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Richard,
Another alternative to the SS inlet tube
welded to the steel housing liner, is welding an Al tube to the Al housing -
inside the water jacket. It's being done locally for racing and lasts longer
than the glued in place tube. In fact they haven't had any trouble with any
leaking ( leaking coolant into combustion chamber) at all.
George (down under)
----- Original Message -----
Sent: Monday, February 09, 2009 4:38
AM
Subject: [FlyRotary] Re: Exhaust
lengths
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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