A Blow-Off Valve (BOV) is an important component of a turbo system that goes by many names, such as a pop-off valve, diverter, recirc (short of recirculation), bypass, and dump. The lingo tends to change in different countries and regions, but the purpose of all these valves is the same. To help you better understand the function of this vital component and avoid confusion, we will refer to all types as BOVs.
Typically, the objective of a blow-off valve (BOV) is to ensure the reliable and smooth drivability of a car, while protecting the turbo system against significant damage. This valve is responsible for producing the loud sound turbocharged engines usually produce. Where most usually replace their BOVs for sound, others do so for performance.
Regardless, it is imperative that if you have a turbo system, you choose the right valve for your ride to keep your engine healthy and happy. For more information about BOVs and how to choose the best blow-off valve, read this guide below:
|Dewhel Universal 50mm V-Band Blow-Off Valve
HKS (71008-AK001) Super SQV4 Sequential Blow-Off Valve Kit
GReddy (11501665) Blow-Off Valve
TurboSmart TS-0203-1061 Blow-Off Valve
LGT TMS Respons Blow-Off Valve Kit
**Below, you’ll find our more detailed reviews, but you can also click the links above to see current prices or read customer reviews on Amazon.
A turbo system comprises a wide range of components and parts that need to work together for creating the power to give your vehicle a speed boost. However, when there is a compressor surge, some serious problems can arise. Your car may suffer from poor performance and your engine parts may even suffer damage. So, what is a compressor surge? In simple words, it is when the throttle plate closes upon suddenly lifting off your foot from the gas pedal.
A rush of power/boost heads towards the engine only to hit a closed throttle plate. This means, the boost has nowhere to go, but circle back into the turbocharger (a common syndrome known as “boost backtracking”). As the boost heads back to the turbo and enters into the compressor outlet, it begins to interfere with the compressor wheel. This is a compressor surge, which can stall the wheel bearing and shaft, resulting in extra stress on turbo and engine components.
This not only proves to be damaging but also kills drivability and messes the turbo response. The wheel begins to lose its momentum, creating a bad “lag”. This prevents your car’s engine from performing optimally, resulting in poor acceleration. Blow-off Valves can prevent a compressor surge and protect your turbo system. It keeps the surge out by venting the boost into the atmosphere, creating that loud and impressive sound.
Blow-Off Valve Basics
A blow-off valve connects to the intake manifold. Inside the valve’s main houses is a vacuum chamber with a valve, spring, and a diaphragm. When the throttle closes or opens, the diaphragm instantly reacts to the pressure changes. At a predetermined vacuum, the diaphragm pulls towards the vacuum source. This results in the compression of the spring inside the housing. This spring connects to a valve that is responsible for releasing the excess boost pressure.
For optimal performance, you need to adjust the BOV in order to control the pressure at which the valve activates in the intake system. This is why most cars that have a turbocharger require tuning on a dynamometer. This huge device measures torque and horsepower output. Depending on the readings, you can slowly adjust the blow-off valve, according to the specifications you want. However, it is imperative you choose the right BOV for your turbo engine.
Diverter Or Recirculation Valve
Bear in mind that not all engines with turbochargers use blow-off valves. Some turbo systems use a different type of BOV, which works on a separate boost controlling and surge preventing mechanism. For instance, if you have a MAF-type system, you may require a recirc or diverter blow-off valve.
These systems typically meter the airflow, after entering the intake system. This causes the ECU to function improperly resulting in stalling, bad idle, rich AFR, and hesitation in acceleration. Diverter or recirc BOVs redirect the excess pressure back to the turbo system, rather than discharging the blow-off into the atmosphere.
Blow-Off Valves And Sound
When a blow-off valve redirects the excess pressure back into the turbo system or discharges the blow-off into the environment, it produces a wide range of distinctive, appealing, and adrenaline-pumping hissing sounds. Depending on the exit design, you can install different BOVs for amplifying and clarifying the sound. For instance, blow-vales with a trumpet-shaped exist usually produce a loud hissing sound. Some vehicle owners with turbocharged engines may even primarily replace their BOVs for a better aural effect.
Qualities Of The Best Blow-Off Valves
Need to buy a new Blow-Off Valve (BOV) for your turbocharged engine? Learn about the qualities of the best products below:
• Simple Installation – The best of blow-off valves feature a simple installation process, whether it is using a hose mount, pipe mount, or a vehicle-specific adaptor. It is a good idea to look for BOVs that come with a “bolt-on” kit. They do not require much effort during installation.
• Easily Adjustable – In order to get the performance and sound you want, you have to adjust the BOV. Depending on the turbo system you are using, you can find various diameters for BOVs. Find one that is easily adjustable to boost response between shifts, eliminate compressor surge, and prevent premature boost leakage.
• Strong Build – The best BOVs feature a strong build that guarantees reliability, longevity, and durability. You should reject any product made from plastic right away. Look for BOVs made from billet aluminum frame and durable cast metal, while featuring a hard-anodized aluminum piston. Products with high stiffness metal die-cast are also good options.
• Good Sound – There should be no compromising on the sound your BOV produces. The best products will produce a dynamic and aggressive sound. However, this may vary, depending on the design you choose. Subsequently, the primary factor you should focus on is the “quality” of sound. You should also avoid any product that produces a rattling sound.
The 5 Best Blow-Off Valves Reviewed
1. Dewhel Universal 50mm V-Band Blow-Off Valve
This blow-off valve from Dewhel Universal is CNC-machined from 6061 aluminum alloy. Using a V-Band design and featuring a large 50mm valve, this BOV boasts aluminum-mounting clamps for easy installation and giving off a unique and clean appearance. Utilizing a Viton O-ring on the valve seal, hard-anodized coating, and Teflon-lubrication, the BOV is wear-resistant. This means, it will not give up on you easily and will continue to offer exceptional performance.
The Dewhel Universal 50mm V-Band Blow-Off Valve comes with a new banjo-type bolt and air fitting, machined with aluminum. Its actuator has a temperature resistant silicone, Nomex-reinforced diaphragm, which guarantees components can withstand the boost backtracking. Available in a selection of colors, this BOV offers 60% more airflow than traditionally designed counterparts. It is without doubt the highest flowing BOV in the market.
- Great for Intercooler and All-Turbo Upgrades
- Machined from 6061 Aluminum Alloy
- Allows for High Boost Pressures via Dual Spring System
- Short Stroke and High-Quality Diaphragm
- Intoxicating Sound
- There are no major cons
2. HKS (71008-AK001) Super SQV4 Sequential Blow-Off Valve Kit
Produced by HKS, this great blow-off valve comes under the mid to high price range. It offers exceptional performance and opens/closes quickly to control the excess pressure from the turbo system. Featuring a sequential design, the BOV proves incredibly efficient at preventing compressor surges. It is a good option if you want to leverage optimal performance, along with a crisp, clean whizzing sound.
This BOV is a little larger than the average product, but it comes with plenty of innovative features. With three zip ties, 2 “T” fittings, an O- Ring, Vacuum filter, C- clips, you have everything in the box for installing the BOV on your turbo system. A small booklet provides a detailed set of instructions on how to make the installation process go smoothly.
As a testament to its popularity, performance, and sound, the HKS Super SQV4 Sequential BOV Kit is one of the most pirated BOVs on the market. Make sure you are purchasing the right one made by HKS to leverage excellent performance. Here is a video of the BOV in action on a Subaru STI.
- Easy to Install and Adjust
- Looks Slick and Sounds Amazing
- Build Quality is Exceptional
- Contains All Essentials for Installation
- There are no major cons
3. GReddy (11501665) Blow-Off Valve
The GReddy Blow-Off Valve is a new generation of BOVs from the brand that boasts a unique “Floating Valve design”. The product maintains the advantages of the previous models silicone diaphragm control and push valve structure, while incorporating a revised adjustable dual spring system that grants for easy opening/closing for preventing compressor surge. The improved design offers added resistance, more airflow, increased valve travel, and better response, guaranteeing exceptional performance.
Weighing under 1 ½ pounds and 9 x 5 x 7 inches in size, the GReddy Blow-Off Valve is smaller than most products but proves to be more efficient. You can install it without having to move engine hoses or parts. The kit comes complete with the Allen gasket, wrench, and all necessary tubing. The only thing you need to buy separately is the flange. It is one of the best sounding BOVs on the market currently. Here is a video of the BOV in action on a Dodge Neon SRT-4.
And GReddy Blow Off Valve FV Sample Sound Clip
- Universal BOV with a Floating Design
- High-Quality and Loud Sound
- Guaranteed Durability
- Compatible with all GReddy BOV Flanges
- No Flange in Kit
4. TurboSmart TS-0203-1061 Blow-Off Valve
If you are looking for a reasonably priced BOV that offers the same performance characteristics as expensive models, there is no better option than the TurboSmart TS-0203-1061 Blow-Off Valve. The product is a consumer favorite for crispness in its whoosh sound when letting off the gas pedal. Its unique design amplifies the blow-off sound. With its solid build, it guarantees long-lasting performance and great sound.
Its 7 x 6 x 5-inch size makes it easy to install and handle. It does not require a lot of space in your engine and you can easily locate it. The valve itself weighs 7 ounces, despite a powerful build. You can rest assured that the product has the capacity to make heads turn with its impressive sound and improve the shifting in your turbo-boosted engine. Here is a video of the BOV in action on a 2013 Ford F-150 Twin-Turbo EcoBoost.
- No idle issues or boost leaks
- Adjustable soft/hard settings
- Excellent “Whoosh” Sound
- Quick Installation Guaranteed
- Not Universal
5. LGT TMS Respons Blow-Off Valve Kit
This is one of the priciest BOVs in the marketplace currently, but it also comes with a 5-star rating. The LGT TMS Respons Blow-Off Valve Kit is a complete compressor surge blocking kit for your turbocharged engine. It has everything you need for easy installation. It delivers both impressive performance and a mind-blowing sound. With fully adjustable settings, you can fine-tune the product to boost performance. It has a sturdy build and will last for years to come. It is small, easy to locate, and among the best sounding BOVs. Here is a video of the LGT TMS Respons in action on a Subaru WRX STI.
- Solid Value for Price
- Looks Exceptionally Good
- Produces an Excellent Sound
- Easily Adjustable for Tuning
- There are no major cons
Our choice: Dewhel Universal 50mm V-Band is the best blow-off valve
Are you facing a tough time selecting the best blow-of valve from the above five? Well, you do not have to spend time contemplating. Just go for the Dewhel Universal 50mm V-Band Blow-Off Valve. Available for a reasonable price, this product offers remarkable build quality. It combines excellent performance with an outstanding blow-off sound that is perhaps unbeatable. However, it is imperative that you beware of phony products. There are many copies of the abovementioned valves on the market. Always look for price and construction material, when differentiating between an original and a fake.