T5 "Kompact Shortie" Compressor Bypass Valve CBV - P1 P3 P2R

You can think of the turbocharger in a car as an air pump, physically squeezing more air (and therefore more air/fuel mix) in to the engine to make more power. Lifting off the gas snaps the throttle shut, and the turbo's pressurized air builds up behind it in the air pipes until the backpressure pushing on the turbo's compressor wheel blades stops it. This "compressor stall" means the turbo has to spin all the way up again, and is also bad for the turbo's health in the long run.

Early turbocharged cars used Blow-Off Valves to vent this excess, closed-throttle boost straight to the surrounding air, but modern turbos instead use Diverter Valves to send it back in to the air intake. You don't get as much of the cool pshhhhhh noise of a classic rally car's BOV, but a DV recirculating that pressurized air in to the turbo inlet helps to keep the turbo spinning and allows the engine to quickly recover when you get back on the gas.

On Volvos, DVs are called Compressor Bypass Valves, and they're attached to the turbo's compressor housing and vent in to the turbo inlet. Time and heat cycles will gradually weaken the stock CBV's spring and tear its rubber diaphragm valve, resulting in your turbo constantly leaking some pressurized air back in to the intake. To the driver, this manifests as slow or sloppy boost buildup, especially from a stop and during "transient" throttle situations (like upshifts) where you're getting off and on the gas pedal quickly.

Turbosmart, a quality manufacturer of turbocharger control systems and components, makes this heavy duty replacement for 5-cylinder turbocharged engines with Borg Warner K-series turbos. It uses a piston valve inside a billet aluminum housing, making it much better at withstanding hard miles and high boost than the plastic-and-rubber Volvo unit, with the added bonus of a little bit of that classic blow-off noise thanks to the quick-opening action of the piston.

This special "Kompact Shortie" unit refers to its size closely matching the factory piece, facilitating drop-in, no-mods-needed installation. Straight and elbow/banjo vacuum fittings are included to ease installation in cramped spaces.