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335i Free BOV DIY
Published by Red Star Rising
04-06-2007
335i Free BOV DIY

Since Active Autowerke insists that their BOV is worth $750, I think this little DIY is great. Not extremely loud. But noticible, and nice. Member JOEVISTA clued me in on exactly how to do it. Thanks!

Tools:

(2) 3/4" Pipe plugs
Electrical tape

WAIT UNTILL CAR IS COOL!!!

Disconnect the ends of the diverter valve hoses that feed into the pre-turbo air ducts. There is one that is easily accessible from under the hood,



and another that is partly covered, direcly behind the air filter housing. Follow the rear facing diverter hose and disconnect it where it ends.

Make sure you do BOTH!!!

Take the 3/4" plugs and wrap them in one layer of electrical tape(to help it fit more snugly). Plug both bungs that have been left exposed and wrap them with more electrical tape. The electrical tape will become sticky and a good sealant when it heats up. (Also, it is completely removable)



REMEMBER THERE ARE TWO DIVERTER VALVES! YOU MUST DO THEM BOTH!!!!!! ONLY THE FORWARD ONE IS PICTURED HERE!

Secure the two free hoses.

Fire it up and enjoy!

Video will be up soon.

YOU DO THIS AT YOUR OWN RISK!
__________________
AA M3 is gone...the new...
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  #1  
By ulises 335i on 04-06-2007, 07:53 PM
why can't you do just one?
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  #2  
By Red Star Rising on 04-06-2007, 11:43 PM
You will get one turbo getting air diverted back in, and not in another one. I wouldn't.
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  #3  
By TiAg335i on 04-06-2007, 11:44 PM
Post some sound clips bra..
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  #4  
By AW335TT on 04-06-2007, 11:48 PM
Can you hear the spool up??
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  #5  
By teknochild on 04-07-2007, 12:15 AM
lol thats kind of cool in a clever way
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  #6  
By skim7x on 04-07-2007, 12:41 AM
uhhh thats kinda ghetto in a way too HAHA...

i have one Q (i don't know much about the exact mechanics / airflow of turbos, so I hope my ignorance doesn't offend you): I'm pretty sure those pipes are there designed for something more than making the turbo's quieter... by disconnecting it, don't you think you're messing with some equilibrium set when BMW designed the system? I don't think these turbos were meant to release their boost into the atmosphere--don't they recycle the air?
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  #7  
By wj4 on 04-07-2007, 12:48 AM
Quote:
Originally Posted by skim7x View Post
uhhh thats kinda ghetto in a way too HAHA...

i have one Q (i don't know much about the exact mechanics / airflow of turbos, so I hope my ignorance doesn't offend you): I'm pretty sure those pipes are there designed for something more than making the turbo's quieter... by disconnecting it, don't you think you're messing with some equilibrium set when BMW designed the system? I don't think these turbos were meant to release their boost into the atmosphere--don't they recycle the air?
This is exactly what you're doing when you buy a VTA BOV that is aftermarket.

Stockwise...your BOV is connected from both sides, so air travels from one end to the other end. VTA, meaning vent to atmosphere, means that the BOV is only connected from one side so air travels from that side and goes out the other...but since the other side isn't connected to the tubing, it gets releases and makes the wooshing sound.
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  #8  
By Fartpimpson on 04-07-2007, 02:51 AM
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  #9  
By SfValley335i on 04-07-2007, 03:19 AM
can you please take pictures of both locations that need to be plugged?
Pictures with arrows just make things much easier for us visual people

Thanks in advance
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  #10  
By M3to335 on 04-07-2007, 08:53 AM
Interesting.
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  #11  
By RRGOO7 on 04-07-2007, 08:59 AM
nice....post sounds clips asap
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  #12  
By PIMP "E" on 04-07-2007, 09:09 AM
B-rad your very funny dude............ u should write more, do something on every new post. lol
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  #13  
By RiXst3r on 04-07-2007, 09:20 AM
you could just by an extra diverter hose, and seal it... then plug your newly created "cap" onto the valves... would be a much better seal, and much less cheesy...

You could even get a bunch of the hoses, chop and seal them, and sell it as a "kit"...

http://www.realoem.com/bmw/partgrp.d...14&hg=13&fg=20
Last edited by RiXst3r; 04-07-2007 at 09:43 AM.
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  #14  
By Red Star Rising on 04-07-2007, 09:34 AM
I had an AA NA Stage II E46 M3, so I'm not one to cut corners. I know all about expensive modding. I just find even the $595 intro price unreasonable.

Considering the total money spent = 2 pipe plugs and some tape, I don't think it looks bad. The sound is actually quite nice. I have to get a good camera that will capture the sound well.

I may consider buying a two new hoses, and cutting them up to fit a universal BOV and see if there's much of a difference.

But I am actually very happy with the current results.
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  #15  
By ///Matt on 04-07-2007, 10:01 AM
Hey bro.....

You should plug them things back in.

The Diverter valves are calibrated to open when there is a specific pressure difference (I beleive .3 bar) between the out let side (which you disconnected) and the manifold pressure side (the small vacuum hose attached to the other end of the diverter.

It's designed to release pressure from the boosted side back into the intake side of the turbos, obviously.

What this does is prevent boost from backing up against the compressor side of the turbo, and causing the impeller to drag. That would cause extra wear (and HEAT) to the turbos. Also, the release of the air back into the intake side performs an opposite function. When the diverter valve dumps back into the the intake side, the extra air supply actually allows the turbos to spin more freely, again saving wear and heat to them snails.

The problem with what you've done is that these diverter valves are NOT properly calibrated for you've done here. As I said, they are designed to open at a specific pressure DIFERRENCE between one side and the other (of each valve). Now you've allowed the dump side to see a constant atmospheric pressure, not the varying intake side pressures.

You could be blowing off too late, allowing backpressure to hit the turbos, and you are definitely not giving the turbos the dump-assist they are designed for.



NOT TO MENTION, you shouldn't be sticking any homeade plugs in a position where they can fall off into your VERY VERY VERY expensive turbocharger.
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  #16  
By Red Star Rising on 04-07-2007, 10:21 AM
Actually, the dump pressure is rather light on the stock valves, with the intention of putting it immediately back into the intake for the "no turbo lag" that BMW claims. It probably dumps to early if anything. Definitely no back pressure to the turbos, this simply releases it to the atmosphere instead of the pre-compressed intake side. I'm pretty sure after market valves will hold the pressure longer before dumping compared to the OEM diverter.

As for the exposed bungs, I used pipe plugs with larger caps so that there would be no possibility of it entering the ducting...

Again, without big boost, there really is no need for a BOV or even a DV. It's all really just for some sound. This is just a way to let the pressure escape to the atmosphere instead of the intake again so you can hear the sound. It comes at the cost of having more vacuum in the intake when you start revving the next gear. The exhaust gas pressure is what will regulate how the turbo's spool.

For the second hose, you have to follow the second diverter hose to where it meets the intake pipe that feeds the rear turbo. Its a bit of a pain. Disconnect and seal.

Don't forget to secure the hoses too!
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  #17  
By RiXst3r on 04-07-2007, 10:25 AM
Quote:
Originally Posted by ///Matt View Post
Hey bro.....

You should plug them things back in.

The Diverter valves are calibrated to open when there is a specific pressure difference (I beleive .3 bar) between the out let side (which you disconnected) and the manifold pressure side (the small vacuum hose attached to the other end of the diverter.

It's designed to release pressure from the boosted side back into the intake side of the turbos, obviously.

What this does is prevent boost from backing up against the compressor side of the turbo, and causing the impeller to drag. That would cause extra wear (and HEAT) to the turbos. Also, the release of the air back into the intake side performs an opposite function. When the diverter valve dumps back into the the intake side, the extra air supply actually allows the turbos to spin more freely, again saving wear and heat to them snails.

The problem with what you've done is that these diverter valves are NOT properly calibrated for you've done here. As I said, they are designed to open at a specific pressure DIFERRENCE between one side and the other (of each valve). Now you've allowed the dump side to see a constant atmospheric pressure, not the varying intake side pressures.

You could be blowing off too late, allowing backpressure to hit the turbos, and you are definitely not giving the turbos the dump-assist they are designed for.



NOT TO MENTION, you shouldn't be sticking any homeade plugs in a position where they can fall off into your VERY VERY VERY expensive turbocharger.
I was wondering about this... thanks for the clarification...

///Matt.. how does this differ from a BOV kit, like from AA?
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  #18  
By JOEVISTA on 04-07-2007, 10:33 AM
guys you don't have to do this this was tried at bmw tech school. if you want to spend $750 on a bov go ahead some of us like to see what our technical abilites are able to save us $ also less than 5 minutes to do or reinstall. by the way i used black tie wraps to seal.
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  #19  
By purplewidow on 04-07-2007, 10:56 AM
i mean this sounds cool for some obviously deff not me!!! but guys why in the world would you buy a 40-55k car which most of us had to make 75k to buy and do performance mods half-assed!!! it just sounds like you shouldn't own one if you can't afford it and half to uses black electrical tape to make a BOV which is usually a cheap non performance mod (unless you include what it screws up) just audible!!! why risk messing it up when you have a knowledgeable bmw tech in Matt giving an informed statement as to why this shouldn't be done!!! why mess with a 50k car and put some tape on parts for sound that sounds like it came out of my fathers ass after he had his colon resection!!! just buy a damn BOV if you have to!!!
________
Kawasaki zr750h
Last edited by purplewidow; 03-29-2011 at 07:51 PM.
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  #20  
By BoostedBMW on 04-07-2007, 11:01 AM
Quote:
Originally Posted by ///Matt View Post
Hey bro.....

You should plug them things back in.

The Diverter valves are calibrated to open when there is a specific pressure difference (I beleive .3 bar) between the out let side (which you disconnected) and the manifold pressure side (the small vacuum hose attached to the other end of the diverter.

It's designed to release pressure from the boosted side back into the intake side of the turbos, obviously.

What this does is prevent boost from backing up against the compressor side of the turbo, and causing the impeller to drag. That would cause extra wear (and HEAT) to the turbos. Also, the release of the air back into the intake side performs an opposite function. When the diverter valve dumps back into the the intake side, the extra air supply actually allows the turbos to spin more freely, again saving wear and heat to them snails.

The problem with what you've done is that these diverter valves are NOT properly calibrated for you've done here. As I said, they are designed to open at a specific pressure DIFERRENCE between one side and the other (of each valve). Now you've allowed the dump side to see a constant atmospheric pressure, not the varying intake side pressures.

You could be blowing off too late, allowing backpressure to hit the turbos, and you are definitely not giving the turbos the dump-assist they are designed for.



NOT TO MENTION, you shouldn't be sticking any homeade plugs in a position where they can fall off into your VERY VERY VERY expensive turbocharger.
Unless i'm not understanding correctly what he did, you won't have to worry about anything that you listed there because the diverter valves are still doing the same job that they have been doing except they are just venting to the atmosphere instead of placing that same air back into the intake plumbing. Turbo's don't need that extra air to function, when that air is vented the turbo's are still spinning without any interference. Basically, if you like the sound go for it because it won't hurt anything.
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  #21  
By BoostedBMW on 04-07-2007, 11:04 AM
Quote:
Originally Posted by purplewidow View Post
i mean this sounds cool for some obviously deff not me!!! but guys why in the world would you buy a 40-55k car which most of us had to make 75k to buy and do performance mods half-assed!!! it just sounds like you shouldn't own one if you can't afford it and half to uses black electrical tape to make a BOV which is usually a cheap non performance mod (unless you include what it screws up) just audible!!! why risk messing it up when you have a knowledgeable bmw tech in Matt giving an informed statement as to why this shouldn't be done!!! why mess with a 50k car and put some tape on parts for sound that sounds like it came out of my fathers ass after he had his colon resection!!! just buy a damn BOV if you have to!!!
A BOV does not screw anything up on a car with a MAP sensor if you have the right spring installed, there will be no compressor surge of any kind. Can you stop posting crap that isn't true. We understand that you don't like BOV's, which is fine, but please understand that on this car it won't hurt anything no matter how much you may hate the sound.
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