X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [68.31.44.10] (account marv@lancaironline.net) by logan.com (CommuniGate Pro WebUser 5.0.5) with HTTP id 906922 for lml@lancaironline.net; Fri, 30 Dec 2005 23:12:02 -0500 From: "Marvin Kaye" Subject: Re: [LML] Re: Where has all the power gone? To: lml X-Mailer: CommuniGate Pro WebUser v5.0.5 Date: Fri, 30 Dec 2005 23:12:02 -0500 Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format="flowed" Content-Transfer-Encoding: 8bit Posted for "George Braly" : Gary, Please.... absolutely no trepidation required. I screw up and get things wrong, all the time. So feel free to jerk my chain when you think I have stepped off of the reservation. However, in this case, it is not my theory. The 15d ATDC as optimal for location of peak combustion pressure in internal combustion engines is a published thermodynamic "proof". I first read it about 7 years ago. I have looked around, but do not find it, handy, or I would give you a reference. Frankly, the math was over my head in the proof, at least for the amount of time I was willing to devote to reviewing the matter. But I could sure as the devil appreciate the benefits to be realized by further investigation. Real world testing shows that the 15d ATDC in the theory conforms to reality to a remarkably close tolerance. For very high RPM engines, it appears to be down at 13 (+-) degrees. For some slower turning engines, it may be around 16 degrees. As it turns out, at very high power settings, the delta Hp across a theta-pp varying from 13 to 17 degrees is VERY small (holding MP, RPM, & F/A constant). By contrast, the magnitude of the delta in the peak pressure is not insignificant at all. Your comments about turbulence as a function of RPM are spot on, as well as most of the balance of your comments. I'm not sure the RSA metering responds to air density ^.5. That is an interesting way of looking at the issue but I have not seen that before and I don't know why it would actually be set up that way, if they have done so. Obviously, by design, the RSA system is responsive to dynamic pressure in the fuel metering servo as the first input, but I'm not sure how the internal fuel metering is scaled off of that input variable. Which is why I was asking for some more information and flight data on that subject. Regards, George