X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [69.171.58.236] (account marv@lancaironline.net) by logan.com (CommuniGate Pro WebUser 5.0.8) with HTTP id 1047806 for lml@lancaironline.net; Mon, 27 Mar 2006 00:38:05 -0500 From: "Marvin Kaye" Subject: Re: [LML] Re: Prop Overspeed - Auto Engine Analogies To: lml X-Mailer: CommuniGate Pro WebUser v5.0.8 Date: Mon, 27 Mar 2006 00:38:05 -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 "richard titsworth" : A personal view on auto conversions.. I love airplane engines (read lyco/cont), but it's based on my personal value "tradeoff", not based on OWT (Old Wise Tale) of engine capabilities. It is certainly true that normal family car engine performance/usage/duty profile is quite different that a typical GA aircraft (even for Corvette's - unless perhaps you live at Bonneville). However, to use a typical auto engine duty cycle to compare the "capability" of aircraft and auto engines is a bit misleading (i.e. OWT vs fact/engineering). Selectively, auto engines are "capable" of much more than driving to the grocery or grandma's (especially if/when setup for a specific application). Likewise, attempting to use a NASCAR/racing engine as an comparative basis aero/auto engine capability is also pretty misleading - they're, designed for "ultimate" HP and aren't intended for extended durability (beyond perhaps 600 miles). For comparison purposes, the "capability" of a (properly setup) auto engine (in an aircraft sense) is somewhere in BETWEEN "workday commute" and "winners circle". While not at all perfect, other analogies exist which provide a better basis for comparing "capabilities" and advantages/disadvantages of auto and aircraft engines. For example, my LT1 (corvette motor) based ski boat spends most of its life around 4000+ RPM with an ungodly number of full throttle starts - probably more "take-offs" than a normal Lyc/Cont ever sees (perhaps some C152 "pattern zombie" trainers that can top it). This is much more analogous to a typical GA aero engine and demonstrates the potential for similar aero/auto engine capabilities. Additionally, It runs with V8 smoothness, but is subject to constant vibration from waves and my unbalanced "dinged" prop, through a geared drive unit. It spends most it's life in a wet/humid environment. It spends winter months just sitting (never fogged it) and it still re-starts each spring. Any idiot can start it - just turn the key - no need to touch anything else. It doesn't need special (overly toxic and expensive) fuel - it's electronic control unit adjusts for the operating conditions and octane used (knock detection). It doesn't get oil changes every 25-50 hours. It's spark plugs last virtually forever (hence doesn't need two per cylinder) and can be purchased at Walmart for a few $. It doesn't benefit from enhanced engine gauges (CHT, EGT, etc) to allow intelligent operation - in fact in the hands of some of my "lake friends" it gets rather rough treatment. It once ran without any cooling water (hose was disconnected), momentarily overheated, and still runs fine. It once had a fuel pump failure and still got home in "limp home" mode. (Those events due tend to highlight the danger of complexity and the need for redundancy in an aircraft application). It provides well over 300 HP in the stock/factory configuration. HP performance improvements can add 50-100% to that. Personal/anecdotal experience aside - this is typical usage/capability for auto engines in marine applications. Aside from lake water vs radiator for cooling, some added redundancies, and attention to a few high weight components, an aircraft auto conversion could be similar. Have to add one OWT, since I am also not immune to their fun. A former (4 cylinder auto engine) boat of mine run fine after being "totally submerged" for a few days (don't ask). I left it in the boat, drained and replaced the oil (milky watery mess), dried out the distributor, and purged the water from the cylinders by cranking it with the sparkplugs removed. Presto, it ran fine till the day I sold it (forgot to provide that part of it's history to the new owner - oh well). Perhaps not a great analogy - but an interesting OWT on the potential for extreme durability. Commercial trucks/busses typically run for "several" thousand hours (way over 2,000 TBO) and I was once told that diesel locomotives (some of which are over 30 years old) run for months without ever being shut off, sometimes in high HP uphill routes, (unverified - any locomotive experts out there?). Those are poor analogies, but do provide some awareness of the potential range of operating envelopes of various piston engines. Auto and aircraft engines have been engineered/set-up for different applications and thus provide different advantages/benefits and limitations/drawbacks. It's not that either is simply any better/worst overall. Both have been improved over time through creativity, science, and testing on the part of "teams" of professionals (there is no "magic" in either). Autos benefit from the economics of relatively high production volume, a highly competitive global marketplace, the desire for idiot-proof operation, and relatively benign "land based" failure scenarios. Aircraft benefit from the "assumption" of a relatively intelligent/competent pilot (trading increased operator workload for mechanical simplicity/durability - i.e. mixture and temp monitoring), acknowledgement of efficient prop RPM's limitations, designed-in redundancy on critical items (mags), and a heightened economic payback for weight reduction. History has demonstrated successful liquid cooled engines in (production) aircraft and successful air cooled engines in cars, when setup/engineered accordingly. Likewise, there have been good (and bad) conversions/installations of auto engines for experimental aircraft. In all cases, it implies a knowledgeable/factual acceptance of the tradeoffs. Those are ultimately personal and the purview of those in the "experimental" world with the time/energy/values to pursue them. For those traveling that path, I respect their motivation and dedication, more power to them - pun intended :-) Rick