Thoughts on BOV?

[Velocewest]

I've seen a couple mentions of people wanting to use the M102 BOV (which pipes excess boost back into the stream to keep the turbo spooled?) on M016 installs using 5 speeds where the DME from the 745i is dumped for an 059 or other ECU. I assume the only downside of no BOV is the turbo loses a little momentum during shifts. Thoughts? Needed, not needed, big difference or no?

Thanks

[gol10dr1]

sounds to me like what is used on an m102 is a diverter valve and not a blow off valve. in order to use a blow off valve tyhe blow off must be before the afm so the dme does not get confused when it meters the air. if you are after the sound of a BOV go for something like an HX diverter valve that has a loud pop when coming out of boost and maintains the diverting of air to the turbo for quicker spooling.

[Velocewest]

Yes, diverter is probably a better description. And no, I don't want my car to sound like a WRX driven by a 25 year old. I'm into stealth. I like that "WTF was that?" look I get from people when an e12 goes by them like they dropped anchor.

[Tjn182]

[QUOTE="gol10dr1"]sounds to me like what is used on an m102 is a diverter valve and not a blow off valve. in order to use a blow off valve tyhe blow off must be before the afm so the dme does not get confused when it meters the air. if you are after the sound of a BOV go for something like an HX diverter valve that has a loud pop when coming out of boost and maintains the diverting of air to the turbo for quicker spooling.[/QUOTE]

Now this is something I never understood. If a BOV dumps the air into the atmosphere, then why again does it screw things up? What exactly would happen..? I had my BPV on my 745i blow to atmosphere for a while, but it caused idling problems because it stayed open during idle - causing a massive air leak - yet, otherwise, the car drove just fine!

[Boru]

Tj, the BOV and BPV need to handle different pressure/vacuum constraints. A BOV has to be adjusted to stay closed while the manifold vacuum is trying to pull it open AND the intake tract upstream of the TB is at atmosphere or lower pressure BUT it needs to open with manifold vacuum+positive pressure upstream of the TB. With the BPV, it doesn't matter if it's open when off boost because ALL the air first goes through the AFM. Air can bypass the compressor this way but it doesn't matter. In either case, boost pressure acting on the BOV or BPV diaphram keeps the valve closed.


[Edit by Sweeney on [TIME]1139407196[/TIME]]

[Tjn182]

So then what about those HKS SSQ BOVs? They are supposed to open only from changes in the vacuum - they claim that no amount of vacuum or boost will open the valves, only a change in the vacuum. The SSQ valves were what I had my eyes on...

[Velocewest]

Thread un-hijack -- Does anyone have a position on the need for some boost bleeding device when running a manual transmission? Even if I run a BOV I can pipe the output somewhere to avoid ricer noises.

[T_C_D]

[QUOTE="Velocewest"]Thread un-hijack -- Does anyone have a position on the need for some boost bleeding device when running a manual transmission? Even if I run a BOV I can pipe the output somewhere to avoid ricer noises.[/QUOTE]

You need a bypass valve for two reasons. First you do not want to close the throttle and leave the charged air in the upstream piping. It will stall the turbo which hurts performance and longevity. You need to keep that air in the system if you are runnign Motronic so a bypass valve allows you to pipe it back into the intake pipe after the AFM and before the turbo.

Todd

[Boru]

[QUOTE="Tjn182"]So then what about those HKS SSQ BOVs? They are supposed to open only from changes in the vacuum - they claim that no amount of vacuum or boost will open the valves, only a change in the vacuum. The SSQ valves were what I had my eyes on...[/QUOTE]

I assume, looking at the picture, that it incorporates a type of gate valve where the pressure applied is normal to the travel of the gate. Pricey little bastards... Still, if you're going to run the Motronic, venting air that has already been metered is going to cause issues.

[Velocewest]

[QUOTE="T_C_D"]You need a bypass valve for two reasons. First you do not want to close the throttle and leave the charged air in the upstream piping. It will stall the turbo which hurts performance and longevity. You need to keep that air in the system if you are runnign Motronic so a bypass valve allows you to pipe it back into the intake pipe after the AFM and before the turbo.

Todd[/QUOTE]

Thanks for the clear answer, Todd. Off I go to Bypasses-R-Us...

[russc]

Oh man, I read the first post, and said, oh my, thats wrong, but Todd and Sweeney cleared it up nicely. My only .02 is that you can vent the BOV for diverter to atmosphere if you have a speed density system like most foreign cars, Honda and Toyotas.

RussC

[Velocewest]

I did a little looking. I think I could start with a basic Bosch diverter valve like used on Audis, Porsches and Saabs. If that works OK I can upgrade to a Forge valve or similar for a little more longevity. There's an interesting article on one of the Audi sites where a guy compared a couple of the stock Bosch valves to the Forge. The Forge is very solidly built, but the stock valves work just as fast, flow just as well, and only cost about 30% as much. Evolution motorsports swears their unit is flow tested and gives 10% more CFM. But hey, who cares, it's shiny!

Tony

[Boru]

Tony, we supply the Bosch valves with our kits. We've seen no reason to switch to a more costly valve... unless you really desire a pertier one.

[russc]

[QUOTE="Sweeney"]Tony, we supply the Bosch valves with our kits. We've seen no reason to switch to a more costly valve... unless you really desire a pertier one.[/QUOTE]

Bling Bling baby....

RussC

[Velocewest]

[QUOTE="Sweeney"]Tony, we supply the Bosch valves with our kits. We've seen no reason to switch to a more costly valve... unless you really desire a pertier one.[/QUOTE]

Hey, this gives me a great business idea. I'll buy the same Bosch valves, paint them silver, and sell them for $20 more than you! Just call me KC Ron... %)

[Boru]

[QUOTE="Sweeney"]Tony, we supply the Bosch valves with our kits. We've seen no reason to switch to a more costly valve... unless you really desire a pertier one.[/QUOTE]

[QUOTE="Velocewest"]Hey, this gives me a great business idea. I'll buy the same Bosch valves, paint them silver, and sell them for $20 more than you! Just call me KC Ron... %) [/QUOTE]

...and refer to them as "billet" plastic

[Jesse]

[QUOTE="Sweeney"]...and refer to them as "billet" plastic
[/QUOTE]

lol


[Edit by Jesse on [TIME]1139531263[/TIME]]

[smackmybutter535i]

This one time at band camp I unhooked my diverter valve and put a magnum condom over it.

Shits and giggles

[Jesse]

Regardless of what setup you have; a BPV is always a better setup. It will keep the turbo spooled up as mentioned above.

Also, the By pass air would be used the best if it where directed right into the input of the turbo along with the intake air stream as opposed to just Tee-ing it in at 90 degrees. Agreed??

Does anyone direct the BPV air that way?? I haven't yet, but I will be soon.

Oh - BTW a BPV and a BOV is the samething - it's the way they are used that is the difference. Just wanted to make that clear.

[Edit by Jesse on [TIME]1139531755[/TIME]]

[Velocewest]

[QUOTE="Jesse "]Oh - BTW a BPV and a BOV is the samething - it's the way they are used that is the difference. Just wanted to make that clear.[/QUOTE]

Based on what I've seen, you're right as far as function or effect -- they both release compressed air from the intake tract -- but if you look at the various models out there, clearly some of the BOV's just are not configured to be a BPV. It would be a major PITA to capture the released air and pipe it anywhere. Check out this one, for instance http://www.tialsport.com/prod_bv_50.htm



[Edit by Velocewest on [TIME]1139627440[/TIME]]

[Jesse]

Right. Some are clearly purpose - built to serve one function and that's it.