blow off valve
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555BCTurbo
- Knowledgeable
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Well...I can try...
My friend has a 924 turbo, and we were looking in his shop manual and it shows the recirc. valve that is a 931 (924 Turbo) only part I think, maybe used on the 951 (944 turbo). Anyway...my memory is foggy, but the valve releases the blownoff air into the turbo in some fashion too keep the impeller spinning...
It's pretty neat and def. noticable when driving the car, as it really doesn't have any turbo lag between gears...
Sorry I can't give more insight...
My friend has a 924 turbo, and we were looking in his shop manual and it shows the recirc. valve that is a 931 (924 Turbo) only part I think, maybe used on the 951 (944 turbo). Anyway...my memory is foggy, but the valve releases the blownoff air into the turbo in some fashion too keep the impeller spinning...
It's pretty neat and def. noticable when driving the car, as it really doesn't have any turbo lag between gears...
Sorry I can't give more insight...
Nick
1987 Audi 4000CS quattro...soon to be 20VT
1994 Dodge Ram 2500 4x4 CTD, #11 plate, 30 psi, Scotty II intake, 4" exhaust
1987 Audi 4000CS quattro...soon to be 20VT
1994 Dodge Ram 2500 4x4 CTD, #11 plate, 30 psi, Scotty II intake, 4" exhaust
yeah all valves relive the pressure but recircs just dont leave the system open, so theirs no air leak. aptmo valves create an air leak. if your woried than get a txs recirc valve and wrx adapter if you are using a wrx top mount. its like 30 bucks
-jason
[quote="Scoobyniteowl"] Chasin' @$$ is a great form of exercise and if you do get any, then that is more exercise[/quote]
[quote="Scoobyniteowl"] Chasin' @$$ is a great form of exercise and if you do get any, then that is more exercise[/quote]
The original by pass valve is appropriatly tapped into the fmic.
I was curious about the Porsche approach
When I go to the bigger turbo it might need a bigger valve.
Tks.
I was curious about the Porsche approach
When I go to the bigger turbo it might need a bigger valve.
Tks.
Subtle (normally aspirated engines suck):
05 Legacy GT Wagon with Cobb chip.
62 Alfa Romeo Spider- had a 1.6 L with 80 hp, now 2 L with 160 torque. Curb weight 2050 lbs.
93 Leg Twgn fmic, vf34, etc. ((sold))
05 Legacy GT Wagon with Cobb chip.
62 Alfa Romeo Spider- had a 1.6 L with 80 hp, now 2 L with 160 torque. Curb weight 2050 lbs.
93 Leg Twgn fmic, vf34, etc. ((sold))
I should be more clear... What i meant to say was that it will help keep the turbo spooled as opposed to no blow-off valve.vrg3 wrote:Why are you guys saying it will help keep the turbo spooled?
98 Ford Contour V6 24V 5MT
98 Chevy Camaro Z28 LS1 6MT
91 Rio Red SS 5MT Sold
91 Flat Black Wagon L+ 4EAT RIP
91 Pearl White SS 4EAT RIP
98 Chevy Camaro Z28 LS1 6MT
91 Rio Red SS 5MT Sold
91 Flat Black Wagon L+ 4EAT RIP
91 Pearl White SS 4EAT RIP
This thread confuses the hell out of me, and there are so many damn contradicting posts!!!
I've got a few questions for all of you who have contributed to this thread:
1. What is this pressure differential?? If the BOV is letting air out when you let off the throttle completely, it keeps the turbo from building up pressure and stalling. Right?
2. How does using a Atmo-venting BOV mess with your MAF??? They way I understood was that when you let off the gas and the BOV starts letting out air, your car will run rich for a second. I don't see how making that air recirculate into the intake of the turbo could possible make any difference. Is there something I'm not taking into consideration???
3. (this isnt a question) I don't think any BOV helps you turbo spool faster, they only prevent the turbo from stalling.
I'm also trying to understand how the BOV can leak when idling. Is it because during idle there is a vacuum just like when you let off the gas? I wonder how having my IAC unplugged will mess with things if I get a BOV
I've got a few questions for all of you who have contributed to this thread:
1. What is this pressure differential?? If the BOV is letting air out when you let off the throttle completely, it keeps the turbo from building up pressure and stalling. Right?
2. How does using a Atmo-venting BOV mess with your MAF??? They way I understood was that when you let off the gas and the BOV starts letting out air, your car will run rich for a second. I don't see how making that air recirculate into the intake of the turbo could possible make any difference. Is there something I'm not taking into consideration???
3. (this isnt a question) I don't think any BOV helps you turbo spool faster, they only prevent the turbo from stalling.
I'm also trying to understand how the BOV can leak when idling. Is it because during idle there is a vacuum just like when you let off the gas? I wonder how having my IAC unplugged will mess with things if I get a BOV
1992 T-Leg = 195whp 197wtq SOLD :(
1988 4Runner RIP
2006 Suzuki DRZ400sm
2007 Miata
1994 Miata
2003 WRX Wagon
2016 Mazda 3
1988 4Runner RIP
2006 Suzuki DRZ400sm
2007 Miata
1994 Miata
2003 WRX Wagon
2016 Mazda 3
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free5ty1e
- Fifth Gear
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OK.
The stock recirculating valve DOES help keep the turbo spooled between shifts. It was very noticable to me when I installed my TMIC and switched over to an atmospheric BOV.
With the stock valve venting back into the compressor inlet, getting back onto acceleration from a shift was smooth and quick. The turbo stayed partially spooled.
With the atmospheric BOV, after a shift it was quite obvious that the turbo had some work to do to get back up to speed. The smoothness of acceleration coming back on was gone; and there was noticably more lag after a shift. Not to mention that I had idle problems after letting off the gas on boost.
edit: the idle problems were due to my GReddy Type S BOV not being hooked up in the most optimal way possible; but before I could figure out what that was, I got me an HKS SSQV valve which never leaks at idle and is guaranteed to hold insane boost pressures, like 50 psi +. Leaking at idle is mainly due to the BOV opening from a pressure differential between the intake tract and manifold, and then not closing properly and leaking instead until you give it some throttle and it sees enough vaccuum to close fully.
BOV's are only useful on autotragics when you let off the gas quickly under boost. Which you'd probably be doing more and more often to hear the valve, and which will similarly make other motorists think you have a manual
But it wouldn't hurt the car in any way.
The stock recirculating valve DOES help keep the turbo spooled between shifts. It was very noticable to me when I installed my TMIC and switched over to an atmospheric BOV.
With the stock valve venting back into the compressor inlet, getting back onto acceleration from a shift was smooth and quick. The turbo stayed partially spooled.
With the atmospheric BOV, after a shift it was quite obvious that the turbo had some work to do to get back up to speed. The smoothness of acceleration coming back on was gone; and there was noticably more lag after a shift. Not to mention that I had idle problems after letting off the gas on boost.
edit: the idle problems were due to my GReddy Type S BOV not being hooked up in the most optimal way possible; but before I could figure out what that was, I got me an HKS SSQV valve which never leaks at idle and is guaranteed to hold insane boost pressures, like 50 psi +. Leaking at idle is mainly due to the BOV opening from a pressure differential between the intake tract and manifold, and then not closing properly and leaking instead until you give it some throttle and it sees enough vaccuum to close fully.
BOV's are only useful on autotragics when you let off the gas quickly under boost. Which you'd probably be doing more and more often to hear the valve, and which will similarly make other motorists think you have a manual
But it wouldn't hurt the car in any way.-Chris
91SS 4EAT stock, 200k mi
91SS 5MT rebuilt engine waiting for a shell
93TW 4EAT, Forester lift, 3" TBE, 11psi, 200k mi
94SS 5MT4.11+rLSD 311k km: RobTune550,TD05-16g @ 18psi,FMIC,3"TBE,Forester lift
91SS 4EAT stock, 200k mi
91SS 5MT rebuilt engine waiting for a shell
93TW 4EAT, Forester lift, 3" TBE, 11psi, 200k mi
94SS 5MT4.11+rLSD 311k km: RobTune550,TD05-16g @ 18psi,FMIC,3"TBE,Forester lift
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vrg3
- Vikash
- Posts: 12517
- Joined: Sun Nov 03, 2002 2:13 am
- Location: USA, OH, Cleveland (sometimes visiting DC though)
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1. The pressure differential across the turbo's compressor. With a recirculating valve, the pressure is equalized very well, even when the pressure upstream of the compressor is below atmospheric.
2. If the air recirculates, it doesn't leave the system until the engine ingests it, which means all the air seen by the sensor still gets burned by the engine with the fuel metered for it.
3. Not true. See #1. Like Chris says.
2. If the air recirculates, it doesn't leave the system until the engine ingests it, which means all the air seen by the sensor still gets burned by the engine with the fuel metered for it.
3. Not true. See #1. Like Chris says.
"Just reading vrg3's convoluted, information-packed posts made me feel better all over again." -- subyluvr2212
hi guy i have a tmic wrx 06 and im planning to get td04
i have already the injector and the jesc maf
i dont have the bov adapter i think!
i never see it on my car unless its really well hide
but this only on engine with intercooler?
i have a legacy 94 sedan turbo
and i found GFB Stealth FX for 120$ right aound my place sound a good price but, if i have one i may not need it.
im planning to use revtronix chip stage 2
around 16 psi
your tough?
i have already the injector and the jesc maf
i dont have the bov adapter i think!
i never see it on my car unless its really well hide
but this only on engine with intercooler?
i have a legacy 94 sedan turbo
and i found GFB Stealth FX for 120$ right aound my place sound a good price but, if i have one i may not need it.
im planning to use revtronix chip stage 2
around 16 psi
your tough?