So you're hear to find out about the diverter valve on your Volkswagen or Audi 1.8T engine. You've come to the right place.
The Mechanics Behind the Diverter Valve
When you hit the gas your throttle plate opens allowing air into the engine. The turbo is in the intake stream and compresses the air and forces it in to the engine at a certain pressure. Well suddenly you need to shift and let off the throttle, throttle plate closes, and the turbo is still spinning. The turbo still spinning is a good thing because it will have less work to catch back up when you reapply the throttle, but... a spinning turbo means it is still compressing air and the throttle plate is closed so there is only one way for the compressed air to get out, back the way it came in. Well this is where the Diverter Valve comes into play. The diverter valve diverts the air that would have gone back through the turbo causing it to stop spinning in one direction and spin backwards, to go back into the intake stream pre-turbo so you recycle that air. Now since your Volkswagen is tuned to run the air back into the system after the MAF sensor the MAF is calculating based on a certain charge still being in circulation when the throttle plate re-opens.
If you were to put an aftermarket Blow-Off Valve on the system that air that is being calculated for just blew out into the atmosphere. This causes the computer to still inject fuel metered for the air that was in the system already as well as the new air coming through the intake. With an aftermarket blow off valve you will get a fun turbo sound but your engine will run a little richer.
If you are looking for an aftermarket upgrade, either an aftermarket diverter valve or a conversion to a blow off valve would work, it just depends on what your goal is and whether or not you want to alter the factory Volkswagen design. There is also a fairly new product on the market called a "splitter" diverter valve made by Forgewhich basically gives you the best of both worlds - the "pssst" sound of a BOV while still maintaining your factory engine management settings and not setting off your check engine light.
What are the benefits of an aftermarket diverter valve?
Your stock valve in your car regulates your turbo power. At idle, your valve is open from vacuum pressure. When you depress the throttle, the diverter valve begins to close. When fully closed, turbo boost is allowed to be delivered to your engine. When you lift the throttle, the boost pressure is released from the valve into your air cleaner box. Inadequate/defective valves have extended lag, loss of boost, sluggish throttle response. A aftermarket diverter valve can clear up the previously mentioned problems. Also, if you have a chip, you need an aftermarket valve now. Chips simply overtax standard diverter valves.
Is the a diverter valve a "blow-off" valve?
No, not technically. A blow-off valve sends the "boosted" air into the atmosphere rather than the airbox/air filter. This is why they usually make a loud noise from the air releasing. In some cases they may cause sophisticated engine management systems, like in the VW or Audi cars, to incur errors and drivability issues.
How to Install a Diverter Valve on Volkswagen and Audi 1.8T
The stock diverter valve is an electronically actuated unit mounted directly onto the side of the compressor housing of the stock turbo. You can access the (3) allen bolts that hold the valve to the turbo by placing the car on a vehicle lift and accessing it from underneath. The valve is nested between the passenger side firewall and the passenger side fender well. This procedure eliminates the use of this stock valve (which can be a source of boost leaks) and replaces it with a more reliable mechanical valve.
When you are ready to make your choice, be sure to bookmark our site extremevdub.comso we can provide you with the best prices and even help with installation of your valve should you need it. Thanks for being a valued customer.
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