|
|
Mark,
I watched the video as you started up in
front of Chris’ hangar and taxied away. I then went back and
watched the video where you made the flight 2 years ago. The difference
in the sound is way more than just volume! That PPort sounds angry!
Bill B
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Mark Steitle
Sent: Wednesday, December 01, 2010
12:44 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Modified
header Calculations
Not sure what you're asking. My p-port will idle down to below
1000 rpm, although not as smoothly as my side port 20B did, or like my LS1
Chevy V-8. This thread was addressing WOT issues caused by an
overly restrictive exhaust system. Changing to my previous
"tangential" exhaust made a HUGH improvement in WOT power
(exactly as the chart that Ed posted earlier showed). I am now in
the process of building an equal-length header/exhaust to maximize power
at around 6500 rpm. The runners on my current exhasut are not
all the same length and are made from 2.0 DIA .140"
304SS. The new exhasut will be made of 625 inconel.
I hope to get it right this time.
On Wed, Dec 1, 2010 at 11:23 AM, <wrjjrs@aol.com>
wrote:
Mark, and group,
If p-ports are so difficult why was the first car with a rotary equiped with
them? P ports can be fairly tame if you put the throttle plate, (butterfly or
slide), close to the port, or in the port. The original powersport guys put
together an in-port butterfly that idled very well. In fact Steve Beckham told
me that when using their pendrolous damper they could idle their p-port engine
at 1000 RPM! Their p-ports were 1-5/8 diameter.
Bill Jepson
Finally, I liked their comment regarding the peripheral ported
engines. It reads, "Traditionally relegated to speciality race
cars, occasionally a peripherally ported engine finds its way onto the street
in some high-performance vehicle. These engines are not, however, for the faint
of heart." LOL Not to worry, my heart is strong!
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,
It took a while, but my copy of Street Rotary - How to Build Maximum
Horsepower & Reliability into Mazda's 12A, 13B & Renesis
Engines finally arrived yesterday. Thanks for the
recommendation. Lots of good info, everyone on the list ought to order a
copy and read it from cover to cover, except for Lynn H. - he ought to
write his own book on rotary engines. (I'd buy the first copy.)
As you suggested, I've been reading the chapter on exhaust systems. I
found a paragraph that is right on target relating to what we've been
discussing (exhaust system restriction). They compare a 2-rotor wankel to
a 2 cylinder 4-stroke where both cylinders share the same exhaust
port.
Quote, "...the exhaust system on a 12A or 13B rotary engine is roughly
analogous to a two-cylinder piston engine in which both cylinders are served by
a single exhaust port. If cylinder #1 was in overlap period, and the
exhaust valve of the #2 cylinder then opened, high pressure gas would flow from
the #2 to #1 cylinders. A highly restrictive exhaust system would
aggravate the situation. This, the authors point out, is the major reason
why a free-flowing exhaust system is so important in a rotary
engine." This explains why I saw such an improvement when switching
exhaust systems.
There is also much discussion on primary header length. Disregarding the
"long" header system as we don't have the room, the "short"
header length shown for a p-port engine is between 10 and 18 inches. So,
your calculations for header length seem to be right in the ballpark. Now
I have to figure how to get the three very short primary tubes of 11 3/4"
to meet on the same tangent at the collector.
Finally, I liked their comment regarding the peripheral ported
engines. It reads, "Traditionally relegated to speciality race
cars, occasionally a peripherally ported engine finds its way onto the street
in some high-performance vehicle. These engines are not, however, for the faint
of heart." LOL Not to worry, my heart is strong!
Mark
On Sun, Nov 21, 2010 at 7:53 AM, Ed Anderson <eanderson@carolina.rr.com>
wrote:
Mark,
I did some additional reading in the rotary book I recommended to you and a bit
more head scratching on exhaust systems.
I modified the tube length formula I used earlier to compensate for
the fact the rotary puts out two exhaust pulses per port per 720 deg cycle
compared to 1 for the piston engine. This in effect halved the length of
tube needed to get the same scavenging effect.
Also using the recommended rotary book values for area of a rotary
exhaust tube , I calculated the tube diameter which came out to
1.8".
In any case, I have attached the spreadsheet with those modifications
Ed
Edward L. Anderson
Anderson
Electronic Enterprises LLC
305 Reefton Road
Weddington, NC 28104
http://www.andersonee.com
http://www.eicommander.com
--
Homepage: http://www.flyrotary.com/
Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html
--
Homepage: http://www.flyrotary.com/
Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html
|
|