Return-Path: Sender: "Marvin Kaye" To: lml@lancaironline.net Date: Thu, 17 Mar 2005 21:21:50 -0500 Message-ID: X-Original-Return-Path: Received: from mxsf37.cluster1.charter.net ([209.225.28.162] verified) by logan.com (CommuniGate Pro SMTP 4.3c3) with ESMTP id 800620 for lml@lancaironline.net; Thu, 17 Mar 2005 13:21:01 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.225.28.162; envelope-from=troneill@charter.net Received: from mxip13.cluster1.charter.net (mxip13a.cluster1.charter.net [209.225.28.143]) by mxsf37.cluster1.charter.net (8.12.11/8.12.11) with ESMTP id j2HIKDrV012827 for ; Thu, 17 Mar 2005 13:20:13 -0500 Received: from sc3-24.217.135.192.charter-stl.com (HELO axs) (24.217.135.192) by mxip13.cluster1.charter.net with ESMTP; 17 Mar 2005 13:20:12 -0500 X-Ironport-AV: i="3.91,98,1110171600"; d="scan'217,208"; a="845338186:sNHT1041453626" Received: from 127.0.0.1 (AVG SMTP 7.0.308 [266.7.3]); Thu, 17 Mar 2005 12:15:30 -0600 X-Original-Message-ID: <013001c52b1d$4d93b960$6501a8c0@axs> From: "terrence o'neill" X-Original-To: "Lancair Mailing List" References: Subject: Re: [LML] Re: supershargers X-Original-Date: Thu, 17 Mar 2005 12:15:30 -0600 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="=======AVGMAIL-4239C94269A9=======" --=======AVGMAIL-4239C94269A9======= Content-Type: multipart/alternative; boundary="----=_NextPart_000_012D_01C52AEB.02B90C10" ------=_NextPart_000_012D_01C52AEB.02B90C10 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Craig, Some questions about the power required to run a supercharger to = normalize or, say, up to 40% boost -- my old B&M Supercharger book says that using a clutch to disconnect the = supercharger only saves 3% in fuel ... referring to a less efficient = roots-type blower. That makes me wonder if someone's earlier note that = a blower required -- was it 70 hp? -- was maybe off by a digit? Sounds = like 7 to 15 hp would be closer... for about 40% boost. It would help = to quantify. Evidence that this smaller blower power requirement might be in the = ballpark, is from Power Transmission Design Handbook, for computing HP = ratings for belts... mine was a 'C' crossection belt, or close to it, i = think, driving a McCulloch (Paxton) centrifugal blower on the 351 ci = Windsor in my Magnum bushplane, and it was driven nicely by its 3/4" = standard automotive V-belt, no problem pumping 42" MP at 4500 rpm. No = waste gate used. I was probably running the blower too fast, as the = intake temp was about 180F... (didn't have to worry about carb ice). ; = ) (See CONTACT! Magazine issue 16) Another indication that not much power is needed to drive the = supercharger was a study Vortech did for my installation, which showed = that for 40% boost, only 14.9 HP input to their supercharger would be = needed. So my thinking is that although a 300-400 hp engine with a turbo = wouldn't use any crank HP, my belt-driven blower used only about 4 to 5% = to blow a 45% boost, and the manifolding was much simpler and much = cooler inside the cowling. Does this sound reasonable? =20 Wish I'd had a dyno for some better data. The B&M book charts for this = engine with my mods showed (estimated) about 380 HP, up from unblown = about 270. Any other comments on engine HP needed to drive a = centrifugal supercharger? T. ----- Original Message -----=20 From: Craig Berland=20 To: Lancair Mailing List=20 Sent: Wednesday, March 16, 2005 06:39 PM Subject: [LML] Re: supershargers Has anyone tried mechanically linking the throttle to a variable wastegate on the manifold between supercharger and carburetor? I was thinking that this way possibly the more-opened-up wastegate = could let the pressure blow off when the throttle was pulled back, and = increase=20 the blow-off level as the throttle was opened. Terrence What has been done, is use an electric clutch similar to the A/C = compressor clutch to disengage the supercharger at low RPM or where boost is not = required. In my opinion, the only real advantage of a mechanically driven = supercharger is low RPM response. I can't see the need in an aircraft. Maybe = aerobatics?? Craig Berland -------------------------------------------------------------------------= ----- No virus found in this incoming message. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.3 - Release Date: 03/15/05 ------=_NextPart_000_012D_01C52AEB.02B90C10 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
Craig,
    Some questions about = the power=20 required to run a supercharger to normalize or, say, up to 40% boost=20 --
my old B&M Supercharger book says = that using a=20 clutch to disconnect the supercharger only saves 3% in fuel ... = referring to a=20 less efficient roots-type blower.  That makes me wonder if = someone's=20 earlier note that a blower required -- was it 70 hp? -- was maybe off by = a=20 digit?  Sounds like 7 to 15 hp would be closer... for about 40%=20 boost.  It would help to quantify.
    Evidence that this = smaller=20 blower power requirement might be in the ballpark, is from Power = Transmission=20 Design Handbook, for computing HP ratings for belts... mine was a 'C'=20 crossection belt, or close to it, i think, driving  a McCulloch (Paxton) centrifugal blower on the 351 ci = Windsor in my=20 Magnum bushplane, and it was driven nicely by its 3/4" standard = automotive=20 V-belt, no problem pumping 42" MP at 4500 rpm.  No waste gate = used.  I=20 was probably running the blower  too fast, as the intake temp = was=20 about 180F... (didn't have to worry about carb ice).  ; )  = (See=20 CONTACT! Magazine issue 16)
    Another indication = that not much=20 power is needed to drive the supercharger was a study Vortech did for my = installation, which showed that for  40% boost, only 14.9 HP input = to their=20 supercharger would be needed.
So my thinking is that although a = 300-400 hp engine=20 with a turbo wouldn't use any crank HP, my belt-driven blower=20 used only about 4 to 5% to blow a 45% boost, and the = manifolding was=20 much simpler and much cooler inside the cowling.  Does this sound=20 reasonable? 
Wish I'd had a dyno for some better = data.  The=20 B&M book charts for this engine with my mods showed (estimated) = about 380=20 HP, up from unblown about 270.  Any other comments on engine HP = needed to=20 drive a centrifugal supercharger?
T.
----- Original Message -----
From:=20 Craig=20 Berland
Sent: Wednesday, March 16, 2005 = 06:39=20 PM
Subject: [LML] Re: = supershargers

Has=20 anyone tried mechanically linking the throttle to a = variable
wastegate on=20 the manifold between supercharger and carburetor?
I was thinking = that this=20 way possibly the more-opened-up wastegate could
let the pressure = blow off=20 when the throttle was pulled back, and increase
the blow-off level = as the=20 throttle was opened.  Terrence
 
What has been=20 done, is use an electric clutch similar to the A/C=20 compressor
clutch to=20 disengage the supercharger at low RPM or where boost is not=20 required.
In my opinion, the only real advantage of a mechanically driven=20 supercharger is
low RPM response. I can't see the need in an aircraft.  = Maybe=20 aerobatics??
Craig=20 Berland

No virus found in this incoming message.
Checked by AVG=20 Anti-Virus.
Version: 7.0.308 / Virus Database: 266.7.3 - Release = Date:=20 03/15/05
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