Return-Path: Received: from [24.25.9.100] (HELO ms-smtp-01-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.2b7) with ESMTP id 312966 for flyrotary@lancaironline.net; Mon, 12 Jul 2004 18:56:36 -0400 Received: from EDWARD (clt25-78-058.carolina.rr.com [24.25.78.58]) by ms-smtp-01-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id i6CMu2Pg006529 for ; Mon, 12 Jul 2004 18:56:04 -0400 (EDT) Message-ID: <000c01c46863$6befdfb0$2402a8c0@EDWARD> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Three candidates for Turbo Failure Date: Mon, 12 Jul 2004 18:56:09 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0009_01C46841.E4A50740" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1409 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1409 X-Virus-Scanned: Symantec AntiVirus Scan Engine This is a multi-part message in MIME format. ------=_NextPart_000_0009_01C46841.E4A50740 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Some reasonable suggestions, Bob The modifications that are offered by the Aussies for the stock = turbo should result in less rotating speed for a give mass flow (which = will not appreciably change). This will tend to minimize the over-boost = problem at higher rpms common to the stock turbo. To compensate for the = lower rotation speed, they are installing a bigger compressor wheel = which will be more efficient that the smaller stock wheel. So for the = same boost should produce a cooler air charge. It will take a bit more = engine rpm to get the same boost, will reduce exhaust back pressure and = should in generally made the turbo better suited for aircraft use. I think the modifications you suggested point toward controlling the = exhaust gas better which would certainly help things. I think the = modifications that John is having made will do that and improve the = intake (compressor) side as well. =20 I believe that Todd's modifications of enlarging the integral waste gate = port and drilling through the scroll divider will also improve control = of boost levels at higher rpms. I guess we will have to wait and see how this all turns out. Ed Ed Anderson RV-6A N494BW Rotary Powered Matthews, NC ----- Original Message -----=20 From: Bob Tilley=20 To: Rotary motors in aircraft=20 Sent: Monday, July 12, 2004 3:42 PM Subject: [FlyRotary] Re: Three candidates for Turbo Failure Ed and John, So this brings us to what do we do now? Test 1: install new modified turbo! Check MAP to see if he is still = producing to much boost. I believe he should get some ramp-up of boost and it appears he is = making to much. Test 2: put a spacer in between the back cover of the turbo and the = turbo, where the wastegate is located.=20 this will allow the wastegate to open farther.=20 Test 3: Remove the wastegate all together. Test 4: Find a more suitable turbine wheel. Bob On Jul 12, 2004, at 12:45 PM, Ed Anderson wrote: 1. we could have a condition whereby the turbine was not in the = "overspeed" territory but operating at a lower (safer speed) and a condition = existed that build up a deposit on the turbine wheel until its out of = balance state caused it to touch the housing and fail. 2. A worn bearing ultimately resulted in failure due to wobbly and = wheel contact (Possibly acerbated by periods of long boost at high speeds = - but, not a true overspeed condition) 3. Overspeed of the rotating assembly resulted in failure (due to = operating too far to the right on the compressor map possibly acerbated by the = leak in John's intercooler and/or BOV valve). 4. Defective weld of wheel to shaft (Pretty remote chance - I = believe - especially with two turbos) 5. Some combination of the above. But, I believe that in all cases = higher turbine speed would acerbate the condition and lead to quicker = failure - whether true overspeed or not. Good addition to the theory stack, Bulent. Ed ------=_NextPart_000_0009_01C46841.E4A50740 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Some reasonable suggestions, = Bob
 
    The modifications = that are=20 offered by the  Aussies for the stock turbo should result in = less=20 rotating speed for a give mass flow (which will not appreciably = change). =20 This will tend to minimize the over-boost problem at higher rpms common = to the=20 stock turbo.  To compensate for the lower rotation speed, they are=20 installing a bigger compressor wheel which will be more efficient that = the=20 smaller stock wheel.  So for the same boost should produce a cooler = air=20 charge.  It will take a bit more engine rpm to get the same boost, = will=20 reduce exhaust back pressure and should in generally made the = turbo better=20 suited for aircraft use.
 
I think the modifications you suggested = point=20 toward controlling the exhaust gas better which would certainly help=20 things.  I think the modifications that John is having made will do = that=20 and improve the intake (compressor) side as well. 
 
I believe that Todd's modifications of = enlarging=20 the integral waste gate port and drilling through the scroll divider = will also=20 improve control of boost levels at higher rpms.
 
I guess we will have to wait and see = how this all=20 turns out.
 
Ed
 
Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
From:=20 Bob = Tilley=20
Sent: Monday, July 12, 2004 = 3:42 PM
Subject: [FlyRotary] Re: Three = candidates=20 for Turbo Failure

Ed and John,

So this brings us to what do we do=20 now?

Test 1: install new modified turbo! Check MAP to = see if he=20 is still producing to much boost.
I believe he should get some = ramp-up of=20 boost and it appears he is making to much.

Test 2: put a spacer = in=20 between the back cover of the turbo and the turbo, where the wastegate = is=20 located.
this will allow the wastegate to open farther. =

Test 3:=20 Remove the wastegate all together.

Test 4: Find a more suitable = turbine=20 wheel.

Bob

On Jul 12, 2004, at 12:45 PM, Ed Anderson=20 wrote:


1. we could have a condition whereby the turbine was = not in=20 the "overspeed"
territory but operating at a lower (safer speed) = and a=20 condition existed
that build up a deposit on the turbine wheel = until its=20 out of balance state
caused it to touch the housing and = fail.

2. A=20 worn bearing ultimately resulted in failure due to wobbly and=20 wheel
contact (Possibly acerbated by periods of long boost at = high speeds=20 - but,
not a true overspeed condition)

3. Overspeed of the = rotating assembly resulted in failure (due to operating
too far = to the=20 right on the compressor map possibly acerbated by the leak = in
John's=20 intercooler and/or BOV valve).

4. Defective weld of wheel to = shaft=20 (Pretty remote chance - I believe -
especially with two = turbos)

5.=20 Some combination of the above. But, I believe that in all cases=20 higher
turbine speed would acerbate the condition and lead to = quicker=20 failure -
whether true overspeed or not.

Good addition to = the=20 theory stack, = Bulent.

Ed

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