[sillygoat]

what do u guys think about putting blow off valves on the e92

i like the sound.

[chaforjohn]

you mean... a blowoff valve?

It sounds cool... I guess - I've had a turboed car before, and I always see Audi's with BOV's, but BMW's? I suppose we'll need to get used to it.

[sillygoat]

Originally Posted by chaforjohn

you mean... a blowoff valve?

It sounds cool... I guess - I've had a turboed car before, and I always see Audi's with BOV's, but BMW's? I suppose we'll need to get used to it.

let me fixt that haha

[FlyingFinn]

For some reason I don't like the Idea to hear BMW "sneezing". It is o.k. with Subaru or maybe Audi as well but BMW, naahh...

[Josh49]

Blow-off valves do not just exist for the sound effects. They have a real purpose, and the sound effect is a result. The purpose of a blow-off valve is to relieve excess turbo pressure that results from reducing the throttle rapidly under boost conditions. If this excess high pressure is not released, it will try to release itselft, back through the turbo (causing the turbo to stop). Then when the throttle is applied again, the turbo needs to re-spool. Having the blow-off valve can save the life of your turbo, and its response..

(Had an A4 1.8Turbo before this car)

[MIKEYMIKE]

A lot of people might consider the hissing sound of the BOV to be ricy...but personally, I LOVE that sound

[foofighter]

Modern turbo cars these days do not expel the excess pressure into the atmosphere. Rather it is recirculated back into the system so as to maintain proper pressure so when you get back on the throttle it minimizes the “lag” that’s inherent w/ turbo cars. There are some companies that now manufacture “hybrid” BOV where it will recirc as well as sneeze the air out so the people that want the sound can have it without compromising the performance of the car.

Just bare in mind that if you install a non-hybrid BOV you will eventually throw a code as most Audi owners were experiencing initially when they just went ahead and installed a normal BOV into their cars. I cant recall but I think it eventually made the car run rich which triggered the CEL. Our cars these days are very very sensitive to changes in emission gasses and will trip off CEL if it detects anything weird. So just be forewarned.

Personally, I think the noise from the BOV gets a bit old after awhile.

[sillygoat]

are BOVs bad for the engine... will it mess it up in the long run?

[timzerofive]

Regardless of recirc or vent-to-atmosphere, you will hear the bov sound, it's just a matter of how loud it is. The type of bov will also determine the type of sound you get. Some gets a clean swoooshh sound, others gets a nice valve flopping sound. Personally, I love the sound of the bov, I miss it. I had a greddy Type-S bov on my last car venting to atmosphere, and I can't get enought of it.

The thing about venting to atmosphere is that the car's map/mas sensor that reads volume of incoming air will be "confused". The sensor reads a certain amount of air traveling through the intake and sends the signal to the ECU to allow it to calculate the amount of fuel to mix in. When the bov releases that air into the atmosphere all of sudden, you'll run very rich as the ecu is injecting the amount of fuel that was suppose to mix with the air you just vented. This means you'll probably stall your engine.

The way I went around it was replacing the OE ECU with an aftermarket standalone racing ecu that doesn't utilize the same type of air volume sensor. I switched to GM 2 BAR MAP sensor and GM Air Intake Temp sensor. This allowed the VTA mode.

Originally Posted by sillygoat

are BOVs bad for the engine... will it mess it up in the long run?

For a turbo car, not having a bov is bad for the turbo, and in terms it also effects the engine. The reason, also previously mentioned in this thread, is that as you abruptly let off on the throttle, all the air compressed by the turbo getting shoved into your engine is all of a suddent without a place to go. This pressure immediately backs to your turbine, and when this happens one too many times, the turbine fails. When the turbine fails and the turbo assembly breaks, you might get parts shooting down the intake pipe into your engine, and it should be pretty obvious that can't be good for the engine.

[rchanou]

I love that sound.

[CreoUCLA]

Originally Posted by timzerofive

Regardless of recirc or vent-to-atmosphere, you will hear the bov sound, it's just a matter of how loud it is.

OEM bypass valves generally do not make any noise that you can hear over normal engine noises. The stock bypass valve(s) in my '01 Audi S4, '03 Subaru WRX, '04 Subaru WRX STi, '05 Subaru Forester XT, and '06 Subaru Legacy GT made/make no discernable noises on throttle lift-off... They engineer it that way. It was only when I switched to a conical intake on the Subarus did I hear the stock bypass valve venting back to the intake tract.

-Mike-

[timzerofive]

Originally Posted by CreoSTi

OEM bypass valves generally do not make any noise that you can hear over normal engine noises. The stock bypass valve(s) in my '01 Audi S4, '03 Subaru WRX, '04 Subaru WRX STi, '05 Subaru Forester XT, and '06 Subaru Legacy GT made/make no discernable noises on throttle lift-off... They engineer it that way. It was only when I switched to a conical intake on the Subarus did I hear the stock bypass valve venting back to the intake tract.

-Mike-

Weird thing is my friend's 04 sti, another guy's A4, and also an EVO MR had noticeable sound, although minimal. They were all stock. I listened for it because we were comparing the turbo sound of our different cars.

AEM EMS standalone ecu and the beautiful sounding greddy type s bov.

[foofighter]

it's a lot more prevalent if you're running an intake...but i have heard my A4 "sneeze" but it's ever so slight.

[CreoUCLA]

*shrug* Maybe you guys just have better ears than me. I can't hear it at all on my Forester XT, and I drive it almost everyday. The Legacy, on the other hand, has a K&N Typhoon and an AVO BOV (50% recirc/50% vent) so I hear everything.



D, where is the bpv on the A4 motor? I'm wondering if location differences might account for me not hearing the S4's.

-Mike-

[timzerofive]

Its a combination of the turbo spooling sound and the "closure" the sound of the bov gives you that makes it so satisfying and addicting. "tsssssssssssssssssssshhhhhh~~~ PSSSSSST!"

[Drag Limited]

Originally Posted by foofighter

Modern turbo cars these days do not expel the excess pressure into the atmosphere.

Ever driven a Noble?

[boostmiser]

Not for me on a $50K car. To each his own.

[Drag Limited]

I've seen a few $300K+ Ferrari's not re-routed into the system, thats enough for me to give it the ok as a mod thats "good enough" for the entry level BMW chassis.

Click Here for a lil youtube video of the turbo F40

[Ryan@Motorwerks]

That's an F50. It doesn't come stock with turbos, meaning they were added later on. The F40 did come with turbos, but doesn't have a BOV. In my mind, BOVs are more for HP beasts.

[Drag Limited]

Originally Posted by 335e90

That's an F50. It doesn't come stock with turbos, meaning they were added later on. The F40 did come with turbos, but doesn't have a BOV. In my mind, BOVs are more for HP beasts.

You're correct!