Return-Path: Received: from [65.33.167.114] (account marv@lancaironline.net) by logan.com (CommuniGate Pro WebUser 4.2b1) with HTTP id 3131050 for lml@lancaironline.net; Sun, 28 Mar 2004 09:48:40 -0500 From: "Marvin Kaye" Subject: Re: [LML] relative temps? To: lml X-Mailer: CommuniGate Pro WebUser Interface v.4.2b1 Date: Sun, 28 Mar 2004 09:48:40 -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" : Wow... Almost everybody is "right" in their comments on this ... and yet the important stuff is being missed. Right now, we don't have enough data from Scott Kruegar to know for sure what is or isn't important. He says ... "Lasar ignition will lower EGTs by 70-90degrees." Somebody else says it doesn't matter, because it is "relative" Please...let's back up. 70-90 degree change in EGT in relation to "what" ? 1) What the engine EGTs WOULD be if it had two properly timed standard magnetos? 2) What the engine EGTs are on ONE magneto ? Compared to ONE Lasar System operating? 3) What the engine EGTs are on both of the standard backup mags in the Lasar system operating without Lasar doing its electronic thing? 4) And is this 70-90 degee drop observed at full power ? Or only in cruise? Or both? So, Scott, help us a bit please? Data, please? If I take off in my engine at book 300 turbonormalized Hp, 22d magneto spark timing, and book fuel flow, the EGTs will be operating around 1250 to 1300F. At 50dF LOP in high power cruise, the EGTs will be about 1450F. IF .... IF ... I advance the timing about 4degrees, and keep everything else the same, I will DROP those EGT temps by somewhere between 60 to 90d F. If I am at takeoff power, that will be a VERY bad thing. VERY VERY bad thing. That will make the peak internal cylinder pressures go up from about 950 PSI up to something like 1050 or 1100 PSI. That is very close to the "drop off the cliff" kinds of bad changes. If I am at 225 Hp, LOP in cruise, it *might* be just fine, although the CHTs will rise considerably (about 25F or so). In this instance, the change in EGTs - - would not be "relative" at all, it would be meaningful to know what the absolute value of the EGTs was before invoking LASAR and afterwords. On the other hand, normally, all EGT readings are only referenced to peak EGT (or TIT) and in that sense, their absolute value is much less important. So...Scott, can you get us a more robust description? Regards, George