Hi all,
Just got on, been consumed this morning with farm and business chores, as well as internal meetings where we've been brainstorming Technical Support processes and possible revisions in light of this dilemma from yesterday. For clarity's sake, I'd like to address that aspect separately from the actual discussion about the BOV's. I'll work with Joe to address the details of separating the two.
elff, to answer your most basic question from last night, it's not actually a standard parameter of a typical compressor-bypass (intake manifold signal-referenced) BOV to establish a maximum boost pressure rating. Their essential internal construction ensures that they will always stay shut under boost. I'll go into greater detail on this in a bit.
Some of the BOV manufacturers do offer different springs, but they are for the purpose of accommodating different idle intake vacuum settings. In a nutshell, engines with bigger cams and porting develop much less idle vacuum than less aggressive setups using stock cams, and thus require a different valve opening pressure and accordingly, a lighter spring. On the other hand, if one uses a spring intended intended for such a low vacuum application on an engine with a strong vacuum signal (such as stock cams would produce), the valve will actually start opening at idle...so a stronger spring would therefore used to keep the valve closed at idle, resisting the stronger vacuum being produced.
Our Billet BOV uses a spring that's intended to accommodate street-type high vacuum/stock or mild cam applications, as that's the bulk of its application. Highly modified cylinder heads engines with cam, valve and port upgrades will typically also be associated with a higher HP range, and thus more airflow, at which time a larger, more adjustable (via available spring options) BOV would be the logical choice.
I'd like to also put a finer point on this "flutter" issue we're examining here. In some LNF applications, we've seen BOV's from multiple manufacturers flutter under full load, high boost, mid-high RPM, when they should not actually be opening at all. Josh and others, is this the issue you're referring to in this thread, or are you referring instead to a flutter when the valve is intentionally opened when suddenly releasing the throttle?
Should anyone like, I'll be happy to also expound a bit further on BOV valve design and function. I can add some detail here I think many will find useful, just let me know.
