I have to figure out if my valve is leaking. I don't want to go aftermarket but it'd be nice to know if this stock one works at 27-28lbs consistantly.

 

Just did a few pull from 3-5th gear... holds 26 PSI no problem.

Nothing else was modified except the pill mod.

I didn't try it at any higher pressures because it is snow here and roads are a bit icy.

I'll post charts in a bit.

 

Nice.

 

Here is a 3rd gear pull... Holds 27 psi easily...

Probably enough for most people. My conclusion is if you want your BOV to hold a bit more you can try this mod. Does not affect driveability at all. Works like stock.

If any one tries this out post your results.

 

Am I right in thinking that while this will delay the opening of the valve allowing it to hold more boost, it will also delay the closing of the valve too? Couldn't that affect the engine's ability to make boost after a gear shift? (with the bov open longer than it should)

 

We use to do this trick on the earlier evo's Works good! I remember back in the day crushing 1G blow off valves! Those were the days.

Michael

 

Using a restrictor pill or completely blocking the port?

 

The bottom reference port is used with a boost setting only. It only helps open the valve fast (response). The opening is still done my vacuum pressure. The closing of the valve is done with the spring . Making the reference hole smaller just delays boost getting to the underside of the diaphragm to pop it off too soon.

I did not notice any issues with gear changes...

 

If I remember correctly, they closed the hole.

 

Yeah, that's the old gus mod. My method uses a restrictor pill of sorts. So it still retains good throttle modulation, but holds a bit more pressure and help slow down the bottom of the diaphragm from seeing boost levels to open the valve prematurely.

 

Great idea ! My only cocern with this mod is the potential for the set screw to backout and fall into the intake stream ! I know it's loctite and all, but still there is alot of vibration in the engine bay.

 

If you are that concerned. Use the red loctite... but beware you will never get it out.

The blue loctite will be sufficent. No worries. The set screw will not get into the intake. One is that the reference hole goes to the underside of the diaphragm and secondly there is a plate that covers the underside of the reference port. If you ever opened your BOV you will realize why the set screw will not go anywhere.

 

this is sweet, i love diy mods on the cheap. it just shows how ingenious people can be.

 

I have a question. I agree that the boost reference port on the bottom of the valve will make it more responsive, since at light throttle, the pressure inside the pipes will actually push the valve open. You say that's it's holding 27psi just fine....how do you know for sure?

There's no way to really know unless you do a dyno run with the hood open and actually watch the BOV to see if it gets pushed open at full boost. Even with a leaking BOV, the turbo can still maintain boost pressure, it just works harder and pushes hotter air. That's the only problem with having a BOV with a boost reference on the bottom of the valve. They can easily leak.

 

why can i never visualise what is actually occuring here??!?!

can someone explain how making a hole in the casing keeps the bov closed?