First, let’s see what a dump valve does. A dump valve serves as the absorber and of extremely high pressure, which it releases to the atmosphere or back to the inlet. It’s the bypass valve that protects the car’s turbo from taking so much pressure than it can handle.
When the car is in full throttle, it creates pressure called boost. When the driver suddenly decelerates, the throttle Cvv dumps butterfly closes and air gets compressed but there is no other escape route. The unused boost then goes back up through the intercooler, creating pressure at the back of the turbo. This pressure acts as a brake on the turbo and tries to stop it from spinning.
How does it perform its purpose? The dump valve will be the leeway, the fire exit if you want to put it that way. It releases the pressure in two ways: into the air outside or back to the air intake system.
Atmospheric valves dump the extra boost to into the air giving out a “whoosh” sound that the drivers love. Re-circulating valves dumps back the unused boost with minimal sound.
As a result, this add-on provides significant decrease in turbo spool up time and there is noticeable improvement in the car’s response between gearshifts. Since there is little lag on the turbo, the next boost is timely. This means increased torque at lower RPM.
What about turbo diesel dump valves?
If you are asking if you can use a petrol dump valve in your turbo diesel car, the pointblank answer is NO. Petrol dump valves are useless to your car because diesel cars are built differently from petrol turbo cars.
Turbo diesel cars are not equipped with the same throttle plates as in a petrol turbo car that controls the engine speed. In a diesel car, the engine needs all the air that the turbo charger can give it. It thrives on compressed air for its cylinders to function optimally. A diesel dump valve will only provide the sound but no performance gain.
Diesel dump valves therefore, are not really needed because your turbo diesel car loves the high-pressure build-up. Should you insist on installing a diesel dump valve in your turbo diesel car, you only get the ‘woosh’ sound when you shift gears.