X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-ew0-f52.google.com ([209.85.215.52] verified) by logan.com (CommuniGate Pro SMTP 5.3.10) with ESMTP id 4586303 for flyrotary@lancaironline.net; Sat, 20 Nov 2010 10:39:42 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.215.52; envelope-from=msteitle@gmail.com Received: by ewy4 with SMTP id 4so3557662ewy.25 for ; Sat, 20 Nov 2010 07:39:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:received:in-reply-to :references:date:message-id:subject:from:to:content-type; bh=dbIq9Vzm1KSOqhfsJArzDYrXv7Xs0GEblp7K0QUTJYU=; b=O9KhbgmW+YooHGN7LZ5dbHSNMlQn0Z2A8nPyRg0iymMRwZHFkXkA5Mw/j5sygdDbLE Rj4zFHKxkE/QKdzMdTACQMW0M8zJPqGhMnwYjJeknIjRQZHKwH110PhsFjdJHvUM/VVd n8MoxCAzBS34Yf5uR9kL1FYKVopU0WEve4pm8= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=roCxv6KSR8hBx0/vD/y+AmQRa5vRdoaR6K1MBVjL+VlHiILyT4cVQRhoSZ/QUcO++U mTHKUZHtR1d/o8z5AAlq1wOjGk6WxIs/iqDs+r5Znr4VQV6yRNhnVb6Ao/Jzhfur/TOD QueT3dIkkpFL+gP9p3FIJaxNkWjaP8uM8YVyU= MIME-Version: 1.0 Received: by 10.213.16.72 with SMTP id n8mr5953652eba.38.1290267543613; Sat, 20 Nov 2010 07:39:03 -0800 (PST) Received: by 10.213.36.17 with HTTP; Sat, 20 Nov 2010 07:39:03 -0800 (PST) In-Reply-To: References: Date: Sat, 20 Nov 2010 09:39:03 -0600 Message-ID: Subject: Re: [FlyRotary] Re: Tangential Muffler From: Mark Steitle To: Rotary motors in aircraft Content-Type: multipart/alternative; boundary=0015174c3fce9a30c004957dd2ad --0015174c3fce9a30c004957dd2ad Content-Type: text/plain; charset=ISO-8859-1 Ed, Thanks for waking up and posting that spreadsheet. It looks like I need 1.5 ID pipes and 34.5" long pipes if I want max power at 6500. That would be a nice sweet spot to shoot for. One question. On your spreadsheet you define EVO = Exhaust Valve Closing. Did you mean to say, EVO = Exhaust Valve Opening? Thanks, Mark On Sat, Nov 20, 2010 at 8:55 AM, Ed Anderson wrote: > Hi Mark, > > From what I have read and heard, a well designed exhaust system for a PP is > more of a challenge than for any other porting scheme. As Lynn has > reported, the PP is even more effected by any back pressure in the exhaust > system than our regular rotary engines. > > That said, I dug out a pretty good book on intakes and exhausts (yes, they > understand and address Finite Amplitude Waves in the exhaust system). > Anyhow I thought I would extract what appears to be some interesting > insights for exhausts in general. There was formulas for getting a rough > estimate of header lengths and diameters - now these were for piston engines > but it would appear the dynamics of the pulse turning would be the same for > the rotary. > > I put the calculations into a spreadsheet (attached) and the results do not > seem unreasonable - one thing I don't know the effect of is the generally > higher exhaust temp of the rotary and what effect it might have on the > numbers. Also I don't know your PP port timing - so the one used is the > factory Mazda PP Exhaust port closing from Paul Yaw's web site - 73 Deg > BBDC. > > There appear to be *two* primary power enhancing benefits from a well > designed exhaust system. > > 1. Minimum restriction to exhaust gas flow - apparently velocity is > critical so diameter of pipes is important - apparently optimum velocity is > between Mach .45 and Mach .5 (got a Mach meter handy {:>)) > > 2. Scavenging effect of the reflected exhaust FAW to aid in pulling more > mixture into the combustion chamber. > > The well design system appear to maximize both attributes but generally for > only a limited rpm range. > > Engine displacement, RPM and intake/exhaust over lap appear to be the major > engine factors in determining the desired exhaust parameters. > > Ok, here are some extracted information - none of it necessarily new, but > perhaps useful to review (even thought I know you know it already) > > Exhaust tuning works by using the proper header pipe length to time the > arrival of the "suction" (expansion) wave reflected back from the end of the > header to arrive at the engine exhaust port during the overlap period - > between Intake Value Opening and Exhaust Valve Closing. > > If the scavenging wave is wide enough (time wise) and the overlap > (intake/exhaust) is short enough (probably not your case), the exhaust > system will remain in tune throughout a wide rpm range. > > High out put, High speed engines with long overlaps periods require much > more precise tubing lengths to optimize power. As power levels increase, > the margin for error decreases. > > Collectors: (Length and Diameter - see spreadsheet for some examples) > > 1. Longer collectors force the torque peak at lower rpm because at higher > rpm the reflected wave from the end of the longer collector does not get > back in time to help scavenge the combustion chamber and vice versa for > short collectors. A "reverse funnel" opening into the collector appears to > broaden the reflected wave and broadens the effective rpm range - but > reduces the amplitude of the wave. > > 2. The Amplitude of the reflected wave is dependent on the difference in > cross sectional area between the pipe and collector. A smaller dia > collector represents less area change and therefore reflects back a lower > amplitude wave and vice versa for a large diameter collector > > > One interesting thing I read was the notion that in some cases, perhaps the > headers should *NOT* be of equal length - *IF* you want a broader power > range. The theory is that with slightly different lengths the scavenging > effect would be spread across a broader range and be less "peaky". I had > never hear of potential benefit of unequal headers before, but it would seem > to make sense if you want a less peaky power point. But, if you want the > bigger boost near one rpm range then equal length headers would appear > to apply > > So there, that's what you get for waking me up. > > Ed > > Edward L. Anderson > Anderson Electronic Enterprises LLC > 305 Reefton Road > Weddington, NC 28104 > http://www.andersonee.com > http://www.eicommander.com > > *From:* Mark Steitle > *Sent:* Saturday, November 20, 2010 6:32 AM > *To:* Rotary motors in aircraft > *Subject:* [FlyRotary] Tangential Muffler > > Guys, > > It has been way too quiet on the list lately, so I thought I would post > this report. Yes, another muffler experiment. Seems I can't get beyond the > exhaust system. > > I did an experiment yesterday... with interesting results. While I am very > pleased with the muffling qualities of the tangential muffler, I have been > suspicious of it being responsible for the less-than-expected performance of > my p-port 20b. So, I removed the tangential muffler and replaced it with > the previous 3-into-1 exhaust w/DNA muffler that I had been running for > about 100 hrs. > > First the bad news. The 3-into-1 system is much louder, to the point that > it almost overwhelms my Zulu. I haven't shattered any windows, but little > children and small animals have been reported running for for their mothers. > FWIW, I'm running the stock exhaust splitters that came in the 20B > housings. > > The positive news is that I picked up 10-12 mph on top speed! So, it > confirms my suspicions that the tangential muffler is too restrictive for my > engine. While definitely not optimal, the 3-into-1 design is clearly better > than the tangential muffler when it comes to making power. > > So, my plan is to build another exhaust from 625 inconel, making all three > runners 31.5". I haven't decided what I will use for a muffler. I'll > report back when I have more data. > > Mark > > -- > Homepage: http://www.flyrotary.com/ > Archive and UnSub: > http://mail.lancaironline.net:81/lists/flyrotary/List.html > > --0015174c3fce9a30c004957dd2ad Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Ed,=A0

Thanks for waking up and posting that spreadsheet= . =A0It looks like I need 1.5 ID pipes and 34.5" long pipes if I want = max power at 6500. =A0That would be a nice sweet spot to shoot for. =A0

One question. =A0On your spreadsheet you define EVO =3D Exha= ust Valve Closing. =A0Did you mean to say, EVO =3D Exhaust Valve Opening? = =A0

Thanks,
Mark

On Sat, Nov 20, 2010 at 8:55 AM, Ed Anderson <eanderson@carolina.rr.com> wrote:
Hi Mark,
=A0
From what I have read and heard,=A0a well=20 designed=A0exhaust system for a PP is more of a challenge than for any othe= r=20 porting scheme.=A0 As Lynn has reported, the PP is even more effected by an= y=20 back pressure in the exhaust system than our regular rotary=20 engines.
=A0
That said, I dug out a pretty good book on intake= s and=20 exhausts (yes, they understand and address Finite Amplitude Waves in the ex= haust=20 system).=A0=A0=A0 Anyhow I thought I would extract what appears to be=20 some interesting insights for exhausts in general.=A0 There was formulas fo= r=20 getting a rough estimate of header lengths and diameters - now these were f= or=20 piston engines but it would appear the dynamics of the pulse turning would = be=20 the same for the rotary.
=A0
I put the calculations into a spreadsheet (attach= ed) and=20 the results do not seem unreasonable -=A0 one thing I don't know the ef= fect=20 of is the generally higher exhaust temp of the rotary and what effect it mi= ght=20 have on the numbers.=A0 Also I don't know your PP port timing - so the = one=20 used is the factory Mazda PP Exhaust port closing from Paul Yaw's web s= ite - 73=20 Deg BBDC.
=A0
There appear to be two primary p= ower=20 enhancing benefits from a well designed exhaust system.
=A0
1.=A0 Minimum restriction to exhaust gas flow -= =20 apparently velocity is critical so diameter of pipes is important - apparen= tly=20 optimum velocity is between Mach .45 and Mach .5 (got a Mach meter handy=20 {:>))
=A0
2.=A0 Scavenging effect of the reflected exhaust = FAW to=20 aid in pulling more mixture into the combustion chamber.
=A0
The well design system appear to maximize both at= tributes=20 but generally for only a limited rpm range.
=A0
Engine displacement, RPM and intake/exhaust over = lap=20 appear to be the major engine factors in determining the desired exhaust=20 parameters.
=A0
Ok, here are some extracted information - none of= it=20 necessarily new, but perhaps useful to review (even thought I know you know= it=20 already)
=A0
Exhaust tuning works by using the proper header p= ipe=20 length to time the arrival of the "suction" (expansion) wave refl= ected back from=20 the end of the header to arrive at the engine exhaust port during the overl= ap=20 period - between Intake Value Opening and Exhaust Valve Closing.=A0=20
=A0
If the scavenging wave is wide enough (time wise)= and the=20 overlap (intake/exhaust) is short enough (probably not your case), the exha= ust=20 system will remain in tune throughout a wide rpm range.
=A0
High out put, High speed engines with long overla= ps=20 periods require much more precise tubing lengths to optimize power.=A0 As= =20 power levels increase, the margin for error decreases.
=A0
Collectors:=A0 (Length and Diameter - see spreads= heet=20 for some examples)
=A0
1.=A0 Longer collectors force the torque peak at = lower=20 rpm=A0=A0because at higher rpm the reflected wave from the end of the=20 longer collector does not get back in time to help scavenge the combustion= =20 chamber and vice versa for short collectors.=A0 A "reverse funnel"= ; opening=20 into the collector appears to broaden the reflected wave and broadens the= =20 effective rpm range - but reduces the amplitude of the wave.
=A0
2.=A0 The Amplitude of the reflected wave is depe= ndent=20 on the difference in cross sectional area between the pipe and collector.= =A0=20 A smaller dia collector represents less area change and therefore reflects = back=20 a lower amplitude wave and vice versa for a large diameter=20 collector
=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0= =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=20
One interesting thing I read was the notion that = in some=20 cases, perhaps the headers should NOT be of equal length -= =20 IF you want a broader power range.=A0 The theory is that= =20 with slightly different lengths =A0the scavenging effect would be spread=20 across a broader range and be less "peaky".=A0 I had never hear= =20 of=A0potential benefit of unequal headers before, but it would seem to make= =20 sense if you want a less peaky power point.=A0 But, if you want the bigger= =20 boost near one rpm range then equal length headers would appear=20 to=A0=A0apply
=A0
So there, that's what you get for waking me= =20 up.
=A0
Ed
=A0
Edward L. Anderson
Anderson Electronic Enterpr= ises=20 LLC
305 Reefton Road
Weddington, NC 28104
http://www.andersonee.com
http://www.eicommander.com

Sent: Saturday, November 20, 2010 6:32 AM
Subject: [FlyRotary] Tangential Muffler

Guys,=20

It has been way too quiet on the list lately, so I t= hought I would post=20 this report. =A0Yes, another muffler experiment. =A0Seems I can't get= =20 beyond the exhaust system. =A0=20

I did an experiment yesterday... with interesting results. =A0While I = am=20 very pleased with the muffling qualities of the tangential muffler, I have = been=20 suspicious of it being responsible for the less-than-expected performance o= f my=20 p-port 20b. =A0So, I removed the tangential muffler and replaced it with th= e=20 previous 3-into-1 exhaust w/DNA muffler that I had been running for about 1= 00=20 hrs. =A0

First the bad news. =A0The 3-into-1 system is much louder, to the poin= t=20 that it almost overwhelms my Zulu. =A0I haven't shattered any windows, = but=20 little children and small animals have been reported running for for their= =20 mothers. =A0FWIW, I'm running the stock exhaust splitters that came in = the=20 20B housings.=A0

The positive news is that I picked up 10-12 mp= h on top speed! =A0So, it=20 confirms my suspicions that the tangential muffler is too restrictive for m= y=20 engine. =A0While definitely not optimal, the 3-into-1 design is clearly=20 better than the tangential muffler when it comes to making power. =A0 =A0= =20

So, my plan is to build another exhaust from 625 inconel, making all t= hree=20 runners 31.5". =A0I haven't decided what I will use for a muffler.= =A0I'll=20 report back when I have more data. =A0

Mark

--
Homepage: =A0http:/= /www.flyrotary.com/
Archive and UnSub: =A0 http://mail.lancaironline.net:81/lists= /flyrotary/List.html


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