February 21, 2001 Hot Stuff: Unison's LASAR Ignition System (Part Two)

Email this article |Print this article

by	Dave Higdon

About the Author ... Dave Higdon has a distinguished background in aviation journalism. As aviation editor for The Wichita Eagle for more than five years, he has established a reputation as one of the best general aviation reporters in the business. Previously, Dave held a variety of aviation journalism assignments with The Journal of Commerce, Air Transport World, and AOPA. He has covered every facet of aviation from sport aviation in Tennessee to the FAA in Washington, DC to Cessna, Beech, Boeing and Learjet in Kansas. He's also a professional aviation photographer. Dave is an instrument-rated private pilot and owns a very clean Piper Comanche. He and his wife Annie live in Wichita, Kansas. Articles in This Series Part One Part Two

In the aftermath of Part One of this two-part series on installing and flying with Unison Industries' Limited Authority Spark Advance Regulator ignition system, or LASAR, for short, many readers wrote me, complimentary and kind, inquisitive about various points and, ultimately, impatient for the appearance of this Part Two. Patience may not be its own reward, but patience has finally paid off, as it ultimately had to. Office demands and inhospitable weather finally gave way enough for my bride and me to venture east from Wichita for a Christmas visit to family and friends in southern Indiana and the Washington, D.C. area.

It's our version of over the river, through the woods to the grandmothers' houses. We fly this round-trip route several times a year; more than a dozen times in the past five years. Our final flying trip of the old millennium finally gave me a lengthy trip over a known, well-traveled route, my first since installing the LASAR hardware in late September. It was this final flying of Y2K that allowed me to check the performance of our LASAR-equipped Piper Comanche 180, 1961 vintage, against fuel burn numbers from prior trips flown over the identical route in the pre-LASAR Comanche.

Despite several other long trips and some plain-old, hole-boring flights around southeast Kansas, I still didn't hit the 50-hour mark I had set for delivering this wrap-up of my LASAR system story. But 42 hours of flying time with legs ranging from an hour to nearly five still provided me with a clear view of the system's benefits, certainly enough to offer a few conclusions.

The Executive Summary

My impressions became apparent very quickly, developing with more data into my baseline conclusion you can read right now: LASAR is a move into modern technology that improved our airplane's fuel efficiency and available power. As you'll see below, converting to the LASAR ignition system provided an easy, direct method to improve the performance and efficiency of our aircraft's engine. The benefits include easier starting, smoother running, reduced fuel consumption and improved performance. For you instant-gratification types, a table, below, summarizes the fuel consumption numbers.

Of course, there is no free lunch. The downsides include (with yeah-buts):

• Cost, since the LASAR hardware is relatively expensive, compared to brand-new conventional mags and harnesses, but pays for itself in long-term fuel savings;
• A bit of added weight, but not even two whole pounds; and,
• An increased load on the electrical system, but it's hardly noticeable on alternator-equipped airplanes.

Installing LASAR is something I'd do again to any other airplane of mine used as heavily as our current bird. In fact, my only serious regret is not making the change sooner, say immediately after we bought the Comanche in mid-1997. Had we opted for an ignition upgrade instead of a one-piece windshield at our first annual, the fuel savings alone would have us within a couple hundred hours of recovering our costs.

The Benefits

Easier Starting Is Only The Beginning

You might recall from Part One that installing the LASAR hardware in our Comanche involved overcoming a number of generally minor problems unrelated to the equipment itself; Murphy prevailed over a process in which the ignition switch broke and in rewiring the new switch we literally got some of our wires crossed. But once the wiring was right, the little O-360 Lycoming came to life with an energy and enthusiasm unseen with the old Slick magnetos we replaced.

After more than 20 cold starts since, only once did the engine not light off on the fourth pass of a propeller blade. That happened one cold November morning after the Comanche hadn't been started in more than two weeks. Two shots of primer did the trick, though, a practice I use anytime the plane has sat longer than four or five days. Any other time, one cycle of the throttle to actuate the accelerator pump is all it takes to prime the engine. Either way, the engine seems anxious to start turning. Hot engine, cold engine, flooded engine; the LASAR system overcomes all of them much more easily and quickly than with the conventional magneto-based ignition system.

The reason? Simple: LASAR engages both magnetos for starting, so the engine gets fire from all eight plugs in our Lycoming. And with LASAR providing four times the spark voltage at start, compared to the conventional system, even engines with old, slow-turning starters like ours should fire up faster with less wear and tear on the starter and battery. Less work by the battery and starter should improve their lives, an intangible source of some savings.

The week before I put the finishing touches on this Part Two, the Comanche went in to "Dead Cow International" (Westport, Kan., 71K) for its annual inspection and the condition of the Autolite plugs we installed during the LASAR conversion was hard to believe. More than 42 hours of flight time and they look like they just came out of their plastic shipping sleeves. No trace of lead contamination, not even a little residue. Remember this point the next time the shop tells you that one or more plugs suffered terminating damage while a mechanic tried to clean lead-fouled plugs and salvage them for one more year of service. Less need to clean translates to less physical abuse and reduced exposure to the potential for cracking an insulator or damaging the conductive surfaces.

How LASAR reduces your potential to lead-foul plugs goes to the heart of the value of variable timing.

Speed Vs. Economy 101

You Still Make The Choice And You Still Win...

Basically, as we explained in Part One, the LASAR system reads engine speed, crankshaft position, manifold pressure and cylinder head temperature to calculate the best point in the combustion cycle to send a spark through the plugs. The result is a combustion event perfectly timed for the engine power you set. In contrast, conventional mechanical magnetos fire plugs at a fixed point in the engine's rotation, a compromise that delivers peak performance at one and only one setting. Run the engine at any other load or speed and the timing is no longer optimum, resulting in some wasted fuel and reduced efficiency.

But that isn't the case when the spark plugs fire at the perfect time. For example, say your engine is set to fire the plugs at 26 degrees before top dead center (BTDC). With the conventional ignition system, you can lean the mixture beyond the point where it would run smoothly at the fixed 26 degrees BTDC. Instead, the LASAR system uses its electronic "brain" to adjust the spark timing for optimal ignition timing, based on a "map" of various RPM and manifold pressure combinations it stores on some silicon. It's this ability to adjust the ignition timing to suit the operation that produces reduced fuel consumption and improved power at all power settings. In turn, the reduced fuel consumption, cleaner spark plugs and easier starting all combine to pay off the investment in a LASAR system.

...But, How Much Do You Win...?

My experience has varied, of course, just as Unison gives a range for fuel savings from 8 percent to 12 percent. At altitudes above 6,000 msl, with the engine leaned to peak EGT, our Comanche's fuel consumption has varied from as little as three quarts per hour lower than before, to as much as five quarts per hour. In no case, significantly, has fuel consumption increased.

The best numbers first showed up flying home non-stop from New Orleans after the NBAA's Annual Meeting and Convention in mid-October 2000. Flying at 8,000 feet, with the engine set for 75-percent power, the Comanche consumed 42 gallons of 100LL during a 4.3-hour flight, compared to the 47 gallons typical for similar legs before. That works out to 1.25 gallons an hour less gas. The week before, on an IFR flight southbound to NEW, pulling 75-percent power at 7,000 msl, the Comanche consumed 41 gallons during a four-hour leg. On previous flights at the same altitude, power and duration, the Lycoming consumed 44 gallons. The savings worked out to not quite one gallon per hour.

At a fuel price of $2.50 a gallon, to use an easy example, saving five quarts an hour translates to an operating-cost reduction of $3.13 an hour. Saving .9 gph cuts the hourly fuel costs by $2.25.

Like to fly for best power instead of best economy? The same savings curve applies here as well, compared to the best-power consumption levels of past trips.

...Another Real-life Example...

For another example, on December 23 we flew nonstop to Leesburg, Va. (JYO), from Clark County Regional Airport (JVY) in Jeffersonville, Ind., my hometown on the Ohio River. Level at 7,000 msl with the engine set for 75 percent and 100 degrees rich of peak (ROP), the Comanche consumed fuel at a rate of 10.2 gallons an hour in cruise, compared to 11.3 GPH before. The entire 2.6-hour leg required 29.2 gallons when we topped off at Leesburg, versus 32 and change before. The return flight at 6,500 msl and 75 percent took 2.9 hours and the fuel tab came to 33 gallons. On that leg, the in-cruise fuel consumption was 10.3 gallons an hour.

Interestingly, these best-power legs gave me true airspeeds of about 146, between three and five knots faster than before, while the best-economy legs came in at about the same true airspeeds of 137, about the same as before.

For those of you trying to make the math work, a note: After nearly 600 hours in the Comanche, it's consistently shown to burn about three gallons an hour more during the first hour than it does in cruise, where climbs didn't go above 9,000 feet. But to eliminate any fudge factor, all four examples used here were confirmed by flying cruise legs precisely timed on one fuel tank, using the other tank for the takeoff and landing legs. Of course, overseeing the refueling process was necessary to assure myself that the lineman brought the fuel back to a starting point marked before the prior departure. And the lower hourly fuel-consumption numbers applied almost exactly to both tanks.

...Putting Them All Together

While not as precise as using a fuel totalizer, this method is close enough for me to be comfortable with my numbers. The before-and-after data presented in the table below sums up the results I've obtained so far.