Electronic ignition possibly certified soon

[mtuomi]

I feel your pain...

There are only a handful of guys I work with who are truly masters of our ECUs and know exactly which table or field to modify to get the desired test conditions. When all else fails they're the ones getting a call.

Yeah, I'm that guy who gets the calls when all else has failed

What ECU types are you working with?

 

[Ted]

Still figuring this ECU type out myself. The function description documentation is 38000 pages of flowcharts though so it will be a while

Oh, is that all?

 

[mtuomi]

Oh, is that all?

It's also obviously all in German

 

[Ted]

It's also obviously all in German

Here's a guide to help you decipher.

 

[mtuomi]

Here's a guide to help you decipher.

Haha, that's very true

I actually speak technical German pretty well, but my social/everyday German is almost non-existent. So I understand things like
"Untere Grenze für Reduktionsfaktor der maximalen Luftfüllung bei Anschlag Bauteileschutz an Fettgrenze" easily (that was just a random copy paste from Bosch), but if I'd have to say "have a great day", I wouldn't have a clue

 

[Ted]

I actually speak technical German pretty well, but my social/everyday German is almost non-existent. So I understand things like
"Untere Grenze für Reduktionsfaktor der maximalen Luftfüllung bei Anschlag Bauteileschutz an Fettgrenze" easily (that was just a random copy paste from Bosch), but if I'd have to say "have a great day", I wouldn't have a clue

I could understand that for sure.

At one point years ago, I did work with a German company on technical matters. I think in those days I probably was better able to understand some of the German warnings that popped up in their software. Today I'm sure it would all go right over my head, been too many years since I used that part of my brain.

Back to ECUs, all of the ones I dealt with were painfully simple in comparison to the modern Bosch setups you're discussing. If you consider what Bosch was putting out in the 80s and early 90s, it was more along those lines. Only one or two 3D maps, the rest were 2D.

Truthfully, I felt that there were some maps missing that would've made things better and allowed for some more (necessary, important) change capabilities. But that's another discussion. Overall, the sheer simplicity of these engines and lack of emissions regulations allowed you to have much simpler setups. Things like variable valve timing offer little benefit on an application that runs at what is essentially constant RPM.

 

[NealRomeoGolf]

Is an ECU and an ECM the same thing?

 

[Ted]

Is an ECU and an ECM the same thing?

Yes. It's the whiz-bang gismo box that controls all them new fangled injectomer dinglehoppers.

 

[mtuomi]

Is an ECU and an ECM the same thing?

Engine Control Module, Engine Control Unit, Powertrain Control Module, Electronic Engine Control Module etc. Same sh*t, different name.

 

[Checkout_my_Six]

Yes. It's the whiz-bang gismo box that controls all them new fangled injectomer dinglehoppers.

zactly....

 

[jaybee]

Aircraft are so woefully and laughably behind modern technology. People are worried about installing a basic electronically triggered ignition in an airplane that has been fairly standard issue since mid-70's automobiles. In regards to what has been discussed SAAB had a workable ion current sensing system in place in 1993 with the first Trionic system.

 

[mtuomi]

Aircraft are so woefully and laughably behind modern technology. People are worried about installing a basic electronically triggered ignition in an airplane that has been fairly standard issue since mid-70's automobiles. In regards to what has been discussed SAAB had a workable ion current sensing system in place in 1993 with the first Trionic system.

Trionic is an interesting story. Trionic 5 was way too complicated for it's own good. It was more of an engineers daydream rather than an usable ECU (which is why they tend to run like crap when they get older, and don't even get me started on the DI cassette failures. Anyone who has calibrated them knows how annoying they are...), T7 was slightly less so, and T8 was a piece of turd. (Thanks GM...)
I wish Saab would've finished their development on the variable CR engine. They already had a running prototype. Thanks GM for killing this one as well.

 

[jaybee]

I've been on the service end of the SAAB. Id say based on field experience it's coil failure rate is on par with other manufacturers digital ignitions. I actually saw a lot higher failure rate on Porsche coil on plug than any other except maybe Ford. That's just one guys data point.

In any event I wouldn't think twice about hopping in a dual coil on plug fadec piston aircraft.

 

[mtuomi]

I've been on the service end of the SAAB. Id say based on field experience it's coil failure rate is on par with other manufacturers digital ignitions. I actually saw a lot higher failure rate on Porsche coil on plug than any other except maybe Ford. That's just one guys data point.

In any event I wouldn't think twice about hopping in a dual coil on plug fadec piston aircraft.

The issue with the SAAB DI cassettes is, that the failure is instant and complete. Failed DI = car won't run and it will die while driving. In other brands, they will start to misfire on one cylinder which is much more user friendly failure mode.
I agree. Dual COP would enough redundancy for me.

 

[Ted]

In any event I wouldn't think twice about hopping in a dual coil on plug fadec piston aircraft.

I wouldn't think twice about it, either, and in fact I've also done it repeatedly. I have the logbook entries to prove it.

Basically it comes down to certification, cost, and having something that's marketable at the end of the day. So far, that combination hasn't happened.

 

[GeorgeC]

One thing to note with aircraft engines is that we have a wide range of CHTs to deal with, and detonation is heavily influenced by CHTs.

By now I know that the real answer is "it depends", but for a given (NA, 100LL) engine, does there exist a CHT (and/or MP) threshold, below which, detonation is no longer a threat?

BTW, these engine/ignition rap battle threads are epic, please keep them coming.

 

[Ted]

By now I know that the real answer is "it depends", but for a given (NA, 100LL) engine, does there exist a CHT (and/or MP) threshold, below which, detonation is no longer a threat?

BTW, these engine/ignition rap battle threads are epic, please keep them coming.

It absolutely depends. Which engine are you talking about?

For a parallel valve Lycoming running on 100LL, the answer is that you basically can't get it to detonate. For an angle valve, CHTs in the mid 300s are generally going to be detonation-free.

The old rule of thumb was that once you got below 65% power regardless of engine, you basically weren't going to hurt the thing. That's a rule that generally applies well even on up to the big TIO-540/TSIO-520 engines. It even applied to the Duke engine.

 

[GeorgeC]

I fly behind an O470 these days. Mainly, I was wondering, if detonation is influenced by CHT (among other things), could one redraw the "red fin" chart in a meaningful way as a function of absolute CHT rather than peak EGT delta?

 

[Ted]

I fly behind an O470 these days. Mainly, I was wondering, if detonation is influenced by CHT (among other things), could one redraw the "red fin" chart in a meaningful way as a function of absolute CHT rather than peak EGT delta?

I haven't spent any meaningful time testing 470s, but my understanding is that their detonation characteristics with 100LL are pretty benign, similar to a parallel valve Lycoming.

Regarding your question of redrawing the "red box" as a function of CHT rather than EGT, you could theoretically do that. However, EGT (fuel) remains your primary lever (both literally and figuratively) that can influence detonation in-flight. While you have a little bit you can do with CHT without changing anything else (cowl flaps, airspeed), you can most easily push the mixture in.

Your primary influencing factors are CHT, mixture setting, induction air temp, and oil temp. CHT is the most influencing factor (other than mixture), though. This is why FAA detonation tests are required to be done with CHTs and oil temps near redline, and induction air temps at ~100F. I forget the exact ranges specified for all of those, but you can look it up in the appropriate AC (the number of which also escapes me right now).

When people ask why you can't simply treat an aircraft engine like a car, it's these sorts of complex interactions in-flight that explain why it's more challenging. Cars at this point have fairly defined air/fuel ratios required (thank you, emissions regs), a cooling system that will keep the engine temps (i.e. CHT) effectively uniform, etc. If you ran at a constant air/fuel ratio in a plane like a car, you would burn way too much fuel, overheat your cylinders, or both. When you consider that stoichiometric air/fuel ratios are right in that ~25-50F ROP range (the worst place you can run an aircraft engine with the highest CHTs), you'd be running too hot, way too hot in climb, and also burning more fuel than you needed to vs. a peak or LOP setting.

All that said, it is very possible to make EFI that will work just fine in an airplane, you just need to understand the differences in the design requirements of the airplane.

 

[unsafervguy]

i do not have the engineering knowledge of these guys but I have been running lightspeed ignitions in my RV-4 for years and they run so much better than mags. the only drawback is that you are electricity dependent with them, but a simple backup power system solves that.
as to turning one off in flight, I have friend that took his rv to 17,999 he turned off the mag and nothing happened, he then turned the mag back on and the electronic off and the engine quit.
plus i only pay 2 bucks a piece for spark plugs.
bob burns

 

[Ted]

as to turning one off in flight, I have friend that took his rv to 17,999 he turned off the mag and nothing happened, he then turned the mag back on and the electronic off and the engine quit.

That was probably because he had a mixture setting that the electronic ignition was able to ignite, but the mag was not. Magnetos will work at 18k just fine on naturally aspirated engines - I've done it.

 

[Tom-D]

as to turning one off in flight, I have friend that took his rv to 17,999 he turned off the mag and nothing happened, he then turned the mag back on and the electronic off and the engine quit.
bob burns

How do we know the mag was working prior to this test? It's a well known that 1 electronic ignition system will run the engine.

 

[Tom-D]

That was probably because he had a mixture setting that the electronic ignition was able to ignite, but the mag was not. Magnetos will work at 18k just fine on naturally aspirated engines - I've done it.

I'll wager there are a lot of old worn out mags that won't do it.

 

[Ted]

How do we know the mag was working prior to this test? It's a well known that 1 electronic ignition system will run the engine.

Possible. The assumption is that the pilot performed the mag check before takeoff that he was supposed to, and that when he got back on the ground the airplane ran correctly. I think that would be natural diagnostics.

I'll wager there are a lot of old worn out mags that won't do it.

I've only flown the 310 up that high (naturally aspirated). It had Bendix 1200 series mags. The 414 has the same mags (non-pressurized) and I haven't heard issues of those mags. I don't know about other style mags.

 

[Tom-D]

Possible. The assumption is that the pilot performed the mag check before takeoff that he was supposed to, and that when he got back on the ground the airplane ran correctly. I think that would be natural diagnostics.



I've only flown the 310 up that high (naturally aspirated). It had Bendix 1200 series mags. The 414 has the same mags (non-pressurized) and I haven't heard issues of those mags. I don't know about other style mags.

I'd believe it's a matter maintenance rather than mag make model.

 

[PaulMillner]

Note that there's a review of the SureFly offering in this month's Aviation Consumer, but there are errors in that review. For instance, it states that SureFly, unlike ElectroAir, won't offer timing advance. That's not correct... SureFly does offer advance, per their website up to 37 degrees BTDC; that's why there's a manifold pressure connection, after all; why else would you need MP info?

SureFly's website also states that they expect to be certified for dual installations; though 95% of benefit presumably comes from the first electronic mag, so they expect the more cost conscious pilot to elect only one electronic system, at least at first. AFAIK, ElectroAir is *not* approved for dual systems.

>> What happens to the other legacy mag? Does it always fire later? If it fires later, is it so much later that it is really only a backup – i.e. it is not contributing to combustion events?

[Well, from takeoff through about 6,000', both mags are firing at data plate timing, 20 to 25 BTDC typically. As manifold pressure decreases in the climb, the electronic mag begins to advance timing. The conventional mag fires late, but still contributes some to combustion dynamics. The conventional wisdom is that since the electronic mag has so much MORE energy in its spark, across a much wider gap, and at a greater dwell angle, that it's very effective at initiating combustion. I think GAMI's work on PRISM showed that shutting off the conventional mag, if you didn't double-PRISM, reduced HP by only 1%.]

>> I believe the other company is Electroair, but possible they only have STCs for certain Continental engines for certified aircraft.

[No, ElectroAir is certified for both Lycoming and Continental.]

>> With an old-style magneto firing at a fixed timing, there will be limits on how far you can "retard" spark timing relative to the mag timing.

[There's no retard required or envisioned. The stock fixed mag timing is as retarded as anyone might wish mag timing, except for TDC for starting.]

>> improvements in efficiency will come from advancing the spark at operating points where the fixed timing is retarded from optimal.

[True; at lower manifold pressures, advancing timing moves the peak of the pressure pulse back toward the approximately 12 degrees ATDC where maximum mechanical efficiency occurs.]

>> You could end up with a timing that is effectively more "retarded" from the fixed mag if desired - fuel takes time to really get going and burn - retard one of the two ignition points and you retard the net effective burn time by retarding one of the two flame fronts so it takes longer to get to 50% or 90% of the fuel burned.

[You could, but that moves the pressure peak out so far that it doesn't do anything useful to contribute to engine power. Why would one want that?]

>> You may recall that GAMI was working on an electronically-controlled ignition system for aircraft which they intended to sell; the project was jokingly named, "World Peace," and the name stuck. Apparently, they thought it was a pretty valuable initiative!

[No. The electronic ignition system is named PRISM: Pressure Reactive Intelligent Spark Management. World Peace is an electronically controlled wastegate, getting rid of the pressure controller, wastegate actuator oil loop, and automatically increasing boost when fuel flow is far enough away from peak EGT, either lean or rich, to allow greater boost without danger of detonation.]

>> Any thoughts on how far off of optimal timing the typical naturally aspirated aircraft engines are at the typical cruising altitudes and power settings we use?

[five to ten degrees?]

>> I've always suspected the timing was likely close and questioned how much improvement adjustable spark timing would make.

[Depends on whether you go for fuel flow savings, or horsepower increase. 10% to 15% for either, though remember that airspeed doesn't increase very much with only horsepower increase... 15% more horsepower gives maybe 5% more airspeed (cube root).]

>> At higher altitudes or reduced MAP, maybe. But if you've ever looked at a spark table for a car, and think about how and where an aircraft engine is run, I suspect the fixed timing the factory sets is adequate.

[True; but airplanes often fly at higher altitudes; or, in the manner of PRISM, moving away from peak EGT allows advance even at higher boost pressures. Paul]

>> The question in my mind is, how many people desire to sit in a non-turboed, unpressurized airplane at altitudes where they may benefit from spark advance?

[5000 to 7000 feet? That's where many of us typically fly.]

>> What's the big deal? Unison's Laser electronic ignition has been certified for years.

[Unison sold that to Champion, who is moving toward no longer supporting the product. To attain certification, Unison gave up on the more advanced timing that ElectroAir and others are now achieving... limiting the advantage. Paul]

>> the guys in Ada were trying to base their system off of actually measuring the cylinder pressure in real time and adjusting the spark to get peak pressure at the optimal point. This is a novel concept (and I believe is also what is used in some modern high-end cars), but it also strikes me as a lot of extra work

[Well, don't know how novel; as you say, it's been done automotively. The innovative thing is the sensor they're using, which is based on oil well down-hole sensors, a fairly hostile environment itself.]

>> Benefits will primarily be on naturally aspirated aircraft which spend a large percentage at their time in the manifold pressure range where you'll see the advance. However, there can be benefits for turbo applications as well.

>> from what others have said, George is a rather peculiar fella.

[Compared to the rest of us? I'd say not at all!]

>> I'm not a dentist, and I'm not a lawyer. So I suppose those two things hurt my knowledge of engines significantly.

[Keep in mind that George got his bachelors in aeronautical engineering, then worked for Ted Smith on the Aerostar in Santa Monica. When the aviation recession hit in the early '70's, he returned to school and got his law degree. FWIW. But I'm not sure degrees from 40 or 50 years ago really limit any of us in terms of useful knowledge. ]

>> most of what I was working on was turbo'd, so there wasn't as much benefit from an efficiency standpoint. "MORE BOOST!" was the motto the customer used.

[That's a start! But to my knowledge, no previous aviation attempt has looked at detonation margins from operating away from peak EGT, or peak CHT, and taken advantage of those in setting timing.]

>> not to say that GAMI's idea isn't a good one, but I personally doubt it offers any significant benefit in terms of efficiency, etc. vs. any of the other systems, but it does add complexity.

[GAMI's focused on improving performance for their turbo'd customers; and the fuel flow mindfulness does add significant benefit. Instead of an absolute or density referenced boost max, they can adjust the boost max based on combustion conditions, and set timing accordingly. It's sexy. Paul]

>> Cylinder pressure transducers would be great, but so far these have not found their way into production engines. They are used to confirm simulations and the internal physics models in the ECUs, but production code runs based on models. They are way too unreliable to be used in production.

[Well, Nissan did it for a while. But it was pricey, for an automotive application. An extra $50 for an aviation installation? We'd never notice it!]

>> engine testing is the key to develop all the needed mapping to determine the settings required for optimal performance for an EFI system. The fancy piezoelectric are not really needed.

[Note that GAMI isn't using piezoelectrics.]

>> The firing pressure transducers I deal with at work are supposed to only be reliable for around 100 hours, so I have my doubts that a production type transducer that is expected to last thousands of hours is realistic, and a problem waiting to happen. Like you, it seems like every time we set up firing pressure it is finicky. I've spent far too much time swapping transducers and troubleshooting.

[Note that GAMI's pressure sensing endures for years in the oil industry, so it's a worthy model to investigate emulating.]

>> I haven't kept up with what BMW is doing, but I thought they were gleaning some information from feedback in the ignition system rather than directly measuring firing pressure?

[That works fine on my pilotless ignition furnace and boiler! ]

>> One thing to note with aircraft engines is that we have a wide range of CHTs to deal with, and detonation is heavily influenced by CHTs. So is power output. At high CHTs, your power output goes down (one of the man reasons why good baffling on aircraft engines is so important). Plus we have a wide range of mixture settings to deal with.

[That's of course a key insight! Cessna popularized their eight-factor diagram on octane requirement, as part of the industry unleaded avgas effort (1991 – 2011, may it rest in peace). Their graph showed each 10 degree increase in CHT above 400 F increased octane requirement one number.]

 

[PaulMillner]

I'm not a dentist, and I'm not a lawyer. So I suppose those two things hurt my knowledge of engines significantly.

OBTW... George has been a CFII since the age of 19, and is probably the “most decorated” piston engine DER in the country holding Powerplant, Engine, Flight Test Analyst and Flight Test Pilot authorizations from the FAA.

I realize that's not enough to offset that he's also a lawyer admitted to the bar... but it's some mitigation perhaps!

Paul

 

[Checkout_my_Six]

that was for a good laugh....

 

[unsafervguy]

thats just it, with a mag the points are only dead on the moment that they are set, after that things are wearing and changing. electronic ignition is far better than a mag will ever be. but progress and invovation has never been accepted well at the FAA.

 

[SCCutler]

I am so ashamed for having mis-rememberated the name of GAMI's electronic ignition product. My marginally-useful minutiae vault is contracting...

 

[jaybee]

thats just it, with a mag the points are only dead on the moment that they are set, after that things are wearing and changing. electronic ignition is far better than a mag will ever be. but progress and invovation has never been accepted well at the FAA.

don't forget that it is statically timed also.

even on a mid 90s GM with a distributor that only goes in one way, you could use a scan tool and dynamically adjust the "cam angle" plus or minus a couple of degrees.

the mag can only be statically adjusted to the accuracy of the tools provided.

at one point in my career i used to dyno cajun sprint car engines. even with only rotating the engine in direction of rotation to remove slop in the valvetrain and utilizing a crank pointer that was set with a dial indicator on the piston top I've never had an engine on the dyno that didn't need to have the ignition timing dynamically tweaked a couple of degrees. now add in the points wear you mentioned....