Mean Green z28

iTrader: (17)

I'm obviously not a genious so I'll put this out there for you'll...

A friend of mine has a '05 Subaru Sti and he's done a 'couple' mods to it (inc. the requisite 5 inch fart-pipe) and assumes he's got like 350HP now. Now regularly, all the ricers have their blow-off valves purge out to the atmosphere (soooo extreme!) but his (although sporting an aftermarket PSHHHT-maker) flows back to the intake turbo like a stock car. Yeah, I drove it and was VERY dissapointed when it didn't have the requisite loud PSHT of a thoroughbred rally car for the street!!!

So I ask him, "why not purge to the atmosphere and sound real cool?" ... 'cos that's the main reason we all love turbos right? ... and he replies, "'cos the pressure from the purging helps keep the turbo spooled during shifts". Now, although this does sound like it it has some sort of truth behind it, unfortunately this could finally turn out to be ricer-logic. SOOOO ... help me out here and try and explain this dilemma to me ... thanks.

FormulaFire

iTrader: (20)

I don't beleive there is any benefit from running the blowoff back into the piping..

Ping King

iTrader: (20)

the air is already metered through their MAF sensor, so they recirculate it behind the MAF, but in front of the turbo.

Theres no advantage other than being quiet, and fuel metering.

KraZy

iTrader: (4)

I would say its a disadvantage because the air is heated, better to pull fresh air.

Ping King

iTrader: (20)

very true, but then more variables get tossed in like efficiency of the IC and such.

Mean Green z28

iTrader: (17)

So were saying it does have some truth but the other factors just doesn't make it worth the effort?

KraZy

iTrader: (4)

I can confidently say the intercooler isnt going to cool the air to ambiant temps, unless he's got a hell of a intercooler setup.

Hennytime

iTrader: (33)

ive asked a couple of my dsm buddies about this and they say that when you vent into the atmosphere the a/f's seem to lean out for a split second, where as in a recirculating setup, it keeps the a/f's stable. i dont know if this is correct, just second hand information

Ping King

iTrader: (20)

i would think it would go rich for a split second.


i get IAT readings about 10-15 degrees above ambient in my ss..and god only knows on my wrx..its stock

navymitch12

iTrader: (1)

yea, the reason it is done by the import guys is cause in most cases their bov is after the maf...and when the bov opens the car will go really really rich for a second or so while the bov is bacially wasting all the air that according to the computer "should" be going into the motor. with our cars the maf is after the bov so it would have no point at all to do this

Mean Green z28

iTrader: (17)

Ahhhh ... I didn't think of that. It's more like the Vortech setup.

hellbents10

iTrader: (10)

Yup, just increases inlet air temps by recerc. Only reasons for doing this is to keep t quite or if it has the maf on a the inlet side of the turbo.

Blue04

A vent to the atm bov with the stock MAF setup will be venting metered air. It will cause the car to run rich between shifts. It will backfire, buck and stutter, etc. The bigger problem can be if the valve starts opening under light throttle because of a spring and vacuum pressure mismatch it will stall out the car

Speed

iTrader: (33)

The idea behind it (and why nearly all stock systems plumb it back) is to maintain a pressurized induction track between shifts. This is supposed to result in better respool times. In theory, if you drop the pressurized and intercooled air back in front of the turbocharger, it won't require as much energy to recompress and move the air back into the induction track thus won't heat it as much so no loss there. A second trip through the IC should, in theory, put the charge in as good or better state than it would be under normal operation. Also, because the air is already moving and pressurized the turbo won't have as much drag on it and will better maintain operational shaft speed.

How any of this works out in practice is another story. I've always dumped mine to atmosphere because I'm lazy lol.

Mean Green z28

iTrader: (17)

that's the same line of though that I thought in ... thanks

lo_jack

iTrader: (27)

Has anyone tested this and run atmo and then recirc or vice versa? If anyone noticed a difference in meantime between shifts or something that lead them to believe temps were effected, I would be very interested to hear their findings.

boostedinaz

iTrader: (2)

It is going to depend on the setup of the car.

On a DSM the BOV is on the cold side of the intercooler so if anything it might actually help cool down the compressed air comming in from the turbo. It also dumps the air from the BOV back to the hotside of the intercooler, so even if it was hotter, which it's not, it would just go back thorugh the intercooler to be cooled again.

If it dumps into the cold side from the hot side then I could see an issue regarding IAT but I doubt it would be worth running rich between shifts.

In anycase if you could put the MAF after the BOV it wouldn't matter.

Smearin

JUst vent to atmo... thats the whole reason you got the BOV anyways

Mean Green z28

iTrader: (17)

Yeah, and you get the whole PSSHHHHT!!!! sound .. COOL!

boostedinaz

iTrader: (2)

Yeah why have a car that runs properly when you can have one that sounds cool.

And I get called a ricer....