BOV stands for blow-off valve, sometimes called a pop-off valve or compressor bypass valve. This is a spring-loaded valve mounted in between the turbocharger and throttle body that opens at a preset pressure. It’s function is to provide an escape route for pressurized air trapped in the intake system when the turbocharger is spinning and the throttle place suddenly closes. Although many turbocharged cars lack a BOV, its presence makes the car more driveable. Opinion on whether it improves turbocharger longevity is divided.
The original DSM BOVs were designed to open at about 30 psi or so. Unfortunately for 2G owners, Chrylser replaced the metal 1G BOV with a plastic one that begins to leak at about 15 psi. This is a major problem for those 2Gers looking to up their boost, since the BOV will start to leak a lot of useful boost pressure back into the atmosphere. For this reason, 1G BOVs are a popular upgrade on 2G DSMs.
Hardcore 1Gers might also find the stock BOV to leak under higher boost pressures (more than 20 psi). To correct this problem, some owners crush their BOVs slightly, so they will open only at higher pressures.
Owners of highly boosted cars have discovered that the stock 1G BOV tends to begin to open too early. This causes a pressure leak in the intake system that limits boost. The valve tends to leak somewhat at lower boost levels, then opens fully when it’s supposed to. This low-level leakage is the problem. The 1G BOV will usually hold pressures to about 22 psi, so this problem usually only appears on cars with upgraded turbochargers.
2G owners have this problem, times two – the stock 2G BOV can just hold stock boost levels, and tends to start leaking at around 15 psi. 2Gers don’t crush their BOV because it’s plastic and won’t crush. Instead, 2Gers often replace their unit with a stock 1G BOV to eliminate the leakage problem. This works until they too reach the limits of the 1G BOV.
One DIY solution proposed to fix this problem is to crush the BOV. This means exactly what it says – stick the valve into a vise or clamp and squish it so it doesn’t open as early. This is really a cheap & dirty method of increasing the spring force holding the BOV shut, and saves the operator from having to install an expensive aftermarket BOV. This techique can, however, restrict the amount of air that can pass through the BOV when it is wide open, making it a less efficient BOV, and therefore not as good as an aftermarket unit.
Although the technique is simple, individuals should use caution in applying it since various BOVs and crushing techniques are different. The essential technique is to crush the BOV so that it begins to open when 18-20 inHg of vacuum is applied to the reference port. Pristine BOVs will begin to open much earlier than this. Crushing should be done a little at a time until the BOV responds properly. Over-crushing a BOV may result in poor performance.
