Return-Path: <13brv3@bellsouth.net> Received: from imf19aec.mail.bellsouth.net ([205.152.59.67] verified) by logan.com (CommuniGate Pro SMTP 4.2b3) with ESMTP id 98648 for flyrotary@lancaironline.net; Tue, 01 Jun 2004 01:03:33 -0400 Received: from rad ([65.6.194.9]) by imf19aec.mail.bellsouth.net (InterMail vM.5.01.06.08 201-253-122-130-108-20031117) with ESMTP id <20040601050304.XNAY6802.imf19aec.mail.bellsouth.net@rad> for ; Tue, 1 Jun 2004 01:03:04 -0400 From: "Russell Duffy" <13brv3@bellsouth.net> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] blow off Date: Tue, 1 Jun 2004 00:03:07 -0500 Message-ID: <00c401c44795$babaa5b0$6001a8c0@rad> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00C5_01C4476B.D1E49DB0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.4510 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 This is a multi-part message in MIME format. ------=_NextPart_000_00C5_01C4476B.D1E49DB0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Hey Rusty, Do you still have that blow off valve? John =20 =20 Never had one :-) =20 =20 Technically, what I had was a "Pop off valve", or "relief valve". A = relief valve, is just a spring loaded valve, that dumps pressure over a certain amount. This is used as a final safety valve on some cars, but not = RX-7's. A blow off valve is something that's standard issue on turbocharged = cars, but probably not needed on airplanes. A BOV is vacuum actuated, and is used to dump the pressure when slamming the throttle shut, such as = between gear shifts. This saves the turbo from sudden over-pressure. =20 =20 I still have the relief valve, and I will certainly sell it to you, but = I have to stress that this is NOT a fix to the problem. Opening the = outlet side of the turbo causes overspeed of the turbine, which is bad, and = this is never considered an acceptable method of turbo control. It also isn't desirable for aircraft, because this is a differential device, meaning = that it looks at pressure compared to ambient. In other words, it adds a = certain amount of boost, which falls as you climb, just like a NA engine. =20 =20 I would urge you, and everyone else that's trying to use a stock turbo, = to look into modifications that reduce the boost level at low rpm. Ed has posted links to a place in Oz that does this, and I'm sure there are = folks in the US that can do the same thing. Unless you can modify the turbo = to be controllable, it's not safe. We don't want the Subaru guys posting your off-airport landing :-) =20 Cheers, Rusty (I need a plenum) =20 =20 ------=_NextPart_000_00C5_01C4476B.D1E49DB0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message
Hey Rusty,
Do you still have that blow off=20 valve?
John  
 
Never had one :-)  =
 
Technically, what I had was a "Pop off valve", or "relief=20 valve".   A relief = valve, is=20 just a spring loaded valve, that dumps pressure over a certain = amount. =20 This is used as a final safety valve on some cars, but not RX-7's.  = A blow=20 off valve is something that's standard issue on turbocharged cars, but = probably=20 not needed on airplanes.   A=20 BOV is vacuum actuated, and is used to dump the pressure when slamming = the=20 throttle shut, such as between gear shifts.  This saves the turbo=20 from sudden over-pressure. =20
 
I=20 still have the relief valve, and I will certainly sell it to you, but I = have to=20 stress that this is NOT a fix to the problem.  Opening the outlet = side of=20 the turbo causes overspeed of the turbine, which is bad, and this is = never=20 considered an acceptable method of turbo control.  It also isn't = desirable=20 for aircraft, because this is a differential device, meaning that it = looks at=20 pressure compared to ambient.  In other words, it adds a certain = amount of=20 boost, which falls as you climb, just like a NA engine. =20
 
I=20 would urge you, and everyone else that's trying to use a stock turbo, to = look=20 into modifications that reduce the boost level at low rpm.  Ed has = posted=20 links to a place in Oz that does this, and I'm sure there are folks in = the US=20 that can do the same thing.  Unless you can modify the turbo = to be=20 controllable, it's not safe.  We don't want the Subaru guys = posting=20 your off-airport landing :-)
 
Cheers,
Rusty (I need a=20 plenum)
 
 
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