Blow Off Valve for Audi A4... YAY or NAY?
2nd Gear
Joined: Feb 2005
Posts: 1,089
From: Seattle
RE: Blow Off Valve for Audi A4... YAY or NAY?
first off, try not to open threads that have been dead for 3 yrs... second you are about to get flamed, but i will let you know that,
audi's have a closed loop system and the car will run very rich if you use a bov. running rich can cause major problems with your cat, you can foul plugs, maf problems, throw codes. go get a DV such as the forge or baileys. if you want that sound a bov makes get an intake, chip and upgraded dv, it is pretty audible.
i am being nice here, try using the search function next time, this topic is covered (unfortunatly) weekly
audi's have a closed loop system and the car will run very rich if you use a bov. running rich can cause major problems with your cat, you can foul plugs, maf problems, throw codes. go get a DV such as the forge or baileys. if you want that sound a bov makes get an intake, chip and upgraded dv, it is pretty audible.
i am being nice here, try using the search function next time, this topic is covered (unfortunatly) weekly
5th Gear
Joined: Sep 2005
Posts: 9,133
From: New Orleans, La
RE: Blow Off Valve for Audi A4... YAY or NAY?
bah thats to technical for him 
ORIGINAL: A4nicator
Ok in a nutshell
DV (diverter valves): "divert" the air back into the intake system hence why they are called Diverter valves
BOV(blow off valves): dump the excess air into the atmosphere.
Now, on an Audi the MAF( mass airflow sensor) is before the diverter valve. Therefore, the air is being hit by the sensor with recycled air and fuel and then determined whether it is running rich or lean, then the valve either puts the fuel/air mix back into the intake or gets rid of it. While, if you install a BOV on this system, the MAF will read the charged air, then be blown out in the atmosphere as a fuel mix, messing with the air fuel ratio on the audi. Essentially, you lose fuel making you car run more rich to compensate. You can buy a Recirculating BOV, but its just a DV with a little more noise. You need that fuel that is being lost by the BOV.
Ok in a nutshell
DV (diverter valves): "divert" the air back into the intake system hence why they are called Diverter valves
BOV(blow off valves): dump the excess air into the atmosphere.
Now, on an Audi the MAF( mass airflow sensor) is before the diverter valve. Therefore, the air is being hit by the sensor with recycled air and fuel and then determined whether it is running rich or lean, then the valve either puts the fuel/air mix back into the intake or gets rid of it. While, if you install a BOV on this system, the MAF will read the charged air, then be blown out in the atmosphere as a fuel mix, messing with the air fuel ratio on the audi. Essentially, you lose fuel making you car run more rich to compensate. You can buy a Recirculating BOV, but its just a DV with a little more noise. You need that fuel that is being lost by the BOV.
ORIGINAL: 98a4T
i am new with the whole audi think can someone put in dumb terms why a BOV is so bad
i am new with the whole audi think can someone put in dumb terms why a BOV is so bad
1st Gear
Joined: Oct 2006
Posts: 460
From:
RE: Blow Off Valve for Audi A4... YAY or NAY?
LOL I like you definition a lot better its far more "red neck" no pun intended.
ORIGINAL: BadLuckAudi
bah thats to technical for him
bah thats to technical for him
ORIGINAL: A4nicator
Ok in a nutshell
DV (diverter valves): "divert" the air back into the intake system hence why they are called Diverter valves
BOV(blow off valves): dump the excess air into the atmosphere.
Now, on an Audi the MAF( mass airflow sensor) is before the diverter valve. Therefore, the air is being hit by the sensor with recycled air and fuel and then determined whether it is running rich or lean, then the valve either puts the fuel/air mix back into the intake or gets rid of it. While, if you install a BOV on this system, the MAF will read the charged air, then be blown out in the atmosphere as a fuel mix, messing with the air fuel ratio on the audi. Essentially, you lose fuel making you car run more rich to compensate. You can buy a Recirculating BOV, but its just a DV with a little more noise. You need that fuel that is being lost by the BOV.
Ok in a nutshell
DV (diverter valves): "divert" the air back into the intake system hence why they are called Diverter valves
BOV(blow off valves): dump the excess air into the atmosphere.
Now, on an Audi the MAF( mass airflow sensor) is before the diverter valve. Therefore, the air is being hit by the sensor with recycled air and fuel and then determined whether it is running rich or lean, then the valve either puts the fuel/air mix back into the intake or gets rid of it. While, if you install a BOV on this system, the MAF will read the charged air, then be blown out in the atmosphere as a fuel mix, messing with the air fuel ratio on the audi. Essentially, you lose fuel making you car run more rich to compensate. You can buy a Recirculating BOV, but its just a DV with a little more noise. You need that fuel that is being lost by the BOV.
ORIGINAL: 98a4T
i am new with the whole audi think can someone put in dumb terms why a BOV is so bad
i am new with the whole audi think can someone put in dumb terms why a BOV is so bad
2nd Gear
Joined: Feb 2007
Posts: 613
From: Hilton Head
RE: Blow Off Valve for Audi A4... YAY or NAY?
HERE IS DUMB TERMS FOR YOU, I CANT STAND SEEING THIS ANYMORE!!!!!!!!!!!!!!!!!!
BOV's AND AUDI
EQUALS
IF YOU WANT A BOV SELL YOUR AUDI AND GET ANOTHER CIVIC, thats disrespect brotha...4 rings diserve better
BOV's AND AUDI
EQUALSIF YOU WANT A BOV SELL YOUR AUDI AND GET ANOTHER CIVIC, thats disrespect brotha...4 rings diserve better
3rd Gear
Joined: Oct 2003
Posts: 1,853
From: United States
RE: Blow Off Valve for Audi A4... YAY or NAY?
Just though I should chime in and make note of the fact that this is complete gibberish.... did anyone actually read it?
Basically yah the maf is before the diverter valve so the CPU asumes that air that enters Will stay in the line when you let off the throttle andthe engine sucks air past the throttlecreating avacuum and thusly opening the recirculation side of the DV releasing the line pressure.
When you have a BOV all the air exits the line to the atmosphere Causing the car to run rich Because it still thinks said volume of air is in line and it adds fuel accordingly....
That being said there is no air being hit by sensors...Thier is no fuel in the released air because air does NOT flow out of the intake manifold where the injectors are located...
Basically yah the maf is before the diverter valve so the CPU asumes that air that enters Will stay in the line when you let off the throttle andthe engine sucks air past the throttlecreating avacuum and thusly opening the recirculation side of the DV releasing the line pressure.
When you have a BOV all the air exits the line to the atmosphere Causing the car to run rich Because it still thinks said volume of air is in line and it adds fuel accordingly....
That being said there is no air being hit by sensors...Thier is no fuel in the released air because air does NOT flow out of the intake manifold where the injectors are located...
Now, on an Audi the MAF( mass airflow sensor) is before the diverter valve. Therefore, the air is being hit by the sensor with recycled air and fuel and then determined whether it is running rich or lean, then the valve either puts the fuel/air mix back into the intake or gets rid of it. While, if you install a BOV on this system, the MAF will read the charged air, then be blown out in the atmosphere as a fuel mix, messing with the air fuel ratio on the audi. Essentially, you lose fuel making you car run more rich to compensate. You can buy a Recirculating BOV, but its just a DV with a little more noise. You need that fuel that is being lost by the BOV.
4th Gear
Joined: Jul 2006
Posts: 3,398
From: Lancaster pa
RE: Blow Off Valve for Audi A4... YAY or NAY?
thats where it dosent make any sence to me
if there is a setting for how much fuel is added to the amount of air comming in (read by the maf)
then in theory when a bov is added shouldnt the maf read that there is less air comming in and tell the ecu less fuel ?
if not then what the hell is the maf even there for ?
if there is a setting for how much fuel is added to the amount of air comming in (read by the maf)
then in theory when a bov is added shouldnt the maf read that there is less air comming in and tell the ecu less fuel ?
if not then what the hell is the maf even there for ?