300 degrees LOP, 100 mpg

Sounds great but I'm a little scared of electronic fuel injection in airplanes. Anecdotally, I know from my last car that once the alternator goes you only have a short range (~30 sm) until your battery can't run the engine. At some point I've also had some flavor of electrical issue with 1/3 of the planes I've flown so far. I'd hate to add "when will the engine stop?" to the list concerns.
 
Pi1otguy said:
Sounds great but I'm a little scared of electronic fuel injection in airplanes. Anecdotally, I know from my last car that once the alternator goes you only have a short range (~30 sm) until your battery can't run the engine. At some point I've also had some flavor of electrical issue with 1/3 of the planes I've flown so far. I'd hate to add "when will the engine stop?" to the list concerns.
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Suddenly your new 172 is going ti have a main batt, a stdby instrument batt, and a stdby ignition batt.
 
I think we urgently need innovation. There has to be a way to get over the ignition power source issue. Otherwise, you'll have to discount all the nice improvements, like FADEC (which, I'd run away from at the moment given how Lycoming sets it up), electronic fuel injection, etc.

We don't need electronic fuel injection to run way LOP, though. It's already possible with balanced fuel injectors, it just takes a lot more effort than it otherwise would if Lyc/TCM would get with the times and provide engines built to tighter tolerances from the factory.

Innovation, please..
 
Well, maybe just an air-turbine alternator, sufficient to operate the EFI and ignition? Or, on a plane like mine, an engine-driven backup alternator of the type which is standard equipment on new Bos.
 
Savier's been flying the thing for a long time... I wonder if he's had issues, and how that worked out.

That design doesn't glide particularly well, and not my first choice for an off-airport landing, but I'd bet with proper planning, he'd be close enough to an airport in the event he was suddenly on battery power alone.

There are many other emergencies that would require a landing much sooner...

The one thing he says in that article that bugged me, though, was "why don't they have mags in cars?" That's silly- the reason is pretty obvious. You can pull over and call AAA if your car's ignition system goes on the fritz.
Theoretically, not having a backup for the spark or injector control is foolish, but how often do pilots exprience "limping home on mags" compared to other problems, I wonder?

There are plenty of ways to add backup to such a system without more bulky batteries- a retractable RAT would be perfect for such an airplane.

Seems we can have all the innovation we want- if we have an Experimental. :rolleyes:
 
SCCutler said:
Well, maybe just an air-turbine alternator, sufficient to operate the EFI and ignition? Or, on a plane like mine, an engine-driven backup alternator of the type which is standard equipment on new Bos.
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GAMI's answer is the Supplenator:

http://gami.com/supplenator/supplenator.php

To power the fuel injection and/or ignition I see little advantage in an alternator driven by anything but the engine but a backup, possibly incorporated into the ignition system component mounted where a magneto goes would seem to suffice.
 
TangoWhiskey said:
http://www.aopa.org/aircraft/articles/2008/081230100mpg.html?WT.mc_id=090102epilot&WT.mc_sect=gan

Non-stop from Southern CA to Oshkosh on less than 30 gallons of fuel, with reserves. Impressive.
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The efficiency and speed of that plane is impressive, but I'm skeptical of the "300 degrees LOP" comment given that most engines are most efficient running 35% power at something like 30 LOP not 300. Could be a typo and I could be wrong about his particular engine but if not that clouds the reliability of the other claims for me. I suppose the "300 LOP @35%" could mean the EGT is down 300 F from what would be peak EGT at full power, with most of the reduction due to the low power itself.
 
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sba55 said:
I think we urgently need innovation. There has to be a way to get over the ignition power source issue. Otherwise, you'll have to discount all the nice improvements, like FADEC (which, I'd run away from at the moment given how Lycoming sets it up), electronic fuel injection, etc.

We don't need electronic fuel injection to run way LOP, though. It's already possible with balanced fuel injectors, it just takes a lot more effort than it otherwise would if Lyc/TCM would get with the times and provide engines built to tighter tolerances from the factory.

Innovation, please..
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You can run lean with current stems, but you really can't get the maximum benefit with fixed spark timing. The timing needs to be advanced as you go leaner to get best efficiency.

lancefisher said:
The efficiency and speed of that plane is impressive, but I'm skeptical of the "300 degrees LOP" comment given that most engines are most efficient running 35% power at something like 30 LOP not 300. Could be a typo and I could be wrong about his particular engine but if not that clouds the reliability of the other claims for me. I suppose the "300 LOP @35%" could mean the EGT is down 300 F from what would be peak EGT at full power, with most of the reduction due to the low power itself.
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Could be. He is probably running wide open throttle and leaning to reduce power.

Running lean buys you two things - first is you can open the throttle and reduce the pumping losses. And second, there is some thermodynamic benefit from the reduced heat loss to the cylinder walls. But the burn rate does way down and (again) to get the most benefit, you really need to advance the spark. You would also want to redesign the intake ports to increase the motion of the mixture inside the cylinder to help push the lean limit out further.
 
rottydaddy said:
(snip) Theoretically, not having a backup for the spark or injector control is foolish, but how often do pilots exprience "limping home on mags" compared to other problems, I wonder? (snip) :rolleyes:
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Twice in less than 2000 hours. The only more frequent problem is radio failure and some of those were due to the failing electrical system.
 
lancefisher said:
The efficiency and speed of that plane is impressive, but I'm skeptical of the "300 degrees LOP" comment given that most engines are most efficient running 35% power at something like 30 LOP not 300. Could be a typo and I could be wrong about his particular engine but if not that clouds the reliability of the other claims for me. I suppose the "300 LOP @35%" could mean the EGT is down 300 F from what would be peak EGT at full power, with most of the reduction due to the low power itself.
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Hard to tell. At 17,500 with a normally aspirated engine he's not going to get more than 35% at a best power mixture setting anyway. Then there's the interesting question of which peak? When you get really, really lean the EGT's bottom out and start to climb again to a second peak. Then they drop again until the fire goes out. In my engine (IO-540) the trough between peaks occurs at about 150° LOP. 300° LOP would have to be on the back of that second peak somewhere. That seriously LOP he'd be getting hardly any power at all. Something certainly isn't right about this story.
 
Joe B said:
That seriously LOP he'd be getting hardly any power at all. Something certainly isn't right about this story.
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That raised a flag for me as well. It would seem there's some missing information here.
 
Joe B said:
Hard to tell. At 17,500 with a normally aspirated engine he's not going to get more than 35% at a best power mixture setting anyway. Then there's the interesting question of which peak? When you get really, really lean the EGT's bottom out and start to climb again to a second peak. Then they drop again until the fire goes out. In my engine (IO-540) the trough between peaks occurs at about 150° LOP. 300° LOP would have to be on the back of that second peak somewhere. That seriously LOP he'd be getting hardly any power at all. Something certainly isn't right about this story.
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It doesn't say that he IS running that lean at altitude, it says he CAN run at that temperature under some unspecified conditions.

[Ignition and Injection changes] "allows his Continental to run an almost incomprehensible 300 degrees lean of peak."

"On a typical long-distance flight, Savier flies at an altitude of 17,500 feet, about 35-percent power, full throttle, 190 KTAS, burning 3.5 gallons of fuel per hour."

That works out to the approximately 50 mpg number quoted - but doesn't mention if he is running lean to get that extra handful of percent improvement in brake specific fuel consumption.

"If he slows to extend range, Savier’s mileage approaches 100 miles per gallon."

If we assume that 35% gets him 190 knots at 17.5K (as stated), then leaning way down to reduce power significantly (and slow down to be closer to the best L/D) could be what gets him to the 100mpg. But the article doesn't say how slow, or how much he leans, or if he is still running wide open throttle, or at what altitude he is flying when he "approaches" the magic 100 (or how close that approach is).
 
Teller1900 said:
Suddenly your new 172 is going ti have a main batt, a stdby instrument batt, and a stdby ignition batt.
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Look at the homebuilt market. I have personally helped on one RV-10 that will be running dual electronic ignition and full electronic panel. Panel instruments (which includes dual AHRS and dual GPS drivers) have built-in back-up batteries. Entire electrical system is running off of two 12v batteries fueled by two alternators - one traditional mounted and one mounted on the accessory pack where the mag would normally go. It's hard to explain in typing, but he has more redundancy in his setup than you can imagine. And priced MUCH MUCH lower than what you would get out of a factory machine.
 
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