X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [66.94.81.250] (account marv@lancaironline.net) by logan.com (CommuniGate Pro WebUser 4.3.6) with HTTP id 625162 for lml@lancaironline.net; Thu, 04 Aug 2005 17:15:21 -0400 From: "Marvin Kaye" Subject: Re: [LML] Re: Lower Cowl Air Temperature - Induction Air - Heater Air Temp To: lml X-Mailer: CommuniGate Pro WebUser Interface v.4.3.6 Date: Thu, 04 Aug 2005 17:15:21 -0400 Message-ID: In-Reply-To: <6f51d6a9d328febf83f9e57ad6cefa3c@advancedpilot.com> References: <6f51d6a9d328febf83f9e57ad6cefa3c@advancedpilot.com> MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format="flowed" Content-Transfer-Encoding: 8bit Posted for Walter Atkinson : Scott: I agree with all of those premises. I also think it wise to consider the effect that the high IAT has on non-intercooled systems. I'm concerned about that effect as it is significant in narrowing the detonation margin. A 100dF rise is not an insignificant rise in IAT in that regard. I think you might find that any reduction in IAT from fuel vaporization at the cylinder induction port will be insignificant. Walter """ I measured lower cowl air (in my airplane only) at its hottest place accumulating all of the heat created, not at the cooler front engine area where the filter draws its air and I found that, generally, the air entering the induction system was at its worst about 100F above the ambient.   I measured the air exiting from the heat muff, a source of carb heat air, and found it hotter and sometimes un-measurable with the temp probe display I had available because it was limited to 99C (210F).   Carb air temp probes are useful in that they measure the temperature of the Fuel/Air mixture and, as such, point out that the combustible mixture is cool enough even after HOT carb heat air is added.   It seems that filtered under cowl air would be usable in an injected environment after raising the initial induction air by 100F, passing it thru the oil sump (just like many carb engines) and finally cooling it down by the F/A atomization at the cylinder head.   If used early in the takeoff phase, the engine will suffer a power loss on the order of 5% to 10% because of the rise in temp (not the total temperature of the air).   This is significant in a commercially built under powered airplane...  It is less significant in something like a Glasair or Lancair because there is an abundance of power available.  Of course, rational pilots using such a system would understand that performance is negatively affected and could choose to use the ram air in questionable circumstances. """