FAQ: All your Blow Off Valve & Diverter Valve / By-Pass Valve Questions!

[1997gtx]

As it seems to be the most popular topic asked in the B5 S4/RS4 forum, this BOV/DV/BPV thread will be for any and all information aimed to help those who are curious about which BOV or DV to run on their 2000-2002 S4.

Please post any informational thread that contains no flaming -- only good, car related information -- that may help others learn why our car reacts differently to various set-ups.

Also, I would greatly appreciate links to the cheapest / most reliable places to purchase aftermarket DV's.

Thanks!
--Adam

[1997gtx]

Credit: FAQ's

Bypass valves (BPVs). Instead of using Blowoff valves, like many turbo cars, the S4 uses BPVs. I will not get into a technical description of what they do, because some knowledge of turbochargers is required. Suffice to say there are two BPVs (one for each turbo) that frequently fail because of a poor design by the manufacturer. Note that the BPVs have an exceptionally high probability of failure if the vehicle is modified to increase performance, but even without modifications, they frequently break. Several fixes are available here as well. The most common solution is to replace each one with the BPVs found in the Audi TT 225 (called 710Ns, by part #), which are a more robust design. Each will run you no more than $35, and can be replaced easily by yourself using the tech write-up on AW. These BPVs are known to perform well even with significant performance modification to the vehicle. Other BPV options exist through aftermarket manufacturers such as Bailey, Forge, Stratmosphere, and many more. The difference between these valves and the TT valves is that they are constructed of metal. They are considered very robust, but require internal lubrication from time to time. These typically run anywhere from $200-$350 for the pair.

[JaredVL]

Last time there was a BOV tech thread it didn't turn out so hot... LOL

I will gladly type up something tonight and add it tomorrow.

[1997gtx]

From this thread:

The S4 uses a "suck-through" MAF. The DV's are located after the MAF, therefore the air passing through them is metered. If you replace them with BOV's, which vent to atmosphere instead of recirculating, you will be venting metered air and the car will run rich.

BOV's work fine on cars where the MAF is located after the BOV.

If you have the average S4 and you want better performance out of your valves (BOV or DV, they're the same shit), get some Baileys or Forge DVs.

If you want a "whoosh" sound WITHOUT the problems of idle surge and running rich, the ONLY BOV you can use are the HKS SSQ. Their design has been the only succesful one with cars that use a MAF.

You can also just get two Greddy Type-S and re-route them back into the plumbing like stock, which is still pretty loud.

First, just because a car has a MAF doesn't mean you can't use a BOV. It's the location of the MAF that matters.

Second, there is no possible way that replacing a post-MAF DV with a BOV will not result in the car running rich, even if only for a moment. The SSQ may remain closed at idle, which should help the idle problem, but when it opens it's still venting metered air.

The SSQ is the only one to be used without problems on all cars with MAFs.. between shifts you'll be a bit rich, and lose a bit of boost - which is why they also offer a reroute kit.. it lessens the spooldown of the turbo between shifts.

Well, if you use the SSQ with a reroute kit... it's not really a BOV anymore

[1997gtx]

Last time there was a BOV tech thread it didn't turn out so hot... LOL

I will gladly type up something tonight and add it tomorrow.

I know. It will be closed after it has enough info with where to buy them, etc. Thanks!
--Adam

[1997gtx]

This tech article explains how our stock DV's fail with pictures.
--Adam

[1997gtx]

Information about the Forge Diverter Valve, a very popular replacement choice for our S4's.

[AMC]

i saw way to many s4's runing BOV's at WF!

[AudiSportB5S4]

how many people actually bought the ones from LLTek, they are SO expensive ! the hybrid valves you can open/close according to how you want it ? i mean have they ever sold any? what would ppl. be running to want to have a BOV/DV mix and spend close to 800 on them ! haha. thats crazy.

[1997gtx]

^^^ I have never heard of anyone getting them.

If people are so obsessed with BOV's, I would try the Greddy Type-S recirculating BOV.
--Adam

[Oscar32]

Credit: FAQ's

Bypass valves (BPVs). Instead of using Blowoff valves, like many turbo cars, the S4 uses BPVs. I will not get into a technical description of what they do, because some knowledge of turbochargers is required. Suffice to say there are two BPVs (one for each turbo) that frequently fail because of a poor design by the manufacturer. Note that the BPVs have an exceptionally high probability of failure if the vehicle is modified to increase performance, but even without modifications, they frequently break. Several fixes are available here as well. The most common solution is to replace each one with the BPVs found in the Audi TT 225 (called 710Ns, by part #), which are a more robust design. Each will run you no more than $35, and can be replaced easily by yourself using the tech write-up on AW. These BPVs are known to perform well even with significant performance modification to the vehicle. Other BPV options exist through aftermarket manufacturers such as Bailey, Forge, Stratmosphere, and many more. The difference between these valves and the TT valves is that they are constructed of metal. They are considered very robust, but require internal lubrication from time to time. These typically run anywhere from $200-$350 for the pair.

hi,
I'm lookin to upgrade diverter valve on my 2004 audi a4 1.8t. What would you suggest? i've been lookin at:
APR R1: i've found around 130
and i heard about the TT DV but not sure whats the part # could it be the one you mentioned "Audi TT 225 (called 710Ns, by part #)"

Thanks for the info.

[jeremy@matrix]

The most common solution is to replace each one with the BPVs found in the Audi TT 225 (called 710Ns, by part #), which are a more robust design. Each will run you no more than $35, and can be replaced easily by yourself using the tech write-up on AW. These BPVs are known to perform well even with significant performance modification to the vehicle.

As well, 710N's are known to fail on even stock TT225's--we've seen it from time to time.
This is why we recommend the Forge DV007P's at $145/ea....do it once and forget it.

[VonPooper]

hyperboost FTMFW.

[1997gtx]

hi,
I'm lookin to upgrade diverter valve on my 2004 audi a4 1.8t. What would you suggest? i've been lookin at:
APR R1: i've found around 130
and i heard about the TT DV but not sure whats the part # could it be the one you mentioned "Audi TT 225 (called 710Ns, by part #)"

Thanks for the info.

I know a few Stage 3 S4's that use 710N's. If you want the top of the line, then go with the Forge. I've heard the APR R1's are having problems. For that money, go with the Forge 007. If you want the 710N, let me know and i'll show you a few links where you can buy them.
--Adam

[McKennaS4]

this is all the input i have...
http://www.youtube.com/watch?v=VbNxu...elated&search=

even though i don't mind BOVs in general, this is hilarious! lol =]

[Kievskiy]

I still have a general question, poping out here and there, i've heard that people running one BOV and one DV on 2.7t engines, i know it is pretty dumb, but just for information and thoughts, will it hurt one turbo? knowing that our air circulating system is a loop...i mean any input for future noobs and for AZ folks in general, will be good to cover that topic.
Andrey.

[1997gtx]

I've never heard of anyone running one DV and one BOV. But seriously, why would you want to do that anyway? Even running two different DV's will not work well, because they circulate the air at different rates, causing an improper continual flow of air. If you use a BOV and DV, I imagine it would be even worse.
--Adam

[Kievskiy]

lol, all i can say, that since we cant really run BOVs, people coming out with alot of hideous ideas just to get closer to that pshhh sound. As for my opinion, i would not run BOVs period, its already enough attention just with a sound of the turbo spool after DPs installed :D

[10SecS4]

The 710N part # is:

06A145710N

They can be bought online for as little as $35-$40 a piece new.

I've been running these diverter valves on my 500+ HP S4s for years and have had zero problems with them.

They get the job done just as well as any of the more expensive aftermarket valves.

Jeremy, what exactly failed on the 710Ns you saw fail?

[InTTruder]

So the 710N and DV are two sides of the same coin?

TIA- noob S4 fixer-upper here.

[sixfiveoh]

Does the A4 have the same motor design as far as the MAF being located before the BPV, making all of this info applicable to the 1.8T motor as well?

[1997gtx]

So the 710N and DV are two sides of the same coin?

TIA- noob S4 fixer-upper here.

I think so -- not sure if I understand your analogy. A 710N is a type/brand of a Diverter Valve (DV). So, you would replace your stock DV with a 710N DV.
--Adam

[1997gtx]

Does the A4 have the same motor design as far as the MAF being located before the BPV, making all of this info applicable to the 1.8T motor as well?

No, it's different. Most 1.8T's that I know of have no problems running a straight BOV.
--Adam

[sixfiveoh]

No, it's different. Most 1.8T's that I know of have no problems running a straight BOV.
--Adam

Really? There's tons of debate on this subject as well on the A4 side. The air isn't metered? People saying it's bad for the car, I for one love the sound of a BOV. You're saying that an A4 would have no problems running a BOV? Sorry for derailing this thread, I can take it to PMs if you wish...

[1997gtx]

^^^ No, that's fine. As this is a thread for B5 S4's, I don't mind some mininformation . I have no doubt that the same debate exists in the A4 world. Since I don't have an A4, nor have I had one, I would largely take what you say with much more weight than what I say. I was merely speaking from personal experience. It can't be that bad if of the dozen or so guys I know with an A4 that 5 are using BOV's and haven't had problems. But again, I don't really know.

But don't do it on a S4
--Adam

[sbdons3]

so basically what are the best valves for the b5 s4

[Mike@Forge]

Here are two links from other forums that I frequent. The information is clearly relevant, however.

The first one is a great deal of information I've comprised about valves:

http://forums.evolutionm.net/showthread.php?t=209640

The second one has another shit-ton of information I've put together, but specifically related to compressor surging:

http://www.mazda-speed.com/forum2/in...c,10972.0.html

I plan to write a similar type of "explanation" for wastegates (both internal and external) soon too.

[1997gtx]

^^^ great links, thanks.
--Adam

[1997gtx]

so basically what are the best valves for the b5 s4

There really isn't a test to compare. I personally Forge 007's. Some would say if price is a factor, 710N's. But, let's put it this way: If someone was going to give you a set of 710N's or 007's for free that you had to use on your car for 3 years, 9 out of 10 would pick the 007's.
--Adam

[sbdons3]

There really isn't a test to compare. I personally Forge 007's. Some would say if price is a factor, 710N's. But, let's put it this way: If someone was going to give you a set of 710N's or 007's for free that you had to use on your car for 3 years, 9 out of 10 would pick the 007's.
--Adam

right on right on

[1997gtx]

Haha, no worries. Sorry, I didn't mean to sound brash
--Adam

[1997gtx]

More good info in this thread, which discusses the Forge 007 valve and which springs to use.
--Adam

[Jung]

ok i never got my answer from my previous dumbass thread yet... what size tubing do I use for the Vac lines coming out of my 007A's? Adam was a scoob and locked the thread before i got an answer.. Thanks
-Matt

[1997gtx]

You can re-use the stockers. Or, if you need longer tubes, i'm not sure the diameter. I would take the stock tube to a car parts place (autozone or Pep Boys will do), and measure.
--Adam

[AudiSportB5S4]

3mm tubing

[1997gtx]

^^^ Thx.
--Adam

[Jung]

^Thanks bro... sorry for the redundant thread haha... got myinfo.. this is an amazing thread BTW.

[1997gtx]

Good to know it's helping. That's why this thread is here!
--Adam

[zepmoreau]

THere are other options as well. Turbosmart (Austrailian made) makes the Dual port BOV/BPV with twist stiffness adjust. unlike stock and cheap BOV/BPV's it also uses a piston rather than a bladder. here's the site http://www.turbosmart.com.au/index.php?id=26
Ive been in contact with many BOV/BPV products and have been running this particular model on my car (400hp) for a few years now: http://www.justfourrings.com/phpBB2/...ic.php?p=40#40 just my $.02

[S-Power]

sorry, so its not possible to put a BOV on the s4 b5 correct? or it is possible but its does harm ?