X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 11 [X] Return-Path: Received: from imo-m27.mx.aol.com ([64.12.137.8] verified) by logan.com (CommuniGate Pro SMTP 5.1.7) with ESMTP id 1919225 for flyrotary@lancaironline.net; Tue, 13 Mar 2007 15:23:51 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.8; envelope-from=WRJJRS@aol.com Received: from WRJJRS@aol.com by imo-m27.mx.aol.com (mail_out_v38_r7.6.) id q.cba.d23b780 (60469) for ; Tue, 13 Mar 2007 15:22:52 -0400 (EDT) Received: from webmail-dd21 (webmail-dd21.webmail.aol.com [205.188.104.21]) by ciaaol-m02.mx.aol.com (v114_r3.4) with ESMTP id MAILCIAAOLM022-ec3545f6fa0c1d3; Tue, 13 Mar 2007 15:22:52 -0400 References: To: flyrotary@lancaironline.net Subject: Re: [FlyRotary] Re: Engine noise and changes in timeing and mixture. Date: Tue, 13 Mar 2007 15:22:52 -0400 In-Reply-To: X-MB-Message-Source: WebUI MIME-Version: 1.0 From: wrjjrs@aol.com X-MB-Message-Type: User Content-Type: multipart/alternative; boundary="--------MB_8C933BC2120BC8E_CD4_4D7D_webmail-dd21.sysops.aol.com" X-Mailer: AOL WebMail 24126 Received: from 65.161.241.3 by webmail-dd21.sysops.aol.com (205.188.104.21) with HTTP (WebMailUI); Tue, 13 Mar 2007 15:22:52 -0400 Message-Id: <8C933BC21231EED-CD4-2A02@webmail-dd21.sysops.aol.com> X-AOL-IP: 205.188.104.21 X-Spam-Flag: NO ----------MB_8C933BC2120BC8E_CD4_4D7D_webmail-dd21.sysops.aol.com Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii" Enerest, Please note I mis-typed the line and I believe the noise will increase again as the tuning improves. There are many factors here, timing, mixture and exhaust tuning. If all the other factors remain the same I have found that ported engines are usually quieter when too rich. This is anecdotal, I haven't recorded it with a DB meter. My personal explaination is that the cylinder pressures are higher when better tuned and the sudden port opening in a rotary or 2-cycle causes a louder "bark" The rotary is particularly bad in this respect. Bill Jepson -----Original Message----- From: echristley@nc.rr.com To: flyrotary@lancaironline.net Sent: Tue, 13 Mar 2007 8:53 AM Subject: [FlyRotary] Re: Engine noise and changes in timeing and mixture. WRJJRS@aol.com wrote: > For Tracy, > When I was actively tuning race cars we had a truism that I often > used, "everything changes everything". This was a drastic > oversimplification, but none the less was true. If you have an engine > running very well, a seemingly minor change WILL change exhaust note > or timber. On the dyno you would find some adjustments did little, > others a great deal. The fact is as you get the mixture closer to > right I am afraid you will hear the exhaust not come back up in volume. > Bill Jepson Maybe not, Bill. Without the snubbers, there would be some unknown and possibly variable delay in the closing. There would also possibly be varying delays between different injectors. This variability might not be enough to feel a vibration, but the exhaust pulse would be slightly stronger from one chamber than the other. It would only be detected as more noise and would express itself as a slop factor in tuning. Remove the variability and the tuning can be more exact since the same amount of fuel will be delivered every time, giving Tracy that extra 100RPM. Possible? -- ,|"|"|, Ernest Christley | ----===<{{(oQo)}}>===---- Dyke Delta Builder | o| d |o http://ernest.isa-geek.org | -- Homepage: http://www.flyrotary.com/ Archive and UnSub: http://mail.lancaironline.net:81/lists/flyrotary/List.html ________________________________________________________________________ AOL now offers free email to everyone. Find out more about what's free from AOL at AOL.com. ----------MB_8C933BC2120BC8E_CD4_4D7D_webmail-dd21.sysops.aol.com Content-Transfer-Encoding: 7bit Content-Type: text/html; charset="us-ascii"

Enerest, Please note I mis-typed the line and I believe the noise will increase again as the tuning improves. There are many factors here, timing, mixture and exhaust tuning. If all the other factors remain the same I have found that ported engines are usually quieter when too rich. This is anecdotal, I haven't recorded it with a DB meter. My personal explaination is that the cylinder pressures are higher when better tuned and the sudden port opening in a rotary or 2-cycle causes a louder "bark" The rotary is particularly bad in this respect.

Bill Jepson

-----Original Message-----
From: echristley@nc.rr.com
To: flyrotary@lancaironline.net
Sent: Tue, 13 Mar 2007 8:53 AM
Subject: [FlyRotary] Re: Engine noise and changes in timeing and mixture.

WRJJRS@aol.com wrote:

> For Tracy,
> When I was actively tuning race cars we had a truism that I often > used, "everything changes everything". This was a drastic > oversimplification, but none the less was true. If you have an engine > running very well, a seemingly minor change WILL change exhaust note > or timber. On the dyno you would find some adjustments did little, > others a great deal. The fact is as you get the mixture closer to > right I am afraid you will hear the exhaust not come back up in volume.
> Bill Jepson

Maybe not, Bill. Without the snubbers, there would be some unknown and possibly variable delay in the closing. There would also possibly be varying delays between different injectors. This variability might not be enough to feel a vibration, but the exhaust pulse would be slightly stronger from one chamber than the other. It would only be detected as more noise and would express itself as a slop factor in tuning. Remove the variability and the tuning can be more exact since the same amount of fuel will be delivered every time, giving Tracy that extra 100RPM.

Possible?

-- ,|"|"|, Ernest Christley |
----===<{{(oQo)}}>===---- Dyke Delta Builder |
o| d |o http://ernest.isa-geek.org |

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