Return-Path: Received: from out004.verizon.net ([206.46.170.142] verified) by logan.com (CommuniGate Pro SMTP 4.1.4) with ESMTP id 2602137 for flyrotary@lancaironline.net; Wed, 24 Sep 2003 16:15:51 -0400 Received: from [65.239.57.243] ([67.227.200.183]) by out004.verizon.net (InterMail vM.5.01.05.33 201-253-122-126-133-20030313) with ESMTP id <20030924201548.YYOM25700.out004.verizon.net@[65.239.57.243]> for ; Wed, 24 Sep 2003 15:15:48 -0500 Mime-Version: 1.0 X-Sender: res0c5l1@incoming.verizon.net Message-Id: In-Reply-To: References: Date: Wed, 24 Sep 2003 13:15:45 -0700 To: "Rotary motors in aircraft" From: Ken Welter Subject: [FlyRotary] Re: turbo math Content-Type: multipart/alternative; boundary="============_-1147687893==_ma============" X-Authentication-Info: Submitted using SMTP AUTH at out004.verizon.net from [67.227.200.183] at Wed, 24 Sep 2003 15:15:47 -0500 --============_-1147687893==_ma============ Content-Type: text/plain; charset="us-ascii" ; format="flowed" > I am planing to put a turbo on my coot and I plan to install a huge >waist gate that will be used a a dump valve to shut the turbo down, >also on the intake side I will have a bypass flapper valve that will >let cool fresh air in when the turbo is shut down, most bigger turbo >setups have these incase of a turbo failure. > With this setup you can have your cake and eat it to, use the turbo >when you need it but for economy cruise your better off without it >and your not putting unnecessary ware and tare on the turbo, also a >great safety factor as you will be coming down if you ever lose a >turbo and with this just kick it in bypass mode. > All of this shouldn't take up much space either. > >Interesting idea, but here are some things to consider. > >You will probably need a muffler if you bypass the turbo. This >isn't a negative if you planned to have one anyway, though you >certainly don't need a muffler with a stock turbo and manifold. I >have to figure that you're talking about using aftermarket stuff >here, and you may very well need a muffler anyway. > >Bypassing the turbo will help with some failure modes, but not >all. Any sort of failure on the compressor side side of the turbo >will send broken pieces of metal through the engine before you can >shut it down. An intercooler will probably catch the bigger pieces, >but it'll be game over if you trash the rotors. If you use a >filter, I don't think this will be a very likely failure mode. I'm >betting that most damaged compressor blades come from ingesting >objects, which would be bad even without the turbo. Of course I >have no filter or intercooler, so I guess I'm SOL. > >I'm not sure how much wear and tear will be saved on the turbo. A >good turbo will run a long time before you wear it out. I really >think that's the least of our problems. > >I can't argue with the idea of saving some fuel at economy cruise >power settings, but for me, it wouldn't be worth the trouble of >installing the redundant exhaust and bypass. I'm guessing that >you're planning to use a part time turbo for takeoff, instead of NOS? > >Cheers, >Rusty (not a turbo expert) > Yes that's the plan to eliminate the NOS and use the turbo at high ALT where the air is cool. I have many years experience drag racing a turbo VW bug running on alcohol pushing 100 inches manifold pressure and have had many turbo failures but have never seen a failure of the intake blades, most were from throwing the tips off the exhaust turbine which only made for turbo lag and surprisingly just a slight drop in boost on the top end. The most common problem was bearing seizure which was like stuffing a potato up the intake and tail pipe and for this the bypass mode would save you, also I had carbon seals fail which would lay out a hell of a big smoke screen and would empty the crank case in a hurry, for this I am going to have a shutoff valve on the oil into the turbo so that if my low oil buzzer and light goes off and I look back and see a smoke screen I will put the turbo in bypass mode and shut the oil down to it. Still have the old turbo bug but haven't run it in 8 years as I have an airplane to fly now. Ken Welter --============_-1147687893==_ma============ Content-Type: text/html; charset="us-ascii" [FlyRotary] Re: turbo math
 I am planing to put a turbo on my coot and I plan to install a huge waist gate that will be used a a dump valve to shut the turbo down, also on the intake side I will have a bypass flapper valve that will let cool fresh air in when the turbo is shut down, most bigger turbo setups have these incase of a turbo failure.
 With this setup you can have your cake and eat it to, use the turbo when you need it but for economy cruise your better off without it and your not putting unnecessary ware and tare on the turbo, also a great safety factor as you will be coming down if you ever lose a turbo and with this just kick it in bypass mode.
  All of this shouldn't take up much space either.
 
Interesting idea, but here are some things to consider. 
 
You will probably need a muffler if you bypass the turbo.  This isn't a negative if you planned to have one anyway, though you certainly don't need a muffler with a stock turbo and manifold.  I have to figure that you're talking about using aftermarket stuff here, and you may very well need a muffler anyway. 
 
Bypassing the turbo will help with some failure modes, but not all.  Any sort of failure on the compressor side side of the turbo will send broken pieces of metal through the engine before you can shut it down.  An intercooler will probably catch the bigger pieces, but it'll be game over if you trash the rotors.  If you use a filter, I don't think this will be a very likely failure mode.  I'm betting that most damaged compressor blades come from ingesting objects, which would be bad even without the turbo.   Of course I have no filter or intercooler, so I guess I'm SOL.
 
I'm not sure how much wear and tear will be saved on the turbo.  A good turbo will run a long time before you wear it out.  I really think that's the least of our problems.
 
I can't argue with the idea of saving some fuel at economy cruise power settings, but for me, it wouldn't be worth the trouble of installing the redundant exhaust and bypass.  I'm guessing that you're planning to use a part time turbo for takeoff, instead of NOS?
 
Cheers,
Rusty (not a turbo expert)     
 

  Yes that's the plan to eliminate the NOS and use the turbo at high ALT where the air is cool.
 I have many years experience drag racing a turbo VW bug running on alcohol pushing 100 inches manifold pressure and have had many turbo failures but have never seen a failure of the intake blades, most were from throwing the tips off the exhaust turbine which only made for turbo lag and surprisingly just a slight drop in boost on the top end.
 The most common problem was bearing seizure which was like stuffing a potato up the intake and tail pipe and for this the bypass mode would save you, also I had carbon seals fail which would lay out a hell of a big smoke screen and would empty the crank case in a hurry, for this I am going to have a shutoff valve on the oil into the turbo so that if my low oil buzzer and light goes off and I look back and see a smoke screen I will put the turbo in bypass mode and shut the oil down to it.
 Still have the old turbo bug but haven't run it in 8 years as I have an airplane to fly now.

 Ken Welter
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