I have Electroair electronic single mag on a manual turbo PA 30 Lycoming IO 320 C1A and am reasonably happy with it. I was an early adopter so there were a few issues but they were responsive and it got sorted. Their website has some quite extensive reports on the original testing also the Vans engine forums have lots of material on aircraft with cockpit variable advance. My view is that the manufacturers have shown little interest in their engines beyond liability/ quality concerns for decades so are not a good info source.
The airframe AML is here. You will find the engine AML and all other documents you need, including a sample 337 on www.surefly.aero. There are separate engine and airframe STCs. For NA engines the timing advance can be configured, see the IM also found on their website.
Are you N reg? Otherwise you’ll have to go the single serial number acceptance rout with EASA. A friend of mine did this, it was not a problem.
PetitCessnaVoyageur wrote:
At those low power settings, CHT is not a concern, or sometimes, a bit low :-)
Yes, the reference provided by @Peter in this post provides evidence of exactly that
@terbang
Can you provide STC references including AML ?
Is advanced timing activated for NA aircraft in the STC ?
10% power gain at altitude would be exceptional. At those low power settings, CHT is not a concern, or sometimes, a bit low :-)
That’s a bit sad. Presumably done to lubricate the STC application.
IIRC they couldn’t get it certified otherwise. I think FAA’s reasoning was that if the hose connecting the pressure sensor to the manifold leaks, consequences with a turbo charged engine might be catastrophic: at high altitude and full throttle timing would be advanced to the maximum what would destroy the engine quickly. With a NA engine this would be a non event – manifold sucks with NA engines (as we all know 😉). I find this a bit odd, a broken fuel hose will kill the engine as well (and probably cause a fire). OTOH, as has been said, benefits with a turbo charge engine wouldn’t be huge.
A turbocharged or turbonormalized engine has much less use for advancing the timing because you don’t run it with low MP and high RPM to extract 65% power at altitude. Instead it is run in cruise (at any altitude) with higher MP and lower RPM, which would ideally utilize ignition timing only a bit advanced from the full power timing, if at all.
Our Mooney is turbo charged, therefore the ignition timing is fixed
That’s a bit sad. Presumably done to lubricate the STC application.
Our Mooney is turbo charged, therefore the ignition timing is fixed, exactly as with a conventional magneto. I didn’t expect any performance gain and in fact she isn’t any faster now. I see two or three knots more, but that’s probably because of the new paint and the improved placement of the ELT antenna.
She runs a few degrees cooler I would say, is a bit smoother LOP and the engine starts even better than before (but this was never a problem anyway). All nice to have but it wouldn’t warrant the effort IMO. My reasoning was to have one maintenance free ignition system and a spare magneto on the shelf that can be quickly swapped every 500 hours (or when required).
I was a bit worried as there have been reports of problems with 28V aircraft and trouble during run up. The latter was due to long startup times when switching mags. Both has apparently been solved, we never had any problems.
Installation was a bit of an effort as quite a few parts had to be removed but that is probably a Mooney thing. I did that myself during the last annual inspection under the supervision of my A&P so I can’t say anything about labor cost.
I’m really interested in the topic.
I d love to read feedback from C182 owner !
@terbang: what is the latest with your aircraft ?
Yes, the fixed ignition timing is set for max power. In a gasoline engine development program the timing is varied to determine the angle for maximum power at whatever RPM makes most power based on other factors, always with full throttle. If the optimum is a relatively small advance angle it is indicative of a good combustion chamber design and small bore. That relatively small advance angle then allows use of relatively low octane fuel. Conversely if the angle for most power is relatively large, indicative of large bore and other combustion chamber design factors then higher octane fuel is required. Sometimes a compromise is made with ignition advance set slightly less than optimum for power, to allow for lower octane fuel with the same safety margin.
Once the optimum advance angle for maximum power is set, real time spark timing adjustments can provide more advance to account for lower MP and thereby slower flame front propagation. That increases partial power efficiency. For a car engine this is called vacuum advance and it often means huge ignition advance at small throttle openings (e.g. 50 degrees) For a plane it can mean more advance at high altitude cruise, with the throttle wide open but with low ambient air pressure.
Also, on an engine with a wide loaded speed range, in combination with vacuum advance a smaller timing advance angle is used at low rpm than high rpm – for fairly obvious reasons. A 3D ignition timing map results. However aircraft engines are nearly constant speed engines so RPM variation is not as important. Impulse couplings are enough to retard the timing for startup at low rpm, when turning on the starter motor.
