Merits of running no BPV

[AnotherNewb]

Quote:
Blow-Off (Bypass) Valves
The Blow-Off valve (BOV) is a pressure relief device on the intake tract to prevent the turbo’s compressor from going into surge. The BOV should be installed between the compressor discharge and the throttle body, preferably downstream of the charge air cooler (if equipped). When the throttle is closed rapidly, the airflow is quickly reduced, causing flow instability and pressure fluctuations. These rapidly cycling pressure fluctuations are the audible evidence of surge. Surge can eventually lead to thrust bearing failure due to the high loads associated with it. Blow-Off valves use a combination of manifold pressure signal and spring force to detect when the throttle is closed. When the throttle is closed rapidly, the BOV vents boost in the intake tract to atmosphere to relieve the pressure; helping to eliminate the phenomenon of surge.



from here

 

Quoting turbowop:
Quoting Muskrat:


3) Because of this increased loading, the compressor slows down faster, meaning you have worse turbo response when you get back on the throttle.
3a) In a race car with anti-lag, this is negated, but increased point #2. As well as turbine wheel damage.





This is the first thing I think of when wondering whether or not one should be used. And weren't most GN's automatics? Not a whole lot of shifting going on there.



All GN's and SY/TY's are auto.

 

[Boostdtalon]

I remember seeing a thing on topgear about a street car Prodrive made and they mentioned it did not have a BPV.
Found it!

click


I've actually had a similiar discussion with Peter Medina. The CEO of Synapse Engineering and he made mention of how the need for a BPV was because of the damage caused without having one and how it would help with response when coming back into throttle. I migh be able to get some more info from him.

 

[Boostdtalon]

Well I got to pick Peters brain some more and here is what he had to say.
"We're getting some gear to prove some
more important points for having a BPV but the main reasons why they are
needed today, even on fuel injected cars are the following:

You'll see all of the new Ecoboost motors with them for 2 major reasons:
*  IC piping is plastic and it will help to reduce the long term stress
*  Guys that don't know turbo will be thrown off by the additional noise of
the gobbling turkey under the hood, so eliminating the noise is a big deal
to the OEs
*  A wide open BPV in bypass mode under vacuum negates much of the
capacitance generated by the intercooler and all of it's surface area
*  An unloaded compressor by way of an open BPV under cruise means less
energy being wasted at the turbine end to compress air against a mostly shut
throttle, which ultimately leads to unnecessary exhaust backpressure, which
leads to bad scavenging, which leads to bad volumetric efficiencies, etc.

But one of the biggest factors that most people don't realize is that a
properly placed BPV between the intercooler and throttle plate will lead to
a higher pressure differential across the throttle plate under braking.
This leads to an additional ~2" of vac behind the throttle plate which helps
the brake booster under heavy braking.

The other reason for BPVs in the future is that it is one of the only
fail-safes if you have wastegate failure via diaphragm, or controls.  A BPV
can be the fuse the saves the motor.  As far as racing goes, there's no way
you can finish a race spanking fuel cut in every gear if your wastegate
fails.  But using a BPV as a compressor-side wastegate can run gear after
gear.

None of these benefits can be realized with BPVs that are always closed and
only vent under heavy vac and throttle lift.  A properly designed BPV should
have reaction times in the sub 70 millisecond range, and be able to close
within the same window.  As far as our testing has gone, none of the
aftermarket units have been able to achieve this.  Synchronic opens or
closes in ~20ms."