Electronic Ignition for GA Pistons

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redwoodcyclist
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Joined: Thu Jan 10, 2008 6:07 pm

Electronic Ignition for GA Pistons

Postby redwoodcyclist » Tue Jul 06, 2010 7:21 pm

Hello,

I was wondering if the forum readers or the podcast could address this. The most recent issue of FLYING had an article about great strides being made by one of the engine manufacturers in producing a piston engine with electronic fuel injection and ignition with the result being a smooth FADEC type performance of the engine. I realize the difficulties in certifying new engines, but we've had EFI in autos for more than 20 years. Why are GA engines stuck in the dark ages with a technology that seems less reliable and less efficient - namely the humble Carb?

Thanks

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champguy
Posts: 1413
Joined: Mon Jan 28, 2008 9:37 pm
Location: Florence, (Coastal) Oregon

Re: Electronic Ignition for GA Pistons

Postby champguy » Tue Jul 06, 2010 9:46 pm

The carb may be humble, but it has a long track record of being reliable.
The real issue with the new electronic ignitions and fuel injections is that they allow the engine to run leaner burning less fuel and hotter without preignition. The benefit is more power on less gas, Win Win.
Of course you have to develop a new engine to withstand the increased stress, which may lead to a smaller engine turnning faster through a reduction drive to keep the weight down. All of which might cost more.
Tried and true is not all bad if it lets us keep flying at a price we can afford.
Remember, not all who wander, are lost.
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gmarshall
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Joined: Fri Sep 25, 2009 1:54 pm

Re: Electronic Ignition for GA Pistons

Postby gmarshall » Wed Jul 07, 2010 3:12 am

By this point electronic systems beat complex electro-mechanical systems or mechanical systems in reliability fairly easily.

The exception comes when the electronic system is made too complex, usually in the name of feature-itis or cost savings.

The best example is the humble window crank in your car. Electric windows are lighter, last longer, and are mechanically simpler.

Electronic injection and ignition systems are very well understood by this point. They are more versatile, and mechanically simpler than the older systems they replace.

A smart engine management system can reduce the stresses on the engine, by optimizing mixtures more accurately than a human with a vernier control ever could, as well as implementing knock prevention etc. Lack of carb-icing with an injected engine is another huge reliability boon. Yes, you can still get throttle body icing, but it's much less common.

The performance benefits are a pretty huge advantage as well.

The reason why they haven't taken over is what Champguy alluded to. The aviation industry is incredibly risk-averse. On top of that, the volumes of small aircraft sales are absolutely puny compared to the heyday of personal aviation in the 50s and 60s.

Development costs for a modern engine have to be amortized over only a few thousand aircraft per year, at most. The certification costs would be on a per engine variant basis, meaning even smaller numbers.

There's a reason we're still flying 50 year old designs with 70 year old engine technology. :-/

For a while I was excited that diesels would revolutionize the market. If a few key models were certified with something like the Thielert Centurions (Cherokees and Skyhawks, etc) and they were available under STC by the time a fuel crisis occurred, I think you might see some economies of scale start to kick in.

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champguy
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Joined: Mon Jan 28, 2008 9:37 pm
Location: Florence, (Coastal) Oregon

Re: Electronic Ignition for GA Pistons

Postby champguy » Thu Jul 08, 2010 10:17 pm

Ya a diesel burning Jet A
Boy would that solve a bunch of problems.
Remember, not all who wander, are lost.
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Dave Higdon
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Joined: Thu Dec 20, 2007 1:02 pm

Re: Electronic Ignition for GA Pistons

Postby Dave Higdon » Wed Jul 14, 2010 4:01 pm

Nice thing -- at least where some engines are concerned -- is that you can get many of the benefits of full electronic-engine management with the installation of a LASAR ignition system; the system provides a full, seamless spark-advance curve based on engine load, atmospheric pressure and rpm...with two mechanical back-up systems in the event the electronics fail...know first-hand that the system can make a significant difference in fuel flow (down in cruise) and starting power (up a bunch...).

Downside: It's not inexpensive; but if you fly 100 hours or more a year, you can pay off the costs in fuel savings over a reasonable period of time...

Other downside: it's not full-electronic engine control, managing spark timing, fuel flow and injection timing...

Full-Electronic systems need uninterrupted electrical power or a way to function without juice; stand-by power is the usual approach...

Dave


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