STORTRANF RHIIDFR Tony Bingelis •
ITTti While some builders will candidly However, we sometimes toy with the Coping With A Fuel admit that their tight cowlings create unidea of making changes for no compelSystem Vapor Problem expected problems, they are somewhat ling reason. I'm sure you have heard If you suspect your installation would less willing to admit that they are comthe admonition, "If it ain't broke, don't pletely satisfied with their engine instalfix it." So, be careful. You could be con- be vulnerable to fuel vapor problems on lations. Here are a few examples of templating changing what has proved those 100 degree days, or you have alwhat bugs them the most. to be a fairly reliable installation, for you, ready experienced a vapor lock problem, here are a number of countermeaA builder experiences what he beinto something that may look better but lieves to be an occasional fuel system could actually become a failure prone sures you might want to try. The trick is to keep it cool, man. vapor problem .. . but only on hot days. feature. Keep the fuel lines cool, the gasA scary experience. Anyway, now that that reservation A surprising number of builders are has been entered in your memory bank, colator cool, the engine driven fuel pump cool, and you will probably have perturbed because blisters and charred let's review a few specific problem eliminated the vapor lock problem in areas are appearing in the cowling areas and the way others cope with spite of a closely fitted cowling. finish . . . obviously, where the exhaust them. This assumes that, if you are using stacks pass too close to the cowling. First, The Logical Precautions auto fuel, you are using fuel that is seaAnother commonly experienced diffiGive your initial attention to securing sonally correct and that its vapor presculty is the prevalence of cracked and and safetying everything properly. sure is not excessive, otherwise, that of broken exhaust stacks, particularly at See to it that your hoses, lines, wiring itself might become a contributing culwelded joints and adjacent to heat and engine controls cannot possibly rub prit to the problem. shrouds and muffler clamps. This is a or chafe against sharp edges where You can believe your EGT (Exhaust more frequent occurrence than you they pass through the firewall metal. Gas Temperature gauge). The exhaust would expect. Often these failures Now, for some specifics. gases leaving the engine cylinders and occur in a new installation after only a few hours of operation. And, still another complaint. Most builders, in time, become quite annoyed ENGINE BREATHER HOSE FITTING 75". with the amount of oil coating the belly of the airplane after each flight. Blame that on an overly abundant oily mist passing through the engine breather line. Then there are more serious ailments. Overheated magnetos and the alternator may be suffering from heat prostration . . . without any early symptoms. These vexations seem to plague some builders and not others. Engine compartment problems and annoyances of this type are more prevalent in homebuilts today than they were in the past when simple installations for the old 65 hp Continentals and SUMP the small Lycomings were the rule rather than the exception. RUBBER HOSE (V4" I D .) Today our engines are more powerful and the installations more complex, ALUMINUM EXTENTION making it increasingly difficult to fit everything into the confines of tightly contoured pressure cowlings. Furthermore, these larger engines generate much more heat, a thing they seem to do best to get the added power. That, of course, creates more entrapped heat and additional problems for the homebuilder. FIGURE I. As any builder knows, an initial engine installation can almost always be OIL BREATHER/SEPARATOR INSTALLATION improved later with a little retrofit work here and there. SPORT AVIATION 29
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It seems like a good idea and works to a degree. However, a more effective cure is possible with the installation of an OIL BREATHER/SEPARATOR to minimize oil losses without restricting the normal breathing of the engine. This is a firewall mounted gadget that looks something like a small high technology coffee percolator. Some Piper aircraft utilize these separators for their Lycoming installations. Maybe you can find one in an aircraft salvage yard or at some fly-in "Fly Market" or "Country Store." However, an enterprising builder could make his own. Both Aircraft Spruce & Specialty Co. and Wicks Aircraft Supply carry a separator with 5/8" outlets which was originally intended for use with Continental engine equipped VariEzes and Long-EZs. In a typical installation, the oil draining from the separator is returned to the engine crankcase oil supply and the separated oil-free engine breather air is dumped overboard. I have always used the engine oil filler neck as a return point for the oil draining from the breather separator. This required tapping a hole (1/8" pipe) into the lower end of the oil filler neck. I then connected a 1/4" oil return line from the oil breather/separator to a suitable fitting at the filler neck. If you want to do the same thing, you should first mark the spot you want the fitting hole to be located before unscrewing the filler neck from the engine. This will ensure that your hole, when drilled and tapped, will be in a location where it will be accessible after reinstalling the filler neck. Also, don't forget to resafety the filler neck after reinstalling it.
Magneto Blast Tubes Magnetos also suffer from excessive
When the engine is shut down, these two freely hinged ventilator doors drop down and allow engine heat to dissipate more rapidly. The idea is to help cool the fuel distributor mounted on top of the fuel injected engine thereby reducing hot starting problems.
engine compartment heat. To be on the safe side, install a short curved 1/2" tube that will direct cooling air over the magneto case from an opening in the rear engine baffle. Alternator Cooling Air Many alternators, especially those lightweight, inexpensive 25-35 amp. units builders are installing in their homebuilts, come from Toyotas, Datsuns, and similar vehicles where they operate in a different environment. Installing one in your homebuilt without providing it with adequate cooling can cause the alternator to be short lived. That is, its diodes could be "fried" due to a lack of cooling air through the rear of the unit where the diodes are located. The remedy is to pipe ram air from a one inch hole in the front baffle to the back case of the alternator through a length of SCAT ducting. The difficult part is devising a means to position and secure the outlet end of the ducting so that it blows directly at the rear case of the alternator. There are all kinds of alternators so it would be a good idea to determine whether or not your particular installation requires any special treatment like
changing the pulley size, replacing or removing the fan blades, or piping cooling air into the laternator case, somehow. Check with your local alternator shop .. . I've already told you everything I think I know.
If you wish to contact the author of this column, Sportplane Builder, for additional information, please write to Tony Bingelis, 8509 Greenflint Lane, Austin, TX 78759.
BOOKS BY TONY
The following books by Tony Bingelis are
available from the EAA Aviation Foundation,
EAA Aviation Center, Box 3086, Oshkosh,
Wl 54903-3086, 1 -800/843-3612, in Wl 1-800/
236-4800. Major credit cards accepted. - Sportplane Builder (Aircraft Construction Methods, 320 pages) - $17.95. - Firewall Forward (Engine Installation Methods, 304 pages) - $19.95.
- Sportplane Construction Techniques (A Builder's Handbook, 350 pages) - $20.95.
Shown here is a heat shield to protect the cowling from being scorched by the hot exhaust pipes that run parallel (and very close) to the cowling. The stainless steel heat shield is clamped to the exhaust pipe with stainless steel clamps. 66 DECEMBER 1990
Add $2.40 postage and handling for each publication ordered . . . or order all three for $52.97 plus $6.95 postage and handling Wisconsin residents add 5% sales tax.
