Welcome to the world of Forced Induction! If you’ve purchased your first turbocharged Audi or VW vehicle, you may be wondering what the difference is between a diverter valve and blow-off valve and which one you should purchase to upgrade your vehicle. A diverter valve and blow off valve are two completely different pieces of hardware. Each has pros and cons depending on which system they are being used on. We will discuss the differences between the two and what would work better for your specific setup.
Upgraded Audi VW OEM Diverter Valves
If your vehicle is stock or mildly tuned with basic bolt-ons, you want to stick to a solid and upgraded OEM diverter valve. The Audi and Volkswagen 1.8T and 2.7T motors use a diverter valve with part number 06A145710N. This version was originally used in the 225hp Audi TT and has a heavy-duty diaphragm. It’s a great upgrade for these motors. The 2.0T motors use a valve with part number 06H145710D. This OEM diverter valve was upgraded several times by the Volkswagen Group and now features a piston rather than a failure-prone diaphragm.
All stock Audi and Volkswagen vehicles come with a diverter valve rather than a blow off valve. The diverter valve is usually located on the side of the turbocharger, it is a pressure release system which diverts unused pressure back into the system preventing compressor surge. By rerouting the pressure back to the compressor inlet, diverter valve keeps the compressor wheel moving and decreases turbo lag. The older style diverter valves used a diaphragm which would rip with any off-the-shelf Stage 1 or Stage 2 tune. If you are running the original pre-revised diverter valve we highly recommend replacing it with a revised unit prior to tuning your vehicle.
A blow off valve can be an upgrade on certain systems and a complete waste of money on others. If you’re running a stock or slightly upgraded turbo, you typically want a diverter valve because it recycles what it didn’t use. If you plan on doing a big turbo upgrade with custom manifolds and upgraded fueling, a diverter valve will most likely not cut it. This is when you need to start looking into blow-off valves. The drawback of a blow off valve is that you will have instances of running rich and a bit of hesitation or stumbling. This is caused by the pressure being released from the system, which also gives you the blow off valve sound that many tuners yearn for.
The revision D and N diverter valves have both been tested and will hold up to Stage 2+ tunes without any issues. If you plan on upgrading your turbo, we recommend using the newer and upgraded OEM diverter valve. Your vehicle will simply run better. There are instances where you will need to run a blow-off valve as a diverter valve will not hold up due to the added pressure from a big turbo. If you have any questions regarding diverter valves or blow-off valves, please feel free to contact us so we can recommend a perfect option for your specific build.