In several of the recent VGS threads, most people come down on the anti-VGS side of the fence. I'd been using the VGS for almost 2 years, and pretty much had forgotten what stock felt like. A couple weeks ago I put the vac lines back to stock, and for sure the BPV closing is much gentler. None of the harsh slam-open, slam closed that the VGS tends to give. But, the downside is that throttle feels mushier with the stock set-up -- no more crisp response of the VGS.

I got to wondering whether there was a way to take just a bit of the harshness out of the VGS. A few minutes of pondering led to the idea of introducing a restriction in the line to the BPV, to slow the development of the vacuum on the diaphram. This could be done with a small orefice in the vac line, but finding the right amount of restriction could be time consuming. A few more minutes, and the obvious became apparent -- just put in a valve, to give infinite adjustability.

So I added a needle valve in the line to the BPV (see pic). I don't have any way to quantify the change, but here are my observations after about 2 weeks of use:

valve closed: boost remains at 0 psi, of course
1/4 turn open: BPV opening/closing is slowed considerably, but I lost about 2 psi boost under WOT (down to 15 psi, from ~17). Apparently, the BPV never saw full vac before redline.
1/3 turn open: A nice compromise, just "sanding off" the rough edges of the VGS, full boost is reach rapidly.
1/2 turn open, or more: full bore VGS.

At 1/4 to 1/3 turn open, the valve is actually barely cracked. Apparently, the BPV diaphram is very sensitive. It takes some time to "tune", but this simple mod may make the VGS work for a wider ranger of motorers.

 

Wow-genius! Good work inimini!

I may have to try that too.

Jeremy