whats a dv?
Senior Member
Joined: Dec 2006
Posts: 1,953
From: Redding, California 1998.5 A4 1.8TQM
audi's have something called a closed loop system...meaning that when boost pressure is released, it is recirculated through the intake, unlike a blow off valve, which disposes all excess boost pressure into the atmosphere...generally makeing a whoosh or pshh sound...
if you run a full blow off valve on your audi, your car will run rich and eventually foul your cat...which will then need to be replaced....
my advice is that if you plan to make a whoosh or a pshh sound, then you should go with a hybrid valve, which recirculates 90% of the discharge and the other 10% will vent to the atmosphere and make the sound that you may be looking for...this is the system that I currently run and have had absolutely no problems over the last couple months...
hope some of that helps, gl!
feel free to pm me if you need help selecting a Dv
if you run a full blow off valve on your audi, your car will run rich and eventually foul your cat...which will then need to be replaced....
my advice is that if you plan to make a whoosh or a pshh sound, then you should go with a hybrid valve, which recirculates 90% of the discharge and the other 10% will vent to the atmosphere and make the sound that you may be looking for...this is the system that I currently run and have had absolutely no problems over the last couple months...
hope some of that helps, gl!
feel free to pm me if you need help selecting a Dv
Senior Member
Joined: Dec 2006
Posts: 1,953
From: Redding, California 1998.5 A4 1.8TQM
maybe the newbie guide should be changed then....since that is where most of the information above came from:
What kind of BOV should I get?
Due to the closed loop turbo system in our A4's you can not release the air into the atmosphere, you have to recirculate it back into the system. The MAF calculates air before the DV so if any air is lost after that calculation by releasing it into the atmosphere you will run rich for a little while. How damaging this is, is disputable, but on 2000+ models the car adapts to running a BOV because of the MAP sensor so you will only run rich for a day or 2. The BOV will need to stay closed at idle. A BOV that remains open at idle is not good for a car with a MAF and you will stutter and stall. Forge 004 and SSQV are both closed at idle and good choices. If you run standalone software (034 Motorsports carries it) you can run any BOV you want.
There are also hybrid BOV's that only vent a portion of the air. The most popular are the Forge Splitter, and GFB. The splitter is the easiest to install and run and the GFB is just a little tougher, but you can adjust the amount released to atmosphere for 10-50%. The GFB is ~$250 and the Forge is $175 and can only release 10% vta or full dv (should only be left as both since it releases more air).
And if you have a B6, they are equipped with a Wideband o2, stock. the ECU is programmed from the factory with the target AFR, and it will adjust fuel trims accordingly to maintain that, tuned or untuned. So you can remove your MAF and run any BOV you want. Won't work with b5's.
If you have a pre-00 A4 can you run a BOV? Technically no, but I run one on my 98.5 with no problems whatsoever. You only run slightly rich right after you "blow-off" and I can't see it doing any damage. Maybe a catalytic converter in the long run, but I doubt it.
**note: I take no responsibility if you put a BOV on your car and it fvcks it up.
Due to the closed loop turbo system in our A4's you can not release the air into the atmosphere, you have to recirculate it back into the system. The MAF calculates air before the DV so if any air is lost after that calculation by releasing it into the atmosphere you will run rich for a little while. How damaging this is, is disputable, but on 2000+ models the car adapts to running a BOV because of the MAP sensor so you will only run rich for a day or 2. The BOV will need to stay closed at idle. A BOV that remains open at idle is not good for a car with a MAF and you will stutter and stall. Forge 004 and SSQV are both closed at idle and good choices. If you run standalone software (034 Motorsports carries it) you can run any BOV you want.
There are also hybrid BOV's that only vent a portion of the air. The most popular are the Forge Splitter, and GFB. The splitter is the easiest to install and run and the GFB is just a little tougher, but you can adjust the amount released to atmosphere for 10-50%. The GFB is ~$250 and the Forge is $175 and can only release 10% vta or full dv (should only be left as both since it releases more air).
And if you have a B6, they are equipped with a Wideband o2, stock. the ECU is programmed from the factory with the target AFR, and it will adjust fuel trims accordingly to maintain that, tuned or untuned. So you can remove your MAF and run any BOV you want. Won't work with b5's.
If you have a pre-00 A4 can you run a BOV? Technically no, but I run one on my 98.5 with no problems whatsoever. You only run slightly rich right after you "blow-off" and I can't see it doing any damage. Maybe a catalytic converter in the long run, but I doubt it.
**note: I take no responsibility if you put a BOV on your car and it fvcks it up.
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Joined: Sep 2005
Posts: 13,664
You gotta use the right BOV. One that doesnt vent at idle. It is true though that DBC engines don't adapt for the lost air as well as DBW engines do. Probably because of the map sensor.
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