xr4tic

While reading <a href="http://home.attbi.com/~mistertam33/THE_GREAT_Diverter_Valve_FACE.htm">"The great diverter valve face off"</a> it says to install the Forge, TT, and TurboXS BPVs in reverse.

The site says "if the spring end can hold more pressure WITHOUT the assistance of boost pressure, then it should be installed in reverse."

I'm trying to figure out how this could be.

Here's my guess:
since we're dealing with pressure, in PSI (pounds per square inch), then I'm assuming if there is more area, then there will be more force (pounds) acting on that area.

So if you look at a Forge BPV piston:
<img src="http://pictureposter.audiworld.com/12130/forge_rebuild3_lo.jpg">
there is more area on the shoulder, then on the tip, so it will take less pressure to overcome the spring, if hooked up normal (with turbo pressure coming in on the side)

Does this sound reasonable?

Either way, there is more surface area on the otherside of the piston, so when pressure is applied there, it should hold no matter how it's hooked up.

So the real question, even if it takes more pressure to open the valve (without the assistance of boost at the small nipple) should it be installed that way?

I would think that it would open quicker if it was installed normally, because you'd have more force helping to open it. And once it's been cracked open a little, it should equalize out, so it should close at the same rate no matter which end is which.

What do you guys think?

johnAWD

The valves are designed to function in a specific manner. Think about what happens when you reverse it, and how it'll handle its work when reversed...

Bad idea IMHO.

Audiboy

not sure what end goes where as far as normal is concerned, but here's how I look at it.

Vacuum on the small nipple overcomes the spring. If the turbine outlet was hooked up to the tip side of that piston, then the pressure pushing the tip + the vacuum in the chamber (due to closed throttle) will make the piston open faster as both forces overcome the spring even more. This to me is the safe connection.

If the turbo outlet was hooked up to the side, that pressure generally cannot open the forged, so it will only be up to the vacuum to open the spring - slower response.

However, when there is no vacuum on the nipple (or chamber), and if there is no funky electronics and solenoids on that vacuum line, then there will be pressure there during acceleration. So, that extra pressure and the spring will push the piston to seal. If the turbine outlet is hooked up to the piston tip part, then effectively, the force of the seal is equal to the force of the spring + the force (area dependent) of the pressure in the vacuum chamber - the force (smaller area) of the turbine pressure pusing the piston.

If there is a sudden increase of pressure from the turbine, this increase in pressure may overcome the force of the spring and the force of the pressure inside the chamber, and it can momentarily open (for spike protection) depending on how fast the increase in pressure can reach the chamber side. That's why it's always smarter to install the BPV as close as possible to the turbine outlet.

However, if the turbine outlet is installed on the side, then the piston seal has maximum sealing from the spring and the force of the pressure in the diaphram. Any sudden boost increase may not open the BPV. But it may be useful for large turbo applications where the BPV opens too easy with changes in pressure when the turbine outlet is installed at the tip.

Anyway, that's me 2cents. Right now, I'm using the forged in the A4 as a BOV Unfortunately, it doesn't make a swish sound, but more like a silent fart - 'shhhhhh'

xr4tic

This isn't the best picture:
<img src="http://pictureposter.audiworld.com/12130/forge_rebuild4_lo.jpg">
but you can see that both ports can affect the piston, as the piston shoulder is higher than the inlet on the side.
Since this is the case, then I would think that since the side port has more surface area, it would open quicker.

Supposedly, this is the correct way:
<img src="http://www.cartogra.com/rs/AFACFA6C-C2B9-11D6-B42C-0090277A760E/screen">
With the pressure coming in on the side.

I'm not getting any boost spikes, I just want to make sure I've got it mounted so it reacts as quick as it can.

Kevin K2

in the forge case looks like the annular area is a touch bigger, confirmed by the simple test. can see the contact ring at the ball end of the piston.

i had emailed forge about 007 and 006, and they said little perf diff between the two, and direction didn't matter much either. tester felt little diff among them.

another issue ... at high hp/flow, there can be a pressure drop from the valve install point, to the manifold tap for the top balance pressure. this would be the case in the pic above, where path includes cross tube, IC, and TB. So the unload force on piston is at compressor exit pressure, and balance top force at several psi less .... may be more likely to leak boost.

some models have the xtra hose from compressor valved in at high boost.

Audi2ptzero

If it is not installed that way and you run higher boost then stock it will rip since it only has a rubber diaphram to hold the valve shut. That is why you want the vacume/return side under the valve which is the bottom tube and the pressure/turbo side going into the side tube.

With a aftermarket valve you can put it either way since they use a piston/spring combo. Changing the pressure of the spring will help close the valve sooner, which helps when you are using a fmic that has a PSI drop.

xr4tic

According to the BPV testing, it takes 13-14psi to overcome the spring, so I would imagine you would have to have a pretty big pressure drop accross the tubing and IC before it would make a difference.

WYSIWYG

my shimmed forge sounds like a BOV even in closed loop. i'll take some clips when i remount it

Audiboy

port exposes a larger area of the piston. They may be equal, or the side one slightly larger. I'll just hook up my forged to an air compressor one of these days and see which one opens easier - with a balloon on one side or soak it in a pail of water

Audi2ptzero

But the psi drop will cause a delay in the bpv closing 100%.