While browsing through some Autospeed articles I found an old article (2001) telling about a variable butterfly valve for reducing exhaust noise.

Variflow butterfly valve

I am wondering if this variflow valve can be used as a replacement for the wastegate?

 

Different application entirely.

The wastegate is intended to divert flow, not restrict it. You'd have to build in a "Y" or "T" into that pipe upstream of the valve. Another thing to consider is that it only takes very small differences in pressure to effect large changes in fluid flow/behavior. Someone measured it once - the stock wastegate with its little valve (much smaller than the butterfly valve on the variflow valve) only open something like 1mm was enough to bleed off boost almost completely. You could probably get it to work, but it'd be very sensitive - probably best for a race car application where you want 100% flow to the turbo all the time except when you hit the regulated level, then "BANG".

Interesting idea, but I think it'd be very difficult to get it to work properly, and it might have some reliability issues.

Go for it though if you have the time - I'd be interested to see what you come up with. . .

 

I was thinking of replacing the wg with the variflow valve. In this setup it will be used to divert flow and there would be no need to build a "Y' or "T".

Your second point (valve size) might be a problem though.

 

That valve will never survive the heat and pressure of being where the wastegate is. It's also more complex than a wastegate, which is actually a very elegant solution.