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Old 18th August 2019, 20:47   #1
MGJohn
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Question Modified T25 Turbocharger OE BOV / Dump Valve question.

About a dozen years ago, I modified the Cap on a T25 BOV [ Re-circulating Boost Blow Off Valve ] so that excess boost on throttle lift off vents to the Atmosphere making the noise so many like to hear. Did this by carefully drilling a series of holes around the cap as in this image :~



On reflection, I believe I overdid the number of holes because the vented boost does not make as loud a noise as it the case with Aftermarket Direct Replacement T25 BOVs... like this one with fewer holes :~



Other aftermarket BOVs do have more holes like this one I used to have :~



Cannot remember how loud they were, so long ago now. So to my question. I have another spare T25 BOV Cap and plan to drill fewer holes in it. About half the number compared to the one in the top image. Before doing so, does anyone know if in so doing, I will affect other things? Probably not harmfully but, you never know.

Any advice, opinions or feedback about this will be appreciated particularly from those who've been there and done that. Thanks in advance.
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Old 18th August 2019, 21:01   #2
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on mine I just blanked it and fitted an after market one, sorry doesn't help you much, I would have said rovertech would have be the ideal place to ask but its gone now although the FB pages are up
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Old 18th August 2019, 23:54   #3
VVC-Geeza
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I have the Forge one John, like the blue one in your picture.It sounds just right imo,noticeable, without being in ya face.Why not base the number of holes on that one.Incidently the diaphragm in the OE one which it replaced had never seated properly from new, so I had been loosing some boost from day one.Oh the look on the chavs faces when they hear a Rover 75 dump. Vroom tishhhh..
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Old 19th August 2019, 00:04   #4
MGJohn
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Quote:
Originally Posted by VVC-Geeza View Post
I have the Forge one John, like the blue one in your picture.It sounds just right imo,noticeable, without being in ya face.Why not base the number of holes on that one.Incidently the diaphragm in the OE one which it replaced had never seated properly from new, so I had been loosing some boost from day one.Oh the look on the chavs faces when they hear a Rover 75 dump. Vroom tishhhh..
Yes that whoooosh-tishhh is an effective signal to those who believe my old Rovers and MGs are easy meat. When "matching strides" away from the Traffic Lights, that first gear change approaching maximum revs sees that sound which when heard, sees most drop back as the 620ti is still accelerating in second approaching the NSL.. Especially so with the now aged [ 20 plus years ] Rover 620ti which still perform admirably in that TLGP.

Have noticed more than once diaphragms "pinched" in OE BOVs. Probably left the production line that way... ... No signs of having been got at. FORGE diaphragms are a perfect fit in OE BOVs.

Despite old age, still young at heart me never tires of that "Whooosh-Tish" effect..
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