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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
BOV performance, 1.5"?

Is there an ideal amount of BOV capacity?

Is bigger better?

The BOV is mostly used to keep to turbo from stalling between shifts. This gets us on boost faster and also protects us from damaging the turbo.

Thus, a larger BOV might keep the turbo spinning faster between shifts. If so, should we consider adding a second one or a larger one.

Just a note, if a 1" BOV were to have an ID of .8" that is a .5 sq inch of cross section. If we up grade to a 1.5" and it has an ID of 1.3" it would have a 1.33" cross section or about 266% more flow potential.

I know the 993TT's have two 1" Bosh BOV's. This might be mostly because it is easier to plumb. However, it might support that more is probably not a problem.

Is there a down side to to much BOV capacity?

If we have to much BOV will this lower the pressure in the inter-cooler to much so that we have to wait to re-pressurize?

Is there room for improvement here?


Some of you know I am an advocate for modifying the BOV to stay open during idle and cruse to keep the turbo spinning faster as a bit of an anti lag strategy. This also makes for less exhaust back pressure at idle and cruse.

I wonder if one is doing this if one could go to far as to bypass capacity?
Old 12-31-2009, 02:21 PM
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