Can A Blow-Off Valve Damage My Engine?

The simple answer is NO. BOV’s are designed to improve the performance of your turbocharger system.

Blow-off valves are important to preserve your turbo. Under full throttle and full boost, when you let off the gas to shift, the throttle body butterfly slams shuts. When the throttle body closes this creates tremendous pressures in the intercooler, 30 and 40lbs aren’t unusual at this point. This is because the turbo is still spinning full tilt, sucking air from the air filter, and cramming it into the intercooler, with nowhere to go, if you don’t invest in a blow-off valve. Without a blow-off valve this event will result in a chirping of the induction system. That chirp is the sudden harsh slowdown of the turbo, as the highly compress air burps backwards through the intake dramatically reducing the inertia of the turbine, suddenly slowing the turbine down to a crawl. This sudden slow down reduces the spool time as you reapply the gas. Worse of all, burp chirping is very rough on turbo chargers. This reverse exit of the pressure, causing the chirp, will shorten the life by up to 50%. This chirping noise is actually your hardware screaming for mercy. In severe case we’ve even seen intake turbine shafts snap off from the sudden stop of the highly compressed air burping backwards, twisting the turbine shaft…… which is not good!

How do they work? Blow-off valves are triggered by a vacuum line that runs from your intake manifold the blow-off valve. When a high vacuum occurs in the intake manifold (during deceleration, or shifting), that vacuum signal triggers the blow-off valve to open, allowing pressure out of the intercooler, preventing damage to the turbo caused from burp chirps.

Blow-off valves are ideally installed between the intercooler and the throttle body valve. This provides the most effective location for fast reaction pressure relief. It’s important to have a very large port blow-off valve setup so it can dump the air pressure build up as quickly as possible.

The benefits are: 

1. Longer lasting turbos. Relieving this pressure is gentler to the turbine.
2. The turbine isn’t suddenly slowed down from the “burp chirp”.

So when you hear those fast cars chirping with every shift, now you know what’s going on. They don’t have a blow-off valve, resulting in over stressing the turbo. The turbos on those cars will fail sooner than if it had a good blow-off valve installed. Yeah, the chirp may sound cool, but now you know they cut corners on their motor and will pay the price sooner than later. The better sound is a whoosh sound from a blow-off valve, kind of like air brakes of a truck being released.




Posted in Technical Articles