Bov Modification

[Bain]

  BRI BRI said:

I have done this to several T's with good results as far as sound goes. It wont make any difference to performance. I block off the plumb back line with a piece of 1 inch broom handle, then I join on a hose aquired from super cheap auto which is about 300 mm long moulded like a slight s bend and joined with a copper 3/4 inch plumbing joiner.

This alows you to hide the blow off valve from the federal agents.

As far as sucking in unfilted air, I can't see this happening because evan at idle there is some pressure in the intake from the tubo, but I would not swear to that, perhaps someone can help on that one. Anyway I can't see an after market one at $ 400 doing anything different. I can supply pics if requested.

<{POST_SNAPBACK}>

Pics are always good

So heres a request for you to post them up!

[cobrav8]

Maybe you should attach an air horn trumpet to the outlet - so every time it goes off you beep your horn! For the alternative types - tape a whistle over the end?

[ENVY-T]

  sykes said:

So does the plug with the 10mm hole in it sound the best? I thought you would just leave it completely open for more sound or does it go a bit ricey?

Mick.

By having the pipe fully open it sounds more like very slow woosh noise, very bad IMO.

[IH8TOADS]

And is the bov open at idle NO , so can it suck air !

it closes while the manifold is still under pressure due to the spring in thr bov.

<{POST_SNAPBACK}>

Trust me, get a boost gauge (with vaccum) and connect it up to the back of the BOV. I'll bet you tickets to the ALF grand final that the engine will operate under vacuum.

Take the standard bosch valve off and have a look at the design. Because it is fitted in reverse it is vacuum operated only (ie boost operates against the side of the piston). If the piston was to move up even slightly, air will enter or leave the BOV.

Because of this design, at idle the engine DOES operate at vacuum (stick your finger in the BOV and check for yourself - I havent and I could just be making a

di(k of myself here!!!) and therefore opens the BOV slightly and unfiltered air is sucked into the engine.

Aftermarket BOVs (eg turbosmart - dual port Kompact) are designed so that the plumb back hole is located below the atmospheric hole. That way under vacuum conditions at idle, the piston only moves enough to expose the plumb back hole and suck air from the filtered intake tract (if adjusted correctly that is!!)

Anyways, you guys do have a good idea and im sure a small amount of unfiltered air is not going to hurt too much. Put a K&N rocker cover filter on (should fit straight over) if you are really concerned. Cheers guys.

[F6_Tornado]

  IH8PORK said:

Trust me, get a boost gauge (with vaccum) and connect it up to the back of the BOV. I'll bet you tickets to the ALF grand final that the engine will operate under vacuum.

Take the standard bosch valve off and have a look at the design. Because it is fitted in reverse it is vacuum operated only (ie boost operates against the side of the piston). If the piston was to move up even slightly, air will enter or leave the BOV.

Because of this design, at idle the engine DOES operate at vacuum (stick your finger in the BOV and check for yourself - I havent and I could just be making a

di(k of myself here!!!) and therefore opens the BOV slightly and unfiltered air is sucked into the engine.

Aftermarket BOVs (eg turbosmart - dual port Kompact) are designed so that the plumb back hole is located below the atmospheric hole. That way under vacuum conditions at idle, the piston only moves enough to expose the plumb back hole and suck air from the filtered intake tract (if adjusted correctly that is!!)

Anyways, you guys do have a good idea and im sure a small amount of unfiltered air is not going to hurt too much. Put a K&N rocker cover filter on (should fit straight over) if you are really concerned. Cheers guys.

<{POST_SNAPBACK}>

Good to see someone else take the time to check this out .. Well done IH8PORK

I’ve explained it again over at FF for the same blokes but I don’t think they believe me …

I’ve explained this many a time but it still gets posted up over and over and the factory BOV should be connected to filtered air NOT Atmosphere.

Edited 21/09/05 12:24 AM by F6_Tornado

[Bain]

Well I did this little mod tonight.

Ive made a 10mm hole, but I get a bit to much 'flutter'. If I open the hole up more this should decrease the amount of flutter right?

Its does make a nice sound though.

Ill look into the K&N filter tomorrow and see what sort of cost they are.

[rboksic]

IH8PORK,

so what your saying there is no spring that forces the piston closed in the std bov.

As there is a spring in a GFB Stealth that holds the piston closed then not venting.

Rob

[rboksic]

answer in this post

http://www.fordxr6turbo.com/forum/index.ph...ndpost&p=296479

Live and learn ,

please don't beat me.

[Bain]

Small update.

Drove to work this morning and ive noticed the BOV is venting from 2500 up while im driving (not under load) . EG: A steady pshhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

Are they meant to do even do that with it plumbed back?

Ill probably revert back to the stock way anyhow as its not the sound im after..

[IH8TOADS]

No rboksic, their is a spring that holds the piston closed......but its not just the piston that holds the valve closed, its also boost that acts on the piston through that little tube that enters from above (that's a way of measuring boost and vacuum that im taling about). Theirfore under acceleration the turbo is producing boost and therefore their is equal boost acting from below and above the BOV and the spring HELPS keep the valve closed. Because the std valve is vacuum operated, as soon as you come of the gas and the throttle body closes, the valve is forced to open under vacuum conditions. The spring tension in the std valve is actually quite strong. When free revved at idle my BOV is dead quiet and is also preety quiet when driving normally as the boost forced out through the plumb back hole that is positioned below the trumpet hole. With the std valve you will be making noise as soon as you come off the gas at any speed (I assume) due to the design.

Bain I suggest to check if the top little hose is connected firmly. Id say if your connections are tight the valve will be doing that when plumbed back, you just cant here it. With an aftermarket design you wont have that noise as it will be still plumbed back until you give her some $hit.

Hope the above explaination can help. Cheers all.