X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [65.33.163.227] (account marv@lancaironline.net) by logan.com (CommuniGate Pro WebUser 4.3c5) with HTTP id 942196 for lml@lancaironline.net; Thu, 12 May 2005 20:53:28 -0400 From: "Marvin Kaye" Subject: Re: [LML] Re: Plasma III on Hi Compression Engines To: lml X-Mailer: CommuniGate Pro WebUser Interface v.4.3c5 Date: Thu, 12 May 2005 20:53:28 -0400 Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset="windows-1252"; format="flowed" Content-Transfer-Encoding: 8bit Posted for "George Braly" : Colyn The PRIMARY reason for using 8.5:1 CR on the 550 with turbo’s is to manage the TIT. Not Hp. They also do get a bit more efficient. The gain in fundamental Carnot efficiency from going from 8.5 to 10:1 compressions is really pretty small. This is an area with a rapidly declining rate of return. It is worth doing in normally aspirated engines - - because they get some Hp with the change to higher CR. But in turbo’d engines, you can get the same Hp increase by adding boost which is much easier and keeps more options available. So, there is very little reason to go much past 8.5 : 1 compression ratio in turbo’d engines - - since the goal of managing the EGTs and TIT limits at the turbine are fully realized by going from 7.5:1 up to 8.5:1. Regards, George PS: REMEMBER, sometimes the enemy of good - - - is an attempt at better. """" Okay -make me ask: Let's suppose I crank my FF to 46 gph WOT full rich for climb and LOP for cruise and have a prism system. (all help manage CHT), and let's say I manage to keep CHT's below 350 at all times. how far can I push the CR on a TSIO-550 without having a detonation problem? """