LAST UPDATED: October 13, 2019
Best Blow Off Valves: Get More Sound From Your Engine
Use any of these blow-off valves to produce great turbo sounds
The Review Team
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PUBLISHED ON October 13, 2019
Many turbocharged cars lack a powerful sound when shifting. That can be changed with a blow-off valve (BOV) that takes the load off the turbo when you are decelerating to create a smooth hissing sound. Our buying guide will help you find the best blow-off valve to keep your turbocharged engine operating at its optimal level.
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Benefits of a Blow Off Valve
- Release high pressure from the engine. At times, too much air may build up in the engine’s intake system. This causes high pressure that leads to a compression surge in the engine, which manifests as an unpleasant sound. A blow off valve safely releases the excess air pressure.
- Compliment the function of the turbocharger. Installing a BOV is typically the next step after you install a turbocharger. It helps the entire turbo system function more efficiently and makes the drive much smoother.
- Make your ride sound impressive. You can install a BOV solely for the impressive sound it produces. Some BOVs have an exit vent that’s shaped like a trumpet so that the air under intense pressure can make a louder sound as it leaves the engine. It can produce a loud whoosh or hissing sound, which can be satisfying and will turn heads as you drive.
Types of Blow Off Valves
Vented BOVs release air into the atmosphere and are the easiest to install. Most are designed with a trumpet at the exit vent to amplify the hissing sound as the air is released. However, traditional BOVs release all the pressure into the atmosphere, and if you are using a manual transmission, you may experience turbocharger lag when shifting gears.
An adjustable or hybrid BOV is designed to solve the problem vented BOVs have by venting some of the air into the atmosphere and recirculating the rest back into the intake system. As a result, the boost pressure no longer needs to start from zero since some of the pressure is retained. This helps reduce lag when you’re shifting gears. You should only use this type of BOV if you have a mass airflow sensor in your engine.
HKS has been making some of the best sounding BOVs and aftermarket parts since 1973. Its main goal is to design products that make vehicles perform better than the manufacturers thought they could. If you want to sample one of its best BOVs, consider the HKS (71008-AK001) Blow Off Valve Kit.
GFB stands for Go Fast Bits. It’s an Australian company that designs a variety of high-quality blow off valves, pulley kits, boost controllers, and short shifters made from high-grade materials. Its products are designed to fit perfectly and to push the limits of high-performance engines. Some of its best-selling BOVs include the Go Fast Bits T9001 and the GFB DV+ Blow Off Valve.
Nic Cooper founded Turbosmart in 1997 in a small workshop in Sydney, Australia. Throughout the years, it expanded its roots from the local scene to global markets in the United States and Europe. Currently, it designs and sells blow off valves, wastegates, anti-lag valves, boost controllers, and a plethora of spare merchandise in over 50 countries globally. If you want to try out one of its hybrid BOVs, check out the Turbosmart Kompact Blow Off Valve.
GReddy is a sub-brand of Trust Company Ltd., which is a Japanese manufacturer of aftermarket car tuning parts. It’s a privately-owned company that was founded by Masamitsu Hayakawa in 1977. GReddy makes blow off valves, exhaust systems, cooling systems, and turbo kits. One of its best-rated blow off valves is the GReddy Blow Off Valve.
Blow Off Valve Pricing
- Under $100: You can get some of the best-sounding BOVs within this price range, but the sound is not a reflection of its performance. While most of the cheaper versions can fit a variety of car models, they are usually not designed to handle too much air pressure.
- $100 to $200: This mid-range price level consists of vented and hybrid blow off valves. Most of the vented versions can produce a high-pitched whoosh sound, while the hybrid versions may not be as loud but can fit a wider range of vehicles.
- $200 and up: Most of these BOVs are heavy-duty and are able to cope with a higher pressure. Installing most of the higher-priced options will go fairly smoothly so long as you have a direct fit for your vehicle's year, make, and model.
The construction or build quality of the BOV speaks volumes as to how long it’s going to last and the expected performance. The best ones are made from a billet aluminum frame with an internal piston made from anodized aluminum. Avoid anything that’s made entirely from plastic since it can melt or crack under intense pressure.
It’s important to consider the type or quality of sound you prefer. Do you like a soft hissing sound, or do you prefer a more aggressive sound that draws attention to your ride? Whatever you choose, ensure that it’s within the recommended noise rating to avoid getting noise complaints.
- Compatibility: There are some universal-fit BOVs available on the market, but it's prudent to do your homework to make sure the option is compatible with your car. To avoid getting the wrong size, always prioritize models that are advertised to be a custom fit for your vehicle’s year, make, and model.
- Ease of Installation: You can’t go wrong by choosing a product that comes with a mounting kit and installation instructions. You will find it easier to install versus buying a stand-alone product and the mounting hardware separately.
- CBV vs BOV: Whether or not you install a BOV depends on how your engine deals with the excess air pressure. Some engines need a compressor bypass valve (CBV) that directs pressurized air back into the non-pressurized intake for better engine performance. Consult with your owner’s manual or a professional on the type of valve to use.
Best Blow Off Valve Reviews & Recommendations 2020
This Turbosmart BOV has a solid build and an innovative design that’s lighter than most BOVs on the market. It also has a sleek body with a space-efficient design to make it easier to install. The performance is outstanding despite its size, and it will produce a sublime whooshing sound once you take your foot off the throttle. It’s designed with an O-ring sealed piston and can handle a boost pressure of up to 30 psi.
It only takes a few minutes to install since it goes in with only three screws and a gasket. Also, we are impressed that it’s reasonably-priced for a product with a solid design that produces great amplified sound.
Naturally, it’s not a perfect product since there have been a few complaints that its performance may diminish over time—it may get too loud and start to rattle. You should also inspect it from time to time since it's prone to leaks.
The ECCP is a budget pick, but the sound is impressive and will make any car owner proud. It’s engineered to offer trouble-free performance with its all-metal construction and trumpet-like exit vent. The valve complements the function of the throttle and the turbine by helping the turbo to maintain speed and ensuring optimal acceleration capacity when the throttle is restarted.
What’s more, it’s easy to adjust the sound coming from this valve with the help of the lever attached at the roof of the unit. You can tune it to produce a softer or more intimidating sound. Also, the lever can help promote the proper use of the turbocharger and engine by controlling the engine’s air operating pressure.
Although it’s not a universal fit for most vehicles, it can fit a variety of Subaru models including the Impreza, Legacy, and WRX. However, it may not fit all of the advertised models on the listing since the exit vent can take up a lot of space.
The GReddy BOV is a versatile valve that fits almost any type of vehicle on the market. This is because of its universal floating valve design that doesn’t need a mounting adaptor. It's a great upgrade from the previous GReddy BOVs since it uses the same mounting holes. In addition, a heavy-duty silicone diaphragm controller is fitted inside the unit to help improve the response time when shifting gears. It also makes the valve more long-lasting.
What's special about this BOV is that it has a CNC outlet with discharge ports that draw more air from the surrounding area to enhance the blow off sound without the need for extra air pressure from the engine. The CNC outlet is customizable and you can replace it with recirculation adaptors of different sizes.
However, this BOV has a few disadvantages. For one, it’s expensive. Also, it’s exterior build construction doesn’t last as long in comparison to other models. Additionally, it might ship with a few parts missing.
Turbosmart makes some of the best blow off valves with clever designs, so it’s no surprise that more than one makes our list. The Turbosmart Kompact is a hybrid BOV with an all-metal build and a unique air recirculating design. Just as with many Turbosmart BOVs, this too has a space-efficient and lightweight design to make it easier to install.
After releasing the throttle, you’ll notice that it produces an impressive sound, which rivals most standard BOVs. It can significantly improve your engine’s performance by promoting smoother shifting. It’s a great choice for anyone looking to maintain the stability of their turbocharged engine.
However, there’s one concern that has plagued many buyers. While the sound produced is impressive, it’s only half as loud as higher-priced BOVs. So, if you want something that produces an intimidating sound, this may not be it for you. Despite that, it's recommended for vehicles with factory Bosch or Denso bypass valves, and Subaru Legacy/ Liberty fifth-generation models.
The Boomba Racing BOV is made from aircraft-grade billet aluminum and an internal brass piston. Brass is a non-reactive metal and, therefore, won’t rust or corrode when the valve comes in contact with water. As a result, it can offer reliable performance for a relatively long time. Also, the brass piston improves its high air pressure tolerance and it can withstand up to 70 psi.
The unit is designed to vent air into the atmosphere, but it may not give you a rich, deeply amplified whooshing sound. Despite that, it’s small and compact form can fit in a vehicle with limited space under the hood.
The main downside we found with this model is that it can’t be fine-tuned or adjusted like other BOVs. This is because most of its functionality is fitted inside the valve and is not easily accessible for fine tuning. That aside, this model is specifically designed for 2013-18 Ford Focus vehicles.
From its outward appearance, you will notice that the GFB DV+ has a sturdy look and a more compact shape than most BOVs. That is because the manufacturer has replaced the housing that’s typical on the valve mechanism with a brass piston and an anodized billet aluminum shell to enhance its pressure tolerance. This sleeker design allows for smoother operation with instantaneous throttle response and minimal turbo flutter.
With this BOV, your gear shifting will be smoother with no noise or bursts of pressure that can result in jerky shifting. To boost its performance, it's designed with a pilot-actuated system for rapid response. Apart from that, it features an OEM-type solenoid coil that’s designed to fit in a designated place for easier installation.
Seeing that it has a unique type of a solenoid coil for seamless integration, it can only fit in specific vehicles. It's only designed to be a direct fit replacement for the factory valve on select BMW models, Fiat Abarth cars, and the Dodge Dart. Make sure that it’s compatible with your vehicle before buying it.
If you are looking to amplify the sound on your Subaru Forester, Impreza, or Legacy, then installing the T9001 is a great place to start. It’s a hybrid model that can recirculate or vent to the atmosphere. It all depends on the type of engine you have. For instance, if you use it on a Subaru WRX, then it will recirculate the air. But that may not produce the best sound.
It has a trumpet exit and can produce a loud whooshing sound when it’s used to vent the air into the atmosphere. The system lets you regulate how much air you can vent or recirculate to control the quality of sound. There are some helpful videos online that will help you install and learn how to regulate it.
However, if you allow it to vent entirely, it can cause the engine to backfire. The price is also one of its most significant drawbacks seeing that there are cheaper options that come with mounting kits.
HKS offers a high-performance BOV that’s a bit on the large side but doesn’t cut corners with its performance. It’s constructed with an aluminum die-cast body that’s designed to tolerate excess pressure from the turbocharger. It doesn’t disappoint when it comes to the authentic whooshing sound that we love with BOVs.
What’s more, it’s a universal fit, and installing this BOV will be a breeze thanks to the extra tools that come with the kit: an O-ring, T-fittings, a C-clip, a vacuum filter, and a complete guide that provides the steps for installing the fittings.
You should note that you may have to purchase a separate flange for a seamless installation and a plug for the recirculating hose. Also, it might cause a compressor surge, but this shouldn’t be a big issue if installed and used correctly.
- Observe a six-month cleaning interval for your BOV to remove dirt and other power-robbing contaminants. A dirty BOV sounds bad and can damage the turbocharger with time.
- Since you have to remove the BOV when cleaning it, you may want to take a picture before removing the unit to ensure that you return everything to the right place. Also, be careful not to crack or damage the brittle fittings when loosening the bolts.
- Remember to inspect the BOV unit for any signs of corrosion, scarring, and wear. Lubricate the metal parts with a non-viscous lubricant, and you can use pressurized air to clean out the BOV before reassembling it.
Q: Can a blow-off valve damage the turbo?
A: Not if it’s installed correctly on the turbocharger. In contrast, it will maintain the best operating air pressure in your engine to prolong its life. It will also minimize surge loading and help maintain turbine speeds in between shifts. It should be fitted between the throttle plate and the turbocharger compressor.
Q: Can I install a blow-off valve in a supercharged car?
A: Blow off valves can cause performance issues in supercharged cars. They are only designed for turbochargers. A supercharger is fitted with a forced induction instead, which is designed to recognize pressure build-up and vent it off. That’s similar to what a blow-off valve does for a turbocharger.
Q: What’s the difference between a blow-off valve and a wastegate?
A: Both units work to regulate the pressure of exhaust gases but in different ways. The turbocharger helps discharge pressure from the turbo when the throttle is suddenly released. A wastegate regulates the level of a boost from the turbo by redistributing the excess pressure from the boost to the turbine wheels with the help of an actuator spring.
We chose the Turbosmart Blow Off Valve as our top pick for the best BOV unit since it’s solidly built to outperform its competitors. It also adds a nice sound enhancement to your turbocharger and is quite easy to install.
If you are looking for a more affordable BOV unit, consider the ECCPP Turbo Blow Off Valve.