5 ms·
It lets you run comparatively higher manifold pressures than an otherwise identical but unleaded fuel.
by na85 4y ago
It lets you run comparatively higher manifold pressures than an otherwise identical but unleaded fuel.
- bombcar 4y agoMore importantly most aviation engines were designed in the 50-70s and need the lead to keep the valves happy.
- p_l 4y agoAnother issue is that replacements for TEL that were fine for cars had issues with high altitudes (and high ambient temperatures)
- NonNefarious 4y agoIt's about detonation; I don't think it's about the valves.
- bombcar 4y agoThe 100 octane is about detonation; the lead is about lubricant for the valves.
- NonNefarious 4y agoMmmm, not sure about that: https://generalaviationnews.com/2011/10/24/why-lead-reduces-knock/ https://generalaviationnews.com/2011/10/24/why-lead-reduces-...
- throwaway0a5e 4y agoIt's about the valves. Plenty of 100+ octane unleaded fuels out there.
- outworlder 4y agoAnd the spark plugs unhappy?
- jabl 4y agoPost-WWI aviation engines overwhelmingly have hardened valves (and valve seats) which work fine with unleaded fuel.
- maximilianburke 4y agoOnly because the engines themselves haven't evolved to handle higher manifold pressures. Lots of advancements in internal combustion engines, like combustion chamber and piston shapes that help manage the flame front, direct injection, wideband O2 sensors, are entirely unknown in certificated aircraft and still on the periphery even in experimental aviation. Like, Mazda is running 14:1 compression ratios in gasoline engines, but 7:1 is considered normal for a naturally aspirated Lycoming and it'll often dip into the 6's for turbocharged versions.
- sokoloff 4y agoMazda sold 332,756 vehicles in 2021. Cessna has the best selling model of airplane of all time, the 172, which has sold around 45K units since its introduction in 1956. Mazda sells that many cars in a typical 2 month period. It’s no surprise that there’s more non-recurring engineering investment in car engines than airplane engines.
- maximilianburke 4y agoI mean, okay? I get that. But it's not like the Cessna 172 is a $25k item either, it's now over $400k. There have been tons of advances in general aviation, look at panel technology between now and 15 years ago. That's awesome! Let's do the same thing but for engines now. But it isn't going to happen as long as no one is pushing for it; we have the efficiency in automobiles we do now because regulators have been pushing for better fuel consumption and lower emissions for decades. It'd be great if there was similar pressure applied to aviation. I'd love to have a 172 that had no mixture knob and no issues with hot starts. Man, wouldn't that be awesome? This is what we should be asking for, not apologizing for why we're stuck with mechanical FI, carb heat, and shock cooling worries.
- sokoloff 4y agoAnd Cessna sold 166 of them last year, a figure that Mazda probably refers to as "Saturday morning".