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Diverter Valves vs Blow-off Valves - EuroSport Tuning | Performance parts and accessories for Audi, BMW, Volkswagen, Mini, Mercedes Benz, Porsche and Volvo

Diverter Valves vs Blow-off Valves

Posted by Eurosport Tuning on 2021 Sep 20th

Diverter Valves vs Blow-off Valves

Are you looking for more information about diverter valves and wondering if they are the same as blow-off valves? Look no further, here's what you need to know about the diverter valve and how it varies from a blow-off valve.

How a Diverter Valve Works

Every time that you hit the gas on a turbocharged vehicle, air goes into the engine because the throttle plate opens up. The air is compressed and forced into the engine by the turbo. If you shift, you let off the throttle. This closes the throttle plate, and the turbo continues to spin. By continuing to spin, the turbo will have less work to do the next time you need it, but the air that it was compressing has to go somewhere. 

The diverter valve takes that compressed air and recycles it through the intake stream. If it had not diverted the air, the air would have caused the turbo to start spinning backwards as the air was sucked back into it. When your vehicle is tuned to recycle the air after the MAF sensor, the MAF will be calculating how much will still be in circulation once the throttle opens back up again.

An aftermarket blow-off valve will simply take that air and send it out into the atmosphere once again. This will cause the computer to inject measured fuel based on the previous air that was in the system plus any new intake. The blow-off valve features a cool "pfftt" sound, but it results in a richer running engine.

When you're looking for an aftermarket upgrade, you could choose either a diverter valve or a combination diverter AND blow-off valve. Your choice will depend upon your performance goals and if you want to alter the Audi/Volkswagen factory design. You can see the available diverter and diverter/blow-off combo valves for Audi and VW here, but you'll see that most of the parts are offered by Forge Motorsport.

Benefits of Diverter Valves

The stock valve on your Volkswagen regulates the turbo power. When you are at an idle, the vacuum pressure opens the valve. The turbo boost is activated when the valve is fully closed. Lifting the throttle releases the boost pressure into the air cleaner box. If the valve is defective or inadequate, you will get a loss of boost, extended lag or a throttle response that is sluggish. These problems go away with the installation of an aftermarket diverter valve. If you are running with a chip, you need to put the diverter valve in because the chip will stress the standard valves.

Is It a Blow-Off Valve?

The difference between a diverter valve and the blow-off valve is where the air is delivered. Blow-off valves send it out into the atmosphere and you get a lot of noise, but in some cases, if your Volkswagen or Audi has a complicated engine management system, you may suffer drivability issues or error codes. A diverter valve recycles the air.

Installation for Volkswagen and Audi 1.8T

You will find the electronically actuated stock diverter located on the side of the stock turbo’s compressor housing. Put your vehicle on a lift and locate the three allen bolts used to hold the valve onto the turbo. It is between the passenger side fender well and passenger side firewall. Now, you can replace it with a more reliable valve. Stock valves can be a boost leak source.

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