X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fmailhost05.isp.att.net ([207.115.11.55] verified) by logan.com (CommuniGate Pro SMTP 5.2.16) with ESMTP id 3839187 for flyrotary@lancaironline.net; Sun, 06 Sep 2009 15:01:44 -0400 Received-SPF: pass receiver=logan.com; client-ip=207.115.11.55; envelope-from=bbradburry@bellsouth.net Received: from laptop (adsl-146-126-207.mco.bellsouth.net[72.146.126.207]) by isp.att.net (frfwmhc05) with SMTP id <20090906190108H05005k5vge>; Sun, 6 Sep 2009 19:01:09 +0000 X-Originating-IP: [72.146.126.207] From: "Bill Bradburry" To: "'Rotary motors in aircraft'" References: Subject: RE: [FlyRotary] Re: DNA muffler Date: Sun, 6 Sep 2009 15:01:12 -0400 Message-ID: <5616FF78B2234DEA945E6D430B44A3DF@LAPTOP> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_001F_01CA2F02.E0906540" X-Mailer: Microsoft Office Outlook 11 Thread-Index: AcovBWBFRspNn/DvSyKTm75q69hengAHKQhA In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 This is a multi-part message in MIME format. ------=_NextPart_000_001F_01CA2F02.E0906540 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Mike, I have the same phenomenon going on at =BE throttle. Tracy once = suggested that there may be more restriction somewhere other than the throttle = body. Thinking about this, I am using a modified stock Renesis intake. The = stock runners are about 1 inch in diameter and the throttle body is same as = the stock 3 inches. So I have about 4 square inches in the runners, but = over 6 square inches (depending on the blockage of the butterfly with it wide = open) in the throttle body. This may be what is happening, but the dimensions = are the same as the stock engine and I have not heard of this complaint = about the car. There is a tube that bypasses the throttle body and injects = air into the primary ports on the car and I am not doing this on my engine. = I read manifold pressure at the back of the plenum and get 29-30 inches = there. I need to read the pressure at the entrance to the ports to see what I = am losing in my manifold. That may explain it?? I plan to also try the = bypass to see if that helps the idle as well. =20 Bill B =20 _____ =20 From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mike Wills Sent: Sunday, September 06, 2009 11:18 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: DNA muffler =20 Mark/Ed/Bill, =20 I did not buy the same DNA that you bought. Mine is a truck muffler with = 2 1/4 inlets and outlets. I figured the larger body/volume of the truck mufflers would help quiet things down. And the truck series mufflers are almost identical in dimension to the muffler I started with. At this = point I'm hesitant to choke the thing down anymore by putting a reducer on the outlet, but I guess there really isnt anything to loose. Except HP. =20 I was thinking along the same lines as Bill - that the DNA is more restrictive resulting in richer mixtures at equivalent MAP. My home made muffler was a copy of the Moroso spiral flow mufflers, but with a larger center tube. With my home made muffler I can look all the way through it = so the DNA is clearly more restrictive. Which is why I'm surprised it didnt work better. =20 The DNA sure looks better than my home made muffler. Weld quality is = great. Time will tell how it holds up. The home made muffler was Inconel so I expect it would be more durable in the long run. =20 The point of something else in the airflow path limiting HP is a good = point. One of things I've noticed is that I reach max power long before I reach = max throttle. Since I'm making enough power for good performance I wasnt too worried about this, but I am curious. Once I reach about 3/4 throttle = I'm maxed out - the last 1/4 doesnt do anything. =20 Mike Wills RV-4 N144MW ----- Original Message -----=20 From: Mark Steitle =20 To: Rotary motors in aircraft=20 Sent: Sunday, September 06, 2009 5:55 AM Subject: [FlyRotary] Re: DNA muffler =20 Mike,=20 =20 I had the same impression of the DNA muffler. Then I remembered what = Tracy said about big pipes being louder than smaller pipes. So, I ordered a tapered transition piece from Burns Stainless, bringing it down from 3" = to 2 1/4". That helped reduce the noise considerably and I couldn't detect = any reduction in hp. Or, you could spring for a pair of those $800 = headsets, or you could do both. =20 =20 Mark S. On Sat, Sep 5, 2009 at 10:46 PM, Mike Wills wrote: Received my DNA muffler this past week and got it installed and running. Havent flown it yet, but have done some taxi and full power runups. So = far I'm a little disappointed. It doesnt appear to be any quieter than my = home made muffler. I'll reserve judgement until I actually fly it, but from = the cockpit the noise level seems the same, and my buddy standing about 50 ' away said he thought the noise level was the same. =20 One thing not the same - the muffler screwed up my tuning. It appears = to be considerably richer now all across the RPM range. And the big bog at the staging point that took me so long to tune out is back with a vengeance. Oddly, in spite of the tune issues it still appears to reach the same = static RPM as previously. =20 Looks like the solution for me is going to be the high $ headset and = the rest of the world is just going to have to live with it. =20 Mike Wills RV-4 N144MW =20 ------=_NextPart_000_001F_01CA2F02.E0906540 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

Mike,

I have the same phenomenon going on = at =BE throttle.=A0 Tracy once suggested that there may be more restriction somewhere other than the = throttle body.=A0 Thinking about this, I am using a modified stock Renesis intake.=A0 The = stock runners are about 1 inch in diameter and the throttle body is same as = the stock 3 inches.=A0 So I have about 4 square inches in the runners, but over 6 = square inches (depending on the blockage of the butterfly with it wide open) in = the throttle body.=A0 This may be what is happening, but the dimensions are = the same as the stock engine and I have not heard of this complaint about the = car.=A0 There is a tube that bypasses the throttle body and injects air into the = primary ports on the car and I am not doing this on my engine.=A0 I read = manifold pressure at the back of the plenum and get 29-30 inches there.=A0 I need = to read the pressure at the entrance to the ports to see what I am losing in my manifold.=A0 That may explain it??=A0 I plan to also try the bypass to = see if that helps the idle as well.

 

Bill B

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mike Wills
Sent: Sunday, September = 06, 2009 11:18 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = DNA muffler

 

Mark/Ed/Bill,

 

I did not buy the same DNA that you bought. Mine is a = truck muffler with 2 1/4 inlets and outlets. I figured the larger body/volume = of the truck mufflers would help quiet things down. And the truck series = mufflers are almost identical in dimension to the muffler I started with. At this = point I'm hesitant to choke the thing down anymore by putting a reducer on the = outlet, but I guess there really isnt anything to loose. Except = HP.

 

I was thinking along the same lines as Bill - that = the DNA is more restrictive resulting in richer mixtures at equivalent MAP. My = home made muffler was a copy of the Moroso spiral flow mufflers, but with a = larger center tube. With my home made muffler I can look all the way through it = so the DNA is clearly more restrictive. Which is why I'm surprised it didnt = work better.

 

The DNA sure looks better than my home made muffler. = Weld quality is great. Time will tell how it holds up. The home made muffler = was Inconel so I expect it would be more durable in the long = run.

 

The point of something else in the airflow path = limiting HP is a good point. One of things I've noticed is that I reach max power = long before I reach max throttle. Since I'm making enough power for good = performance I wasnt too worried about this, but I am curious. Once I reach about 3/4 throttle I'm maxed out - the last 1/4 doesnt do = anything.

 

Mike Wills

RV-4 N144MW

----- Original Message ----- =

Sent: Sunday, = September 06, 2009 5:55 AM

Subject: = [FlyRotary] Re: DNA muffler

 

Mike,

 

I had the same impression of the DNA muffler.  Then I = remembered what Tracy said about big pipes being louder than smaller pipes.  So, I = ordered a tapered transition piece from Burns Stainless, bringing it down from = 3" to 2 1/4".  That helped reduce the noise considerably and I couldn't detect any reduction in hp.  Or, you could spring for a pair of those $800 headsets, or you could do both.  =

 

Mark S.

On Sat, Sep 5, 2009 at 10:46 PM, Mike Wills <rv-4mike@cox.net> = wrote:

Received my DNA muffler this past week and got it = installed and running. Havent flown it yet, but have done some taxi and full power runups. So far I'm a little disappointed. It doesnt appear to be any = quieter than my home made muffler. I'll reserve judgement until I actually fly = it, but from the cockpit the noise level seems the same, and my buddy standing = about 50 ' away said he thought the noise level was the = same.

 

 One thing not the same - the muffler screwed up = my tuning. It appears to be considerably richer now all across the RPM = range. And the big bog at the staging point that took me so long to tune out is = back with a vengeance. Oddly, in spite of the tune issues it still appears to = reach the same static RPM as previously.

 

 Looks like the solution for me is going to be = the high $ headset and the rest of the world is just going to have to live with = it.

 

Mike = Wills

RV-4 = N144MW

 

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