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There's tons to optimize! Timing is a big one; magento fired engines have fixed timing. The engines can't remove or add timing to get more power. Fuel ratios

There's tons to optimize! Timing is a big one; magento fired engines have fixed timing. The engines can't remove or add timing to get more power. Fuel ratios are determined by the pilot with current Lycoming and Continentals. Why should the pilot need to worry about this? EFI has been around for 40 years now and would help decrease the cognitive load on the pilot. Like, how many engines have cooked valves because the pilot (or student) forgot to richen the mixture before descending? Cooling is a huge one. There are a few liquid cooled aircraft engines and they just make everything easier. The engines are more reliable, and it also removes a carbon monoxide poisoning risk due to corrosion in the exhaust cuff. Yeah, a Cessna can get better fuel economy than a car traveling at 140mph but it could be _so much better_ than what it is. And not just better fuel economy, but better all around experience for the pilots (lower cognitive load), and owners (lower cost of living, more reliable engines).

sokoloff 4y ago
Many racecars and boats also run fixed timing. Variable timing is needed when the load is variable. If the load is constant, the timing can be fixed. Modern engine monitors have given us more insight than ever into engine operation and I don’t find the engine management particularly taxing. After initial takeoff, I’m likely to set the power (throttle, RPM, and fuel mixture) at 1000’ above the ground and not touch it again for 4 hours (when it’s time to transition to landing).
- maximilianburke 4y ago
  That's still not particularly efficient. There's still variable load: circuit work, obstacles to climb over, flying around (or into) airspace. Air density isn't fixed, your engine may be running richer or leaner than you need to be. Pilots aren't nearly as efficient as setting the mixture as a computer, nor are the currently used single injector (or carburetor) as efficient as multi-point, or direct, fuel injection. GAMI got their start selling more balanced fuel injectors, but there's only so much you can do when you squirt gas into a tube and hope that it makes it equally to all cylinders. There's a _lot_ on the table in terms of efficiency and it puzzles me why there has been almost zero progress on this front.
avalys 4y ago
I’m not disputing that GA engines could be significantly improved and modernized in numerous ways. But none of the improvements you mention actually relate to efficiency at cruise power.
- maximilianburke 4y ago
  I feel like I've said this already but carbureted and mechanical FI in aircraft often do not have even fuel distribution; that is not all cylinders receive the same amount of fuel. If you have an injector on (in) each cylinder, you do. If you have O2 sensors on each sensor the ECU can adjust mixture on the fly and ensure that each cylinder is running optimally The SDS EFI people claim up to a 20% fuel effiency gain by going to multipoint fuel injection on existing engines. If you have consistent cooling (hey, guess what, those rear cylinders on an O-540 are running hotter than the fronts), you can run more timing and more compression. More timing, more compression, less fuel = more efficiency. Basically everything I'm talking about is more cruise power efficiency!
  - sokoloff 4y ago
    The premise of GAMI injectors is that not all cylinders are supposed to receive the same amount of fuel, because they don’t all receive the same amount of air. The intent is to achieve the same air-fuel ratio, which means having different injector sizes for different cylinders. I have GAMIs; they are one per cylinder, just like the factory injectors were, but provide closer matched air-fuel ratios. I also have per-cylinder EGT and CHT instruments and have measured less than 0.3gph spread (about 2%) between the leanest and richest cylinder. Modern cars are rarely measuring per-cylinder fuel, but rather measuring the average of half or all the cylinders and using that to adjust short and long term fuel trims.
  - sbaiddn 4y ago
    Youve added a pretty sophisticated complication to that engine. What happens if the O2 sensor fails in flight? Also, I dont know that you want to increase the compression on the hot cylinder. If anything Id run rich to make sure it doesnt knock
jdhn 4y ago
>better all around experience for the pilots (lower cognitive load) Can you elaborate further on this? Is this lower cognitive load because the engine is more reliable?
- NegativeLatency 4y ago
  Lower cognitive load because you as the pilot wouldn't need to manually set the fuel mixture In the gallery here: https://cessnaowner.org/pilots-perspective-cessna-340/ https://cessnaowner.org/pilots-perspective-cessna-340/ The red controls are the mixture and have to be manually adjusted by the pilot, so you could potentially remove 1/3 of the controls from that area
  - maximilianburke 4y ago
    Plus the associated gauges too (cylinder head temperature, exhaust gas temperature, fuel flow).
    - TylerE 4y ago
      Absolutely not. Engine health is VERY important, even in a fully managed "one lever" engine.
outworlder 4y ago
So what I'm hearing is... get a Diamond? :)

sokoloff 4y ago

Many racecars and boats also run fixed timing. Variable timing is needed when the load is variable. If the load is constant, the timing can be fixed. Modern engine monitors have given us more insight than ever into engine operation and I don’t find the engine management particularly taxing. After initial takeoff, I’m likely to set the power (throttle, RPM, and fuel mixture) at 1000’ above the ground and not touch it again for 4 hours (when it’s time to transition to landing).

maximilianburke 4y ago
That's still not particularly efficient. There's still variable load: circuit work, obstacles to climb over, flying around (or into) airspace. Air density isn't fixed, your engine may be running richer or leaner than you need to be. Pilots aren't nearly as efficient as setting the mixture as a computer, nor are the currently used single injector (or carburetor) as efficient as multi-point, or direct, fuel injection. GAMI got their start selling more balanced fuel injectors, but there's only so much you can do when you squirt gas into a tube and hope that it makes it equally to all cylinders. There's a _lot_ on the table in terms of efficiency and it puzzles me why there has been almost zero progress on this front.

avalys 4y ago

I’m not disputing that GA engines could be significantly improved and modernized in numerous ways. But none of the improvements you mention actually relate to efficiency at cruise power.

maximilianburke 4y ago
I feel like I've said this already but carbureted and mechanical FI in aircraft often do not have even fuel distribution; that is not all cylinders receive the same amount of fuel. If you have an injector on (in) each cylinder, you do. If you have O2 sensors on each sensor the ECU can adjust mixture on the fly and ensure that each cylinder is running optimally The SDS EFI people claim up to a 20% fuel effiency gain by going to multipoint fuel injection on existing engines. If you have consistent cooling (hey, guess what, those rear cylinders on an O-540 are running hotter than the fronts), you can run more timing and more compression. More timing, more compression, less fuel = more efficiency. Basically everything I'm talking about is more cruise power efficiency!
- sokoloff 4y ago
  The premise of GAMI injectors is that not all cylinders are supposed to receive the same amount of fuel, because they don’t all receive the same amount of air. The intent is to achieve the same air-fuel ratio, which means having different injector sizes for different cylinders. I have GAMIs; they are one per cylinder, just like the factory injectors were, but provide closer matched air-fuel ratios. I also have per-cylinder EGT and CHT instruments and have measured less than 0.3gph spread (about 2%) between the leanest and richest cylinder. Modern cars are rarely measuring per-cylinder fuel, but rather measuring the average of half or all the cylinders and using that to adjust short and long term fuel trims.
- sbaiddn 4y ago
  Youve added a pretty sophisticated complication to that engine. What happens if the O2 sensor fails in flight? Also, I dont know that you want to increase the compression on the hot cylinder. If anything Id run rich to make sure it doesnt knock

jdhn 4y ago

>better all around experience for the pilots (lower cognitive load) Can you elaborate further on this? Is this lower cognitive load because the engine is more reliable?

NegativeLatency 4y ago
Lower cognitive load because you as the pilot wouldn't need to manually set the fuel mixture In the gallery here: https://cessnaowner.org/pilots-perspective-cessna-340/ https://cessnaowner.org/pilots-perspective-cessna-340/ The red controls are the mixture and have to be manually adjusted by the pilot, so you could potentially remove 1/3 of the controls from that area
- maximilianburke 4y ago
  Plus the associated gauges too (cylinder head temperature, exhaust gas temperature, fuel flow).
  - TylerE 4y ago
    Absolutely not. Engine health is VERY important, even in a fully managed "one lever" engine.

outworlder 4y ago

So what I'm hearing is... get a Diamond? :)