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Subject: Re: [FlyRotary] Re: Modified header Calculations
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Date: Wed, 1 Dec 2010 12:23:46 -0500 (EST)
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Mark, and group,
If p-ports are so difficult why was the first car with a rotary equiped=20
with them? P ports can be fairly tame if you put the throttle plate,=20
(butterfly or slide), close to the port, or in the port. The original=20
powersport guys put together an in-port butterfly that idled very well.=20
In fact Steve Beckham told me that when using their pendrolous damper=20
they could idle their p-port engine at 1000 RPM! Their p-ports were=20
1-5/8 diameter.
Bill Jepson

Finally, I liked their comment=C2=A0regarding the peripheral ported=20
engines.=C2=A0 It reads,=C2=A0"Traditionally relegated to speciality race c=
ars,=20
occasionally a peripherally ported engine finds its way onto the street=20
in some high-performance vehicle. These engines are not, however, for=20
the faint of heart."=C2=A0 LOL=C2=A0 Not to worry, my heart is strong!=C2=
=A0
=C2=A0=C2=A0
Mark


-----Original Message-----
From: Mark Steitle <msteitle@gmail.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Wed, Dec 1, 2010 8:37 am
Subject: [FlyRotary] Re: Modified header Calculations


Ed,
=C2=A0
It took a while, but my copy of=C2=A0Street Rotary - How to=C2=A0Build Maxi=
mum=20
Horsepower & Reliability into Mazda's 12A, 13B & Renesis=20
Engines=C2=A0finally arrived yesterday.=C2=A0 Thanks for the recommendation=
.=C2=A0=20
Lots of good info, everyone on the list ought to order a copy and read=20
it from cover to cover, except for Lynn H. - he ought to write=C2=A0his=20
own=C2=A0book on rotary engines.=C2=A0 (I'd buy the first copy.)=C2=A0
=C2=A0
As you suggested, I've been reading the chapter on exhaust systems.=C2=A0 I=
=20
found a paragraph that is right on target relating to what we've been=20
discussing (exhaust system restriction).=C2=A0 They compare a 2-rotor wanke=
l=20
to a 2 cylinder 4-stroke=C2=A0where both cylinders share the same exhaust=
=20
port.=C2=A0
=C2=A0
Quote, "...the exhaust system on a 12A or 13B rotary engine is roughly=20
analogous to a two-cylinder piston engine in which both cylinders are=20
served by a single exhaust port.=C2=A0 If cylinder #1 was in overlap period=
,=20
and the exhaust valve of the #2 cylinder then opened, high pressure gas=20
would flow from the #2 to #1 cylinders.=C2=A0 A highly restrictive exhaust=
=20
system would aggravate the situation.=C2=A0 This, the authors point out, is=
=20
the major reason why a free-flowing exhaust system is so important in a=20
rotary engine."=C2=A0 This explains why I saw such an improvement when=20
switching exhaust systems.=C2=A0
=C2=A0
There is also much discussion on primary header length.=C2=A0 Disregarding=
=20
the "long" header system as we don't have the room, the "short" header=20
length shown for a p-port engine is between 10 and 18 inches.=C2=A0 So, you=
r=20
calculations for header length seem to be right in the ballpark.=C2=A0 Now =
I=20
have to figure how to get the three very short primary tubes of 11 3/4"=20
to meet=C2=A0on the same tangent at the collector.=C2=A0
=C2=A0
Finally, I liked their comment=C2=A0regarding the peripheral ported=20
engines.=C2=A0 It reads,=C2=A0"Traditionally relegated to speciality race c=
ars,=20
occasionally a peripherally ported engine finds its way onto the street=20
in some high-performance vehicle. These engines are not, however, for=20
the faint of heart."=C2=A0 LOL=C2=A0 Not to worry, my heart is strong!=C2=
=A0
=C2=A0=C2=A0
Mark


On Sun, Nov 21, 2010 at 7:53 AM, Ed Anderson=20
<eanderson@carolina.rr.com> wrote:


Mark,
=C2=A0
I did some additional reading in the rotary book I recommended to you=20
and a bit more head scratching on exhaust systems.
=C2=A0
I modified the tube length=C2=A0formula I=C2=A0used earlier to compensate f=
or the=20
fact the rotary puts out two exhaust pulses per port per 720 deg cycle=20
compared to 1 for the piston engine.=C2=A0 This in effect halved the length=
=20
of tube needed to get the same scavenging effect.
=C2=A0
Also using the recommended rotary =C2=A0book values for area of a rotary=20
exhaust tube=C2=A0, I calculated the tube diameter which came out to 1.8".=
=C2=A0
=C2=A0
In any case, I have attached the spreadsheet with those modifications
=C2=A0
Ed
=C2=A0
=C2=A0
Edward L. Anderson
Anderson Electronic Enterprises LLC
305 Reefton Road
Weddington, NC 28104
http://www.andersonee.com
http://www.eicommander.com


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