kbracing96

iTrader: (26)

Pretty much all the kits I've put together, the BOV spring is stiff enough that it is always closed during cruise and idle. Tial recommends that you use a spring just stiffer then what your vac is at idle so it will be closed unless there is a couple psi positive pressure in the cold piping. Only down side to that is the little compressor surge the OP is experiencing. Very few turbo setups actually have a BOV with a spring soft enough that it is open during cruise and idle.

Rick_Vor

iTrader: (36)

Makes sense. Thanks for the info.

Just wondering. Would a turbo kit be more efficient with a BPV (open under cruise) that allows the compressor to freewheel reducing the load (like the OEM turbo cars)? I would imagine another benefit would be that the freewheeling turbo would be spinning faster than a turbo under load so it will transition into boost more quickly. Make sense?

Rick

foose04

iTrader: (3)

Correct spring pressure and correct vacume line size is key to control the surge.

"Version 1" Tial BOV:
-22 to -23 in/Hg use Pink - 11 Psi spring
-18 to -21 in/Hg use Un-painted -10 Psi spring
-14 to -17 in/Hg use White -8 Psi spring
-10 to -13 in/Hg use Black -6 Psi spring


"Version 2" Tial Q BOV:
-22 to -23 in/Hg use -12 Psi spring (not available)
-20 to -21 in/Hg use Pink -11 Psi spring
-16 to -19 in/Hg use Un-painted -10 Psi spring
-12 to -15 in/Hg use White -8 Psi spring
-8 to -11 in/Hg use Black -6 Psi spring
0 to -7 in/HG (or supercharger) use 3 PSI Spring (Pink)
0 to -7 in/HG (or supercharger) use 3 PSI Spring (Pink)


I got this info from: http://www.extremepsi.com/store/cust...me.php?cat=390

foose04

iTrader: (3)

Rick that load you speak of is being supported from exhaust energy your engine is creating anyways. As that load increases on the turbine, so does the airflow generated by the compressor going into the engine. Why would you want to vent that "freely" generated air and have to apply more throttle and engine RPM just to get that same air flow back?

smokeshow

iTrader: (16)

Not to mention pulling in unfiltered air.

Rick_Vor

iTrader: (36)

Just like your Mom told you, Nothing is free. If my motor is seeing that "free" pressurized air at cruise, then the turbo(s) are loading up the exhaust to create the boost which in turn is putting an unnecessary load on the engine + the PCM is adding fuel to maintain the proper A/F ratio. My BPV lets the turbo(s) freewheel so they aren't a restriction in the exhaust and makes the engine run more efficiently. Every decent OEM and Aftermarket Supercharger kit and just about every OEM turbo car comes with a BPV to let the motor run N/A at cruise to increase MPG and reduce engine wear.

See post 28-30. I'm pretty confident I'm not pulling any unfiltered ait through my BPV. I used the same Vortech Race BPV on my Procharger kit. I used an old radiator hose and ran it from BPV throught the fenderwell up to a piece of 1" PVC pipe that reached the driver's window. I drove the truck around my neighborhood at various throttle positions and speeds and I always felt presurized air till the vacuum dropped enough for the BPV to close for boost. One of these days I'll have to tap the cold side before the TB for a boost/vacuum gauge and and see how pressurized it is.

Rick

foose04

iTrader: (3)

Rick your not any where near creating "pressurized" air at cruise, hint the -10 or more vacume you see on your gauge. That turbine wheel is already freewheeling, as the engines naturally aspirated air demands are greater then the compressor flow at those low shaftspeeds.

BOV's perform better in "Performance" turbo vehicles, the R&D is supported by the largest names in the game. Go buy "turbo magazine" and go cover to cover and see how many BPV's remain. Mitsubishi ,Nissan, Toyota, and even our beloved GM camp with APS's $14,000 turbo kit for the C6/z06, use BOV's. The SRT guys remove them to get the sounds, the STI and EVO guys remove them because they leak, all being replaced with a BOV.

OEM turbocharged vehicles have a BPV to help with fuel mileage and wear because they have small turbochargers, where a blimp of the throttle brings boost instantly, resulting in more air/fuel/power, resulting in bad fuel mileage and more wear. Also the noise in not something every one wants to hear. Also, some cars don't have previsions for a vent type system, either engine management or engine bay layout.

Bottom line, BPV have there place on belt driven chargers and OEM cars, like a volkswagen bug taking a lady to work.