X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.121] verified) by logan.com (CommuniGate Pro SMTP 5.2.14) with ESMTP id 3748335 for flyrotary@lancaironline.net; Tue, 07 Jul 2009 15:49:33 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.121; envelope-from=eanderson@carolina.rr.com Received: from computername ([75.191.186.236]) by cdptpa-omta04.mail.rr.com with ESMTP id <20090707194854841.QTVP2041@cdptpa-omta04.mail.rr.com> for ; Tue, 7 Jul 2009 19:48:54 +0000 From: "Ed Anderson" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: SAG was: [FlyRotary] Re: Muffler Date: Tue, 7 Jul 2009 15:49:12 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0045_01C9FF1A.79C424E0" X-Mailer: Microsoft Office Outlook, Build 11.0.5510 Thread-Index: Acn/IjUB4ciLRHqARyWMjqwt0CKj7gAGRkhg X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 In-Reply-To: Message-Id: <20090707194854841.QTVP2041@cdptpa-omta04.mail.rr.com> This is a multi-part message in MIME format. ------=_NextPart_000_0045_01C9FF1A.79C424E0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Hi Jeff, Oh, I don't throw them out - I have a bushel basket of used plugs. But, you are right they are around $5.00 down here when purchased in bulk/box. The 3 electrode ground shields the ceramic cone from the typical abrasive blasting pretty well. Make it a pain to clean the stock plugs, but they certainly do not have any noticeable wear after 25 hours so I save them. I tried several methods - but despite what the gun shops advertise there is no solvent for lead short of foaming nitric acid (or something equally hazardous). I believe that if someone had a powerful ultrasonic cleaning machine that placing them in a solution of alcohol or something similar and using ultra sound to blast the lead crystals off the ceramic might do the job. But, that is one device I do not have. But, you never know when one may appear on ebay for $5.00 {:>) Ed Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://www.dmack.net/mazda/index.html http://www.flyrotary.com/ http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.rotaryaviation.com/Rotorhead%20Truth.htm _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Jeff Whaley Sent: Tuesday, July 07, 2009 12:44 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: SAG was: [FlyRotary] Re: Muffler Hey Ed, now might be the time you cleaned a few SAG plugs and tested them? It seems hard to believe that plugs need be thrown out after 25 hours. BTW, up here in Ottawa, I had to pay $17 each ($68 per set) for stock Mazda plugs, on a trip south I picked up some in Ogdensburg NY around $5 each. Jeff From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed Anderson Sent: Tuesday, July 07, 2009 7:10 AM To: Rotary motors in aircraft Subject: [FlyRotary] SAG was: [FlyRotary] Re: Muffler There are undoubtedly numerous possibilities as to what is happening/causing SAG. However, two things are very clear: 1. 100 LL does definitely reduce the time spark plugs can be used before SAG occurs. The nominal time period that I have found in my engine is 24-30 hours. You can take the plug out and examine the ceramic cone and see the glint of what I believe (but have not done a chemical analysis) of lead crystals. Folks using MOGAS (such as Tracy) have reported going over 150 hours without SAG. So I do believe there is a connection between 100LL and the short interval of use before SAG. I even attempted to use TCP which is used in some aircraft engines and is reportedly suppose to reduce lead deposits. It simply make the problem worst, but upon further research I discovered that for this chemical to work the cylinder head temperature has to be much higher than what our water cooled sparkplugs typically see. In my case, the chemical caused further deposits (of some sort) on the sparkplug and I barely got 5 hours out of the set I used. This may in part explain why our sparkplugs seem to foul more with 100LL than aircraft sparkplugs - they don't get hot enough? 2. If you encounter SAG, then replacing the sparkplugs immediately eliminates the SAG problem (for a period of time). So both of those factors lead me to believe it is fouling of spark plugs rather than pre-ignition. If pre-ignition then my dozens of times of SAG (like every 15 minutes on the 5 hour trip from Louisiana) would surely have resulted in damage to the engine. In any case, whatever the cause, since I have been replacing my sparkplugs regularly at 25-30 hour intervals I have encountered no SAG. YMMV Ed Ed Anderson Rv-6A N494BW Rotary Powered Matthews, NC eanderson@carolina.rr.com http://www.andersonee.com http://www.dmack.net/mazda/index.html http://www.flyrotary.com/ http://members.cox.net/rogersda/rotary/configs.htm#N494BW http://www.rotaryaviation.com/Rotorhead%20Truth.htm _____ From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of William Wilson Sent: Tuesday, July 07, 2009 12:09 AM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Muffler While the rotary design is a little more resistant to the onset of preignition, once it happens, the rotary is damaged just as easily as a piston engine or even more so. Drag racers suffering preignition have dismantled their motors and found rotors dented in from excess chamber pressure. It is possible that you have been having mild preignition not enough to damage the engine, I suppose. Do you suppose you have been running really excessively rich? That would also contribute to plug fouling, low power and low EGT. If you have fuel injection, a fuel map problem showing up only at high manifold pressures (higher than you normally attain in your usual operating regime) maybe? You should get WAY more than 10 hours on spark plugs even running 100LL. If combustion were still taking place as you speculate then it would ignite the incoming mixture during the intake cycle and cause a backfire. So I think that is not it. I assume you've seen this but I found it interesting: http://www.wankel.org/74_Ignition/74-22%20Spark%20plug%20life%20.htm On Mon, Jul 6, 2009 at 7:17 PM, Steven Boese wrote: I never found the broken muffler part in the outlet of the muffler where it might have caused increased back pressure even though it was possible for it to end up in that location by standing the muffler on its end. The symptoms after repairing the muffler were the same as before the repair was made so at this point, I don't think the broken part was a factor in the performance issue. Looking back at the data log, the #2 rotor EGT dropped by about 250 degrees during the power deficit. Back pressure would probably affect both rotors in a similar fashion so that would also point to SAG as the culprit. In response to your and Bobby's questions, at the onset of SAG, there were a total of 15 hours on the plugs, 106 gal total of fuel burned, 53 gal of that was 100LL. Ed is most likely right that operating at the increased manifold pressure available at low altitude made the SAG show up while it didn't at lower manifold pressures that I normally see. The relatively small amount of time and fuel that the plugs had seen when SAG occurred may also be due to the low power levels and correspondingly lower combustion temperatures permitting more rapid lead deposition on the plugs. It looks like I should routinely change plugs every 10 hours or so. I did have extra plugs along on the Texas trip and it would have been easy to have installed them at the rotorfest. The nature of SAG is puzzling. The symptoms of decreased EGT, decreased power output, and increased heat transfer to the oil and coolant are all consistent with descriptions of pre-ignition more than that of spark plug misfire. In piston engines, pre-ignition can rapidly lead to destruction, but the rotary engine may be more tolerant of it. Maybe it isn't a matter of no ignition due to the spark plug not firing, but a matter of the fire not going out between sparks. The lead in 100LL increases the octane rating by slowing the combustion rate and thereby decreasing the tendency for detonation. Maybe there is enough gas phase lead in the vicinity of the spark plug with lead deposited on it that the combustion rate is slowed enough to persist from one cycle to the next while the normal combustion rate occurs in the rest of the chamber. This could result in a process similar to pre-ignition. This theory probably has as much probability of being right as the one I had concerning the apex seals clicking. Maybe I can accumulate a pile of SAGGING spark plugs as big as Ed's. That would be verifiable at least. Steve Boese -----Original Message----- From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Todd Bartrim Sent: Monday, July 06, 2009 6:23 PM To: Rotary motors in aircraft Subject: [FlyRotary] Re: Muffler Hi Steve; So you now assume that your power loss is directly attributable to SAG and not to the partially blocked muffler? Is this correct? I'm curious as I also use a homemade muffler (SpinTech copy) and have wondered what the result would be if any of the internal came loose. I wonder if your increased backpressure contributed to the onset of SAG? And do you only burn 100LL, occasionally, or never? Todd C-FSTB RV9 Turbo13B __________ Information from ESET NOD32 Antivirus, version of virus signature database 3267 (20080714) __________ The message was checked by ESET NOD32 Antivirus. http://www.eset.com ------=_NextPart_000_0045_01C9FF1A.79C424E0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Hi = Jeff,

 

Oh, I don’t throw them out = – I have a bushel basket of used plugs.  But, you are right they are = around $5.00 down here when purchased in bulk/box.

 

The 3 electrode ground shields the = ceramic cone from the typical abrasive blasting pretty well. Make it a pain to = clean the stock plugs, but they certainly do not have any noticeable wear = after 25 hours so I save them. 

 

I tried several methods – but = despite what the gun shops advertise there is no solvent for lead short of = foaming nitric acid (or something equally = hazardous).

 

I believe that if someone had a = powerful ultrasonic cleaning machine that placing them in a solution of alcohol = or something similar and using ultra sound to blast the lead crystals off = the ceramic might do the job.  But, that is one device I do not = have.

 

But, you never know when one may = appear on ebay for $5.00 {:>)

 

Ed

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Jeff Whaley
Sent: Tuesday, July 07, = 2009 12:44 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = SAG was: [FlyRotary] Re: Muffler

 

Hey Ed, now = might be the time you cleaned a few SAG plugs and tested = them?

It seems = hard to believe that plugs need be thrown out after 25 = hours.

BTW, up = here in Ottawa, I had to pay $17 each ($68 per set) for = stock Mazda plugs, on a trip south I picked up some in Ogdensburg NY around $5 each.

Jeff

 <= /o:p>

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Ed Anderson
Sent: Tuesday, July 07, = 2009 7:10 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] SAG = was: [FlyRotary] Re: Muffler

 

There are undoubtedly numerous possibilities as to what is happening/causing SAG.  However, two = things are very clear:

 

  1. 100 LL does definitely reduce the time spark plugs can be used before = SAG occurs.  The nominal time period that I have found in my = engine is 24-30 hours.  You can take the plug out and examine the = ceramic  cone and see the glint of what I believe (but have not done a chemical analysis) of lead crystals.  Folks using MOGAS (such = as Tracy) = have reported going over 150 hours without SAG.  So I do believe there is a connection between 100LL and the short interval of use before = SAG.

 

I even attempted = to use TCP which is used in some aircraft engines and is reportedly suppose to = reduce lead deposits.  It simply make the problem worst, but upon further research I discovered that for this chemical to work the cylinder head temperature has to be much higher than what our water cooled sparkplugs typically see.  In my case, the chemical caused further deposits = (of some sort)  on the sparkplug and I barely got 5 hours out of the set I used.  This may in part explain why our sparkplugs seem to foul = more with 100LL than aircraft sparkplugs – they don’t get hot enough?  

 =

  1. If you encounter SAG, then replacing the sparkplugs immediately = eliminates the SAG problem (for a period of time).  =

 

So both of those factors lead me to believe it is fouling of spark plugs rather than pre-ignition.  If pre-ignition then my dozens of times of SAG (like every 15 minutes on = the 5 hour trip from Louisiana) would surely have resulted in damage to the engine.  =

 

In any case, whatever the cause, = since I have been replacing my sparkplugs regularly at 25-30 hour intervals I = have encountered no SAG.  YMMV

 

Ed

 

 

From: = Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of William Wilson
Sent: Tuesday, July 07, = 2009 12:09 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: = Muffler

 

While the = rotary design is a little more resistant to the onset of preignition, once it happens, = the rotary is damaged just as easily as a piston engine or even more = so.  Drag racers suffering preignition have dismantled their motors and found = rotors dented in from excess chamber pressure.  It is possible that you = have been having mild preignition not enough to damage the engine, I = suppose.  Do you suppose you have been running really excessively rich?  That = would also contribute to plug fouling, low power and low EGT.  If you = have fuel injection, a fuel map problem showing up only at high manifold pressures = (higher than you normally attain in your usual operating regime) maybe?  = You should get WAY more than 10 hours on spark plugs even running 100LL.

If combustion were still taking place as you speculate then it would = ignite the incoming mixture during the intake cycle and cause a backfire.  So = I think that is not it.

I assume you've seen this but I found it interesting:
http://www.wankel.org/74_Ignition/74-22%20Spark%20plug%20life%20.htm=

On Mon, Jul 6, 2009 at 7:17 PM, Steven Boese <sboese@uwyo.edu> = wrote:

I never found the broken muffler part in the outlet of = the muffler where it might have caused increased back pressure even though = it was possible for it to end up in that location by standing the muffler on = its end.  The symptoms after repairing the muffler were the same as = before the repair was made so at this point, I don’t think the broken part = was a factor in the performance issue.  Looking back at the data log, the = #2 rotor EGT dropped by about 250 degrees during the power deficit. =  Back pressure would probably affect both rotors in a similar fashion so that = would also point to SAG as the culprit.

 

In response to your and Bobby’s questions, at = the onset of SAG, there were a total of 15 hours on the plugs, 106 gal total of = fuel burned, 53 gal of that was 100LL.

 

Ed is most likely right that operating at the = increased manifold pressure available at low altitude made the SAG show up while = it didn’t at lower manifold pressures that I normally = see.

 

The relatively small amount of time and fuel that the = plugs had seen when SAG occurred may also be due to the low power levels and = correspondingly lower combustion temperatures permitting more rapid lead deposition on = the plugs.  It looks like I should routinely change plugs every 10 = hours or so.  I did have extra plugs along on the Texas trip and it would have been = easy to have installed them at the rotorfest.

 

The nature of SAG is puzzling.  The symptoms of decreased EGT, decreased power output, and increased heat transfer to = the oil and coolant are all consistent with descriptions of pre-ignition more = than that of spark plug misfire.  In piston engines, pre-ignition can rapidly = lead to destruction, but the rotary engine may be more tolerant of it.  = Maybe it isn’t a matter of no ignition due to the spark plug not firing, = but a matter of the fire not going out between sparks.  The lead in 100LL increases the octane rating by slowing the combustion rate and thereby decreasing the tendency for detonation.  Maybe there is enough gas = phase lead in the vicinity of the spark plug with lead deposited on it that = the combustion rate is slowed enough to persist from one cycle to the next = while the normal combustion rate occurs in the rest of the chamber. This could = result in a process similar to pre-ignition.  This theory probably has as = much probability of being right as the one I had concerning the apex seals = clicking.

 

Maybe I can accumulate a pile of SAGGING spark plugs = as big as Ed’s.  That would be verifiable at least.     

 

Steve Boese  

 

   

 

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Todd = Bartrim
Sent: Monday, July 06, = 2009 6:23 PM
To: Rotary motors in aircraft

Subject: = [FlyRotary] Re: Muffler

 

Hi Steve;
    So you now assume that your power loss is directly = attributable to SAG and not to the partially blocked muffler? Is this correct?
     I'm curious as I also use a homemade muffler = (SpinTech copy) and have wondered what the result would be if any of the internal = came loose. I wonder if your increased backpressure contributed to the onset = of SAG? And do you only burn 100LL, occasionally, or = never?

 

Todd
C-FSTB
RV9 Turbo13B

 

 



__________ Information from ESET NOD32 Antivirus, version of virus = signature database 3267 (20080714) __________

The message was checked by ESET NOD32 Antivirus.

http://www.eset.com

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