DUMP VALVE PROJECT: STRANGE PROBLEM!

[hamleto]

Hi,
I have a strange problem with my new recirculation air system.
One year ago I mount a open air filter with a damp valve as you can see in the picture below:



Now I want change this system and re-mount original bin like airbox, but when I connected all hose and intake and go on the street to test the car THE PROBLEM go out:(
In the picture you can see my actual configuration:


indeed I can't hear the typical sound of the air shot off by dump valve, but if I remove the blue hose from the exit of dump valve the problem disappear and I can hear the sound of air shot out from the dump valve.

Why??????

[tigerdog]

The noise is gone because it's being trapped/mufflled by the air filter cannister. As an experiment, try removing the cannister lid (temporarily) and see if the sound is louder.

The alternative would be to mount a dump-valve that vents to atmosphere instead of recirculating into the turbo intake. You can even get them with a small horn attached to make them Really F_ing Loud! See here: www.turboxs.com/shop_prod.php?what_category=2

That'll make the neighbors really like your car.

[Doug]

The noise is gone because it's being trapped/mufflled by the air filter cannister. As an experiment, try removing the cannister lid (temporarily) and see if the sound is louder.

exactly right


you just muffled the sound within the factory airbox, and even proved the valve is still working. It should be fine as you have it -- just quieter than before.

[hamleto]

Hmmm....if I understand exactly you think that my dump valve work fine, but I don't hear the sound of air shot off because it is adsorbed by original airbox?

Why if I remove the blue hose connected with the exit of the dump valve I hear the noise?

[ailwyn]

Why if I remove the blue hose connected with the exit of the dump valve I hear the noise?

Because it's venting to air there is nothing to hide the whoosh sound.

[Elanlover]

Standard Blow Off Valve = "Woosh" noise when its activated (vents to engine compartment)

Recirculating BOV = No "Whoosh" noise as air is vented back into air intake thus silencing the process

Disconnected Recirculating BOV = Same as Std. BOV as you're simply venting back to engine compartment

Did you want quiet or noisy operation?

[tigerdog]

For me, the strangest part of this discussion is that in both photos, the dump output is venting back into the intake. From the initial discussion, I thought it dumped to atmosphere. I guess the open filter doesn't effectively silence the dump output. The quieting must come from the turns and angles in the sound-path through the stock airbox.

[Doug]

correct, dog.

[Elanlover]

I wonder if there's another issue involved. I confess to no expertise in this area but..........

I've always wondered about the nature of the connection from the BOV outlet into the air intake. Most of the ones I see are of a "T" connector type. In other words, they mate to the air intake perpendicular to actual airflow in the air intake. To me, this could/should cause a disruption in the air intake flow. When air from the BOV is vented back into the air intake at that angle its not going to smoothly integrate its flow into the direction of the air intake flow. Some will go in the direction of the flow, some against it (initially). This could not only cause disruption in the air intake flow but also some noise.

(This all making sense to anyone )

When all the little parts and pieces I've ordered arrive (which seems to be harder to make happen than it should be), I'm planning on orienting the direction of air flow from the BOV to match, as closely as possible, that of the air intake flow. Maybe this will have an impact????? Or, is it all simply due to differences in the open air filter/OEM filter box.

Someone much smarter than me can confirm or rebuff these ramblings............

[Doug]

it's not critically important, but yes orienting the bypass flow more down the intake pipe can't hurt.

you also have to consider the relative vacuum from the spinning turbo as the pressure wave comes in . . . . not worth a giant physics dissection IMHO


open filter by bypass area = you will hear it a bit or more

relatively more closed or convuluted system = you won't hear it

[tigerdog]

My thought was to route the vent into a hole in the top of the "filter on a stick", opposite the clean air discharge and pointing into it. From what I'm reading, this might have the desired flow direction but it probably won't be quieter than venting to atmosphere. A steeply angled inlet junction on the pipe between the airfilter and the turbo, pointing at the turbo inlet would be my second alternative.

Of course for me, this is all just a thought experiment...

[Elanlover]

Tdog, you may not be able to plumb the BOV outlet into the top of the filter. I had the same idea only to find that the, while the outside "top" of the filter appeared to have a flat spot Icould drill into, the inside of it was actually a tapered "cone" designed to improve airflow. This was on a K&N filter.........your's could be different. I'm hoping to installed a sealed cold air intake that has hi flow capability and that can suck air from the original cold air intake plumbing that the old OEM filter setup drew air from. Will require a little custom piping to make it work.