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If someone wants to do a Renesis P-Port I would be
glad to do the rotor housings. I just finished the two rotor housings for my
first flyable engines. The port insert is as it is in the engine I have been
running up to now. I know it works.
Mark Steitle's welding might work, but I am not
aware of any engine running with it so far.
Richard Sohn
N2071U
----- Original Message -----
Sent: Sunday, February 08, 2009 11:40
AM
Subject: [FlyRotary] Re: Exhaust
lengths
FWIW, the people at Racing Beat said that the Renesis is a very
different animal than peripherial exhaust port rotaries when it comes to
exhaust systems. As I recall, they said they got only about an 8 HP
improvement when going from stock (RX-8) exhaust system with cats & the
works, to a full race setup with headers, race mufflers, etc. That is
TINY in comparison to the earlier engines.
In other words, the
Renesis is very non-critical when it comes to exhaust systems. Just keep
the back pressure down and you'll do pretty well. At least that was my
conclusion. Note there is zero overlap in intake / exhaust cycles in the
Renesis.
BTW I'm still waiting for someone to build & test a
peripheral intake port Renesis. I think that would be a great setup for
aircraft applications.
Tracy
On Sun, Feb 8, 2009 at 12:13 PM, The Mallorys <candtmallory@cebridge.net>
wrote:
Lynn,
Thanks for the
info. So it looks like the total length after the collector doesn't
really matter. I'm using the stock Renesis tubing up to the 180* bend,
so I'm assuming(maybe incorrectly) that they have done the math and have the
lengths right.
Chris
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mark
Steitle
Sent: Sunday, February 08, 2009 9:47 AM
To:
Rotary motors in aircraft
Subject: [FlyRotary] Re: Exhaust
lengths
Lynn,
Thanks for the excellent
response. So, there is sort of a dynamic tuning effect going on as
happens in the 2-rotor intake. Appreciate your sharing your knowledge
with the group.
Mark S.
On Sun, Feb 8, 2009 at 8:10 AM, Lynn Hanover <lehanover@gmail.com>
wrote:
Lynn,
I have a question regarding exhaust/inlet lengths that I've
wanted to ask for quite a while.
Q: Do the optimum
lengths of 12/24/36/102 hold true only for the 2-rotor engines or does it
work for the 3-rotor engines too?
Mark S.
The object of the headers, is that the supersonic pulses need to be
neatly laid into the collector one after the other in exactly the same
spacing. This makes for a good sounding engine, even after muffling. It also
makes for great scavenging, and if the muffler is not too restrictive, can
maintain a low pressure in the exhaust system. That becomes free HP. For
example: I use GE silicone tub and tile caulk on the exhaust header flange.
No gasket. It need not be high temp anything because it just is never very
hot being clamped to the rotor housing. There is no pressure at all to deal
with in this junction, as the supersonic flow is well below sea level
pressure (One Barr). If it did ever leak it would draw in local air into the
header pipe, and make cracking sounds on closed throttle. If it leaks at
all, it will leak at idle because velocity is nearing
zero.
The lengths are from collections of street headers designed to help
street engine build up the rotaries dismal low speed torque. The longer the
header pipes the more solid the slugs from each firing event, and the better
the scavenging and low end torque.
Once you have a 11" of header, you have two full pulses from each
housing and if you collect them with the exact same length of pipe you have
done as much as you need for anything over 3,000 RPM. As the revs go higher,
the headers (In effect) become longer because more full pulses
will fit in each pipe. And here is the important part.
The pipes need to be exactly the same length to the collector. The
collector needs to be uniform and silk smooth inside. At 6,000 RPM you are
blending 12,000 pulses together, or 18,000 pulses from a three rotor, just
like cards being shuffled. If you get any two pulses impinging on each
other there will be far less than the very best performance available.
Plus the engine will be annoying. Too loud but sounds great entering the
pattern is way better than nobody talks to you, and Jimmy's dog won't come
out from under the truck.
I had a length of corrigated plastic hose looking stuff, used to cover
bundles of wire in trucks. It just fit inside of 1 7/8" ID tubing. I
had bends made up and with my abrasive saw I would fit together the headers,
tacking on pieces and fitting them into the spaces as I went along. I
smoothed the joints inside just as though each piece would be a finished
piece. Once at the collector. (both pipes parallel for 3 inches) I would
shove the plastic hose up each pipe to the flat plate gasket over each
exhaust port. Add masking tape to the hose at the end of the front header,
then pull it out and shove in the rear header, to see where the tape ended
up. It is easy to lengthen and shorten the straight runs out of the flange
to correct small differences in length.
I am not trying to tune the engine with header length. Just trying to get
the exhaust out without screwing away any HP that a poorly designed system
will do. The 4 cylinder engines seem to favor a 32-34 inch header to fluff
up the torque that a big cam will take away. So if you need help in a 4
cylinder from 3,000 to 4,500 there is your header length. I used 24" because
the engine builder uses that on the dyno. It is typical to have two nodes
where any paticular header length will add a bit of power. The lower of the
two is seldom high enough to use for anything but a street engine.
Just as in piston engines, long, shallow angle collectors produce better
torque over a wide RPM range. Short, steeply angled collectors produce
better torque over a short range of RPM.
The two rotor is two one rotor engines on the same crankshaft. The three
rotor is three one rotor engines on the same crank shaft. The best outcome
is to have both, or all three perform at about the same rate as the others.
You will notice that there seem to be complaints as to EGT, water temps,
compression, vibration fuel flow, exhaust color, and so on with every
recoverable piece of data. The front housing gets the coldest coolant on one
side and the hottest coolant on the other side. The three rotor (I
suspect) may have even greater differences). So in those areas where you can
get the same outcome, you should try to get the same outcome. As in the
intake and header lengths. There you go..........
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