Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.
Issue link: http://experimenter.epubxp.com/i/149316
Un d e r t h e C o w l 2013 issue of Experimenter.) He also does contract work for many others on his dynamometer so he was happy to hook his new engines up and run them. He said, "We weren't hired to test these engines; we bought them for our own airplanes. Our tests didn't depend on their being nice to us." Still, he noted that ULPower's responsiveness was great: "Whenever we needed anything, they've just sent it right away." Te 7-main crankshaf is well-supported. As for performance, Scott noted that his four-cylinder 350iS ran closer to its rated power than most, at 118 hp. One would expect even closer performance-to-rating from the sixes, because many of the components that use horsepower—the alternator and oil pump, for example— are the same across models and thus represent lower proportionate horsepower drains. He also noted, "When you get to 3300 rpm, you hit the [automatic electronic] rev limiter, so we didn't test beyond that. Best torque is around 2500," which is great for takeoff since fixed-pitch props don't reach full rpm until there's some airspeed. Billet 4140 steel cylinders are stable and tough. Te piston has cutaway for combustion and valve clearance. 32 Vol.2 N o.8 /August 201 3 It's important to understand the difference between manufacturers' ratings and real-world performance. Scott said, "Pretty much no matter how you arrange cooling blowers in a dyno room, you won't get cooling that's as good as what you see in the air, at speed. So, temperatures ramp up pretty fast, and sometimes because of that, dyno runs are not representative of the maximum achievable horsepower. Offsetting this, a lot of (especially manufacturers') dyno runs are on 'optimized' engines, where all adjustments are perfect, where the spark plugs may have been indexed, where there's (nonrecommended) lightweight oil, and only the minimum quantity of oil may be in the crankcase, or where accessories may be disconnected. Some shops are known to alter the ignition timing from specification, or to run the valve tolerances a bit tight—all in the name of 'enhancing' the horsepower rating." Scott preferred to run "real-world" tests, with the engines as-is, with the right oil, and with the alternators producing 15 amps. (The two coils each use about 5 amps at cruise and 6 amps at full speed.) Also, it's worth noting that instrument readings may be imperfect. "At 3300 rpm, a single foot-pound of torque gives a big boost to horsepower," Scott said. That, too, is telling. Exactly how accurate and repeatable do you think anybody's dyno stand is, day after day? "Don't put too much stock in variations of under a percent," he added. Scott just took the engines from their crates, hooked everything up, poured in the oil, checked everything, and ran them. His summary (as a customer, not a hired gun): "Of all the engines I've tested, I'd say it's one of the nicer pack-