Recently, in another article, I discussed the installation of electronic magnetos on the PA-30.
It’s important to understand that the STCs (“Supplemental Type Certificates”) offered by electronic magneto manufacturers are essentially identical in their basic purpose.
You replace an older, heavier component with a lighter and more efficient one. The main objective is to eliminate the need for costly magneto overhauls — and that’s exactly what the STC authorizes.
The Non-Guaranteed Benefits
Now, there are advantages that are not part of the STC — things like easier engine starts and fuel savings in cruise as a result of improved combustion efficiency.
Manufacturers “guarantee” only that their magnetos will run beyond 2,000 hours without maintenance. That’s it.
The other attractive claims about performance improvements are not listed in the STC — meaning: not guaranteed.
The reason is simple — the certification flight testing process and the cost of producing new performance charts for each approved aircraft type would be prohibitively expensive.
Therefore, the manufacturer simply advises you to continue using your aircraft’s original performance charts.
Of course, fuel consumption will likely improve noticeably, but the original charts remain valid by default — and, following installation of electronic mags, they become quite conservative.
On some manufacturers’ websites, many satisfied customers share testimonials describing the benefits, though without precise numbers.
Each pilot who comments on performance gains flies their aircraft differently and usually lacks the test-pilot background to quantify results. Rest assured, I make no such claim myself.
It’s also worth noting that manufacturers holding an STC are not required to produce their product under the same strict standards as an aircraft type certificate.
Their first obligation is simple: “First, do no harm.” As long as the aircraft’s airworthiness isn’t degraded, that’s sufficient.
As a result, even if performance improves, those gains remain unofficial.
Flight Data — Fun with Numbers
Since acquiring the PA-30, I’ve been logging cruise data for every flight. Some might call it overkill, but combined with an engine monitoring system, this provides tight tracking of both engines and the airframe overall.
Over the years, various aerodynamic STC installations have shown favorable results, with clear improvements in true airspeed performance.
The story with the electronic magnetos, however, has been somewhat different.
Let’s set aside the well-known benefits for a moment:
- Elimination of costly magneto overhauls
- Easier starting
- Noticeable empty-weight reduction
So what about fuel savings from more efficient combustion at altitude for a given power setting?
Flying at Peak EGT
In general, I cruise at about 65% power at peak EGT.
Lately, I’ve even been running 50°F Lean of Peak (LOP) — sacrificing a few knots of TAS for the sake of efficiency. (I’ll return to LOP operations in a future discussion.)
At Peak EGT, around 8,000 feet, I’ve recorded a consistent average fuel flow of 14.6 GPH with 22.0 inches of MP and 2,350 RPM.
For reference, the PA-30 is equiped with Lycoming IO-320 engines.
Observed true airspeed: 160 KTAS at 3,500 lbs gross weight.
Yes — the various aerodynamic mods on my PA-30 since it left the factory have given it about 7 KTAS more than the original POH values.
Flying Fast, but Smarter
In my flying “neighborhood,” a good cruise speed is always appreciated.
However, with the SureFly electronic mags installed, when leaning to peak EGT, the true airspeed took a noticeable hit.
Yes, fuel flow dropped impressively to 13.5 GPH, but true airspeed fell from 160 KTAS to ( ouch ) 156 KTAS, at a constant weight of 3,600 lbs. At 3,400 lbs, of course, TAS improves slightly.
The original Lycoming performance charts are no longer valid with the new magnetos. So how can we now determine engine power output in horsepower? The goal was to find the actual power produced with the electronic mags.
You might think working backward from the TAS vs. density altitude chart could yield an approximate “established power. “But in the case of my PA-30, that’s imprecise — those charts assume conventional magnetos, 91/96 octane fuel, and an unmodified airframe with higher drag. I know, I know what does drag has to do with power.
Falling into what I call the “Overthinkers Anonymous” club (famous from AOPA’s Ask the A&P podcast), I took a different — and certainly unnecessary — path purely out of curiosity.
If you’re still reading at this point, hang in there!
Average Cruise Data (Old Magnetos, 100LL)
| Setting | Value |
| MP/RPM | 22.0” / 2350 |
| Mixture | Peak EGT |
| Total Fuel Flow | 14.6 GPH (2 × 7.3 GPH) |
| True Airspeed (Old System) | 162 KTAS (thanks to drag reduction) |
Thermal and Aerodynamic Efficiency
Next, I looked at thermal efficiency, expressed as Brake Specific Fuel Consumption (BSFC) in lb/HP/hr.
For context, this is a theoretical concept taught in Canada’s commercial pilot curriculum.
Typical Lycoming engines have a BSFC of about 0.420 lb/HP/hr, while data suggests that engines using electronic magnetos achieve roughly 0.406 lb/HP/hr — a modest but meaningful gain in efficiency.
I then combined this with aerodynamic efficiency, expressed in nautical miles per gallon (nm/gal). (Sorry, metric purists — I admire you, but switching units here would only add confusion.)
The results in the table below are preliminary, but clearly conclusive.
Touch-and-Go Performance? Not the Point.
So what does this all mean when I’m sitting back comfortably at 7,000 feet?
The POH indicates an endurance of 6.5 hours in economy cruise ( peak EGT ), landing with a 0.5-hour reserve. And just to be clear — operating with such tight margins is not recommended.
Recently, after a smooth 6-hour-14-minute cruise, I still had 2.1 hours of fuel remaining in the tanks.
For many, flying 6 hours non-stop is unthinkable. Naturally, a very simple “organic evacuation system” is carried on board. Still, that kind of endurance is appreciated — leaving generous fuel reserves upon landing.