Return-Path: Sender: "Marvin Kaye" To: lml@lancaironline.net Date: Wed, 26 Jan 2005 11:58:29 -0500 Message-ID: X-Original-Return-Path: Received: from systems3.net ([68.14.236.16] verified) by logan.com (CommuniGate Pro SMTP 4.2.8) with ESMTP-TLS id 623099 for lml@lancaironline.net; Wed, 26 Jan 2005 11:26:22 -0500 Received-SPF: none receiver=logan.com; client-ip=68.14.236.16; envelope-from=cberland@systems3.net Received: from systems0d3b724 ([192.168.1.81]) by systems3.net (8.13.1/8.13.1/Debian-12) with SMTP id j0QGPpc3024065 for ; Wed, 26 Jan 2005 09:25:52 -0700 X-Original-Message-ID: <00bd01c503c2$f9df31e0$5101a8c0@systems0d3b724> From: "Craig Berland" X-Original-To: "Lancair Mail List" Subject: [LML] Re: Plugs and Mags for IVP X-Original-Date: Wed, 26 Jan 2005 09:20:34 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00BA_01C50388.4A6B2AA0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1437 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1441 X-Virus-Scanned: clamd / ClamAV version 0.75-1, clamav-milter version 0.75c on linux X-Virus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_00BA_01C50388.4A6B2AA0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Walter, as long as the discussion/argument remains non-personal, I enjoy = and learn. With that said: ... don't diminish the effects of a good ignition system. Poor plugs, = bad wires, worn out mag (even hotter spark) all can make a significant = affect for the same reason the RPM drops on one mag vs both.=20 Your comments are correct except for the reason the rpm drops on one = mag. EGT rises on one mag because the total burn time is almost half as = much as with two plugs. The rpm drops because the thetaPP becomes = excessive. Walter, that is correct. The problem here is you do not buy into the = ignition system performance does affect angle of peak pressure. The = data I have is viewing very high speed video thru a quartz combustion = chamber. As in everything related to the IC engine, there are numerous = aspects that affect performance and one cannot be ignored while = evaluating another. ---------------------- The idea is to have as fast of combustion as possible without it being = an explosion (non controlled combustion).=20 No, the speed of the flame front is determined by the bulk gas = temperature and the internal cylinder pressure. We do not want it as = fast as it can be. Yes it is so. I think you are viewing this as one working on an = existing engine and I view it as one designing a new engine (my = background). My position more clearly stated is...An engine design that = has faster burn will perform better than one with slower burn. (let's = say an engine with peak torque at 18 deg BTC will be less sensitive to = detonation and will have a higher BMEP and lower BSFC than engine with = peak torque at 24 deg BTC. ------------------- With 2 flame fronts (two spark plugs per cylinder) the combustion time = is greatly reduced and therefore power is increased and BSFC is reduced = (fuel economy is improved). No, power is not increased as a result of two flame fronts. The total = burn time is shorter, yes, but that is calculated for in the timing = choice. It is quite possible to go to one mag and INCREASE the power = output. If you takeoff on one mag in almost all of these GA engines, = power output will be higher because the thetaPP will move away from TDC = closer to 16? ATDC where power is at max from mechanical advantage of = the crank. Frankly BSFC does not come into play here, and that's a whole = 'nuther discussion I don't want to get into in this post. I will accept the INCREASE as true, but I find it as very surprising. = However, this can only be explained by the ignition timing is not = correct/optimum for dual ignition at take off RPM's. ??? ------------------- This post has become to long.....relative to octane....don't confuse the = issue by varying timing and octane together....as you pointed out the = latency period of 130 octane fuel is longer. This requires the timing to = be advanced to produce the same angle of peak pressure (thetaPP) This = can not be done in general aircraft real time. My point was...if the = timing was optimized for 100 octane fuel, then there would be a power = loss with 130 octane fuel. Finally, a meaningless bit of trivia, diesel = fuel has more BTU's per gallon than gasoline. Regards, Craig Berland ------=_NextPart_000_00BA_01C50388.4A6B2AA0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Walter, as long as the = discussion/argument remains=20 non-personal, I enjoy and learn. With that said:
 
... don't diminish the effects of a good ignition system. Poor = plugs, bad=20 wires, worn out mag (even hotter spark) all can make a = significant=20 affect for the same reason the RPM drops on one mag vs both. =

Your=20 comments are correct except for the reason the rpm drops on one mag. EGT = rises=20 on one mag because the total burn time is almost half as much as with = two plugs.=20 The rpm drops because the thetaPP becomes excessive.
 
Walter, that is correct. The problem here is you do not buy = into the=20 ignition system performance does affect angle of peak pressure.  = The data I=20 have is viewing very high speed video thru a quartz combustion chamber. = As in=20 everything related to the IC engine, there are numerous aspects that = affect=20 performance and one cannot be ignored while evaluating = another.
----------------------
The idea is to have as fast of combustion as possible without it = being an=20 explosion (non controlled combustion).

No, the speed of the = flame=20 front is determined by the bulk gas temperature and the internal = cylinder=20 pressure. We do not want it as fast as it can be.
 
Yes it is so.  I think you are viewing this as one working = on an=20 existing engine and I view it as one designing a new engine (my=20 background).  My position more clearly stated is...An engine design = that=20 has faster burn will perform better than one with slower burn. (let's = say an=20 engine with peak torque at 18 deg BTC will be less sensitive to = detonation=20 and will have a higher BMEP and lower BSFC than engine with peak torque = at 24=20 deg BTC.
-------------------
With 2 flame fronts (two spark plugs per cylinder) the combustion = time is=20 greatly reduced and therefore power is increased and BSFC is reduced = (fuel=20 economy is improved).

No, power is not increased as a result = of two=20 flame fronts. The total burn time is shorter, yes, but that is = calculated for in=20 the timing choice. It is quite possible to go to one mag and INCREASE = the power=20 output. If you takeoff on one mag in almost all of these GA engines, = power=20 output will be higher because the thetaPP will move away from TDC closer = to 16˚=20 ATDC where power is at max from mechanical advantage of the crank. = Frankly BSFC=20 does not come into play here, and that's a whole 'nuther discussion I = don't want=20 to get into in this post.
I will accept the INCREASE as true, but I find it as very=20 surprising.  However, this can only be explained by the ignition = timing is=20 not correct/optimum for dual ignition at take off RPM's.=20 ???
-------------------
 
This post has become to long.....relative to octane....don't = confuse=20 the issue by varying timing and octane together....as you pointed out = the=20 latency period of 130 octane fuel is longer. = This=20 requires the timing to be advanced to produce the same angle of peak = pressure=20 (thetaPP) This can not be done in general = aircraft=20 real time. My point was...if the timing was optimized for 100 = octane fuel,=20 then there would be a power loss with 130 octane = fuel. Finally, a=20 meaningless bit of trivia, diesel fuel has more BTU's per gallon=20 than gasoline.
Regards,
Craig = Berland
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