X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imo-m27.mx.aol.com ([64.12.137.8] verified) by logan.com (CommuniGate Pro SMTP 4.3.5) with ESMTP id 1022010 for flyrotary@lancaironline.net; Sun, 26 Jun 2005 10:31:06 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.8; envelope-from=Lehanover@aol.com Received: from Lehanover@aol.com by imo-m27.mx.aol.com (mail_out_v38_r1.7.) id q.7e.6c4a7e2d (4012) for ; Sun, 26 Jun 2005 10:30:16 -0400 (EDT) From: Lehanover@aol.com Message-ID: <7e.6c4a7e2d.2ff015f8@aol.com> Date: Sun, 26 Jun 2005 10:30:16 EDT Subject: Re: [FlyRotary] Exhaust Splitters - Lynn?? To: flyrotary@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1119796216" X-Mailer: 9.0 SE for Windows sub 5012 -------------------------------1119796216 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 6/26/2005 5:46:56 AM Pacific Daylight Time, eanderson@carolina.rr.com writes: I have not seen any dyno data that would provide enlightenment on this question. Lynn do you folks race with exhaust splitters? Ed I have only 12A engines so I have never seen a splitter. This is a production car trick to reduce the amount of materials required to control sound energy for the street. Pressure released as the port opens is still so high that flow is instantly supersonic. The ports are opened well past the rotational point where much work is being extracted just for that reason. So this is a huge problem for a street car. The stock cast iron pillow and the exhaust system from a RX3 would kill you if it fell on you. It seems apparent that the splitter reduces the speed of part of the shock wave and this would reduce the energy at the very front of that wave. So the amount (and cost) of downstream muffling structure could be reduced. Another natural fix is the turbocharger. Much less muffling (if any) required. The muffling schemes I have seen so far are costing far more power than the suggested splitter losses. The design should have as its base, primary tubes with exactly the same length, and if possible the same bend radius into a collector. Yes, these things are true 4 Otto cycle machines. However, they tune just like 2 Otto cycle machines. If you run the exhaust into a mixing chamber right outside the engine, don't be surprised if you get the same 115 HP of a stock (and very quiet) RX3. If you have been flying your radio controlled models you have been using the exhaust restriction as a throttle have you not? You only need one complete exhaust cycle in the primary runner at the RPM you want to run for the tuning part to work. If you get them the same length and get the pulses into the collector to homogenize into a solid (supersonic) stream, you have 90% of the tuning done. The opening port will be exposing the next charge into a low pressure tube behind the preceding charge. In the race car there is a megaphone from 2.5" to 4" over 20 ." This where the flow velocity slows to near subsonic, and enters the muffler. This is a see through stainless monster that homogenizes the pulses into all subsonic flow. It isn't quiet. Still 97-98 dB at 50 feet. We were getting close to the limit of 103 dB with this rig, so I added a ring of material around the inside of the 4" tailpipe just before the outlet. It is just a washer with a 4" OD and just over a 3" ID. I read that the most offensive frequencies travel along the walls of the tubing. This did work. But I have no equipment or data to prove that the ring did it or if so how the ring did it. I can still hear my car all the way around the track, but the sound readings are down at each track we race at. The driver noticed it also, which is sort of a breakthrough on its own. Once in the aircraft, the engines are riding in a dynamometer. Get a copy of the SAE correction sheets and correct your readings to sea level standard day after each test (of anything) to see if it helped or hurt performance. I made those into big graphs to make data recovery quick while on the dyno. If the splitter seem to cost too much, try a set of housings without the splitters and compare the numbers. Since most engine mounting systems are to some extent compliant, it should be possible to connect a fixed location on the mount to a position on the engine and connect them with a rheostat or strain gage. Lock the starter ring gear and calibrate the sensor with a big torque wrench on the prop hub. Instant flying dyno. If you didn't see it on the dyno, you didn't see it. Lynn E. Hanover -------------------------------1119796216 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
In a message dated 6/26/2005 5:46:56 AM Pacific Daylight Time,=20 eanderson@carolina.rr.com writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>I have=20 not seen any dyno data that would
provide enlightenment on this=20 question.   Lynn do you folks race with exhaust=20
splitters?


Ed
 
I have only 12A engines so I have never seen a splitter. This is a=20 production car trick to reduce the amount of materials required to control s= ound=20 energy for the street. 
 
Pressure released as the port opens is still so high that flow is insta= ntly=20 supersonic. The ports are opened well past the rotational point where much w= ork=20 is being extracted just for that reason. So this is a huge problem for a str= eet=20 car. The stock cast iron pillow and the exhaust system from a RX3 would kill= you=20 if it fell on you.
 
It seems apparent that the splitter reduces the speed of part of the sh= ock=20 wave and this would reduce the energy at the very front of that wave. So the= =20 amount (and cost) of downstream muffling structure could be reduced. Another= =20 natural fix is the turbocharger. Much less muffling (if any) required.
 
The muffling schemes I have seen so far are costing far more power than= the=20 suggested splitter losses. The design should have as its base, primary=20 tubes with exactly the same length, and if possible the same bend radius int= o a=20 collector.
 
Yes, these things are true 4 Otto cycle machines. However, they tu= ne=20 just like 2 Otto cycle machines. If you run the exhaust into a mixing chambe= r=20 right outside the engine, don't be surprised if you get the same 115 HP of a= =20 stock (and very quiet) RX3.
 
If you have been flying your radio controlled models you have been usin= g=20 the exhaust restriction as a throttle have you not?
 
You only need one complete exhaust cycle in the primary runner at the R= PM=20 you want to run for the tuning part to work. If you get them the same length= and=20 get the pulses into the collector to homogenize into a solid (supersonic)=20 stream, you have 90% of the tuning done.
The opening port will be exposing the next charge into a low=20 pressure tube behind the preceding charge.
 
In the race car there is a megaphone from 2.5" to 4" over 20 ." This wh= ere=20 the flow velocity slows to near subsonic, and enters the muffler. This is a=20= see=20 through stainless monster that homogenizes the pulses into all subsonic flow= . It=20 isn't quiet. Still 97-98 dB at 50 feet.
 
We were getting close to the limit of 103 dB with this rig, so I added=20= a=20 ring of material around the inside of the 4" tailpipe just before the outlet= . It=20 is just a washer with a 4" OD and just over a 3" ID. I read that the most=20 offensive frequencies travel along the walls of the tubing.
 
This did work. But I have no equipment or data to prove that the ring d= id=20 it or if so how the ring did it. I can still hear my car all the way around=20= the=20 track, but the sound readings are down at each track we race at. The driver=20 noticed it also, which is sort of a breakthrough on its own.
 
Once in the aircraft, the engines are riding in a dynamometer. Get a co= py=20 of the SAE correction sheets and correct your readings to sea level standard= day=20 after each test (of anything) to see if it helped or hurt performance. I mad= e=20 those into big graphs to make data recovery quick while on the dyno. If the=20 splitter seem to cost too much, try a set of housings without the splitters=20= and=20 compare the numbers.  
 
Since most engine mounting systems are to some extent compliant, it sho= uld=20 be possible to connect a fixed location on the mount to a position on the en= gine=20 and connect them with a rheostat or strain gage. Lock the starter ring gear=20= and=20 calibrate the sensor with a big torque wrench on the prop hub. Instant flyin= g=20 dyno. 
 
If you didn't see it on the dyno, you didn't see it.
 
Lynn E. Hanover
 
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