Return-Path: <13brv3@bellsouth.net> Received: from imf23aec.mail.bellsouth.net ([205.152.59.71] verified) by logan.com (CommuniGate Pro SMTP 4.1.3) with ESMTP id 2589913 for flyrotary@lancaironline.net; Mon, 22 Sep 2003 21:27:19 -0400 Received: from rad ([68.212.12.251]) by imf23aec.mail.bellsouth.net (InterMail vM.5.01.05.27 201-253-122-126-127-20021220) with ESMTP id <20030923012709.TVVH20055.imf23aec.mail.bellsouth.net@rad> for ; Mon, 22 Sep 2003 21:27:09 -0400 From: "Russell Duffy" <13brv3@bellsouth.net> To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Some turbo thoughts from a pro .... Date: Mon, 22 Sep 2003 20:27:12 -0500 Message-ID: <00b501c38171$d0f8a6f0$0201a8c0@rad> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00B6_01C38147.E8229EF0" 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_01C38147.E8229EF0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Over the past couple of years, I have been occasionally back and forth = with "Turbo Tom" on the Subaru list who has been in the turbo business = forever. I sent him a brief rundown of the recent thread and Rusty's = [mis]adventures and asked for his thoughts. Here is his reply. Makes pretty good sense = to me... Thanks for taking the time to do this Jim! Charge-air temps are EVERYTHING. The flying rotary turbo guy should = measure his. As you might imagine, 30-inches of MAP at 80F degrees is not at all = the same thing as 30-inches of MAP at 140-150F degrees. That's a pretty = typical output temp for a well-matched turbo. So yes, intercooling is a MUST. Well, my intake temp at 30" MAP was 167F on a 90F day, so he's right on = with his figures. =20 Also, centrifugal compressors are way below 50% eff at less than 10" of boost. That's where most compressor maps start. Operating "off the map" = is never a good thing. It adds tremendous heat for no boost, a poor = trade-off. And yes, you are correct. It would take a few pounds of boost just to = make up for the density loss from heating. About 10 psi with no intercooler, = 3 psi with. 10 psi!!! Ack! Must fit intercooler...=20 Av gas give great margins of safety with boost. We ran 50" MAP on car = gas. Hey, testing to destruction [commonly shortened to just "testing"] is a BITCH, and not for everyone. It only looks easy. ;-) Well, I can verify that nothing blew up at 50" on the ground, with an = intake temp around 250 F (est). =20 Where are you measuring charge temp? I stuck a thermocouple inside the hose from the turbo, where it = connected to my pressurized airbox. =20 Is it not an input to Tracy's fuel control? Yes, there is a temp sensor installed in the airbox. Can you capture and monitor it? Not until the EM-2 arrives. Additionally, if you have excess heat rejection resources (oversize = oil coolers, radiators, etc.) perhaps you could lighten up on that stuff and = get some sort (any sort at all) of intercooler in there. I haven't seen = your installation, and am not even an RV guy, but it just seems as if there = MUST be SOME way to get what you need in there without the cowl getting this thyroid condition you describe.=20 OK, I'm certainly convinced enough to install an intercooler. At the moment, I can probably put one in the right cheek, and add some duct to = it, or I can mount it in front of the "extra" portion of the radiator. I've spent a huge amount of time trying to figure out the best way to arrange cooling items in the rev-2 cowl, but haven't factored the intercooler = into my thoughts at all. I go ahead and find a way to mount one in BUC as a test, which is the logical way to help me decide what stays, and what = goes when the rev-2 cowl comes along. I'll find the 2nd and 3rd gen IC's in = the attic, and see which one fits best. I'll also try to measure them for whoever was asking the other day. =20 Also, TT seems to confirm what a number of folks are suggesting that you = can give it 6 or 8 psi of boost and see what happens - the chance of = screwing anything up at that level seems pretty remote. Roger. Thanks again, Rusty (a new reason to live) ------=_NextPart_000_00B6_01C38147.E8229EF0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message

Over the past couple of years, I have been = occasionally back and=20 forth with "Turbo Tom" on the Subaru list who has been in the turbo = business=20 forever.  I sent him a brief rundown of the recent thread and = Rusty's=20 [mis]adventures and asked for his thoughts.  Here is his = reply.  Makes=20 pretty good sense to me...

Thanks = for taking the=20 time to do this Jim!

Charge-air temps are EVERYTHING.  The flying rotary turbo guy = should=20 measure his. As you might imagine, 30-inches of MAP at 80F degrees is = not at all=20 the same thing as 30-inches of MAP at 140-150F degrees.  That's a = pretty=20 typical output temp for a well-matched turbo.  So yes, intercooling = is a=20 MUST.

Well, my intake temp at = 30" MAP was=20 167F on a 90F day, so he's right on with his figures. =20  

Also, centrifugal compressors are way below 50% eff = at less=20 than 10" of boost. That's where most compressor maps start. Operating = "off the=20 map" is never a good thing.  It adds tremendous heat for no boost, = a poor=20 trade-off.  And yes, you are correct.  It would take a few = pounds of=20 boost just to make up for the density loss from heating.  About 10 = psi with=20 no intercooler, 3 psi with.

10 psi!!! Ack!  Must = fit=20 intercooler... 

Av gas give great margins of safety = with=20 boost.  We ran 50" MAP on car gas. Hey, testing to destruction = [commonly=20 shortened to just "testing"] is a BITCH, and not for everyone.  It = only=20 looks easy. ;-)

Well, I can verify that = nothing blew up=20 at 50" on the ground, with an intake temp around 250 F=20 (est).   

Where are you measuring charge = temp?

I stuck a thermocouple = inside the hose=20 from the turbo, where it connected to my pressurized airbox. =20  

  Is it not an input to Tracy's fuel control?

Yes, there is a temp = sensor installed=20 in the airbox.

 Can you capture and monitor it?

Not until the EM-2 = arrives.

  Additionally, if you have excess heat rejection resources = (oversize=20 oil coolers, radiators, etc.) perhaps you could lighten up on that stuff = and get=20 some sort (any sort at all) of intercooler in there.  I haven't = seen your=20 installation, and am not even an RV guy, but it just seems as if there = MUST be=20 SOME way to get what you need in there without the cowl getting this = thyroid=20 condition you describe. 

OK, I'm certainly = convinced enough to=20 install an intercooler.  At the moment, I can probably put one in = the right=20 cheek, and add some duct to it, or I can mount it in front of the = "extra"=20 portion of the radiator.  I've spent a huge amount of time trying = to figure=20 out the best way to arrange cooling items in the rev-2 cowl, but haven't = factored the intercooler into my thoughts at all.  I go ahead and = find a=20 way to mount one in BUC as a test, which is the logical way to help me = decide=20 what stays, and what goes when the rev-2 cowl comes = along.  I'll find=20 the 2nd and 3rd gen IC's in the attic, and see which one fits = best.  I'll=20 also try to measure them for whoever was asking the other day.  =

Also, TT seems to confirm what a number of folks are suggesting that = you can=20 give it 6 or 8 psi of boost and see what happens - the chance of = screwing=20 anything up at that level seems pretty remote.

Roger.  Thanks = again,

Rusty (a new reason to=20 live)

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