9k Aero BOV question (diaphragm vs spring) - Saabnet.com Bulletin Board

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9k Aero BOV question (diaphragm vs spring)
Posted by SMP (more from SMP) on Tue, 31 May 2016 08:05:43
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Hey all,

I've done a lot of searching with very mixed answers.

I have had an original, "bosch" brand diaphragm type BOV valve on my 1993 9k Aero (has a stg1 tune and a K&N drop in filter but otherwise stock motor) for the longest time. The boost was decent and pretty solid on the needle and I would always get a consistent, singular "whoosh" sound when the throttle would snap close during shifting or letting off under boost.

I recently installed the later "viggen" style BOV (with the spring) after hearing some whistling noise that sounded like boost leak and suspected an old, weak BOV valve. I could not find a "new" Bosch style diaphragm valve...

The throttle response is better and the boost builds a bit quicker and holds higher with the newer, spring style valve installed. This I like.
The problem is that now I get an obviously choppy "whoosh" sound when the throttle plate gets snapped close. This I don't like as much...

Instead of the smooth PSHHHhhhh noise its more like PSHhh SHhhh Shhh.
I have read people say "Oh nice I love that sound" and others say "Oh that's bad the air isn't dumping all the way and its hitting your turbo blades which will cause premature wear.

Can someone please give me a straight, educated answer? :P

Or maybe one based on experience? I'm honestly not that worried about how it sounds. I just want better performance and not to worry about "turbo surge" or "compressor stall" or any of that negative stuff.



posted by 24.104....

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