blow off Valve questions
11-09-2005 | 11:01 PM
#2
Its because a full atmospheric BOV's can cause your car to run rich. The car is setup with a 100% recirculation BOV, so when you vent air out of the system the ECU doesn't know how much air is in the system. It will cause the car to run rich off of idle and between shifts. Its not too horrible, but it can ruin the drivability.
11-10-2005 | 07:49 AM
#3
VIP Member
Joined: Nov 2004
Posts: 376
From: Moved to Portland, OR
Car Info: 2005 Black WRX STI
Fyi
So here is a post of mine from another BOV thread that may help explane why the car runs rich with a VTA... hope it helps all to understand how a BOV works in our Subys.
Actually, if the BOV is a VTA (vent to atmosphere) - it absolutely should cause the car to back fire. Unless modified, the BOV is positioned after the MAF (mass air flow sensor). As your turbo pressurizes air, it pulls more air through the intake past your MAF, this air travels from your turbo (now pressurized), to your IC, past the BOV and into your intake manifold. More air = more fuel = more power. Fuel calculations are made by your ECU using the input data from your MAF sensor.
Under WOT (wide open throttle) and running with boost, you are pumping a serious amount of air and fuel into the cylinders to give you the power you need. You rev up and shift, at the point that you shift - your BOV vents to atmosphere but you are still drawing a huge amount of air through the MAF, for a split second your ECU gives an proportionate amount of fuel but you just blew off all the air that would have leaned out your mixture to the correct point. End result is a super rich mixture for a split second at shifts. The unburnt fuel travels out of the block into with your exhaust gas, hits the oxygen rich atmosphere (end of the tail pipe) and ignites... tada! Backfire.
Anyway - its not a bad thing. Lots of seriously high performance cars run this way but if you don't like flames shooting out of your ars and big booms as you pass the HWY Patrol, recirculating is helpful. Personally, I have the best photos of my car with a VTA BOV - nothing says power like fire out of your tailpipe. Anyone see the December Issue of Sport Compact Car? The Skyline on the cover... I think it says "BOSS" is demonstrating the photo power of a VTA BOV.
Actually, if the BOV is a VTA (vent to atmosphere) - it absolutely should cause the car to back fire. Unless modified, the BOV is positioned after the MAF (mass air flow sensor). As your turbo pressurizes air, it pulls more air through the intake past your MAF, this air travels from your turbo (now pressurized), to your IC, past the BOV and into your intake manifold. More air = more fuel = more power. Fuel calculations are made by your ECU using the input data from your MAF sensor.
Under WOT (wide open throttle) and running with boost, you are pumping a serious amount of air and fuel into the cylinders to give you the power you need. You rev up and shift, at the point that you shift - your BOV vents to atmosphere but you are still drawing a huge amount of air through the MAF, for a split second your ECU gives an proportionate amount of fuel but you just blew off all the air that would have leaned out your mixture to the correct point. End result is a super rich mixture for a split second at shifts. The unburnt fuel travels out of the block into with your exhaust gas, hits the oxygen rich atmosphere (end of the tail pipe) and ignites... tada! Backfire.
Anyway - its not a bad thing. Lots of seriously high performance cars run this way but if you don't like flames shooting out of your ars and big booms as you pass the HWY Patrol, recirculating is helpful. Personally, I have the best photos of my car with a VTA BOV - nothing says power like fire out of your tailpipe. Anyone see the December Issue of Sport Compact Car? The Skyline on the cover... I think it says "BOSS" is demonstrating the photo power of a VTA BOV.
11-26-2005 | 12:47 AM
#4
Registered User
Joined: Oct 2005
Posts: 18
From: socal
Car Info: white/gold sti
Originally Posted by Tyconjr
And does anyone have any go fast bits BOV for sale?
11-27-2005 | 08:52 AM
#5
iClub Silver Vendor
iTrader: (25)
Joined: Nov 2002
Posts: 15,494
From: Participating in some Anarchy!
Car Info: 2005 LGT wagon
"Hell yes" that an atm bov will cause after fire!
I got the sequence down pat to cause great ***** of fire to come from the *** end of the car.
But this comes at the price of drivability, rough idle, and lower mpg without an increase in power.
My advice is to spend the money on go fast parts that will actually make power.
I got the sequence down pat to cause great ***** of fire to come from the *** end of the car.
But this comes at the price of drivability, rough idle, and lower mpg without an increase in power.
My advice is to spend the money on go fast parts that will actually make power.
11-28-2005 | 11:46 AM
#6
VIP Member
Joined: Nov 2004
Posts: 376
From: Moved to Portland, OR
Car Info: 2005 Black WRX STI
Originally Posted by Oaf
"Hell yes" that an atm bov will cause after fire!
I got the sequence down pat to cause great ***** of fire to come from the *** end of the car.
But this comes at the price of drivability, rough idle, and lower mpg without an increase in power.
My advice is to spend the money on go fast parts that will actually make power.
I got the sequence down pat to cause great ***** of fire to come from the *** end of the car.
But this comes at the price of drivability, rough idle, and lower mpg without an increase in power.
My advice is to spend the money on go fast parts that will actually make power.
Oaf - whats your sequence to get your fire *****?
11-28-2005 | 04:18 PM
#7
iClub Silver Vendor
iTrader: (25)
Joined: Nov 2002
Posts: 15,494
From: Participating in some Anarchy!
Car Info: 2005 LGT wagon
Originally Posted by depdivr
Oaf - whats your sequence to get your fire *****?
Example: Approaching red light in 4th @ 5K, blip throttle and down shift into 3rd. Takes some practice, but is worth the look on the other driver's faces!
11-29-2005 | 10:31 AM
#8
VIP Member
Joined: Nov 2004
Posts: 376
From: Moved to Portland, OR
Car Info: 2005 Black WRX STI
Originally Posted by Oaf
Ancient Chinese secret.
Example: Approaching red light in 4th @ 5K, blip throttle and down shift into 3rd. Takes some practice, but is worth the look on the other driver's faces!
Example: Approaching red light in 4th @ 5K, blip throttle and down shift into 3rd. Takes some practice, but is worth the look on the other driver's faces!
12-14-2005 | 12:39 AM
#10
VIP Member
Joined: Dec 2005
Posts: 103
From: Essense / Bear Creek, Wisconsin
Car Info: Subaru Impreza GC8
Originally Posted by depdivr
So here is a post of mine from another BOV thread that may help explane why the car runs rich with a VTA... hope it helps all to understand how a BOV works in our Subys.
Actually, if the BOV is a VTA (vent to atmosphere) - it absolutely should cause the car to back fire. Unless modified, the BOV is positioned after the MAF (mass air flow sensor). As your turbo pressurizes air, it pulls more air through the intake past your MAF, this air travels from your turbo (now pressurized), to your IC, past the BOV and into your intake manifold. More air = more fuel = more power. Fuel calculations are made by your ECU using the input data from your MAF sensor.
Under WOT (wide open throttle) and running with boost, you are pumping a serious amount of air and fuel into the cylinders to give you the power you need. You rev up and shift, at the point that you shift - your BOV vents to atmosphere but you are still drawing a huge amount of air through the MAF, for a split second your ECU gives an proportionate amount of fuel but you just blew off all the air that would have leaned out your mixture to the correct point. End result is a super rich mixture for a split second at shifts. The unburnt fuel travels out of the block into with your exhaust gas, hits the oxygen rich atmosphere (end of the tail pipe) and ignites... tada! Backfire.
Anyway - its not a bad thing. Lots of seriously high performance cars run this way but if you don't like flames shooting out of your ars and big booms as you pass the HWY Patrol, recirculating is helpful. Personally, I have the best photos of my car with a VTA BOV - nothing says power like fire out of your tailpipe. Anyone see the December Issue of Sport Compact Car? The Skyline on the cover... I think it says "BOSS" is demonstrating the photo power of a VTA BOV.
Actually, if the BOV is a VTA (vent to atmosphere) - it absolutely should cause the car to back fire. Unless modified, the BOV is positioned after the MAF (mass air flow sensor). As your turbo pressurizes air, it pulls more air through the intake past your MAF, this air travels from your turbo (now pressurized), to your IC, past the BOV and into your intake manifold. More air = more fuel = more power. Fuel calculations are made by your ECU using the input data from your MAF sensor.
Under WOT (wide open throttle) and running with boost, you are pumping a serious amount of air and fuel into the cylinders to give you the power you need. You rev up and shift, at the point that you shift - your BOV vents to atmosphere but you are still drawing a huge amount of air through the MAF, for a split second your ECU gives an proportionate amount of fuel but you just blew off all the air that would have leaned out your mixture to the correct point. End result is a super rich mixture for a split second at shifts. The unburnt fuel travels out of the block into with your exhaust gas, hits the oxygen rich atmosphere (end of the tail pipe) and ignites... tada! Backfire.
Anyway - its not a bad thing. Lots of seriously high performance cars run this way but if you don't like flames shooting out of your ars and big booms as you pass the HWY Patrol, recirculating is helpful. Personally, I have the best photos of my car with a VTA BOV - nothing says power like fire out of your tailpipe. Anyone see the December Issue of Sport Compact Car? The Skyline on the cover... I think it says "BOSS" is demonstrating the photo power of a VTA BOV.
So there really isn't any point on installing a BOV at all...eh?
12-15-2005 | 01:22 AM
#11
VIP Member
Joined: Nov 2004
Posts: 376
From: Moved to Portland, OR
Car Info: 2005 Black WRX STI
Originally Posted by Daisuki
So there really isn't any point on installing a BOV at all...eh?
Maybe I am not understanding your point?
12-24-2005 | 08:29 PM
#15
Registered User
Joined: Dec 2004
Posts: 29
From: Fremont/Milpitas
Car Info: '05 PSM STI
Can someone post a pic of thier afterfire? I have the Blitz DD and I can hear the afterfire almost everytime through 1st-4th. My friends that follow me see it everytime but I haven't had a chance to ride behind my car. Just kind of curious of how big the flame gets.
I know I know. It's not "good" for the car and my MPG sucks *** now, but I still dig the sound. If you really want the sound, just put it on for a few months to get it out of your system, then switch it back.
I know I know. It's not "good" for the car and my MPG sucks *** now, but I still dig the sound. If you really want the sound, just put it on for a few months to get it out of your system, then switch it back.