Does a Recirculation (plumbed) valve reduce turbo lag?

Does a Recirculation (plumbed) valve reduce turbo lag?

Thought we would stay on theme and look at another BOV myth. "Removing the recirculation hose will increase turbo lag". Or to put it another way, the air from the recirculation valves is plumbed into the air intake to help keep the turbo spinning.
The "experts" making these claims have missed one critical thing.. "physics".
Air will always take the path of least resistance....

So what is that? Push some compressor blades, or flow back out the air filter?
The only way for the air to pass through the compressor and out the turbo is if that was the easiest path. And for that to be the case there would need to be significant pressure build up in the air intake.
Remember, sometimes the laws of physics are smarter than forum experts!

Check the video below for a very graphic explanation. We blast pressurized air into the recirculation hose port on the factory AMG intake. The air passes back through the filter and out the inlet. 


So why does AMG plumb back the Recirculation valve into the intake?  Sound.

A vent to atmosphere type valve will make a "woosh" sound when the throttle is closed. AMG (quit rightly) thinks most of their customers do not want a loud sound each time they back off the gas.

There is a disadvantage to this though. And the main reason why our ZAC Motorsport Cold Air Intakes do not include the plumb back port. HEAT! That air has passed through the turbocharger, and has got VERY HOT in the process. How hot? Well hot enough to melt the factory recirculation valve piston (another blog). We don't want that hot air passing back through the system. So we let the valves vent to atmosphere.


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