Return-Path: <13brv3@bellsouth.net> Received: from imf16aec.mail.bellsouth.net ([205.152.59.64] verified) by logan.com (CommuniGate Pro SMTP 4.1.3) with ESMTP id 2576172 for flyrotary@lancaironline.net; Thu, 11 Sep 2003 13:17:40 -0400 Received: from rad ([68.212.14.21]) by imf16aec.mail.bellsouth.net (InterMail vM.5.01.05.27 201-253-122-126-127-20021220) with ESMTP id <20030911171738.ZDUI21511.imf16aec.mail.bellsouth.net@rad> for ; Thu, 11 Sep 2003 13:17:38 -0400 From: "Russell Duffy" <13brv3@bellsouth.net> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: turbo wastegate requirements Date: Thu, 11 Sep 2003 12:17:38 -0500 Message-ID: <00b501c37888$9a0ca070$0201a8c0@rad> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00B6_01C3785E.B1369870" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.4510 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Importance: Normal In-Reply-To: This is a multi-part message in MIME format. ------=_NextPart_000_00B6_01C3785E.B1369870 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Of course you're right about residual boost with wastegate open. My 30" take off would have to be done at partial throttle. Am I correct in my inference that gradually closing the wastegate as I go higher and higher will minimize intercooler requirements and wear and tear on the turbo? =20 =20 I'm counting on not needing an intercooler using this same logic, so I = guess we'll find out if my engine blows up. It would also seem like it would = save some wear on the turbo bearings by bypassing as much exhaust as you can, = but I'm not sure how significant this would be. =20 =20 Additionally, I have put a 36" or so limit on MAP to safeguard the = engine. Does the turbo also have a boost limit? If the turbo has, say, a 10" = boost limit, then as ambient pressure dropped off, I would reach my turbo normalize limit at about 20" ambient or around 10k'. What would the = boost limits be on the Mazda stock turbo? Are they a factor in normalizing to 15k' - 18k'? =20 =20 Take it away, Ed :-) =20 =20 Yes, turbos have limits, but this is the part of the turbo class that = I'm not qualified to teach. As I understand, each turbo unit has a = "compressor map" that shows it's efficiency range as a function of absolute = pressure, and airflow. Absolute pressure is basically the boost that the turbo produces above ambient pressure, which is why I maintain that a = traditional boost gauge is handy to have. =20 =20 My (over)simplified way of looking at this is- I'm using the same turbo = as Mazda sized for this engine, so airflow, and boost needs to be kept in = the same range that's been proven to be durable in the cars. The = difference is the duration of the boost, and the extremely free intake and exhaust = systems that we have compared to a stock car, though many modified cars are in = about the same situation. I figure that guys can easily run 8 psi of boost on = the street, so I should be able to do the same in the air. 8 psi gives me = about 16 inches of mercury, which is 15-16 thousand feet of normalization. = That's plenty for me. =20 =20 Another thing to consider is just how much normalization you really = need. I don't think too many people are planning to cruise at full sea level = power. If you do, I hope you're flying a fuel tanker :-) Let's just say that = we'll use 75% like you would with a Lycosaur. A NA Lycosaur can still produce = 75% power up to 8k ft, so our turbo only needs to make up the difference = between 8k and whatever our max cruising altitude is. Even at 18k ft, that's = only 10k ft of normalization for cruise power, or 5psi (roughly). I really = wish I knew how much boost the 9.7 rotors would tolerate. If 6 psi is safe, = then I'd be tempted to just set the relief valve there, and try to adjust the throttle for 5 psi. I suspect this will still be with a fully open wastegate. Did I mention that I can't wait to actually try some of this stuff :-) =20 Rusty ------=_NextPart_000_00B6_01C3785E.B1369870 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable Message
Of course you're right about residual boost with wastegate = open.  My=20 30" take off would have to be done at partial throttle.  Am I = correct in my=20 inference that gradually closing the wastegate as I go higher and higher = will=20 minimize intercooler requirements and wear and tear on the = turbo?  
 
I'm counting=20 on not needing an intercooler using this same logic, so I guess we'll = find out=20 if my engine blows up.  It would also seem like it would=20 save some wear on the turbo bearings by bypassing as much = exhaust=20 as you can, but I'm not sure how significant this would=20 be.  
  
Additionally, I have=20 put a 36" or so limit on MAP to safeguard the engine.  Does the = turbo also=20 have a boost limit?  If the turbo has, say, a 10" boost limit, then = as=20 ambient pressure dropped off, I would reach my turbo normalize limit at = about=20 20" ambient or around 10k'.  What would the boost limits be on the = Mazda=20 stock turbo?  Are they a factor in normalizing to 15k' - = 18k'?  
 
Take it away,=20 Ed :-)   
 
Yes, turbos=20 have limits, but this is the part of the turbo class that I'm not = qualified to=20 teach.  As I = understand, each=20 turbo unit has a "compressor map" that shows it's efficiency range as a = function=20 of absolute pressure, and airflow.  Absolute pressure is = basically the=20 boost that the turbo produces above ambient pressure, which is why I = maintain=20 that a traditional boost gauge is handy to have.  =
 
My=20 (over)simplified way of looking at this is- I'm using the same = turbo as=20 Mazda sized for this engine, so airflow, and boost needs to be kept in = the same=20 range that's been proven to be durable in the cars.  =20 The difference is the duration of the boost, and the extremely free = intake=20 and exhaust systems that we have compared to a stock car, though many = modified=20 cars are in about the same situation.  I figure that guys can = easily run 8=20 psi of boost on the street, so I should be able to do the same in the=20 air.  8 psi gives me about 16 inches of mercury, which is = 15-16=20 thousand feet of normalization.  That's plenty for=20 me.  
 
Another thing=20 to consider is just how much normalization you really = need.  I=20 don't think too many people are planning to cruise at full sea = level=20 power.  If you do, I hope you're flying a fuel tanker :-)  = Let's just=20 say that we'll use 75% like you would with a Lycosaur.  = A NA=20 Lycosaur can still produce 75%  power up to 8k ft, so our = turbo only=20 needs to make up the difference between 8k and whatever our max cruising = altitude is.  Even at 18k ft, that's only 10k ft of normalization = for=20 cruise power, or 5psi (roughly).   I = really wish I=20 knew how much boost the 9.7 rotors would tolerate.  If 6 psi = is safe,=20 then I'd be tempted to just set the relief valve there, and try to = adjust the=20 throttle for 5 psi.  I suspect this will still be with a fully open = wastegate.  Did I mention that I can't wait to actually try some of = this=20 stuff :-)
 
Rusty
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