Q: The O233 LSA engine uses the new E-mag electronic ignition that they say advances the timing to 38° BTDC, much like other systems. Does this much spark advance also have Lycoming’s blessing for the O320 and O360? I realize that the spark advance is rpm and manifold pressure controlled.
LYLE FORSGREN, via e-mail
A: Lycoming is putting forth an all-out effort to focus on new technology and the electronic ignition system is probably one of the first results of its efforts. I’m certain we can look forward to several new exciting things like this to enter the marketplace in the not-to-distant future. While we all understand the market is a bit down, it’s quite evident more concentrated efforts are being put on research and development during these slow times. While it may be difficult to justify the expense during difficult financial times, the rewards will come for all of us as the industry rebounds and this new technology is incorporated into the products of the future. Hopefully, the engines currently in operation will be the recipient of some of this new technology as retrofittable options.
Let me step back in time a bit and tell you about a system that I watched develop during my time at Lycoming. Unison, the parent company of Slick Magnetos, introduced an electronically enhanced ignition system known as LASAR (Limited Authority Spark Advance Regulator), which was used on not only production engines at Lycoming, but was provided as a retrofit kit for field installation. One of the benefits of this system was that it provided a much hotter starting spark (200-300% hotter) than the conventional mag system — great for those of us who operate in cold climates.
Basically it used a pair of electronically enhanced mags controlled by a preprogrammed computer chip, which was developed after the specific engine model operating parameters were mapped at Lycoming.
The purpose of the system was to allow the engine to operate at optimum performance, say in a cruise power configuration. To do this the system monitored engine rpm, manifold pressure and cylinder head temperature. Alarm thresholds, dictated by the specific engine model, were programmed into the chip, which controlled the system so that no operating parameters were exceeded. Once the engine was in a cruise configuration, the timing was allowed to advance per the preprogrammed computer chip. As the timing advanced the cylinder head temperature would begin to increase and the EGT would begin to decrease as a result of better combustion taking place within the cylinder. With the timing continuing to advance, the CHT would continue to rise until it reached the preset alarm threshold programmed into the computer chip.
If we look at the Lycoming Operators Manual for the O-320 series we see the maximum CHT is 500° F. When the alarm threshold was burned into the computer chip it was probably set at 475° F. When the CHT reached this point, the timing would begin to retard to bring the CHT back down to a predetermined temperature, then advance again so that the engine was always operating at the optimum performance. Yes, it is possible that the timing would advance as far as 38°. Sitting in the aircraft you had no notion of what was taking place under the cowl except that you were benefitting from this new technology that allowed your engine to operate more efficiently than you could do by doing it with fixed timing.
There were other benefits this system, which was the beginning of the technology that will help our industry move forward and provide more efficient engines. This type of technology will also help lead us to systems that will make it easier for us to adapt to the aviation fuels of the future.
By the way, these new systems will be suitable for most, if not all, new engines and I would think be available for retrofit of those engines currently in the field.
It’s things like this that keep the future of general aviation looking bright and exciting.
Paul McBride, recognized worldwide as an expert on engines, retired after almost 40 years with Lycoming. Send your questions to: AskPaul@GeneralAviationNews.com.