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1) Though it is true the volume of air may be similar on the ground as it is in the air, however one definitive factor is this. On the ground with no cowl and no ducting, you can not get air to circulate around the cylinders as it needs to. Air rushing past a cylinder is not the same as air being "forced" around a cylinder. In the air with proper ducting, air is "forced" across the fins and around the cylinder, thus giving a much more efficient cooling effect. 2) Props are loaded on the ground, again... air is not being efficiently circulated around the cylinders. In the air, props unload and the air flowing across the cylinders is a much cleaner and balanced air pressure. 3) Because twins normally heat more on one cylinder than the other, it is especially important to not only duct the motor for proper cooling, but also to use the correct oil. Take a look at how I ducted my 3W 157cs on my SD Models 42% Extra 260. (https://www.flyinggiants.com/forums/...tra+260&page=4) I've now got 44 flights on this once brand new motor. Does it still even with all the ducting I did, heat just a smidgen? According to some, a little maybe. But, (and here is the kicker) I've used a quality oil from day one. I recently inspected the motor for any signs of problems. It is as shiny and new looking inside as the day I mounted it to the airframe. "GOOD OIL". As most do not understand, (and this information comes from over 30 years in the automotive repair industry) Oil is "NOT" just to lubricate a motor. Oil is also designed to cleanse the mechanical movements of an engine as well as help the cooling of the moving parts. If the oil is not cleaning, cooling "AND" lubricating properly, any motor...I don't care who the manufacturer is, that motor is going to seize. Period, no doubts and no second guessing. It "WILL" lock up. From past experience with General Motors Corporation, It is purely possible to run a motor "HOT" and have it continue to run and perform and "NOT" quit or seize up. Reason being is the oil is helping to keep the motor parts cooled. Will it last this way for ever? Not on your life, but certainly long enough to recognize an issue. A good quality oil resists break down of extreme pressures and temperatures. Low quality oils, (Penz) will break down and stop doing their job in a matter of seconds. Liquid cooled engines are no different that air cooled. Semantics actually... I do not for one instant mean to relay the fault is operator error. I will however say that cylinder pitting is most certainly "NOT" normal. Liquid cooled automotive engine or air cooled engine... No pitting should ever be allowed to pass quality inspection. If you were told it was, then basically you were "blown" off by a company that does not want to stand by the product they are marketing. It is also quite evident that the "seized" cylinder is very dry. As in lack of oil residue. A properly tuned motor may seem just a smidgen rich on one cylinder. That is perfectly normal. When properly tuned, you will get efficient lubrication and cooling to all parts of the motor. Last thought, Use a "GOOD" quality oil that is "PROVEN" and has a track record of success. Broke all my DLE's and 3dub in on Red Line. In fact... all my gassers were, even the ones I no longer own. And of those I no longer own, reports tell me these motors still continue to run and preform flawlessly. I fully intend to use it on my next new motor for my Sukhoi. Lastly.....Cool that motor....cool...cool....cool that motor. |
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