Can someone explain, Recirculating BOV to me please?

[xXEclipse]

I want to buy an SSQV and install it myself but don't know how/what recirculating is. This is what im looking at,
HKS UNIVERSAL BLOW OFF VALVE BOV SQV SSQV BLACK LIMITED - eBay (item 250501027789 end time Jan-11-11 23:15:27 PST)


What do I need to install this? Do i need to recirculate?

 

[akira235]

you HAVE to recirculate unless you have a 3" gm maf and translator, or dsmlink, or are running speed density.

to do so you will need something like this HKS SSQV Recirculation Kit 08 Mitsubishi Evo GSR & MR on eBay!

 

[TSi Kid]

What do I need to install this? Do i need to recirculate?

You need to recirculate because your maf reads this air and if it were to be just "blown off" (unless you changed your maf setup) then your car won't read the air properly.

Go speed density or GM maf w/translator if you want to hear your blow off, if not then stick to your 2g maf and recirculate.

 

[Achelea]

This is my reply to a similar question.
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To actually answer your question though, The reason you need to recirculate your BOV is the you are dumping metered air, and as a result, you will go extremely rich between shifts, and possibly have a difficult time idling.

Let's take a trip through your engine. The air goes through the filter and pass the MAS. IT measures the air and tells the computer how much is coming through. The air goes through the turbo, and the intercooler, and towards the intake manifold, and on through the engine. And since the turbo is moving air, the air pressure begins to build. We call it boost. This is fine during Acceleration, but what happens when you need to shift? You let off the throttle. Now you have a turbo that's still spinning and still pushing air. But since the throttle plate is now closed, it needs to go some where. This is where the BOV (Actually called a Bypass valve) comes into play. Due to the magic of springs, vacuum lines and some clever routing, when you let off the throttle, the BOV opens to allow the pressurized air to escape safely back into the preturbo intake tube. The computer is programmed for this. It's calibrated for X amount of air to be released, and therefore X amount of air to be there when you get back into the throttle.

But when you open to atmosphere, You're losing metered air. So when you get back into it, it has to pull MORE air through the MAS. So the ECU will try to send fuel for the air it measured, PLUS the new air. Meaning it will run Extremely RICH. Which will result in bogging, black smoke, and crappy idle.

The other reason you want to keep the bov recirculated is during idle, the Recirc valve may be partially open. IF it's connected, it's pulling metered air. If it's open, it's pulling in unmetered air, and the car can't send the proper amount of fuel.

That's the reason people will wait til they run a GM Maf Blow through set up. (They put the MAF down stream of the BOV so anything released is unmetered air.) Or the can tune the engine specifically for the lift off situation.

I know it's Long, but it's as close as I can come to an explanation.

That explain it well enough?

 

[TSi Kid]

The other reason you want to keep the bov recirculated is during idle, the Recirc valve may be partially open. IF it's connected, it's pulling metered air. If it's open, it's pulling in unmetered air, and the car can't send the proper amount of fuel.

That's the reason people will wait til they run a GM Maf Blow through set up. (They put the MAF down stream of the BOV so anything released is unmetered air.) Or the can tune the engine specifically for the lift off situation.

I know it's Long, but it's as close as I can come to an explanation.

That explain it well enough?

If you block everything off correctly you can have it so that there is no surge and that no new air is being introduced to the system.

But it's all about the air that's getting measured. That's why when you do a gm maf and you change where the air is being metered it's after the bov so it doesn't matter whether or not it is being registered.

 

[xXEclipse]

So If I Recirculate I wont hear it?

 

[Achelea]

If you block everything off correctly you can have it so that there is no surge and that no new air is being introduced to the system. But it's all about the air that's getting measured. That's why when you do a gm maf and you change where the air is being metered it's after the bov so it doesn't matter whether or not it is being registered.

This is true, but physics is still in play. There will be a build up of pressure when the throttle plate closes. How much depends on how fast the BOV can open to relieve pressure.

And that's what I said. GM maft is down stream of the BOV. By the air flow, it would pass the bov before the maf.

 

[Absit]

You will, bust most people outside the car won't, just the way it should be.

 

[Achelea]

So If I Recirculate I wont hear it?

You'll hear it. But it won't be as loud. Not til you do hard intake piping.

 

[xXEclipse]

Most BOV's can be heard from outside the car from the ones ive seen 0.o

 

[TSi Kid]

If you do a stock 1g crushed, it will be effective, louder and recirculatable Full of win.