Recently realized that the noise I thought was my BOV chattering was actually the turbo surging. I know compressor surge is a bad thing, but what exactly happens to make the surge noise, and what does it do to the turbo?

 

Do you have a BOV? If you have a BOV and you are still hearing the CHA-CHA-CHA sound when you get out of it, your BOV isn't functioning. During WOT, you'd never hear the BOV because it will stay closed the entire time.

Basically the CHA-CHA-CHA surge noise is a result of you snapping the throttle blade closed when the turbo is spun up and pushing air. There's no place for the air to go so it goes back out the compressor. While this sounds like somethings about to explode at times, I've been told there's nothing wrong with it at all (unless you're running high boost where it can be more of an issue). It does slow down the turbo's spin which is why a manual car really benefits from a BOV (this gives an alternate route for the air and keeps the turbo spun up while shifting).

 

I did have a BOV that I thought was working correctly. I didn't install it yet on my new setup, which is how I figured out that the noise was NOT the BOV like I initially thought, since it is still doing it. Apparently mine is adjustable (twist it and it changes the spring pressure), but I went ahead and ordered a new TiAL 50mm BOV today anyway. I was just wondering if it was doing any damage. I have heard my old BOV open at high RPM/high boost before, so I know it was working in extreme circumstances.

 

Most BOV that are diaphram style will not react fast enough to discharge to prevent compressor surge. The diaphram needs to stretch to lift the valve up to allow the BOV to discharge comletely. The only BOV that elimated most of the surge was a Synapse Synchronic BOV. This is a piston pull style BOV which react very quickly. We have the same problem with our S2000 and my Denali STS. With the Synapse BOV compressor surge is gone and quicker response on the turbo between shift or throttle release. Here are some videos of the BOV in action.

http://www.youtube.com/results?search_query=synapse+bov

Richard

 

I like my Greddy RS knock off, i get a little bit of suge (like 3 Cha's) and a huge WWOOOSSSHHHHH sound.... BUT, those sync BOV sound badass!

the total Shiznit yo!!!
http://www.youtube.com/watch?v=VbNxu...elated&search=

 

I Don't know if it's the same thing, but the diesel guys call it "Barking the turbo" When you have way too much boost and all the sudden close the throttle. My brother did it with a 1 week old BD turbo, He revved it up to launch and snapped the rear end . all that boost had to go back though the turbo, It didn't live. He said it didn't sound sound pretty, and after further inspection, it wasnt , bearings where history. anyway, if you can avoid doing that, try by all means. I guess the thrust faces of the bearings can only take so much. good luck....

 

He has a Turbosmart piston style BOV. It isn't an ebay knock off either since I'm the one that bought it originally. I know I had it loose to start with with no vacume hose on it and it worked ok and then put the vacuum hose on it then tightened it up with the vacuum line on it so I could hear it and know it was working. Everything will work differently with more cubes somewhat so adjustments might be necessary. If I remember correctly the BOV would flutter when you had it tight.

 

That fluttering wasn't the BOV, at least on my setup. I don't have the BOV on it right now and it makes the same noise still. I would have adjusted the spring tension on the BOV if I knew anything about them.

 

Chris,
BOV's springs are rated by engine manifold vacuum (at operating temp). Below is a chart for the Tial 50mm BOV... the one I have. My BOV came with the lightest (black) spring. I did buy the next up size (white) but found that the BOV was less sensitive to boost/vacuum transistion... which is the event that briefly opens the BOV for blow off. So, I put the black spring back in... even though my typical vacuum range when at idle is within the white springs range. On my setup if I tool around town and get into a few pounds of boost and immediately lift then slight compressor surge will take place. But if I get on it hard and allow the turbo to spool to max (9psi in my case) boost and then immediately lift then the Tial immediately opens. So, spring tension (or its rating) is important when adjusting sensitivity.

Bill

 

Thanks for the info. When I ordered mine today I got the white (9psi) spring. Hopefully that will work ok with my setup. How do you like your BOV?