If you are not an owner of a turbocharged car, then check out these photos of Christine and then skip the rest of this page. However, if you’re driving behind the wheel of STI, Evo or SR20-swapped 240, or want to turbocharge your Civic or Z – this article is deisnged for you. Why? Because it’s more than essential to know what type of blow-off valve you should be investing your money in. And to clarify – the primary objecitve of your blow-off valve (BOV) is to ensure that the turbo of your car stays inact as well as its drivability is smooth and reliable. Also, the valve is what makes the crazy loud noise that takes all eyes on you. However, while the sound is something many are highly interested in, in reality, what you should be concentrating on is whether you’re purchasing the right valve, which will help you prolong the life of your turbo.
Compressor Surge
The components of the turbo system should work together, but there is one thing that can create a lot of problems – the compressor surge. Compression surge is backtracking of the boost into the compressor outlet, which interferes with the compressor wheel. When does it occurs? It takes place when you unexpetedly take your feet off the gas pedal and the throttle plate closes. The produced boost will then hit a closed plate on its way to the engine so the only way left is back into the turbo. Such a surge can mess up completely the performance and immensely damage your car. In case you haven’t figure that out – it is incredibly bad for the car as it can slow or stall the wheel by pressurizing the wheel shaft and bearings. By messing up with the turbo response, the compressor surge is powerful enough to kill drivability. The right blow-off vavle is your saviour, letting the surge out of the turbo into the atmoshpere.
How does the blow-off works?
A blow-off valve connects to the intake tract. There is a vacuum chamber with a spring, a diaphragm and valve inside the valve’s primary chamber. The diaphragm is responsible to reace to any pressure changes and at a predetermined vacuum it get pulled toward the vacuum source compressing the spring inside the housing. The spring is mated with the a valve that moves to let the extra and unwanted boost pressure out. Some BOVs let you adjust at what pressure in the intake system the valve to get activated. You will also have the option to replace the spring to alter the activation point.
When to Bypass
Some turbocharged engines might not require blow-off valves, but instead require a bypass valve. They do the same, but in a different way. When choosing your valve you need to consider the type of engine management your car uses. The airflow in a MAF-type system is metered after it enters the intake system. Because of that, when a blow-off is released into the atmosphere, the ECU is incapable to properly fuel the engine which lead to rich AFRs, bad idle, hesitation and stalling. Why we need a bypass here? To plumb the excess pressure back into the turbo system before the compressor inlet. So the key to choosing a valve is knowing your car and what it needs. Below you can find our top picks for BOVs, all of which selected from top merchants. But, please, please, please – no matter what you do – don’t be interested in the noise it will make.
