Blocking off intake when installing vented bov

[Drew Sale]

How important is it to block off the intake when replacing a recirc bov with a vented bov?

[Brett Haviland]

hahah  VERY.  (if ur running  MAS)


it will barly run right if its not plugged off.

Also blocking it off and venting your BOV will also make your car run like shit and super pig rich on shifts...  I wouldnt recommend doing so.

Venting your BOV on a stock DSM was cool in 2001... but now its just old...


I have my greddy type S BOV recirculated.... Stainless steel intake pipe and aluminum intercooler pipes... and its LOUD!!!  you would never know that i have it recirculated from listening to it.


Personally drew, i would leave it recirculated untill you can either install a GM MAS in the intake pipe after the BOV, or get a eprom ECU socketed chipped to run DS MAP.  Then your car will still run normal with the BOV vented.

[Paul Pigar]

Oh yeah! u want the vroooom vrooom psssssshhhh! Most guys say it's bad, but i run it and my car run fine. I guess fuel economy goes down, your not going to pass aircare, no hp gain other than making psssshhhhh sound and some say your car will stall if you let off the gas pedal(mine doesn't stall though).

[Robert Vorley]

If you introduce a bypass into your intake air route around the ecu(maf) it will not be able to accurately calculate your air/fuel ratio, hence it will run rich, stall, etc. The same thing happens with a vented to atmosphere bov.

Allowing unfiltered air into the turbo will accelerate its wear and  subsequent failure rate. Which in turn will increase charge temps lowering your detonation threshold.

It seems to be a popular question for some reason.

As I run sd the bov is hella loud....but it can attract the wrong kind of attention, if you know what I mean.

[Drew Sale]

Thank you for all the input so far, I really appreciate it.
I'm not too concerned with attracting the wrong attention or anything like that though. All I want is to be able to run it vented. Seeing as the issue seems to stem from air/fuel ratios, would an air/fuel controller (such as an HKS SAFR) solve the problem? I also have a newer style Gm map sensor that I'm not sure if I can use. It has 3 pins (5V, out, gnd) but I'm not sure if it'll help or moreso how/where to install it.

If anyone around the Burnaby area has some spare time and would like to come check it out I'd greatly appreciate it. I can provide transportation if need be

[Shane Sawatzki]

if your gunna do it, go with DS map, I had a gm maf and maft and was never happy with it, the car ran and didnt stall coming to a stop but it didnt run as good as stock and it definetly was running rich.

[John Hartman]

you have to run a speed density setup, no matter what brand it is.

a small leak, from the vented bov is bad enough.  But a huge ass leak from letting the open hole from the bov return will make it probably un driveable.  If you look at the diameter of the actual stock turbo inlet and compare it to the diameter of the bov return,you will see that you are letting in close to 50% more air.  Un metered air.  Un filtered air.

There is absolutely no benefit in venting a bov.  There is no need to do it.

And, besides all the valid reasons that have already been put forward, there is another one.


When the bov lets go, especially with lots of boost, it actually dumps quite a lot of air and at a very good velocity.  This air, if plumbed back into the intake pipe, will add positive pressure to the inlet side of the compressor.  This helps keep boost inbetween shifts.  So in fact, besides all the other valid points, you are actually hurting performance by venting.

[Drew Sale]

I'm aware of all the negative side effects of venting and why, all I'm looking for is what I need to run it vented. Thank you for all the input, but until I start racing it I'd like to vent it. The hunt continues for a Speed density setup

[Brett Haviland]

get a eprom, socket it... wire in a 3 bar MAP and a IAT and code DS MAP to the chip... then shell out  hundreds of dollars to get it all tuned perfectly!!

simple as that.

[Drew Sale]

Perfect. Thanks Brett!

[Jason Harwood]

Waste of money.
Just re-circ it and remove the silencer thats in the intake.
Its plenty loud from outside so long as you run a cone filter.

[GlenMartin]

i went with a gm-maf and i have it placed after my vented bov. it doesn't run any better or any worse than when it was stock. with the recirculated bov. however running rich......never had that problem. infact i run a bit lean at half throttle.

[Mikael Mikkelsen]

I ran vented for a long time, swore up and down that it didn't affect ANYTHING.

Long story short.. I put it back in and it did make a difference.

Car without the proper mods was not made to work like that. Sure you can do it tho, its your car. You can also put a pencil in your oil pan "just to see what happens"

[jesse dobbin]

I ran vented for a long time, swore up and down that it didn't affect ANYTHING.

Long story short.. I put it back in and it did make a difference.

Car without the proper mods was not made to work like that. Sure you can do it tho, its your car. You can also put a pencil in your oil pan "just to see what happens"

That is very true even when I ran a GM maf on my 1g it still ffelt asa if I wasn't seeing its full potential..

[Jason Harwood]

I ran vented for a long time, swore up and down that it didn't affect ANYTHING.

Long story short.. I put it back in and it did make a difference.

Car without the proper mods was not made to work like that. Sure you can do it tho, its your car. You can also put a pencil in your oil pan "just to see what happens"

That is very true even when I ran a GM maf on my 1g it still ffelt asa if I wasn't seeing its full potential..

Your between shifts will be slower with out the re-circ, you gotta make full boost again. Unless you shift extremely fast.