Official BOV/BPV Thread

[irishking03]

****Updated 2/2015 by @Inquisitive;! Thank you!***

BPV / BOV

A Blow-off Valve (BOV) or Bypass Valve (BPV) is a pressure release system present in most turbocharged engines. Its purpose is to prevent compressor surge, and reduce wear on the turbocharger and engine. Blow-off valves relieve the damaging effects of compressor "surge loading" by allowing the compressed air to vent to atmosphere, making a distinct hissing sound, or recirculated into the intake upstream of the compressor inlet. They provide improved / quicker throttle response, better boost handling capacity / higher clamping load to maintain boost pressure more reliably and quicker spool recovery.

A compressor bypass valve (CBV), also known as a pressure relief valve or diverter valve, is a manifold vacuum-actuated valve designed to release pressure in the intake system of a turbocharged vehicle when the throttle is lifted or closed. This air pressure is re-circulated back into the non-pressurized end of the intake (before the turbo) but after the mass airflow sensor.

A blow-off valve, (sometimes "hooter valve", not to be confused with a bypass valve) performs the same task but releases the air into the atmosphere instead of recirculating it. The blow-off action produces a range of distinctive hissing sounds, depending on the exit design. Some blow-off valves are sold with a trumpet-shaped exit that intentionally amplifies the sound. Some turbocharged vehicle owners may purchase a blow-off valve solely for the auditory effect even when the function is not required by normal engine operation. Motor sports governed by the FIA have made it illegal to vent un-muffled blow-off valves to the atmosphere.[citation needed]

Blow-off valves are used to prevent compressor surge, a phenomenon that readily occurs when lifting off the throttle of an unvented, turbocharged engine. When the throttle plate on a turbocharged engine closes, the high pressure air in the intake system is trapped by the throttle and a pressure wave is forced back into the compressor. The compressor wheel slows rapidly and may even stall, and the driver will notice a fluttering air sound. The rapid slowing or stalling stresses the turbo and imparts severe turbo lag if the driver accelerates immediately after the surge event.

Disadvantages
In the case where a mass airflow sensor (MAF) is used and is located upstream from the blow-off valve, the engine control unit (ECU) will meter out excess fuel because the atmospherically vented air is not subtracted from the intake charge measurements. The engine then briefly operates with a fuel-rich mixture after each valve actuation.

The rich mixing can lead to hesitation or even stalling of the engine when the throttle is closed, a situation that worsens with higher boost pressures. Occasional events of this type may be only a nuisance, but frequent events can eventually foul the spark plugs and destroy the catalytic converter, as the inefficiently combusted fuel produces soot (excess carbon) and unburned fuel in the exhaust flow can produce soot in the converter and drive the converter beyond its normal operating temperature range.

An alternative method for utilizing both a MAF and a blow-off valve is to have the MAF located down stream between the intercooler and the throttle plate. This is known as Blow-through rather than the traditional Draw-through set up. Care must be taken as to the position of the MAF to prevent damage to the sensitive element. (I.E. on a SR20DE motor, the MAF must be at least 12" from the throttle plate, and the blow-off valve must be 6" from the MAF sensor). By using a draw-through method, the MAF won't be affected by the blow-off valve opening as the pressure is vented before the air reaches the MAF.

One approach used to mitigate the problem has been to reduce the boost pressure, which reduces the required venting volume and yields less charge over-calculation by the ECU. The air can also be recirculated back into the intake, a typical stock setup for cars with an upstream MAF sensor. The situation can also be corrected by switching the fuel metering system over to a manifold absolute pressure sensor, a conversion that usually requires a compatible aftermarket ECU or piggy-back fuel controller. The MAP sensor monitors the absolute pressure in the manifold at all times and will correctly detect the change that occurs when the valve vents, allowing the ECU to reduce fuel metering accordingly.

Operation
A blow-off valve is connected by a vacuum hose to the intake manifold after the throttle plate. When the throttle is closed, the relative manifold pressure drops to below zero bar and the resulting pressure differential operates the blow-off valve's piston. The excess pressure from the turbocharger is then vented into the atmosphere or recirculated into the intake upstream of the compressor inlet.

FYI
Most BOV/BPV will need some maintenance through the years. Basically they need to be re-oiled.

The following list will be discussed below with images:

• Forge (both V1, V2 and unknown versions purchased) BPV
• Turbosmart Dual Port BPV / BOV Combination
• Go Fast Bits (GFB) Respons BPV / BOV Combination
• Forge V2 BPV
• Forge V1 BPV
• HKS SSQV BOV
• CorkSport (CS) MZR BPV
• Cobb XLE BPV / BOV Combination
• Synapse Synchronic BOV
• Forge V? BPV
• TurboXS BPV
• Tial QR BPV
• Turbosmart Kompact Plumb Back BPV
• GReddy RZ BOV
• CX Racing BOV (comes with their FMIC)
• JBR DISI Bypass Valve Return Hose
• Synapse Synchronic DV

Turbosmart Dual Port Maz Type 5 BPV / BOV Combination

Billet aluminium; Holds boost more efficiently over stock valve; BPV spring rate is tuneable to the vacuum of your car; Choice of high pressure and low pressure springs; Gain Top End Horsepower; vents to intake, atmosphere becoming a blow off valve or adjustable mixture of both, while the Sleeper version is quiet during mild boost; note: both are taller, therefore, will not work with stock air-box
Available from: Turbosmart Dual Port Maz Type 5 BPV / BOV Combination
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $482.96

Go Fast Bits (GFB) Respons BPV / BOV Combination

Dual action, twist BPV to BOV adjustable
Available from: Go Fast Bits (GFB) Respons BPV / BOV Combination
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $268.68

Forge BPV

Made from billet aluminium
V1: Makes a ping / swords clashing noise
V2: stealth
Available from: Forge BPV
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $169.95

HKS SSQV BOV

Info: http://www.hksusa.com/
Nickel-plated, die-cast metal secondary valve, which is swaged to the primary valve, a stainless steel C-Clip and spring to increase sealing and durability; First Sequential Blow-Off Valve featuring a unique, pull-type, sequential valve structure and a differential pressure control system allowing for stable operating ranges from low to high boost pressures. Note that a separate flange must be purchased and fitted to the BOV before installing on your car; comes with inline filter on the vacuum line; can keep closed at idle. The recirculating kit is an optional extra (additional expense), but note that 100% VTA can damage your CAT.
Requires a separate (extra cost) mounting flange kit which is difficult to install properly (ex. CP-E, Jay Racing / JSC Speed, etc.)

Available from: Hasegawa, Kitagawa, and Sigma (HKS) SSQV BOV
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $331.95

CorkSport (CS) MZR BPV

Half the spring height, 30% larger piston, 33% faster to vent
Available from: CorkSport (CS) MZR
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $188.99

Cobb XLE BPV / BOV Combination

Different vent modes, pre-load adjustable, compatible with alcohol / water mix, reliably holds high levels of boost without leaks, fast venting, Teflon coated, hard anodized piston providing low sliding friction, reduces surface wear and minimizes maintenance requirements, can hold up to 60 psi
Available from: Cobb Tuning XLE BPV / BOV Combination
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $295

Synapse Synchronic BOV

Eliminates the need for diaphragms by using a piston actuator that does not require frequent lubrication; can hold 60 psi yet still prevent compressor surge; can install as pull or push type valve
Available from: Synapse Synchronic BOV
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $289.95

TurboXS BPV

Each flange is beefy to keep it from warping and allowing you to have the best mating surface possible
Available from: TurboXS BPV
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $239

Tial QR BPV

6 spring options (3 PSI to 12 PSI)
Available from: Tial QR BPV
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $259 silver, black, red, purple, blue

Turbosmart Kompact Plumb Back BPV

Available from: Turbosmart Kompact Plumb Back BPV
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $184.49

GReddy RZ BOV

Easily adjustable to eliminate compressor surge and preventing premature boost leakage while increasing boost response between shifts; made of durable cast and billet aluminium frame; valve to diaphragm ratio provides performance that cheap piston types cannot offer; spring stiffness adjustment screw; three models
Available from: GReddy RZ BOV
MS6 (?), MS3 Gen1 (?), MS3 Gen2 (? Although several Genpu owners have installed this) $360 for Type FV for RX-7

CX Racing BOV (comes with their FMIC)

Available from: CX Racing BOV (comes with their FMIC)
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $399

JBR DISI Bypass Valve Return Hose

Direct (5 layers silicone & 4 layers of reinforcement) replacement for OEM, which will show signs of deterioration and cracking within a year degrading performance to eventually throwing a CEL.
Available from: JBR DISI Bypass Valve Return Hose
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $35 in red, blue, black or white

CP-E Helihose

4-ply reinforced silicone hose, helical cut throughout for flexibility, steel wire routed through the hose to prevent kinking, while maintaining extreme flex, two SS liner clamps are included, providing clamping pressure without tearing silicone, gloss silicone finish with CP-E logo, 14.5” in length, made in the U.S.A., lifetime warranty
Available from: CP-E Helihose
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $64.48

CorkSport (CS) DISI Silicon Bypass Valve Hose

Made from long lasting, four-ply reinforced, high quality, molded silicone for a strong flexible connection for ideal flow from the bypass valve to the turbo inlet pipe, comes in black, red, blue or white with two T-Bolt clamps
Available from: CorkSport (CS) DISI Silicon Bypass Valve Hose
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $39.99 in black, red, blue or white

Synapse Synchronic DV

Eliminates the need for diaphragms by using a piston actuator that does not require frequent lubrication; can hold 60 psi yet still prevent compressor surge; extremely fast response (< 25 msec) to eliminate compressor surge, 6061 aluminium, use a bolt on adaptor or weld Al or SS flange
Available from: Synapse Synchronic DV
Caps for Synapse Synchronic DV
MS6 (Yes), MS3 Gen1 (Yes), MS3 Gen2 (Yes) $282.95; standard black cap (or colours: blue, red, orange, raw - add $29.99)

[Raider]

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BOV/BPV Thread