RV-4 #2366, tail # N52BT made it's first flight today. It didn't make
 enough power , so only one lap of the traffic pattern was made before the
 pilot
 landed it. From a standpoint of flying qualities, it was just like any
 other  RV-4s- no out of trim conditions or other bad habits. No note was
 made of
 MP at  WOT, either on the ground or in the air, that's first on the agenda
 tomorrow.

 But-- I only revved up to 4800 rpm on the downwind, so th


 e flight was
 terminated. I have gotten 5500 on the ground with the cowl removed, which
 means
 the air cleaner was not in use. I am using a Fram paper filter, 6 inches by
 14  inches. I think I am getting a big restriction from it, so I will
 remove it and  try some ground runs. I also think I'm running way too rich,
 about
 34- 7/8s up  the scale on my EM2.



 Brian,

 I'm trying to figure out an exhaust for my RV6 and was wondering what you
 have under that heat shield.

 Thanks
 BrianG
 Iowa


 Here are some recent pictures I have.
 Looks like  a Hush Power formed stainless steel.
 These are turning out to be more durable than your average
 muffler used on rotary engines. I think it is due to
 a more uniform temperature gradient around the front
 of the muffler. Less likely to crack in this area.
 They are also a bit better streamlined when mounted under
 the fuse. I suggest using the 2.5 inch version as it

 cuts the exhaust temperature and the exhaust gas velocity.

 http://www.hushpower.com/product/30/HP-2+Series+Muffler+-+304S.html

 Thirty two inch 2" diameter down pipes into one 2" dia. collector
 about 12 inches long might give the best power. The 12 " section
 puts a vacuum on the other pipe 180 degrees out of phase.
 A time tested design for rotary engine headers.
 I would then add  another section after that that expands the pipe
 from 2" to 2.5" into the muffler. Every time you expand the pipe
 diameter it slows the exhaust gases and reduces the exhaust gas

 temperature.

 P1V1/T1 = P2V2/T2  where P = press. V = Volume and T = temperature.

 Paul Lamar



 The hushpower is certainly quiet. at 2500 rpm, people can converse
 without shouting when only about 40 feet away from the plane. YOu
 can really hear the prop at that power level, compared to the exhaust.

  We'll have to see about longevity though....

 Brian Trubee

Hey Brian
Congrats!!!   I am sure you will work out the details on the power.  FWIW, I
don't use an air filter.. not sure if that is a great idea or not.  I think
you will find that the innards of the hushpower only last a few hours, but
the shell will hold up and offers some quieting ability.  But a long
straight pipe (or SS flex tube) works almost as well.