?

[Pic 2] View of the vent from behind the fender linning.

[Pic 3] Take a water carton (or any plastic sheet for that matter) and cut a 4"x6" rectangle; secure/seal with a hot glue gun

[Pic 4] Final result

Great thing about this is if you're caught in the rain, the water can still run down to the bottom vs. accumulating w/in the airbox itself.

So basically you just cut off part of the air boxes breathing? Why?

I dont know what you mean by top end HP loss doesnt this car make power all the way to redline?

Do you have somethin to support that the car runs better with less air??

unfoundhorsepower · 29th February 2008, 20:58

A+ for effort.....But a waste of time , actually detrimental for air to brakes and not really of any positive use to the air intake system...why don't you devise a blower for the M5 instead...

P97 · 29th February 2008, 21:08

Honestly, I don't do enough heavy braking to even consider it hindering the cooling of the brakes. And do you honestly think with the current design of the air box that the vents to the brakes actually work? If the intake is drawing all the air from the vents, how much air at speeds would actually make it to the brakes? If BMW's goal was to use the airbox for cooling the brakes, they are going at it wrong. Why not just build venturies from under the body to route air to the brakes (see Porsche Turbo, GT3, GTR)? Why steal air from the intake to feed the brakes? Huh?

The goal was to pressurize the airbox at speeds. With the vents the way it is, there's no way it'll build up pressure.

When the RPM is high, you'll need more "reserve" to accomodate the extra intake requirements. Basic physics. Lets say you're jogging, would you rather breath through a big box or a box 1/2 the size? And would you want forced air or you have to expend energy to draw in air?

"Do you have somethin to support that the car runs better with less air??"...No car will run better with less air! But I do know that the more air, the more efficient (read more HP) the engine is. Why else do motorcycles, F1, etc... uses presurized air box?

Anyways, it's a cheap mod and easily reversible. :P

550Chris · 29th February 2008, 21:28

Quote:

Originally Posted by P97

Honestly, I don't do enough heavy braking to even consider it hindering the cooling of the brakes. And do you honestly think with the current design of the air box that the vents to the brakes actually work? If the intake is drawing all the air from the vents, how much air at speeds would actually make it to the brakes? If BMW's goal was to use the airbox for cooling the brakes, they are going at it wrong. Why not just build venturies from under the body to route air to the brakes (see Porsche Turbo, GT3, GTR)? Why steal air from the intake to feed the brakes? Huh?

The goal was to pressurize the airbox at speeds. With the vents the way it is, there's no way it'll build up pressure.

When the RPM is high, you'll need more "reserve" to accomodate the extra intake requirements. Basic physics. Lets say you're jogging, would you rather breath through a big box or a box 1/2 the size? And would you want forced air or you have to expend energy to draw in air?

"Do you have somethin to support that the car runs better with less air??"...No car will run better with less air! But I do know that the more air, the more efficient (read more HP) the engine is. Why else do motorcycles, F1, etc... uses presurized air box?

Anyways, it's a cheap mod and easily reversible. :P

What I am saying is that the air box is already pressurized. BMW has already done this. Why did you think that it was not pressurized already? And do you think that blocking air flow adds pressure?

Breathin less cubic volume of air from a box is starving an engine and you just blocked one of its main arteries. Just like you said above more air is better so why cut off supply, this will reduce pressure

P97 · 29th February 2008, 21:37

Quote:

Originally Posted by 550Chris

What I am saying is that the air box is already pressurized. BMW has already done this. Why did you think that it was not pressurized already? And do you think that blocking air flow adds pressure?

Breathin less cubic volume of air from a box is starving an engine and you just blocked one of its main arteries. Just like you said above more air is better so why cut off supply, this will reduce pressure

How can you say the airbox is pressurized? There's a big hole at the bottom of the box? Air comes in and flows back out. So you are telling me that the F1 guys should drill out all their air box so that it can take in more atmospheric pressure vs. pressurized air?

550Chris · 29th February 2008, 21:44

Quote:

Originally Posted by P97

How can you say the airbox is pressurized? There's a big hole at the bottom of the box?

that big hole is fed by the tube that was blocked off

AgentSteel · 29th February 2008, 21:59

What's the point if this "mod" doesn't really do anything? Obviously its not recommended that you close any open ports, unless you have a schematic and know what each port does, etc. Are you getting the extra 5HP now? Hard to confirm that this improves anything...

P97 · 29th February 2008, 22:08

Well, I'm just trying to improve on RPI's air box block off plate (which they've dynoed to gain 5-7 WHP) http://www.raceprecision.com/php/com...art/Itemid,26/
and others that have a similar solution and results. Where else can you get 5-7 WHP for under $2? :P

Anyways, just figured I share with the community for a cheap and effective mod.

///Marshall · 29th February 2008, 22:31

Quote:

Originally Posted by P97

Well, I'm just trying to improve on RPI's air box block off plate (which they've dynoed to gain 5-7 WHP) http://www.raceprecision.com/php/com...art/Itemid,26/
and others that have a similar solution and results. Where else can you get 5-7 WHP for under $2? :P

Anyways, just figured I share with the community for a cheap and effective mod.

Interesting variation. I'd like to see it on a dyno, or as some folks are
doing these days, with a v-box.

Here are my dynos from just plugging the hole at the bottom of the
airbox:

RPi Air box plugs: New Dyno

It does show a midrange gain.

Thanks for sharing!

P97 · 29th February 2008, 22:48

Hi ///Marshal,

Well, you were the catalyst for my mod after seeing your results. See what you started?