Fox T-Bird/Cougar Forums

Technical => Engine Tech => Topic started by: 87badbird2613 on July 05, 2006, 12:16:11 PM

Title: blow off valve???
Post by: 87badbird2613 on July 05, 2006, 12:16:11 PM
can you install a blow off valve on the stock 2.3 setup.  if so how would i go about that!  im very mechanically inclined just not really keen on the turbos yet  but im gettin there!
Title: blow off valve???
Post by: Ether947 on July 05, 2006, 12:26:20 PM
Yes you can. Most (if not all) tap into the intercooler. It really depends on your bov as to how you would mount it.
Title: blow off valve???
Post by: CougarSE on July 05, 2006, 12:41:47 PM
From what I've read installing a BOV after an air metering device and before the T/B can cause stumbling problems when you go back into throttle.
Title: blow off valve???
Post by: Chuck W on July 05, 2006, 12:55:38 PM
I'd just use a BPV (recirculating) on a stock set-up.
Title: blow off valve???
Post by: Ether947 on July 05, 2006, 07:24:06 PM
I thought the stumbling/stalling was caused by the bpv/bov staying open.
Title: blow off valve???
Post by: 88turbo on July 05, 2006, 07:27:44 PM
Shawn would be the one to talk to about this he seems to know quite a bit about turbo setups
Title: blow off valve???
Post by: CougarSE on July 05, 2006, 08:26:40 PM
Quote from: darkthunder
I thought the stumbling/stalling was caused by the bpv/bov staying open.

Think of it this way..
 
Boost is up
 
You let off the gas
 
Bov opens
 
Air meter is still reading as much air as it was when the throttle was open.
 
Enough fuel is still being injected for that amount of air.
 
When you open the throttle again there would be a rich condition caused by this scenario.
 
Stumble....
Title: blow off valve???
Post by: tbirdscott on July 05, 2006, 08:46:26 PM
You need to reroute the air coming out of the valve back in somewhere between the turbo and air meter otherwise it creates a momentary rich condition.
Title: blow off valve???
Post by: CougarSE on July 05, 2006, 08:51:52 PM
Convert to a blow through VAM...
Title: blow off valve???
Post by: Chuck W on July 05, 2006, 09:13:39 PM
I didn't say it wasn't possible to use a BOV on a stock system, but for the way the stock stuff is set up, a BPV works better.

You can use a BOV if you want to deal with the "quirks"
Title: blow off valve???
Post by: 88turbo on July 05, 2006, 10:49:12 PM
might be a dumb question but what is a blow through vam?
Title: blow off valve???
Post by: CougarSE on July 06, 2006, 11:29:52 AM
A stock TC sucks air through the air meter, under the air box into the turbo.
 
Some guys convert the setup so that the VAM (air meter) is in the charge  pipe going to the intake. 
 
What you can do with that is install a BOV in the charge pipe, but before the vam.  When the BOV opens it will vent the excessive pressure but before the air meter...  so the air meter still reads the correct amount of air going into the engine.
Title: blow off valve???
Post by: Ether947 on July 06, 2006, 04:49:41 PM
Quote from: CougarSE
Think of it this way..
 
Boost is up
 
You let off the gas
 
Bov opens
 
Air meter is still reading as much air as it was when the throttle was open.
 
Enough fuel is still being injected for that amount of air.
 
When you open the throttle again there would be a rich condition caused by this scenario.
 
Stumble....

I get that. All I am saying is that occurs in BPV and BOV setups. Less often in BPV of course, but it occurs none the less. Inferior components and improper setup (not allowing the valve to close) are usually main causes.

After reading numerous topics on the issue, I have concluded that no one is really certain of the momentary rich condition between shifts. It seems to be a myth that gets passed around much like the 8.8 vs. 7.5 weight myth.

Personally I would just ditch the VAM (which is to blame) for a MAF and be done with it but then that wouldn't be stock. :p
Title: blow off valve???
Post by: 88turbo on July 06, 2006, 05:28:43 PM
so do we really need the vam?
Title: blow off valve???
Post by: Tbird232ci on July 06, 2006, 06:03:57 PM
Alright, i have a blow off valve on my car, and i know the Pro's and Con's.

Pro's:
-easier plumbing
-neat sound
-cleaner appearance

Con's:
-Drivability

The momentary rich condition happens wether the car is stock, or if its running a BOV. Thats a myth, but the stumble and stall issues are not a myth. Ive adjusted my driving around those issues, but anyone else who would hop in my car would stall it out once they got into boost.

The biggest issue is that when the air vents, theres nearly enough fuel being shot into the cylinders to momentarily foul the plugs, so if youre in boost, you cant press the clutch and let the car idle, it will immediatly stall. I let off the throttle, and stay in gear for a bit, so that it will clear itself out.

Another issue is starting it. The engine vacume will yank the BOV open since theres not much suction in the intake tubes at that moment, and itll sometimes stumble and stall.

Also, sometimes coming to a stop, itll want to stumble and stall, unless i ride out the gear.

MAF or VAM, the issue will persist, youre still venting metered are, regardless of how its metered. The only way to solve the problem is to run a bypass setup, or convert to blow through.
Title: blow off valve???
Post by: Ether947 on July 06, 2006, 07:46:42 PM
Aye sirs, danke for the lesson. :)

Say Shawn, what type of BOV do you have?
Title: blow off valve???
Post by: Tbird232ci on July 06, 2006, 08:50:45 PM
I have the HKS SSQV. I was under the impression that it wouldnt cause the issues it does, so i spent the 220 on it, but the issues are less severe with it.

The REAL reason i went that route is because its one of those most obnoxious ones you can buy ;)
Title: blow off valve???
Post by: 88turbo on July 06, 2006, 08:52:10 PM
would a bosch bpv work in my setup shawn? I dont want to have to sell my arm to get one I still need it to shift :hick:
Title: blow off valve???
Post by: Tbird232ci on July 06, 2006, 08:53:37 PM
If you set it up as a bypass valve, it will work very well actually. Its not the *ultimate* solution, but its better than nothing.
Title: blow off valve???
Post by: 88turbo on July 06, 2006, 08:55:56 PM
I'll see what I can do :D btw where did you get your cold air kit?:confused:
Title: blow off valve???
Post by: Tbird232ci on July 06, 2006, 08:56:45 PM
ebay, for a 5.0 mustang

youll probably need to buy a 3" hump hose, and do some tpuppies of one of the tubes though
Title: blow off valve???
Post by: Chuck W on July 06, 2006, 10:25:18 PM
Gee, it's not like I didn't mention all that.  :p

If you want to deal with the issues a BOV causes with a metered system, then by all means..go for it.

I had no issues (other than not sounding "cool" ) using a BPV on the metered systems.

On the current SD system in the TBird....by all means ...sure as hell I'm gonna use a BOV......
Title: blow off valve???
Post by: JeremyB on March 29, 2007, 10:32:40 PM
What is the benefit to a BOV rather than a BPV?
Title: blow off valve???
Post by: Chuck W on March 29, 2007, 10:47:35 PM
BOV's can be less complicated in their installation due to the fact that they just vent to atmosphere.

On a system that is metering air before the BOV, such as a MAF application, when the BOV vents, it vents metered air, thus causing a momentary rich condition, which may or may not pose problems.

On a SD system, the air that is vented is not metered previously, and thus causes no issues.

A BPV recirulates the metered air back into the "system" after the meter, but before the turbo.  They are also usually quieter.
Title: blow off valve???
Post by: JeremyB on March 29, 2007, 10:50:36 PM
Are there any performance benefits of a BOV wrt a BPV with an application that vents metered air? It seems they're mostly for show [sound].
Title: blow off valve???
Post by: CougarSE on March 29, 2007, 10:57:46 PM
Holy thread resurrection Batman!
Title: blow off valve???
Post by: JeremyB on March 29, 2007, 11:02:53 PM
Keeps all the tech in one place...now go tell the man what rear-end he needs!
Title: blow off valve???
Post by: Chuck W on March 29, 2007, 11:21:20 PM
Quote from: JeremyB;137193
Are there any performance benefits of a BOV wrt a BPV with an application that vents metered air? It seems they're mostly for show [sound].


Nope....


Well maybe in extreme boost situations, but for the normal folks, no.
Title: blow off valve???
Post by: 87badbird2613 on March 31, 2007, 12:07:35 AM
ok buys thanks for all the very helpful info...  im oing to install my bailey motorsports twin piston bov in a day or two ill let you know how it goes!!!  thanks again!
Title: blow off valve???
Post by: 87badbird2613 on April 02, 2007, 12:20:10 AM
ok so i installed the bov today and so far so good!!  had to adjust the throttle set screw a lil but otherthan that eveythings ok!!!  thanks guys