X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from willowsprings.uwyo.edu ([129.72.10.31] verified) by logan.com (CommuniGate Pro SMTP 5.4c2o) with ESMTPS id 4885248 for flyrotary@lancaironline.net; Mon, 28 Feb 2011 12:20:04 -0500 Received-SPF: none receiver=logan.com; client-ip=129.72.10.31; envelope-from=SBoese@uwyo.edu Received: from ponyexpress-ht2.uwyo.edu (ponyexpress-ht2.uwyo.edu [10.84.60.209]) by willowsprings.uwyo.edu (8.14.4/8.14.4) with ESMTP id p1SHJH7a005069 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=FAIL) for ; Mon, 28 Feb 2011 10:19:25 -0700 (MST) (envelope-from SBoese@uwyo.edu) Received: from ponyexpress-mb5.uwyo.edu ([fe80::9813:248c:2d68:a28b]) by ponyexpress-ht2 ([10.84.60.209]) with mapi; Mon, 28 Feb 2011 10:19:16 -0700 From: "Steven W. Boese" To: Rotary motors in aircraft Date: Mon, 28 Feb 2011 10:19:12 -0700 Subject: RE: [FlyRotary] Re: Steve Boese TDC Finder Thread-Topic: [FlyRotary] Re: Steve Boese TDC Finder Thread-Index: AcvXaD2wnWSl1bngTmCoJaD6sWOuUAAANb8w Message-ID: References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: multipart/alternative; boundary="_000_E1AA3B1AF41D8049B1E3FBD5E225626008872D2435ponyexpressmb_" MIME-Version: 1.0 --_000_E1AA3B1AF41D8049B1E3FBD5E225626008872D2435ponyexpressmb_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable When I adjusted the timing by the apex seal in the spark plug hole method, = I was getting spark plugs with the appearance of overheating and significan= t erosion of the center electrode along with SAG after 15 hours or less of = operation on stock spark plugs and mostly unleaded fuel. This lead me to verify the ignition timing and I found that I had been oper= ating at 35 degrees BTDC at 5200 RPM and 23" MAP with the default controlle= r timing setting and Tracy's recommended CAS position. After setting the t= iming using the minimum chamber volume method, the spark plug life has inc= reased along with the time it takes SAG to develop. I did not notice any d= ifference in power or fuel consumption as a result of the change. I may ha= ve been fortunate that at my location, the density altitude is nearly alway= s in excess of 7000 ft and MAP is limited to 23.5" since the engine is norm= ally aspirated. These are just my observations and I am not contending that they are of any= consequence. Steve Boese From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Beh= alf Of Al Gietzen Sent: Monday, February 28, 2011 9:55 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Steve Boese TDC Finder First let me point out the big error in the procedure I wrote: -The center of the combustion chamber is 60o on the rotor from the tip seal= ; or 120o (should read 180) on the E-shaft. - Count the total number of teeth on the ring gear, and divide by 3 (should= read 2). Now rotate the engine by that number of teeth (either direction) = and rotor 1 will be very close to TDC. I wouldn't argue the precision of the method; but for the housings you show= , the offset appears to be much less than 10 degrees. The e-shaft TDC offse= t would then be 1 =BD times that as you split the difference between the pl= ugs and multiply by 3:1 ratio. And being a few degrees off on the rotary is= not of much consequence. Ultimately the timing at which we operate is determined by the timing curve= built in to the engine controller. I'm pretty sure Tracy has modified tha= t some over the years. And then there in-flight tuning of the timing at cr= uise condition that you may like to look at. When I got my 20B with a 12A front housing from Atkins, the relationship of= the pointer to the marks on the pulley made no sense. I used my simple met= hod to determine a TDC mark, and worked from there. On the dyno we put a p= ressure transducer into a trailing plug hole and adjusted timing a bit whil= e operating (I don't recall conditions - I think 22" MAP) to get the pressu= re trace to look right. We chose a point 2 steps retarded on the EC2, - 3.7= 5o. Subsequently I did some variation at cruise conditions to see effect on per= formance, and again ended up at two steps of retarding, although I found pe= rformance change almost undetectable over a 3-4 step range (~7o) to either = side. So that setting is pretty consistent with Lynn's data that the method= leads to a TDC that was a bit BTDC; but is of no consequence. That's my story, and I' sticking to it:). Al --_000_E1AA3B1AF41D8049B1E3FBD5E225626008872D2435ponyexpressmb_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable

When I adjusted the timing by = the apex seal in the spark plug hole method, I was getting spark plugs with= the appearance of overheating and significant erosion of the center electr= ode along with SAG after 15 hours or less of operation on stock spark plugs= and mostly unleaded fuel.=A0

 

This lead me to verify the ignition timing and I found t= hat I had been operating at 35 degrees BTDC at 5200 RPM and 23” MAP w= ith the default controller timing setting and Tracy’s recommended CAS= position.=A0 After setting the timing using the minimum chamber volume met= hod,=A0 the spark plug life has increased along with the time it takes SAG = to develop.=A0 I did not notice any difference in power or fuel consumption= as a result of the change.=A0 I may have been fortunate that at my locatio= n, the density altitude is nearly always in excess of 7000 ft and MAP is li= mited to 23.5” since the engine is normally aspirated.=A0 =

 

These are just my obse= rvations and I am not contending that they are of any consequence.

 

Steve Boese=A0 =A0

From: Rotary motors in= aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al Gietz= en
Sent: Monday, February 28, 2011 9:55 AM
To: Rotary m= otors in aircraft
Subject: [FlyRotary] Re: Steve Boese TDC Finder=

 

First let me point out the big error in the proce= dure I wrote:

 

-The center of the combustion chamber is 60o on the rotor from the tip seal; or 120o= (should read 180) on the E-shaft.

- Co= unt the total number of teeth on the ring gear, and divide by 3 (= should read 2). Now rotate the engine by that number of teeth (e= ither direction) and rotor 1 will be very close to TDC= .

 

I wouldn’t argue the precision of the metho= d; but for the housings you show, the offset appears to be much less than 1= 0 degrees. The e-shaft TDC offset would then be 1 =BD times that as you spl= it the difference between the plugs and multiply by 3:1 ratio. And being a = few degrees off on the rotary is not of much consequence.=

 

Ultimately the timing at which we operate is determined by the timin= g curve built in to the engine controller.  I’m pretty sure Trac= y has modified that some over the years.  And then there in-flight tun= ing of the timing at cruise condition that you may like to look at.<= o:p>

 

When I got my 20B with a 12A front housing from Atkins, th= e relationship of the pointer to the marks on the pulley made no sense. I u= sed my simple method to determine a TDC mark, and worked from there.  = On the dyno we put a pressure transducer into a trailing plug hole and adju= sted timing a bit while operating (I don’t recall conditions – = I think 22” MAP) to get the pressure trace to look right. We chose a = point 2 steps retarded on the EC2, - 3.75o= .

 

Subsequently I did some variation at cruise condi= tions to see effect on performance, and again ended up at two steps of reta= rding, although I found performance change almost undetectable over a 3-4 s= tep range (~7o) to either side. So that setting is pretty consis= tent with Lynn’s data that the method leads to a TDC that was a bit B= TDC; but is of no consequence.

 

That’s my stor= y, and I’ sticking to itJ.

 

Al

 

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